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Archive for the ‘Repair’ Category

Drive By Wire Throttle Body

Posted by davidjbod on October 16, 2016

My car has a GM 3800 Series II V6 motor that has a so called drive by wire system which is fairly common on vehicles today.  Drive by wire systems measure the position of the accelerator pedal. This reading is then sent to the car’s computer which sends signals to the throttle body’s motor which moves the throttle body’s blade.  The computer monitors the position of the blade via the appropriately named throttle position sensor which is also in the throttle body.   Prior to these systems a steel cable ran from the accelerator pedal to the throttle body to move the blade.  I should probably add that the throttle body meters the amount of air going into a gas motor.

The system in my car has been reliable for over 200k miles. Lately, though, I’ve been getting an intermittent trouble code and the car would drop into a reduced power mode.  The code indicated that there was disagreement between the 1st and 2nd throttle position sensors.  In other words, the car’s computer wasn’t sure where the throttle blade was and was unhappy.  I looked into replacing the throttle position sensor and quickly became unhappy myself.

I’ve replaced throttle position sensors before.  They’re pretty cheap at around $20-$30.  Remove two screws, swap sensors, put the screws back on and you’re done.  Well, on this car, the throttle position sensors cannot be replaced separately.  It turns out that you have to buy a whole new throttle body assembly because it is a “non-serviceable sealed system” or some BS like that.  The dealership wanted $800 for it and online parts warehouses wanted $360. No, thanks.  I found a used one from a junkyard car with 44k online and purchased it.  I swapped them out and all seems to be good again.

Since the old throttle body is now a paper weight I figured I’d look into what makes it so special.  Here’s my throttle body.  Air goes into the top, through the mesh, and then hits the blade inside the throttle body.  It this exits the throttle body into the motor.  The sensor in the middle of the screen is the MAF (mass air flow) which tells the computer how much air is going into the engine.  One the lower right is where the connector for the throttle body motor and throttle position sensors go.  Note that the black plastic sides are riveted on so you can’t mess with it.


A drill made quick work of the rivets and the cover was easily removed.  Here’s the throttle position sensor module.  The shaft that the throttle blade is attached to goes through the middle of the throttle position sensor module.  Note the throttle position sensor module is secured by regular screws.  More on it in a minute.


Under the cover on the opposite side, is the actuating motor and a bit of gearing.  There’s also a coil spring that closes the throttle blade mechanically.


The idler gear rides on the shaft and is easily removed.  Then just two Phillips screws hold the DC motor in.  Thats pretty much all there is to it electronically.      tb4

Let’s take a closer look at the throttle position sensor module.  The throttle position sensors are completely enclosed and connect to the motor through a plastic connector.  So, it is easily capable of being replaced.  Grr…


The back has a little panel that has been plastic welded on.  The weld can be scrapped off easily allowing access to the inside.


Inside is pretty much what I expected.  A throttle position sensor is a potentiometer which is just a variable resistor.  A potentiometer has a resistive area and a piece of metal, called a wiper, moves along this area.  The total resistance of the area from end to end is a constant resistance.  The wiper can be moved which changes the resistance between the ends and the wiper.  The amount of resistance affects the voltage out of the potentiometer.   Anywhere you turn a knob on something electronic, that doesn’t have distinct positions, you’re probably dealing with a potentiometer.  In the picture below the resistive areas are around the inner walls and the wipers are on the middle piece.


Here’s a close up of the resistive areas.  There’s two separate throttle position sensors in the module with one on each side of the inside of the module.  The resistive areas (the grayish areas) for each throttle position sensor are split in two connected by the wiper.  If you look closely, you can see three stripes inside the wide bands of resistive material.  This is where the wiper fingers have worn through the resistive material.

tb8The center piece holds the wipers and is rotated by the throttle blade’s shaft.  The separate fingers on each wiper add redundancy to the sensor


With the throttle position module removed, I was able to check it with my multimeter.  I connected one probe to the wiper pin and another to the end pin with the multimeter set to measure resistance.  Next, I slowly rotated the wiper while watching the multimeter.  I expected and saw the resistance linearly increasing.  At one spot the meter showed infinite resistance indicating that there was a break in the resistive material due to the wiper scratching it off over time.  This was my problem.  The sensors would agree for most of the time until one sensor hit this area and sent bad date to the computer.  The computer noted that the voltage value didn’t match and set the error code.  This check could have been performed without disassembling the throttle body.

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Ball Peen Hammer Cleanup

Posted by davidjbod on June 6, 2016

I picked up a couple old ball peen hammers that need a little clean up.  I want to use some of my ball peen hammers for working metal which is why they’re getting this treatment.  This hammer is in good shape.  The handle is straight, tight, and not cracked.  So, I won’t be removing the head from the handle.  Cleaning up the head would be easier without the handle but can still be accomplished with it.  The hammer I’ll be cleaning up is an unbranded 8oz head.


