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Full Version: A dividing head/indexer from old pistons.
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I have posted this project on other sites, but I would like to share it here and maybe glean some more ideas as I build it. Hopefully it will give others some ideas too.

I decided to start on the dividing head I've been planning to make for years. I saved two Deutz diesel engine pistons WAY back when for this project. They are good solid aluminum chunks with a precision hole and a precision steel wrist pin in that hole. The wrist pins are bored through with a precision hole too, so in my eyes, these were instant headstock and tailstock for a dividing setup. Well, not exactly instant...

I managed to find them in the junk in the shop and set up one on the mill table and decked off the top with a fly cutter. Tomorrow I'll do the other one and see if I can find a proper gear to use for the 'divider' and dream up a stop for that. I think I'm going to buy a Harbor Freight wood lathe 4 jaw chuck. It appears to be perfect for this. It is 6" in diameter and mounts on a 3/4"x10 thread. That means a standard bolt can become the headshaft for this thing. I'll make a taper for the tailstock and copy a design for the adjustment from Gingery's book on the dividing head.

Oh, the plan is to run them 'upside down', that is with the top becoming the bottom. That makes the distance from the table greater for clearance.

Here are the pistons before starting and one of them cut. This is one of the first projects for my new Grizzly G0705 mill.



and here is the chuck I'm thinking about, it is actually a wood lathe chuck from Harbor Freight.


I remembered I have a 4" rotary table I have never used. So, making a base with a step on it will put the centerline of the rotary table the same height as the centerline of the center of the wrist pin in the piston. Hooah, I like it when things work out well. I have some 1/2" aluminum plate so I'll cut a base for mounting both the rotary table and the headstock on. That will allow me to clamp the base to the mill table with the rotary table hanging out over the end if necessary for long stock cuts. A similar but smaller base on the tailstock will work well.

Also, the bore of the wrist pin is .704, so a 3/4" bolt will be perfect. I can turn down the shank of it for a nice slip fit through the wrist pin and machine a flat on the end to fit into the slot in the rotary table. Good stuff!

Here's the table and headstock.


and the headstock piston.


I think I will be able to squeeze about 22" between centers, and a 16" plus carbine barrel will be a piece of cake.

So, here's a simple drawing of how the thing should go together.


That's all I have done so far.

Just so I understand correctly, you are basically using the pistons as "pillow blocks" then? Or am I off base? 17428

I'm guessing he's going to use the wrist pin hole in the cylinder for his tailstock center ram location. Or am I also way off base?

My impression is exactly as is Willie's. I don't think the "sketch" is to scale because it looks to me like the blue "axles/spindles" are low in the red "bushings"?
I'm wrestling with the reason for using the pistons, their height to wristpin woudn't be terribly precise, especially after machining the face of the piston as shown in a previous post.17428
the drawing is not to scale, just a box diagram to show the relationship of the parts.

The pistons are machined on the bottom, the distance from that bottom 'deck' to the wrist pin hole is the same and I didn't move the cutter height during machining the pair. I'll double check the distance from the machined top (which will become the bottom) before I finish the 'pillow blocks'. So, yes, the purpose of the piston is just to hold those nice nice big heavy precise wrist pins.

The reason I used the mill and fly cutter is that I couldn't find the other set of jaws for my 3 jaw chuck. Since then I found the jaws, now I can turn them in the lathe. Much easier... and when I do that, I'll make sure that both wrist pin holes are at the same height.

I thought of doing this many years ago, actually was considering making a wood lathe with this idea at one time. I just thought it would be fun to re-purpose the pistons for something useful.
Those nice, big wrist pins look like some very useful chunks of steel.

Looking forward to this build
Wrist pins make great tube squares
They are ground to much finer tolerances than most of us work to
(they make good paper weights as well)Smiley-dancenanaSmiley-dancenana
now you guys with the comment that the wrist pin will make a cylindrical square have me going out on another scavenger hunt for a couple of them. I hadn't even given a though to how precise they are made.

So now its off to the join down the road to see if they got any laying around.

Now I wish I had saved more than 2. Those are quite some chunks of steel, they just float through the piston holes.
(07-23-2012, 07:09 PM)NevadaBlue Wrote: [ -> ]Now I wish I had saved more than 2. Those are quite some chunks of steel, they just float through the piston holes.

I wouldn't mind having a few of those wrist pins around myself. I used to be up to my neck in them (albeit smaller diameters for passenger cars) when I was still working. Wouldn't you know, I never saved a single one. Bash

I was going to mention them serving double duty as cylindrical squares, but I see that John beat me to it. He doesn't miss a single trick, that one. Cool
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