A Blog Devoted to my Many Hobbies

Archive for February, 2012

Splitting Wood

Posted by davidjbod on February 29, 2012

So what do you do if you need to split a piece of wood that is too big to go through your bandsaw?  You could saw it with a hand saw but, as Roy Underhill would tell you, you can split the wood along the grain. Let’s say you have a block of wood you’ve savaged with a chainsaw like the one below.  The first thing to do is scribe a line you’d like to split it at.

Using a ax or chisel start breaking away wood from the edge. I placed my ax where I wanted to split the wood and hit the back of it with a wooden mallet.  Never use a metal hammer that is of the same hardness or harder than your ax or you’ll tear up the ax’s poll (back side).

If the ax is too blunt you might have to use a large chisel to get a crack started and then finish splitting with your ax.

Keep splitting pieces off until you get close to your line.  Then work up and down the line splitting it a little bit at a time.  Once a good split is established you can go ahead and drive the ax through.

When you’re done, you have a surface you can clean up with a plane.

 

If you know your old tools you’re probably asking “Why not use a froe?”  That’s because I don’t have one.  The froe is an older tool specifically designed to splitting wood along the grain.  You hammer it in and then rotate it to split the wood.  Yes, finding one is on the list.

 

Posted in Woodworking | 1 Comment »

Longworth Chuck

Posted by davidjbod on February 11, 2012

I’ve been using the lathe to make bowls and realized I needed a way to grip the top of a bowl so I could work on the bottom.  There are commercial products out there to do this but they cost a fair amount.  So, I looked around and came across something called a Longworth Chuck.  It’s named after the inventor and consists of two disks that rotate and move self centering jaws to grip the bowl.  As opposed to repeating the instructions of how to make one I’ll refer you to a couple sites:  Site1 and Site2.

To build my chuck I used a piece of 1/2 and 3/4 plywood. Since my lathe has a capacity of 16″ I made my disks 16″ in diameter.

Next, I mounted the mounted a faceplate on the 3/4″ piece and screwed the two disks together.  I then turned them round on the lathe.

What makes the chuck work is a series of arcs that are routed into both disks.  The web pages linked to above describe how to layout the arcs.  The arcs are cut into both disks at the same time with a router using a 1/4″ bit.  You then flip one of the disks over.  Now the combination of two arcs results in a hole that a 1/4″ bolt fits through that will move when one of the disks is rotated against the other. Note that four of the arcs are larger than the others.  This was done to keep from weakening the disks too much.  Since smaller bowls don’t require as much holding power, the four bolts in the shorter arcs are removed to allow the jaws to contract more.

Since using the bare bolts on the bowls would mar the surface, rubber stoppers are used to create soft jaws.  The stoppers don’t have holes in them so I had to cut some.  To do this I created a “cork borer” by sharpening the end of a 1/4″ brass tube.  I used a piece of PVC to hold the stoppers and chucked the brass tube up in the chuck on the tail stock.  With the lathe running at a low speed I advanced the borer into the stopper resulting in a centered hole.  The longest step in this process is removing the rubber plug out of the borer each time.

With all the stoppers bored assembly can commence.  I used 1/4-20 x 3.5″ long bolts and wingnuts to permit hand tightening.  Below is a picture of the completed chuck opened as wide as it will go.  The two large holes allow you to rotate the disks with your fingers.

The front disk is rotated to move the jaws in as shown below.

Here’s a view of the back of the chuck showing the wingnuts and faceplate.

Here’s a shot of the chuck in use on one of my bowls.  It works well though it doesn’t perfectly center the bowl every time due to the bolts tilting, the rubber bending, etc.  But with careful placement of the bowl and tightening down opposite wing nuts at the same time the bowl can be centered well enough.

It cost about $10 since I had the plywood and faceplate on hand and only took 2-3 hours to make.  For the time and money spent it works great!

Posted in Woodworking | 2 Comments »

Ideal Tachometer

Posted by davidjbod on February 3, 2012

Unlike step pulleys where there are discrete combinations and speeds, Reeves pulleys have a continuous range of speed.  On machines with Reeves you turn a knob until an indicator points at your desired RPM on a tag.  But how do you know if the it is correct?  To determine the speed measure in revolutions per minute (RPM) a tachometer is needed.  I was curious to know if my machines were rotating at the speeds listed on the tags so I started looking for a tachometer.  Sure, I could pick up a cheap digital tachometer from Amazon or I could look for something else.   So, off I went to Ebay where I was able to win an auction( against no one else) for an Ideal Electric Tachometer.  Specifically it is a Model 50-002B made by the Ideal Commutator Dresser Co. of Sycamore, IL.  The Ideal Commutator Dresser Co was a previous name of todays Ideal Industries that still makes electronic equipment.  It looked to be in great shape with the exception of a broken leather handle which didn’t bother me.  Here’s the nice case it came in.

Here’s what’s inside the quasi padded wooden case.  As you can see everything looks great.

Here’s all the parts out of the case.  From left to right on the top row there is the Indicator, Generator, and an extension cord for “Separable” use.  On the bottom row from left to right there is a wheel for measuring feet per minute (FPM) and several rubber tips.

The tachometer requires no batteries.  When the Generator is spun it creates a voltage which moves the needle on the indicator.  The tachometer can be used with the Generator directly attached to the Indicator as shown below or it can be connected with the extension cord.  The Hi/Lo switch changes the range of the Indicator from 0-2500 to 0-5000 RPM.

Here’s a picture of the extension cord hooked up for use in “Separable” mode.

In the box, underneath the Indicator, is a calibration card from the Ideal company.  I’m guessing this is the calibration card that came with the tachometer when it was made.  As you can see it was made some time in 1945 and calibrated in July.  It was calibrated at different speeds in both hi and lo modes.  The instructions state that it is “accurate within plus or minus 1% of the full scale deflection.”  Doing the math reveals this to be true.  All things considered it seems to be a fairly accurate machine.

Speaking of the instructions, here’s a picture of them if you’re interested.  Per #7, I wonder if I could still send it back for service.  I’m guessing no.

Just because it was accurate 67 years ago doesn’t mean it still is of course.  So, to test it I used the motor on my band saw.  Without a load on an electric motor should turn at the rate listed on the motor tag.  In the case of the Century motor on my bandsaw the tag lists 1750 RPM.   Using the tachometer is simple.  You set the switch to the RPM range you expect to be in, or Hi if you don’t know, and then press the rubber tip of the generator to the end of a spinning shaft.  The shafts on most machines have tapered holes in them from the machining process at the factory giving you a good place to put the tip.  Here’s a picture of the tachometer testing the RPM of the Century motor.

Lets take a little closer look at it. Note the tachometer was in Lo mode so the top scale is read.  It looks pretty close to me.  I also tested it in the Hi range with similar results.

Now that I know it works I can use it on my other machines.  Here’s a picture of me testing the speed on my Clausing 15″ drill press.  I’ve set the drill press to 3000 RPM but as you can see the tachometer reads about 300 RPM high.  This is probably caused by the old belt that I have on the machine which has stretched over time.  Changing the speed to 2000 RPM showed 2200 RPM on the tachometer so the drill press speed error seems to get larger at higher speeds.  Perhaps I’ll pick up a new belt at some point and adjust the drill press to turn at the correct speed.

For my outlay of $22 bucks on Ebay I’m happy with the tachometer.  It certainly is better built that the cheapies.    If it has lasted this long and is still accurate I don’t think it’ll suddenly go haywire in the light duty application I use it in.

Posted in Tools, Use | 3 Comments »

 
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