To work sheet metal or thin plate with a hammer a smooth face is beneficial.  A rough face will texture the surface with each blow leaving you a problem to deal with later.  Depending on what you plan to do with the hammer, you may want to round the surface.  A rounded face is useful when pounding metal as is puts pressure over a smaller area and allows you to land blows that won’t have a sharp edge marking up the metal.  The radius of the face depends on the use of the hammer.  If you’re pounding into a depression the face needs to have a radius smaller than the radius of the depression.  I made a template out of cardboard for my chosen radius and then headed to my small belt sander.  I started with a 100 grit belt griding away metal in circles from the outside in.  After each pass, I checked my progress with the template and ground as needed.


The 100 grit paper leaves scratches in the surface and requires a finer belt.  So, I replaced the belt with a 400 grit one and went over the face again with a light touch.  The 100 grit belt cuts much faster than the 400 grit belt but you still have to be careful with the finer grit as it can put flat spots into the face.


Speaking of flat spots, I also cleaned up the ball on the opposite side of the hammer.  It was fairly pitted so I used the sander again with the 400 grit paper and a light pressure.  Even using the part of the belt not over the platen I still ended up with numerous flat spots.  This is ok though.BPH4

The next step is to start hand sanding.  I started at 120 grit paper and used it until all of the flat spots were gone.  It’s important to do a good job with this first grit as it will save time later.


Eventually, I worked my way up to 600 grit paper.  I used it to smooth both the face and ball of the hammer.


At this point the surfaces would probably be ok for use.  But, to put the final finish on my hammer I pulled out my 6″ buffer.  It’s a Harbor Freight branded buffer but it is impossible to beat for the value it provides.  One can be picked up cheaply on sale and buffers are much quicker than hand polishing.  I used a green stick of compound and polished up the face and ball.


The last thing I did was give the handle a light sanding and a coat of boiled linseed oil.  Some hammers have a lacquer finish and I prefer to remove them as I find an oiled finish to provide better grip.


If you have other ball peen hammers you get the joy of getting to go through the process again and again!    In the middle is a 32 oz surrounded by a 24, 12, and a couple 8 oz hammers.  I might have a few more not pictured…  But hey you can find hammers all over and do your part to restore them!  You can’t have too many, right?


Posted in Repair, Restoration, Tools | 4 Comments »

More Work on the Fritz

Posted by davidjbod on August 2, 2015

While I’m waiting to find a 3 phase transformer, I’m continuing to clean up the Fritz Werner mill.

I found another cover to pull off.  It is on the gear box that adjusts the table’s feed speed.  Everything in there looks pretty good and I didn’t see any broken teeth.  On a side note, there is a port to add oil into the gear box that was missing the correct cap.  While digging through the sludge in the cutting oil reservoir I happened to find the actual cap.  Yes, I could have made a replacement but all the correct caps have a little oil can stamped into the top dripping oil.


The machine also has a handful of these recessed zerk fittings.  I can’t get to them with a normal grease gun.


Not to fear though.  A quick trip to the lathe solved that problem.  Well, it was multiple trips because I was trying to take off as little material as possible.  Eventually I got it though.  From what I’ve read online, most milling machines use oil to lubricate everything as opposed to grease.  One of the reasons this is done is because grease will trap chips which increases wear on the machine.  From what I’ve seen on my machine, the zerk fittings on it are for grease.  The one on the spindle also has a tag that says “Grease”.  I’m going to switch over to oil on the zerks that feed the ways and slides though.  Comparing grease and oil, I think the oil slides better anyways.  The zerks that feed the thrust ball bearings and other unknown parts will still get grease though.


At some point, someone whacked the Y axis hand wheel that sticks out of the front of the machine.  To fix this I first had to remove the lead screw for it.  While removing it, I noticed there was a lot of grease with chips in it around the “nut” that the lead screw runs in.  That needs to be cleaned up and requires removing the table.  More on that in a few.  As you can see, it’s a little bent.


To straighten the lead screw, I mounted it in the lathe and miked the end of the screw.  This was all unpowered.  I was turning the spindle by hand.  The lead screw was rotated until I found the low point and marked it with a piece of tape.


I took the lead screw over to the arbor press and used it to gently push on the screw.  Then it was back over to the lathe to see how I’d done.  I kept going back and forth from the lathe to the press until the run out was around 0.01″.  I figured this was good enough for a hand wheel.


Here’s the straightened shaft.  I’d like to point out that the thread on the lead screw has a 20mm major diameter with a 5 TPI pitch.  It’s also left handed.  This is a mix of metric and UTS.  It isn’t a standard thread I’m likely to find stocked somewhere. FW26

Back to the machine, I noticed that what I’d previously though was some kind of plug was actually a smashed zerk fitting.  It had to come out and be replaced.  After I’d removed it, I measured it and discovered that it is a 6mm press in zerk.  I’ll be ordering some of those soon.


