Author Topic: A small dividing head  (Read 533 times)

Offline RReid

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A small dividing head
« on: June 08, 2021, 01:46:54 AM »
Before starting the next engine project I decided to build a diving head that can be used on either my Taig mill or lathe. With a tip of the hat to a dividing head published by Tony Jeffree, I came up with my own design built around a Taig headstock spindle and a 30:1 worm gear. The frame is based on two pieces of 3” x 3” aluminum angle, which will be trimmed and screwed together to give the “box” dimensions I want. A riser block will raise it high enough for the 4 jaw chuck to clear the mill table, but with the block removed it will be on be on spindle center line when bolted to the lathe cross slide


The hub of the gear wheel I have is 0.75" diameter, which doesn't leave much meat for a set-screw after boring to 0.67" for the spindle. So I made an “auxiliary hub” from some 0.875” hex brass. I turned a short .25” spigot on one end to center it in the gear bore for silver soldering, and a longer 0.375”  on the other side so it can be mounted in an ER-16 collet for boring and parting off.

« Last Edit: June 08, 2021, 02:10:22 AM by RReid »
Regards,
Ron

Offline kuhncw

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Re: A small dividing head
« Reply #1 on: June 08, 2021, 02:32:08 AM »
Ronald,

That is an interesting design.  I'm looking forward to your build updates.

Chuck

Offline joe d

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Re: A small dividing head
« Reply #2 on: June 08, 2021, 02:35:50 AM »
Ron:

I built one more or less to Jeffree's design, it's been very useful.  I suspect you will like yours once you've completed it.

Joe

Offline Thor

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Re: A small dividing head
« Reply #3 on: June 08, 2021, 05:00:48 AM »
Hi Ronald,

 Your dividing head looks very nice. I too was inspired by Tony Jeffree to make my own dividing head using a MT 2 spindle from a Sieg X1 milling machine: http://files.thor-hansen.webnode.no/200000013-0eebe10dd7/Delehode2.pdf

Thor

Offline RReid

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Re: A small dividing head
« Reply #4 on: June 08, 2021, 03:44:14 PM »
Chuck, Joe, and Thor - Thanks for the input guys, much appreciated!

A note on the drawing might be in order. At the bottom of the page in the first picture you can see printed "Solidworks Eductional Product". I don't know if this is commonly known within this forum or not, but one of the nicest perks of a membership in the Experimental Aircraft Association (EAA) is a free annual license to that version of Solidworks. At only $40/year it's a bargain for 3D modeling software that is hardly reduced in functionality at all versus the big buck full version.
Regards,
Ron

Offline RReid

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Re: A small dividing head
« Reply #5 on: June 09, 2021, 12:42:58 AM »
Most of today's work involved easy but slightly boring brass boring. That included the gear wheel and two bushings to support the spindle in the frame. Didn't take any process pictures because, as usual, I forgot to. Pretty standard stuff anyway. Here's the end result.


That portion of the spindle to the right of the nut will be surplus, and I'll cut most of it off eventually. The only part still to make for the spindle is the brake.
Regards,
Ron

Offline RReid

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Re: A small dividing head
« Reply #6 on: June 11, 2021, 01:11:44 AM »
Switching focus now from the spindle to the frame. The frame consists of two pieces of nominal 1/4” x 3” aluminum angle. The “A” piece forms the base and the front (working) face. The upright leg was cut down to 2.5”, and both faces have to be machined for flat and square. Here I'm about to flycut that front face. These are very light cuts, so the blocking isn't really needed, but helps to dampen any vibration. Also visible is the 3/16” pilot hole that locates the future position of the spindle.


And the result.


Next was to drill and tap 6 6-32 holes to fasten the “A” and “B” angles together. A selection of table clamps and C clamps keep everything together and in line. Three of the screws go up from the bottom, so those holes were also counterbored with an end mill to accept the heads of the SHCSs.

I usually start taps either in the drill press or the mill. In this case I did the drilling on the mill, so the tap goes into the chuck which is held by loosely tightened collet. The collet holds the chuck vertical and aligned, but is loose enough for it to slide up and down, making it easy to start a few threads worth by hand. Then over to the bench to finish the tapping, knowing the tap has been started straight.




With the basic frame now assembled, it's time to think about boring it for the spindle. I plan to do this on the lathe, first with drills then a between centers boring bar. Here I've mounted the frame to the cross slide and am indicating it in.


Then I lined up on that previously drilled pilot hole, and drilled through the back face.


Ultimately that bore needs to be 0.8” diameter. I'll go as far as I can with drills, up to 0.75” if all goes well. Then switch to a boring bar, which I will have to make. Hopefully out of this old piece of shafting.

« Last Edit: Today at 01:37:52 AM by RReid »
Regards,
Ron

Offline Thor

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Re: A small dividing head
« Reply #7 on: June 11, 2021, 07:44:17 AM »
Hi Ronald,

 You are making good progress. Using a between centres boring bar will make the holes for the spindle the same diameter and parallel to the lathe bed.

Thor

Offline RReid

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Re: A small dividing head
« Reply #8 on: June 12, 2021, 12:52:34 AM »
I left off yesterday having drilled the start of the spindle bore to 3/16”. Today I continued drilling, going up in steps each time. Here is the last drill I used, 5/16”. It's roughly half as long as the lathe bed!


I could have gone a little farther with drills, but I decided that since I now had clearance for that piece of old shaft I showed previously, I would switch from drilling to boring. But first I had to drill the bar for a cutter and a set-screw.  Turns out that key slot was really handy. It provided a nice indexing surface, making it easy to rotate the work 90 degrees for laying out and drilling those two holes. Here I'm laying out the center line of the first hole by measuring from the fixed jaw of the vise.


Then rotate and do the set-screw hole. I start taps on the drill press by turning the spindle by hand while applying downward pressure with the quill handles. Just a few turns, then back out carefully. A little dab'll do ya, then finish on the bench.



Here's the boring bar, mounted between centers (well, between 4J and center), cutter installed, ready for work. The cutter was ground from a broken center drill. Because of its geometry, the cutting edge is facing “down” and towards the headstock, so the boring proceeded by moving the carriage from left to right.


Almost there.


Success! Everything fits and the spindle turns nice and smooth. I'm pretty pleased with how that went. There's obviously no micrometer adjustment on that boring bar, so it would have been easier to have turned the bushings to fit the bore rather than the other way around, but it worked out by going slow and careful.


Regards,
Ron