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Rex
03-10-2005, 06:33 PM
All this loose talk about dividing heads has me curious about the one I picked up a few weeks ago.

It has no markings of any kind as to brand or model.
Appears to use the 1.5-8 TPI spindle, MT3 taper.
I suspect it's 40:1., though I'm not sure how to check it.
It came with only the plate that was on it. Appears to be a progression of prime numbers.
Questions:
Do I need more plates?
How do I get them?
Can I make the missing plates?
How do I use it, say to cut a 36-tooth gear?
Do I need a chart?

John Stevenson
03-10-2005, 06:50 PM
The ratio of most heads are 40:1
Cincinatti is one exception at 90:1
To find the ratio mark the spindle and wind the worm hand counting turns until the spindle does one turn., usually 40 winds.

Three plates to a standard Brown and Sharp set.
15,16,17,18,19,20
21,23,27,29,31,33
37,39,41,43,47,49

Plates come up on ebay quite regular.
There is a seller on ebay.co.uk who sells blanks, the holes are in but the centre is unfinished so you can make it fit your head.

Charts are available in Machinery handbook and on the web.

John S.

Rex
03-11-2005, 10:13 AM
Counted the ration, and it's 48:1
Apparently that's quite odd, but I suspect it's workable.

Plate has
25
23
19
17
15
13
11
9
7
7

I've had it almost completely apart and there is no brand, number, or other markings of any kind. Yet it's obviously a production piece, not a one-off.

I'll plug the above numbers into the spreadsheet someone else posted and see if I need additional plates. For that matter, it looks like I could make more plates with the one I have.
Since I don't have a current project that requires it, it may be moot.

Thanks for the help.