I’d mentioned earlier that the table would need to come off and here we are.  To remove it I had to remove the lead screw shown above and remove the gib.  I also had to remove the studs the gib fits onto and the drive shaft that controls the table movement.  After removing a few more small parts Chris and I were able to tilt the table and remove it.  Unwiring it didn’t seem easy and I wasn’t planing on going very far with the table.  So, it is still tethered to the mill.  If you look in the middle of the pic, you’ll see a couple bevel gears.  The one with the hole that points down is where the lead screw goes.


I moved the table from side to side so I could remove more chips.  It also gave me a chance to look at the grease/oil passages that feed the slides.  They look pretty good and I took the opportunity to push oil through them to purge any grease.


Above I’d mentioned the studs that hold the gib in place.  Here’s the three regular studs.  There’s a fourth that is used to lock the table in position and isn’t shown.  I guess at some point someone tightened one the nuts down to tightly, broke the stud, and said “Oh well”.  That won’t do.


With one of the good studs in hand, I headed back over to the Hendey lathe.  After a screw up, I manged to reproduce the part.  This little stud has M8 x 1.25 threads on both ends.  Since my lathe only does SAE threads, I used a steel (12L14) I could run a die over to make the threads.


Shown below is the assembly that houses the “nut” and the bevel gear for the lead screw.  The piece up top is the “nut” and is made out of brass.  It’s made from brass so that it will wear instead of the lead screw since it is cheaper to replace.  The assembly has a couple alignment pins that for some reason have threaded ends.  They’re metric threads too.


Shown below is a close up of where the assembly from above sits.  You’ll notice a bunch of holes in the surface.  The two smaller holes are to get grease into the assembly which is supposed to lubricate the lead screw by seeping out of a hole I think.  The lubricant being grease then traps chips as you can see on the bevel gear.  The two medium holes are for the alignment pins and the largest holes are for the bolts that hold the assembly on.  One of the bolts was gone and the other was very loose.  To top it off, they’re UNC 3/8-16 threads.  I checked multiple times and compared the bolt to a metric bolt that was almost the same.  In the end though, they were UNC.  Odd and annoying.


Remember I was talking about wear and how the brass “nut” is meant to wear instead of the lead screw?  Here’s a pic of it.  The internal thread here should have nice wide flats on the crest of the thread like the lead screw.  Instead it has almost worn always leading to slop in the lead screw I can feel.  While I had this part out, I made a dimensioned drawing of it.  One day I’d like to make a replacement.  I think I’ll need to practice a bit before then though.


That’s the latest update.  I plan to get it put back together soon while crossing my fingers that I’ll find a used transformer.

Posted in Metalworking, Repair, Restoration, Tools | Tagged: , | 3 Comments »

Speaker Crossover

Posted by davidjbod on May 23, 2015

Over 10 years ago I made a center channel speaker for my home theater sound system.  “Home Theater” is over selling it a bit but it was my center channel speaker.  I made it from some scrap plywood my dad had I think along with some 4″ woofers and a tweeter that Radio Shack was clearancing out.  The tweeter came with a capacitor attached to it to filter out low frequencies which I considered good enough for a crossover at the time.  I assembled it and used it for several years.  Eventually, we moved and the center channel got shelved as we were using the TV’s speakers.

A couple weeks ago we decided to move the TV into one of the spare bedrooms and create a game room.  I grabbed a surround sound receiver a friend had given me and decided to pull out the center channel again.  Here’s a pic of the speaker as it sits now.


At some point some kids (not mine) had poked in and ripped the old tweeter as you can see below.  I picked up the one you see above from Parts Express and fit it to the cabinet.  Note that the old tweeter had four screws holding it on while the new has three.  This and the larger back of the tweeter required modifying the cabinet a little bit.


Before I get into making the cross over, I should probably explain what a crossover is.  As I’m sure you know, speaker drivers (the actual transducer not the box) reproduce sound.  They do this by moving in and out at a specific frequency to reproduce a specific tone.  Put a lot of movement together and you get music or the spoken word.  There are numerous types of drivers.  Some are made for very low frequencies known as subwoofers.  Some for low frequencies called woofers, higher up the frequency spectrum comes midrange drivers, and at the top of the spectrum are tweeters.  This leaves out some but covers it for the most part.  Drivers work best when they’re reproducing the frequencies they were designed for.  Trying to make a driver produce other frequencies can result in poor, quiet, or no sound at these frequencies.  In the case of tweeters, passing them the high power signal that should go to the woofers can burn them up.  Some speakers, typically poor ones, have one driver.  Others have two, three or more driver.  A speaker with two different drivers is typically known as a two way system.  A three way system has three different drivers.  In a two way speaker there’s a driver for producing lows/midrange and one for producing highs.  A three way splits up the work even more.

This is where the crossover comes in.  The crossover filters out certain frequencies for each driver letting pass what’s best for that driver.  My center channel is a two way speaker despite having two woofers.  They’re the same and in this design the two woofers correct an audio issue I won’t bore you with.  In a two way crossover, frequencies below a certain point get sent to the woofer(s) and those above the point get sent to the tweeter(s).  Once again, I’m glossing over details, but thats the basic idea.  For my speaker I set the crossover frequency at 2000 Hz.  I found a website that calculates the values of the required electrical components to filter the signal.

