Thread: Unknown lathe gear change set

I have a set/partial set of change gears from a lathe - new/unused. They came with some Hercus spares from a Tas. school/Tafe. The change gear set is on a 4 spline centre (about 22mm outside and 19mm inside the splines) and DP by my calculations is 17 (the 35 tooth gear is about 2.175" OD) The gears I have are 25,27, 28, 30, 32, 32, 34, 35, 36, 40, 42, 48, and 50 teeth (plus others of same tooth counts).

There are also two other gears - and DP by my calculations is 12.75 (the 35 tooth gear is about 2.9" OD) - the 35 tooth gear is 2.9" OD and has the same 4 spline as the above set but the smaller 28 tooth gear has a keyed 12mm hole.

Any one know what lathe they could be from?


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17DP sounds very weird...I'm tipping it's 16DP but measures smaller because the blanks are turned under theory OD, then gear cut.

EDIT: 17DP works out to almost exactly 1.5 Module, so it might well be that. It's certainly more likely than 17DP...that's not really a thing.

Originally Posted by elanjacobs

17DP sounds very weird...I'm tipping it's 16DP but measures smaller because the blanks are turned under theory OD, then gear cut.

EDIT: 17DP works out to almost exactly 1.5 Module, so it might well be that. It's certainly more likely than 17DP...that's not really a thing.

You might be right with the module. I have edited the DP on the second set of gears to 12.75 (it was copied/pasted as 17!) - which is close to mod 6.

I measured 2 gears for each set (with a digital calliper, so no fantastic accuracy). They were, set 1 - 28T, 1.765"OD and 35T, 2,175"OD giving close to DP17 (or Mod1.5) and set 2 - 28T, 2.353" and 35T, 2.901" giving close to DP12.75 or Mod6 (sorry about the inches, but I took a guess they would be imperial.)

What lathe uses a set of Mod change gears? On splines?

Many years ago I looked at a Colchester round head belt driven lathe with splined change gears. The lathe was of about 12x36 inch size. My memory is that the gears had four splines: not certain of this now though.This was the only lathe in this size range advertised locally over several months. Before buying it I asked the then Colchester agent whether replacement change gears were available, since most of the originals were missing, and if so, for a "ballpark" price to replace them. The lathe would have been late forties vintage at the latest. The answer was that the drawings were still available, so the missing gears could be supplied, the price in the low $20000s!

Since the lathe was not in wonderful condition and over priced @ $3000 I let it go, and bought a new Chinese geared head lathe in the same size range for very little more than the asking price for the Colchester. Glad I asked the gear price before I bought it!

Module gears I suspect would limit it to continental Europe. Also, 12.75DP is 2 Mod, not 6... 6 Mod is HUGE
There was an old German Weiler lathe at trade school that I think was 4-spline, never measured the tooth pitch so can't confirm that.

Our old Colchester Bantam Mk 1 (late 60s) is 16DP 14.5 degree on 7/8" 8-spline bore

John recently a neighbour purchased an ex high school 260 Hercus with no spare gears I came into a set which match the dp but not the spline. Ive not been able to check i f the lathe at some stage may have been converted to a metric set up or is imperial. Couod that be your priblem also.?