Colchester Bantam gear spline profile?

I'm hoping to machine a splined shaft to take the change gears on my Colchester Bantam. Although I have a set I can make measurements from, ideally I'd have an original dimensioned drawing to work from.

Does anyone either have a dimensioned drawing showing the splines or know if they are based on a British Standard perhaps?

Thanks

Which bantam is it?

http://www.lathes.co.uk/bantam/

5 types apparently

Drunken ramblings removed.

Edited By John Stevenson on 30/01/2014 09:21:40

I have the 1600 model which is pretty much the same as the 800. It's got an Imperial leadscrew and gearbox but all the slides and tailstock are metric which seems to be not uncommon. Most of the threads on the machine are imperial and the machine was made in the late 60s.

Apparently the change gears are 16DP and they have a 6 splined bore with straight sides (the splines that is). It seems unlikely they are metric, as the metric std for splines of this size would have a depth of about 1.5mm (and a pressure angle of 30 degrees). My digital calipers measure the 2 diameters as 20.6mm and 22.2mm, so much shallower at 0.8mm. That would be 7/8" OD and possibly 13/16" ID.

It's possible that Colchester just made them up but there may have been a prevailing std at the time. I'm probably going to end up milling these splines on the rotary table with a std end mill but I'd like to get the angles and measurements fairly close.

Edited By Muzzer on 30/01/2014 04:49:51

I'm probably looking for BS 2059:1953 Part 1 "Straight Sided Splines and Serrations". These are non-involute splines, it seems.

Machinery's Handbook which is US-focused makes a passing reference to this: "Part 1 of the standard deals with 6 splines only, irrespective of the shaft diameter, with two depths termed shallow and deep. The splines are bottom fitting with top clearance". I guess mine will be "shallow".

Muzzer, don't take this as gospel but I'm guessing they are special to Harrison because I have seen two types that are very close together but still have the same number of splines.

Usually in a BS there will only be one standard with that number of splines.

Other reason is that they are very shallow splines, far shallower that any other BS straight sided splines I have had to do.

Having said that I do have a copy BS No 46 - part 2 - 1929 Six splines shallow but can't find a modern reference to it.

They go in nominal sizes measured across the tops of the teeth i.e. major diameter. What size is yours ?

I do have some change wheels here that I think are Colchesters I can double check these tables against one of those if i know what size I'm looking for.

(EDIT) Looking at the table there are 4 fits, two clearance fits, one transition and one interferance.

In all cases the OD is the same but the fit is made up by altering the minor diameter only slightly but the width if the spline is the critical measurement for the fit.

Edited By John Stevenson on 30/01/2014 09:59:10

Update.

These Colchester gears are 8 spline so not much use in this conversation.

Murray,

Further to my comments on another forum I found the measurements for the Harrison spline (common to the M250 and 300)

Spline OD 26.4mm ID 22.84mm tooth depth by eye 2.25mm. John also back up what i found as I could not find a matching standard.

I do also recall that some models of the Chipmaster also had 6 spline wheels and they are not the same - I know that as I bought my Harrison set from a Chippie owner who picked them up on the off chance that they would fit his machine

Tony

Yes, it seems clear that the Harrison gears are a larger diameter and the ones that John S has are also larger if they are indeed Colchester. As I noted above, mine are 22mm OD ie presumably 7/8" shallow.

John - sounds as if you have the BS 46 1929 spec which may be similar if it mentions a "6 spline shallow". If so, could you send me a photo of the critical dimensions? Short of coughing up 200-300 quid for the full BS 2059:1953 spec it doesn't look as if I will easily get my hands on a copy. With only a 0.8mm step, it's hard to tell if the faces are radial or angled and also if the faces are all at 30 degree increments.

Thx!

Embarrassingly, when generating a CAD model for the spline shaft, I noticed that it actually has 8 splines. Ho hum! Anyway, I should be able to derive the coordinates from that to enable me to machine one up with a standard end mill. Once on the rotary table, I can always finesse the finished part to fit the change wheels if it's not spot on. The splined shaft I'm working from has taken some wear over the years so I can't take consistent measurements from it.

I can measure some of these 8 spline wheels I have here if you want ?

Hi

My first lathe was a vintage Colchester it was a version of this one. I was very sad to let it go due to lack of space.
It used splined centers for the change gears.
That looks like a very nice set in good condition. There should be a 127 tooth Gear.

The flat belt driven black japan finished lathe second photo down. **LINK**

Regards
John

Edited By John McNamara on 09/08/2019 09:44:16