When crossovers filter a signal they don’t just chop everything else off.  Instead, they slowly decrease the signal outside of the bounds.  The rate at which they decrease the signal is known as the crossover order.  The crossover I chose attenuates the signal at 12 dB/octave.  The crossover frequency is actually the frequency at which the signal has been attenuated by 3 db.  If the crossover is designed correctly the two drivers will complement each other and there won’t be a noticeable frequency range that is attenuated around the crossover frequency.   I don’t feel like putting the effort into verifying this for my speaker though.  So, I’ll just cross my fingers and be ok if everything isn’t perfect.

With the theory out of the way, we can turn to the actual crossover.  The calculator asks for the impedance of the drivers and the crossover frequency desired.  With this information, it generates a diagram with some capacitors and inductors and the value of each.  Each capacitor/inductor combination will filter the signal for a speaker or speakers depending on how it’s wired.  The picture below shows the diagram of the crossover and the parts I’ll make it out of.  In the diagram the signal comes in from the left and gets spit up into the crossover components.  The signal is routed up towards the tweeter and to the right to the woofer passing through the cross over components first.  Capacitors let high frequencies pass and inductors let low frequencies pass when wired in series with a driver.  That’s the role of the C1 and L2 components in the diagram below.    Without L1 and C2 I’d have a first order cross over but the addition of these components results in a second order crossover.


One of the fun parts of electrical work is figuring out how to actually wire things together.  The diagram has lines connecting all the components that you might think of as wires.  In reality there doesn’t have to be any wire and you can connect the parts together directly.  To figure it out, I first laid all the parts out on a piece of wood I’d build the crossover on.  Then I made all the connections to assemble the crossover taking time to triple check the connections.  Here’s what it looks like on it’s own.  The capacitors are the black cylinders and the inductors are the wound copper loops.


Happy with how it looked, I pulled out the hot glue gun and stuck the components to the wooden base.  This keeps everything from rattling around in the speaker cabinet and putting strain on the wires.


Next, I added all the leads and soldered it all together.  I hooked up all the speakers and checked the resistance value of the crossover at the input leads.  All I wanted to check was that there wasn’t a short.  A multimeter checks resistance with DC which you can think of as a 0 Hz signal.  So, this signal is blocked by the capacitor from the tweeter and passed trough the inductor to my two woofers.  I got a reading of around 4 ohms which makes sense for my two woofers wired in parallel.  With this check and a final review of the whole circuit I hooked it up to a small amp.  I ran music through it for a bit and everything seemed to be working well.


Next, I clipped the extra leads off of the components and taped them up with electrical tape.  Not pretty, but who cares.  No one else will ever see it…other than you of course.  Finally, I glued it in the bottom of the cabinet, stuffed my fiberfill back in and put it all back together.



Hooray sound.  But not good sound.  Something is off but what.  I put my ear close to each speaker and as expected heard lows out of the woofers and highs out of the tweeter.  For some reason though the speaker sounded odd like it was missing some lows and like there was re-verb when listening to voices.  Music sounded like it was missing the lows as well.  After a little bit, I decided to place a book over one of the woofers with some music playing.  The lows instantly came back and I knew what had happened.  I swapped the book to block the other woofer to confirm and heard the same results.  Somehow, one of the woofers was out of phase and canceling out some of the sound from the other woofer.  If you remember your wave theory, two waves that have peaks and valleys that occur at the same time are said to be in phase.  When you combine them they add together.  If they are out of phase a little bit then the frequency can shift.  If the waves are opposite, known as 180 degrees out of phase, they will cancel each other completely.   This is what my woofers were doing.  They didn’t cancel completely of course but they were fighting each other.

I pulled the woofers to see what was going on and realized how I’d messed up.  I reused the leads with the crimped on connectors that I’d made years ago.  The woofers have a large and small tab for the positive and negative terminal respectively.   When I went to wire the driver leads up I only looked at the stripe on the wire sets to determine polarity.  I’d put the wrong connectors on of the woofer back then and had never fixed it.  I suppose that when I’d wired it up years ago I hooked the wires up intentionally backwards instead of recrimping the connectors since I didn’t have the odd sound before.  Anyways, I changed out connectors and put everything back together correctly this time.  Much better!  Low and midrange frequencies were back.

Speaking of phase, here’s another note.  In a second order crossover system one part of the crossover will lag by 90 degrees while the other will lead by 90 degrees.  This results in a phase difference of 180 degrees.  To correct for this, I wired the tweeter “backwards” so that it will be in phase with the woofers.


PS – I picked up an old Sony Cybershot camera at a thrift store for $10 and tried it out on this post.  I don’t think it’ll replace the D50 though.  So, no bounce flash like normal this time.

