A dividing attachment I made

[george wilson]

This brass dividing attachment was made with a Jet 10" lathe. I made it for a 6" rotary table that I still have. It won't fit anything else.:)

What is Neanderthal about it is that the holes were made with only simple Starrett dividers,and then the holes were actually drilled with a 18th.C. pump drill. I did it in the musical instrument shop.

I actually got where I could make a slight tightening motion on the nut of the dividers and come very close to making the next row of holes,with one extra tweak of the dividers.

The plate is 5" in diameter. After I got the holes spaced out,and pre drilled with the pump drill,I finished drilling them with a center drill in a drill press at home. I had also made the pump drill and the bits.

The numbers are 1/32" high. This,with the 90 to 1 gear ratio of the rotary table,will give quite an assortment of possible hole spacings.

[harry strasil]

Beautiful George, makes mine look like the crude thing it is. LOL

[Bruce Page]

Beautiful craftsmanship once again George. I remember very clearly my first encounter with a Pratt and Whitney dividing head. Scared me to death. Once you learn how to use them they are really slick. I had a Hardinge dividing head that I traded for a Bridgeport right angle head. I still have the Bridgeport head.

I fixed the title. :)

[Leigh Betsch]

Looks great! I've been thinking about making a dividing head for indexing to cut flutted legs with my router. I will be out of wood and not be anywhere as nice as yours!

[Jim Koepke]

Absolutely Amazing!

jtk

[David Weaver]

I could find one in use on a lathe to index a blank to cut straight gear teeth in it.

What is it used for in general. Not being a machinist, never seen anything like it.

Great looking turned nut. The whole thing is excellent looking.

[Roy Lindberry]

It looks beautiful...but I have no idea what its for.

What does it do?

[george wilson]

It is used to index spaces around circles to do things like cut gear teeth,do fluting,or anything that requires exact spacing around a circle.

I take the handle off my rotary table,and substitute this dividing attachment for it.

I also have a German made universal dividing head. This can be mounted on the end of a universal type horizontal milling machine(one which has a swiveling table), and can be geared to the handle that advances the table. This rotates the gear blank as the table advances past the cutter,and you can cut helical gears with it.

This is a simple dividing attachment just for straight teeth. It is also known as a piece of "male jewelry".:)

[Trevor Walsh]

This is awesome, I really love looking at all the things you post, did you or will you do a post about the pump drill and bits? I'm really interested in seeing that. I've been wanting to make a similar setup for a while now.

Thanks for posting it George,

[george wilson]

I left the pump drill at the musical instrument shop when I became toolmaker. They were supposed to find their own tools,but never did.

I have made a bunch of those,though. One time I was going to the big flea marker at Kutztown in the 70's. I had made up about 6 of them,and had a back pack on with them sticking up out of it. I sold every one of them! Paid for the stuff I bought.

Then,I made some to sell to dealers and a few for other craftsmen in town.

I was making the bits for the silversmith's piercing person for some time,until they located a source for them. They were quick to make out of 1/8" drill rod.

I found that I could drill very accurately placed holes with them by running them slowly into a center punch mark. They drilled better on a mark than modern twist drills.

[Trevor Walsh]

Were the drills like D bits, or the flattened point kind of spade bit? And on the drill, was there a jaw chuck or some sort of driver mechanism like found on some wooden brace drills?

This is fascinating Geroge, thanks for talking about your work.

[george wilson]

The bits were just flattened out points,with 2 cutting edges. Since the bits are flattened quite thin,they will enter a punch mark easily,and not wander off. These type bits are not for deep hole drilling,though. I drilled maybe 1/16" at the most deep,to provide a good start for finishing up with a small lathe type center drill afterwards.

The chuck was a simple type used normally on pump drills. It only takes 1 size of shank. The chuck was a split type,with a tapered thread on its outside. Screwing a threaded collar over the tapered thread tightened the split hole onto the drill shank.

I hope this makes sense.

D bits would never work for starting a hole. They have to enter a pre drilled hole exactly their diameter. Then,the D bit will drill holes quite truly,without running off to 1 side like twist drills can do.

On that brass pistol barrel I posted last week,I drilled the bore with a D bit I made about 16" deep. It was only off center .002" where it emerged out the other end. That was done in a lathe. If I had used a long twist drill,it could have gotten off center 1/8" or more on that deep a hole.

[Trevor Walsh]

Yes the split chuck makes sense, and the bits too.

Are the D bits so accurate because there isn't a point guiding the bit, just the diameter following the hole?

[george wilson]

If you bore an exact fitting hole for the D bit to enter,and are careful to extract it often(it doesn't have much room to store chips),it will bore very straight. I THINK it may be because twist drills have a lot of their metal ground away in making their flutes. Also,MANY twist drills are not perfectly straight,and may not be ground quite on center,either. The D bit has a short half diameter front part,then the body is full diameter solid steel.

When I bore a starting hole,I drill a somewhat smaller hole,then enlarge it to exact diameter by BORING the hole with a single point boring tool. That is the best way to make a starting hole that will be as accurately concentric as the lathe can make it.