A dividing attachment I made

[gwilson]

I made this dividing attachment for my 6" rotary table. The holes were indexed solely with dividers,and the holes were drilled with an 18th.C. style pump drill. It is possible to drill extremely accurately positioned holes with a simple pump drill. You start the flat spade bits from zero RPM with the bit in the center punch mark. After drilling these holes with the pump drill,I re drilled them with a small lathe center drill in the drill press to bevel the edges of the holes.

By pump drill,I do not mean the "Yankee" type pump drills that use a spiral mechanism. I mean a simple vertical steel shaft. There is a small brass flywheel near the bottom. A cross handle made of wood with a loose fitting hole is fitted horizontally to the vertical steel shaft. A leather thong is fastened to the ends of this handle,and to the top of the steel shaft. To start,you wind the leather thong around the shaft,and push the wooden handle up and down for forward and backward rotation. I made the pump drill and bits also.

The plate on this attachment is about 5" in diameter,made from 1/4" 260 brass plate. The whole attachment is 260 also.

After a few circles,it got easy to give a slight twist to the divider's wheel,and within 2 or 3 adjustments,I'd have the required number of holes coming out evenly.

The knurling was done with a knurl I made also.

[gwilson]

Another view of the attachment.

[gwilson]

The plunger knob. These curves are turned out just freehand using a simple tool rest and turning tools I make from W1 steel.

[jugs]

Nice work, but you should have got sir John to drill your plates.

[Gravy]

I made this dividing attachment for my 6" rotary table. The holes were indexed solely with dividers,and the holes were drilled with an 18th.C. style pump drill. It is possible to drill extremely accurately positioned holes with a simple pump drill. You start the flat spade bits from zero RPM with the bit in the center punch mark. After drilling these holes with the pump drill,I re drilled them with a small lathe center drill in the drill press to bevel the edges of the holes.

By pump drill,I do not mean the "Yankee" type pump drills that use a spiral mechanism. I mean a simple vertical steel shaft. There is a small brass flywheel near the bottom. A cross handle made of wood with a loose fitting hole is fitted horizontally to the vertical steel shaft. A leather thong is fastened to the ends of this handle,and to the top of the steel shaft. To start,you wind the leather thong around the shaft,and push the wooden handle up and down for forward and backward rotation. I made the pump drill and bits also.

The plate on this attachment is about 5" in diameter,made from 1/4" 260 brass plate. The whole attachment is 260 also.

After a few circles,it got easy to give a slight twist to the divider's wheel,and within 2 or 3 adjustments,I'd have the required number of holes coming out evenly.

The knurling was done with a knurl I made also.

Nice work as usual. I'd love to see photos of the pump drill. I can't quite picture it.

[John Stevenson]

I have done a fair bit of research on plates and dividing apparatus in general and where clock making is concerned I have often wondered about the fascination with brass ?

All the old clock wheel engines were in brass and even if they had iron frames, admitted very ornate, the wheel was always in brass.

Given that brass isn't the best material as regards wear can anyone put any theories forward.

[The Artful Bodger]

I have done a fair bit of research on plates and dividing apparatus in general and where clock making is concerned I have often wondered about the fascination with brass ?

All the old clock wheel engines were in brass and even if they had iron frames, admitted very ornate, the wheel was always in brass.

Given that brass isn't the best material as regards wear can anyone put any theories forward.

Looks nice? Looks very 'instrumenty'?

[gwilson]

Maybe it doesn't rust? Also is a beautiful metal used when craftsmen took pride in their work and went the extra mile to make it nice.

Such devices were not made for high production at the time. This dividing head is 30 years old,and as you can see,not worn out from sloppy handling since I am the only one who uses it.

Why get John to drill the holes,Jugs? They are perfectly accurate as is.

Actually,they weren't always brass anyway. We have a factory made "Lancashire clock engine"(sp?) in Williamsburg which was a dividing engine commonly used in the 18th.C.. It has an iron wheel.

Wrought iron isn't the most trustworthy metal,though. It always has silicon inclusions and other imperfections in it that might have been a threat when drilling small,accurately placed holes. Brass was perhaps more consistent in structure. The Lancashire engine was not geared down either. Its holes were used directly to locate gear teeth positions for cutting. Mine goes through a 90 to 1 ratio.

Anyway,I don't expect everyone to have an appreciation of beauty,anyway. And by everyone,I mean a VERY small number. It does require someone with a teeny bit of art in their soul to appreciate nice things.

[Bob Fisher]

Doesn't rust. Looks pretty.Maybe more plentiful and cheaper than steel in those days. I don't know, Brass today,is scary when you look at the cost of a decent sized piece. I still like it tho. Bob.

[gwilson]

I just got my 4' X 8' sheet of 1/2" bronze plate sawed up. Plenty on hand now!

The things I'll make out of it will probably also annoy John.

[lynnl]

I googled pump drill, and saw one in action. But it still wasn't clear how the cord gets rewound.

Is it just the angular momentum that keeps it turning, so that it rewinds in the opposite direction during each upward movement of the handle?

Why would you drill the holes that way, if you had a drill press available? Just for personal satisfaction...?

[gwilson]

It's like the old kid's toy of winding a button back and forth with a double string through it,pulled by the fingers. Momentum rewinds it,but a LOT slower than the light weight button. Pump drills are still sold in some watch maker's supply catalogs,or jeweler's supplys. They are quick,handy,and silent.

[sasquatch]

Nice piece of work Geo!!

[J. R. Williams]

Dividing Plate

What is the count of holes in each circle ? Nice job. I shows simple hand tools can be used to make accurate equipment.
JRW

[gwilson]

I'd have to go out to the shop and get the attachment,but it's set up to work with a 90 to 1 ratio(rotary table) instead of the 40:1 index head.

Yes,simple hand tools can do accurate work. That was most of my reason for showing it. The first chronometers were made with simple tools. They had to be exceedingly accurate to allow accurate navigation over months at sea,pitching and rolling,too.

In fact,the inventor of the chronometer wasn't even a clock maker. He somehow made the MOST accurate clocks from WOOD. Better than existing metal ones at the time. Then,he invented the first chronometer to get the Admiralty's prize. I can't recall the details off hand. Would have been a feat in itself if he had gotten paid. The Admiralty seemed best at cheating inventors. The guy who invented the large range clocks that were used on WW1 British battleships wasn't paid for many decades,IIRC.