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Replacement Focusing Knob

Posted by davidjbod on May 17, 2015

I have an old Bushnell spotting scope that I bought a while back.  Overall, it is in good condition.  One of the problems is that the focusing knob has been cracked from tightening down the set screw that holds it on.  As a result, it slips on the shaft and you cannot adjust the focus reliably.  Time to fire up the lathe.


I took some measurements and sketched out a rough drawing to work from.  Basically, it is a cylinder with a stepped hole in the middle and a threaded hole normal to the center axis where the set screw goes.


I decided a steel 1″ knob would be a little overkill.  Instead, I chose to use some aluminum I’d recently ordered.  This is the first aluminum project I’ve done on my lathe.


The original knob was a little over 1″ but 1″ is the largest piece of aluminum I have.  The outer diameter isn’t a critical dimension though.  I took a light pass to clean up the surface. I was very happy with the surface finish I got from the old girl.


Next, I put a slight bevel on the bottom of the knob.  I did the same to the top after removing a little material.


To increase grip on the knob I wanted to put a knurl on it.  I only have one size knurl with my quick change tool post which made selecting the size of the knurl easy.  I slowed the lathe down, fed the knurling tool in, and engaged the feed to move it to the top of the knob.  The knurl didn’t come out perfect though as the final spot I knurled is slightly different than the rest.  I’m not sure why.  Knurling takes a bit of practice.


Moving on, I removed the live center from the tail stock and used the chuck to drill the small hole that the focusing shaft will go into.


Next, I removed the small drill bit and drilled the larger hole to fit the spotting scope.


To drill the perpendicular hole for the set screw, I removed the bar of aluminum and headed over to the drill press.  I then drilled and tapped the 8-32 hole for the set screw.


Before I’d removed the part from the lathe, I turned my tool post to bevel the edge of the large hole I’d drilled in the bottom.  Before I can part off the knob I need to align the tool post to be perpendicular to the work.  This is important for the cutoff operation.  If the cutoff tool isn’t perpendicular to the part then the sides of the tool will rub the work which can result in a poor finish and possibly break the tool.  (Technically, the cutoff tool has to be aligned with the direction it is being fed in.  Since I’m feeding in with the crossfeed it needs to be perpendicular.)


I parted the knob off, filed down the post left on the top of the part, and sanded the top down to 600 grit to leave a nice brushed finish look on the knob.  I thought this was a good alternative since I couldn’t think of a way to hold the knob to clean up the top of it.  After that, I put the knob back on the scope and can now focus without issue.


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Making a T-Bolt for the Hendey Lathe

Posted by davidjbod on December 6, 2014

In the process of grinding the jaws on my lathe, I tightened down one of the compound bolts…but it never got tight.  Hmm.  I looked at it carefully and noticed the nut and stud were both turning.  Not good.  I disassembled the compound and found one of the T bolts had broken.  I pulled the bolts out and found one had sheared apart.  It turns out that this wasn’t an original bolt.  Someone had made it by welding a stud to a small plate.


As you can imagine, I need a replacement T bolt and you can’t just pick up a replacement part.  Luckily, Gill offered the use of his lovely Monarch 10EE to make a new one.  I ordered some 1″ 1144 steel to make the bolt and headed down to his house once the steel had arrived.  I cut off a piece to use and mounted it to the lathe to being work which first involved facing the piece.


The T bolt uses a 7/16″ – 14 tpi thread.  To cut the thread on the new bolt the diameter of the piece was brought down to the major diameter of the thread.  behind the section to be threaded, the bolt was brought down to the minor diameter so that the tool would have a place to stop after making a pass to cut the threads.  Without this area, the cutter would cut a V shaped groove into the part when the carriage stopped moving.


Cutting the threads required making several passes advancing the compound each time.  After demoing how it worked, Gill turned the threading operation over to me.  After a small error at the beginning of the first pass, cutting the threads went well.  In the picture below you can see the results of the threading operation.  In this pic, I’m about to reduce the diameter of the T, which explains the cutter.


Once I was happy with the part, it was parted off and rechucked to clean up the opposite side of the T bolt.


Here’s a pic of the new bolt fresh off the lathe compared to the original T bolt.  The original T bolt has a kidney bean shaped head.  So, there’s a little more work to do.


To shape the head, I painted the bottom of the bolt, held both bolts back to back, and scribed the correct shape on my new bolt.  I set to work using a file to shape the bolt after putting it in my vise with Aluminum jaws in place.  I used couple coarse files to remove most of the material and then finished the edges with some smooth files.


Here’s the final part compared to the original.


With the new bolt in place, it’s time to make chips again.  I’ve added a green arrow to show where the bolt goes.  They’re loosened and tightened to rotate the compound.


Making the T bolt I learned a couple things.  First, 1144 steel machines very nicely on Gill’s lathe with carbide and on mine with HSS.  I even got a good surface finish with a regular cutting tool profile.  Second,  you have to be quick when threading. Threading involves the carriage moving pretty quickly.  When the tool exits the area you’re threading you’ve got to disengage the carriage feed before the tool hit the work piece.  Third, quick change tool posts are wonderful.  Being able to just drop the tool in place and go without setting the height is great.  Finally,  Gill’s lathe is very nice.  Well, that last one was just reaffirmed.


