Machine Shop Tooling

One thing every model engineer will eventually find himself making is a piece of tooling. Sometimes, either a special tool isn't available, or if it is available the price is prohibitive. So, you wind up making the tool. Here are some of the tools that I've made for use in my own shop.

Center Indicator

One critical piece of tooling needed to do any work in a 4 jaw chuck on a lathe is a center indicator. Kozo Hirakoa, author of several locomotive construction articles in Live Steam magazine, published drawings for a simple center indicator in his book "Building the Shay".

I followed Kozo's plans, changing a few dimensions based on the lathe I was using at the time. I used Piano Wire for the rod, purchasing it at a local model railroading shop. Piano Wire is a good material for this as its extremely hard (I had to cut it with a grinder, wire cutters don't even dent it), and it doesn't bend easily at this diameter. The full length of the rod isn't visible in the photo, but its about 12" long from end to end.

To use it, put it in the tool holder, and put the point in the dot left by the centerpunch. Rotate the chuck by hand. If the piece isn't centered in the chuck, the error is magnified by the long end of the rod. Adjust the piece until there is no movement in the long end of the rod. Usually, I declare "close enough" when the movement in the rod is less than its diameter. A good way to see any error is to put a dead center in the tailstock and move it so it is close to the end of the rod.

I made this one to fit in a South Bend 9" lathe. Unfortunately, I then purchased a 10" South Bend, so I have to shim it when I use it...

Tailstock Die Holder

Another handy piece of tooling is a die holder which can be mounted in the tailstock of the lathe. After turning a piece to be threaded, this tool will put the thread straight on the piece. The thread is also going to be fairly close to concentric to the center.

My father had a couple that he built years ago, and I was about to copy his, when I found a set of plans for this one for sale at the 2002 "Cabin Fever" model engineering expo. What I liked about it was that it was "double-ended", that is it holds 13/16th dies in one end and 1" dies in the other. It also came with plans for a tap holder, but I haven't built that part yet...

While talking with dad about copying the ones he built, we discussed the shank which is inserted in the tailstock. What we did was take an old, dull taper shank drill, and I asked dad to anneal it so I could machine it to size. When I went back to pick up the annealed drill, I found dad had machined it to a 1/2" diameter for me. OK, that made one less part for me to machine.

I did make a few minor modifications to the plans. I changed the diameter and length slightly to match a piece of stock I had lying around. The plans called for a 5/8" diameter on the shank, which I reduced to 1/2" to match the one dad provided. I also added the handles, to give myself more leverage when using dies for large/coarse threads (like 1/2-13). The handles are removable for when threading small pieces while the lathe is under power.

Here's a photo of the die holder, disassembled, so you can see the shank and the removable handles. If you compare the two photos, you can see both ends of the die holder, showing the ability to handle two different size dies.

This was my first attempt at knurling, and I think it came out pretty good. I did find that I had to do a light knurl to make sure that I would get a good diamond pattern with the knurl. If you don't get a good pattern, you have to change the diameter of the piece. I had to take about .010 off the diameter to get a good knurl pattern.

Small Diameter Pipe Bender

A friend showed me a small "universal" pipe bender he made. It was designed by Derek Brown and published in Model Engineers Workshop in the Feb/March 2000 issue. The pipe bender could be used to bend small pipe to a radius of 3 X pipe diameter. The took had been designed such for each size pipe, you needed two round formers and one anchor. The drawings showed all the formers and anchors needed to bend any size pipe from 3/32" and 1/4", by 32nds.

Two projects I'm working on required neat and clean bends in small pipe. One required 7/32" and 1/8", the other required 3/16". I thought this design would be great, as I could make the three formers and anchors needed immediately, and if I ever needed other sizes in the future, I could make the appropriate parts then. My friend let me borrow the magazine for a short time.

The photo shows the bender in use. What you do is put one former on an post mounted in a hole in the base. Depending on the size of the pipe, you put the anchor in a different hole in the base. You then attach a lever to the anchor post, and use a second post to hold the second former. The formers will be just about touching, forming a hole for the pipe between them. You slide the pipe into that hole, which will also go through a hole in the anchor. When you pull on the lever, the pipe is held stationary by the anchor, and the pipe gets bent as one formers revolves around the other. Its much easier seen than explained, so hopefully the photo helps show what I'm talking about.

Here's a photo of the pipe bender disassembled, which also shows the three different size formers and anchors I've already made. You can also easily see the slots in each of the formers, as well as the relief slot.

The article said to grind lathe tools to cut the slot in each former for the pipe. I didn't like this suggestion, as that meant I would have to make 6 lathe tools, and I thought that it was prone to chatter. What I did was use a spin indexer in the milling machine to make the formers. I made an arbor, mounted that in a collet in the spin indexer, and mounted a blank on the arbor. I then used the appropriate size end mill to cut the slot, rotating the spin indexer by hand (slowly). After the slot was cut, I locked the spin indexer and machined away the notch needed to clear the anchor. This worked great.

In order to test out each set of anchors and formers, I made some test S shaped bends, 90 degrees off, in some K&S brass tubing

This page is always under construction!

Last Updated June 23, 2006

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