3-1/4 inch dividing head

**threesixesinarow** · May 21, 2019, 08:07 AM

This dividing head replaces a more delicate one I made from Unimat parts. It combines features from Hardinge and Cincinnati dividing heads but is simpler and a lot smaller.

Like those, it indexes indirectly, in this case with a 40:1 ratio, or directly by disengaging the worm, and it tilts from about -5° to 90°. It has a brake to lock the spindle, and works with a small adjustable tailstock.

It’s not universal - the hub for dividing plates is stationary. I mostly just use combinations of change gears to make divisions, though, and figured it will be easier to add stepper motor control than to make tiny parts for a differential feature I might never use.

It’s about 3 x 3 x 3”. The spindle nose is threaded M22-1.5, with a 16° included taper for ER-16 collets, and has a 3/8” bore. The spindle is prehardened medium carbon steel, and the bearings, worm gear and brake sleeve are bronze; the body from cast iron bar stock, and most of the base is made from a piece of heavy angle iron.

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Turning the hubs between centers, and cutting a timing belt pulley to convert it to stepper drive

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Cincinnati, and Hardinge

**DIYer** · May 21, 2019, 04:12 PM

Thanks threesixesinarow! We've added your Dividing Head to our Measuring and Marking category,
as well as to your builder page: threesixesinarow's Homemade Tools. Your receipt:

Dividing Head by threesixesinarow

tags: divider

**wizard69** · May 25, 2019, 04:44 AM

Pretty nice. I probably should take a closer look when I’m not on my iPhone (old eyes + small screen = bad).

Now for a question, do you ever get the feeling that ER16 is too small? I ask because I’m trying to equipe a shop for model making in retirement. Think steam engines for G/F scale and larger. I’ve been trying to decide on an optimal ER size to invest in.

**tonyfoale** · May 25, 2019, 05:30 AM

Originally Posted by wizard69

Now for a question, do you ever get the feeling that ER16 is too small? I ask because I’m trying to equipe a shop for model making in retirement. Think steam engines for G/F scale and larger. I’ve been trying to decide on an optimal ER size to invest in.

There is rarely an optimum size, get one size today which looks like it will cover your requirements and tomorrow you find it either a touch too small or large. I got equipped with ER25 and that was great for a while but occasionally I could do with bigger but I can then get by with other means. More recently I needed smaller and had to get ER11. I think with ER11 and ER25 I am pretty well covered.

**threesixesinarow** · May 25, 2019, 06:53 AM

Originally Posted by wizard69

Pretty nice. I probably should take a closer look when I’m not on my iPhone (old eyes + small screen = bad).

Now for a question, do you ever get the feeling that ER16 is too small? I ask because I’m trying to equipe a shop for model making in retirement. Think steam engines for G/F scale and larger. I’ve been trying to decide on an optimal ER size to invest in.

My guess is if you think it might be too small it probably is.

ER-16 has been a good match for my underpowered, limited travel machine tools. I use it for holding tools and work, or at least arbors for it. Along with the dividing head and a couple Unimat-compatible quills I made, both the vertical, and horizontal (with a 2MT adapter, and a cork in it, in the action photo above) spindles on my Atlas mill take it. To save even more space I made and modified some accessories like the cheap 3-jaw scroll chuck in the first picture so I can screw them onto the threads.

It’s great holding stuff up to 3/8”. I also use 3C, which isn’t much bigger, as well as ER-11. I’ve been looking at bigger ER sizes now, though, to use instead of rarer 4S collets on the neat little mill I just picked up.

**threesixesinarow** · May 26, 2019, 05:27 PM

I showed this before, but this is what all the weird parts are for in the rear view of the dividing head above.

**threesixesinarow** · May 28, 2019, 11:38 AM

ER-16 compared to my Stark’s 4S or 42S - whichever collet has a 1” body. I guess that makes them a little smaller than 5C.

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**old_toolmaker** · Jun 1, 2019, 08:42 PM

threesixesinarow,

That is nice work! Also at 3" X 3" X 3" it is nice and compact for smaller work.
Thanks for sharing with us!

**threesixesinarow** · Jun 2, 2019, 07:02 AM

Thanks, Dick,

The table on the Atlas doesn’t go more than 6 inches below the centerline of the spindle so space, and work is pretty limited. The dividing heads made to use with them by Marvin are a bit bigger, though.

⁃ Clark