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Hendey Finishing Touches: Jaw Grinding

Posted by davidjbod on November 28, 2014

I decided to address another problem with my Hendey lathe.  This time I turned my attention to my three jaw chuck.  My chuck had two issues I wanted to address.  The first is that it would not hold a part perfectly centered which is known as runout.  Runout is measured by holding a ground bar in the chuck and placing a dial indicator to measure the surface.  The spindle is turned through a complete revolution and the maximum and minimum values noted.  The difference of these values is the runout.  It’s easier to set the dial indicator to zero at the low point and then find the high spot.  I measured 0.008″ runout with a 1.25″ diameter ground rod.


The second issue with the chuck was that the jaws were wider at the front of the chuck than the back.  I’ve seen this referred to as being “bell mouthed”.  This is easy to see because you can see light between the part and the jaws.  To illustrate this I’ve slipped a 0.006″ feeler gauge between one of the jaws and the part.  It goes in about 0.25″ and thinner gauges went in further.


To fix these problems the jaws are ground on the lathe.  As there is slack in the jaws, they must be forced outward to take out this slack.  I used a method I came across on Home Metal Shop Club‘s website.  The author of the article suggested using shims to push the jaws apart as opposed to the more commonly seen ring.  Using my friend Gill’s Bridgeport, I made a set of 1.25″ shims.  In the picture below, you can see I’ve also marked the jaw faces with Dykem to monitor progress on the jaws.


Professional machine shops and well equipped hobbyists use tool post grinder for grinding the jaws.  It is setup to be mounted in the tool post to easily attach it to the lathe.  I lack such a tool and instead used the arrangement you see in the picture below.  It’s a pneumatic die grinder that I’ve “attached” to the tool post.  Though it looks rather shoddy it held the grinder tightly enough for what needed to be done.


I don’t have any pictures of the actual grinding because I wanted to focus on that.  First, I covered my lathe as best I could to keep out grinding dust.  Grinding is done with both the lathe and grinder spinning.  I ran my lathe at ~100 rpm during grinding after trying several slower speeds first.  To start the actual grinding, I advanced the grinding wheel to the back of the jaw until it contacted to locate my zero.  I dialed out 0.002″ with the cross slide and slowly moved the grinder out with the feed wheel.  From here I kept advancing the grinder out and making passes checking my progress frequently.  At first I was only contacting one jaw but eventually all three were being ground.  As expected, in the beginning the area ground was in the back of the jaws.  As work progressed the ground area moved outward.  Once I was happy with the results, I moved the grinder in, dialed out another thousandth, and made a pass out of the jaws.  I figured that this would impart a slight taper into the jaws which would be wider at the back since the grinding stone wears as the pass is made.

Seen below is a picture of the results.  Note that my shims now have a concave edge on them.  Before I started grinding I noticed they would get hit first by the grinder.  I pulled them off and ground them on my bench grinder.  The jaws all showed an evenly ground area everywhere except at the very tips.  The tips were banged up and I didn’t want to remove the material required to get the last little bit ground.


While I was set up for grinding, I figured I’d touch up the front face of my jaws.  As you can see below, the front faces of my jaws near the middle are a little dinged up.


I made passes with the grinder taking a couple thousandths off each time until most of the front face was cleaned up.


Once I was done grinding, I wiped all the surfaces of the lathe down to remove any grinding dust.  I also removed my chuck, disassembled it, and gave it a cleaning as well.  I put it back on the lathe and proceeded to take another measurement of the runout to see if there was improvement.  I was rewarded with a runout a small bit over 0.003″.  I’ve seen this runout specified on some new chucks.  So, I was pleased with my results.


The “bell mouth” was also gone.  I couldn’t see any light between the chuck jaws and the part.


If you’re wondering why I don’t have zero runout, there are a few reasons.  The first is that inside of the chuck is a large scroll which also wears some over time during operation.  The jaws ride different portions of the scroll depending on how wide open the jaws are.  Thus, the area the jaws were pressed against on the scroll when I ground the jaws is not the same as when the jaws are at some other position.  Since the scroll has probably worn unevenly, even if my jaws were perfectly ground in one position you can’t say that they would be perfect in another position.  This also means, that my ~0.003″ runout measurement is only at that one diameter.  I measured runout with a ground 0.25″ rod and had less than 0.001″ runout.  Another reason would be my grinding set up.

I’m happy with the improvements I’ve seen in my chuck.  I’m not sure how old the chuck is but I imagine it is quite old.  I’m glad to keep running it with the lathe.  Even if my runout had not decreased the removal of the “bell mouthing” will result in a better grip on the work piece.  I’m hoping this will translate into an easier time parting off on the lathe.

Unfortunately, while tightening down one of the locking nuts on the compound, I broke one of the T bolts.  It looks like someone had fabricated it from a stud by welding a piece of steel on top of it.  So, I will be fabricating a replacement T bolt in a future post.  For that, I’ll be taking a field trip to Gill’s.


Posted in Metalworking, Projects, Repair, Restoration, Tools, Uncategorized, Use | Tagged: , , , | 1 Comment »

Jack Repair

Posted by davidjbod on November 15, 2014

I was doing some automotive work last weekend when the release mechanism on my jack broke.  I had jacked the car up and placed jack stands under it.  When I went to lower the jack, which requires twisting the handle, there was a little bit of resistance and then the handle spun freely.  Hmm, not good.  I used another jack to free my broke jack and was able to get the car safely back on jack stands.  I inspected my jack and found that the universal joint had broken.  My jack is an aluminum Craftsman jack and they felt like saving an ounce by making the U joint out of aluminum as well.  This doesn’t seem like the best decision in my mind.  Anyways, seen below is my broken universal joint.  The square end on the left fits inside of the jack handle and rotates the valve on the right side of the pic.  The U joint has two pins of different sizes and the body piece that the larger pin went through broke.  I looked online but Craftsman didn’t offer a replacement part that didn’t involve buying the cylinder.  Guess I’ll make a replacement part.


To start I chucked up a piece of 3/4″ steel rod into the lathe to drill a hole through it.  Before drilling, I used a center point to start the hole.


Next, I drilled to an appropriate depth with the lathe.


I cleaned up the surface with a few light cuts to eliminate the mill scale.  The original part was 3/4″ diameter.  So, my part will be a little smaller but made of a stronger material.


Here’s my piece once I’d parted it off the lathe.


From this point, making the part will require drilling three holes through the part.  Two holes are for pins and the other hole is to remove a large amount of material to form the U.  I used my height gauge (Thanks Gill!) and some Dykem to scribe the location of the holes.  I also used a small machinist square to scribe a vertical line to align the two pin holes.  Finally, I lightly punched the hole locations to keep my drill bit from wandering.


Here’s the point I’d use a mill…if I had one.  Since I don’t, it was off to the drill press that did a good job.  I oriented the part as best I could under the drill bit and proceeded to drill the two pin holes.  JR7

I rotated the pin 90 degrees and drilled out what would be the bottom of the U shape.  After drilling I noticed that this hole wasn’t exactly 90 deg from the two pin holes.  This was unfortunate, but not bad enough to trash the piece.


I held the piece in the vise and used a hack saw to remove the material between the large drilled hole and the end.  Then, I used a file to round over the edges and clean up the inside of the part so that the cross journal block would fit.


I dressed the ends of the pins I’d removed and then reassembled the universal joint with my arbor press.  Once I was satisfied with how everything fit I peened the ends of the pins to keep them in place.


I reinstalled the part back into the jack, bled it, and gave it a couple test releases.  Success!


Now back to putting the transmission back in the car.

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Hendey Finishing Touches: Part 1

Posted by davidjbod on November 10, 2014

As expected, as I’ve been using my lathe, I’ve run into some issues.  The first issue I mentioned in my last post.  During drilling with the tail stock, the spindle would seize in the conical bearings.  My Hendey employs two conical bearings for the spindle to run on.  The face of the front bearing runs against a spacer that presses against a flange on the spindle.  Over time this spacer and the bearings will wear.  As a result the spindle can contact the bearings instead of riding on a cushion of oil.  Shims can be added to the spacer (or a new spacer made) to maintain the correct spacing between the bearing and spindle.  Thanks to the folks at Practical Machinist I knew why I was having this issue and expected to run into it.

The first thing I had to do was get the back plate off the threaded nose of the spindle.  To do this I removed the chuck from the adapter plate.  The adapter plate is held on with three screws with recessed hexes.  Unfortunately, the screws had somehow been damaged to the point where I couldn’t remove them with a hex key.  I ended up drilling out the heads enough to where I could remove them with a screw extractor.


With the adapter plate removed, I had access to the back plate.  Though I’d tried to get this off before, I was able to finally.  After seeing the idea in a post on Practical Machinist, I wedged a tapered piece of wood under the bull gear to immobilize the spindle.  Then, with a piece of mild steel and a hammer, I struck the shoulder of the cut outs on the back plate.  After a hand full of moderate blows the back plate broke loose and I breathed a sigh of relief.


Here’s the nose of the spindle.  It looks to be in great shape.


From posts on Practical Machinist, I was able to determine what size shim for the spindle was required.  The method to determine the proper spacing first requires you to remove the spindle, wipe the oil from the spindle and bearings.  Then, remove the stock spacer and reinsert the spindle using firm hand pressure to seat it.  Next, measure the spacing between the front of the bearing and the inside of the spindle’s flange.  For my lathe the space was 0.129″.


Next, you need to measure your spacer, as I’m doing in the picture below, and subtract this from the gap size. Then add about 0.006″.  I say about because there was a small range I saw discussed and this was in the middle.   The 0.006″ provides the correct spacing for the bearings.  Doing the math says I needed a 0.011″ shim.


I ordered some 0.012″ shim stock from McMaster and went to visit my friend Gill to cut it out on his Bridgeport.  Try as we might, we were not successful.  In the end, I picked up a piece of 0.01″ thick brass locally which we were able to successfully cut.  I didn’t get a picture of the shim because my camera was dead but you can see it installed in the picture below.  Brass will probably wear faster than if I’d used steel but I think it will last a long while under the light use it’ll see from me.


Once I had the shim taken care of, I reinstalled the chuck.  To replace the screws I had to drill out, I bought some from the store and then turned the heads down to fit on Gill’s superb Monarch lathe.

Next up, is the issue of the rear bearing leaking oil profusely.  As the machine is running oil is picked up by a ring and carried onto the spindle.  It then runs out both ends of the bearing into a flanged section of the bearing and then back into the reservoir via a small hole.  As you can see below, a piece of the flange was broken before I got the machine which lets the oil leak out.


To take this back to factory would require making a new bearing which is something I’d like to avoid right now.  Instead, I cut a piece of flashing and formed it to the shape required.  It is held in place with a metal band clamp.  The back side of the flashing was covered with a thin coating of RTV sealant before putting it on to keep it from leaking at the edges.


With the guards back in place the bandage on the rear bearing doesn’t stand out that much.


The last thing I did was to replace the key in the tail stock.  The original one had been worn and allowed the tail stock spindle to rotate slightly under load.  This key fit tightly into the tail stock and took some filing to fit correctly.


Once the lathe was back together, I tried drilling steel with a 1/2″ drill bit like I’d done previously.  This time the drilling went well and produced some nice chips.  Yay!


Now I can get back to making stuff on the lathe.

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Hendey Assembly: Part 5

Posted by davidjbod on October 15, 2014

In my previous post on the lathe, I’d reached the point where the lathe was running.  I still had a few more things to do though.  When I’d started on the lathe I set the tail stock aside since it is pretty much a separate item.  It came apart easily as it was covered in gunk like the rest of the lathe.


I ran all the parts through the parts washer and then hit them with a wire wheel/cup.  The parts were cleaned and then painted.   I hit all of the shiny parts with a buffing wheel and they cleaned up nicely.  I reassembled the tail stock and noticed that the spindle didn’t move in and out easily.  I removed the main screw and mounted it between centers on my woodworking lathe.  Using a dial indicated I determined that there was about 0.03″ run out on the shaft.  To fix this, I took the screw over to my arbor press and straightened it.  After one iteration the screw showed 0.005″ of run out which allowed the tail stock spindle to move freely.


Here it is back on the lathe.  Luckily, the tail stock spindle has a #3 Morse taper instead of the hybrid Morse-Hendey taper I feared it might have.  The #3 Morse taper is a standard size and arbors can easily be purchased today.H132

I removed the motor and the motor mount I fabbed up.  I added a simple metal electrical box to cover the cord to motor wire connection.  I then used double sided tape to hold the box in place in case I decide to remove it later.   I also painted the motor mount black to match the rest of the lathe.


While I had the motor off I replaced the motor pulley.  The old motor pulley is poorly made and allowed the belt to slip excessively.  I replaced it with the gray pulley which works much better.  Shown below, are both pulleys for comparison.  I removed the old pulley before reinstalling the motor.


With the combination of V belt pulleys, the countershaft turns at 266 rpm.  After taking measurements of the cone pulley diameters I should have spindle speeds of approximately 93, 193, 368, and 761 rpm.   I measured the actual spindle rpm unloaded at 97, 193, 351, and 678 rpm.  There seems to be a little slippage on the upper two speed values.  I’m not sure what it slipping but I’d place my money on the V belt.  Additional tension may solve this but I think the slippage can be attributed to the combination of really large and small pulleys.  The belt doesn’t get a lot of contact with the small pulley since the wrap angle is small.

The first project I completed on my lathe was to turn some plugs for the two spindle oil holes in the head stock.  I patterned my replacement plugs after the original ones on Chris’ lathe.  They have a ball on top which flares out to a rim and then reduces to a cylinder.  You can see them in the picture below the front and back tie bar contact points.


Here’s a few pictures of the finished lathe.

H136 H137 H138

Overall, I feel the lathe works pretty well.  There’s some backlash in the movements but that’s probably not surprising given that the lathe is around 100 years old.  The nuts for the cross slide and compound are brass and I imagine they have worn instead of the screws.  As such, I could probably make new nuts in the future.  I may also make new half nuts as the threads show a lot of wear as well.  There’s also some tightening in the cross slide as I move it in and out due to wear but so far it isn’t problematic.  One of the gears on the side of the late is made of brass and seems a little loose on its shaft.  When running it tends to make a ringing noise.  At some point, I’d like to bore this gear out some and make a new shaft for it to run up.

Here are a couple videos of the lathe in operation. In the first video, I’m taking a light cut on some hot rolled 3/4″ steel. I’m also showing the automatic stop feature.

In this video I’m taking a little heavier cut.



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