Colchester Student headstock taper?

[6ply]

A guy contacted me via the Internet - he wants a headstock reducing sleeve for a Colchester Student. I don't know whether he has attempted to measure the internal headstock taper but I seem to recall this is not the MT5 taper found on a Harrison M300 lathe. In addition to some MT5 sleeves, I have a few other headstock taper reduction sleeves in my "spares" drawer so I attempted to measure them this evening. My method was to mount them between centres on my M300 and using a DTI measure the taper per inch by traversing the saddle by exactly one inch (I used a gauge block and travel stop). This gave me a taper of 0.05275" per inch which equates to 0.633" per foot.

The measured taper is very close to MT5 but the sleeve is just slightly too big to fit my M300. It is tricky to take useful measurements of the sleeve big end/ small end diameters due to the end bevels. Initially I thought this could be a Jarno but looking at the tables again I don't think this is likely.

Any ideas?

 

[6ply]

 

[6ply]

 

[6ply]

 

[6ply]

The slightly oversized sleeve that does not fit my M300 MT5 bore:

 

[Agroshield]

Table 1a is for Morse stub tapers which may not be the best reference.

The big end of anything you measure is irrelevant. The gauge diameter in the Morse dimensions is not at the large end of the bush, but a little way down. See dimension A in table 1A - the male item continues to increase outside the hole.

 

[6ply]

Table 1a is for Morse stub tapers which may not be the best reference.

The big end of anything you measure is irrelevant. The gauge diameter in the Morse dimensions is not at the large end of the bush, but a little way down. See dimension A in table 1A - the male item continues to increase outside the hole.

Agree with your comment about stub tapers. Probably a poor choice of screenshot but it has the taper per foot listed.

I'm still wondering about the "oversize" sleeve that I showed above. I wonder what it is.

 

[Agroshield]

...I wonder what it is.

It may be based on the taper per foot of a standard Morse taper but with a different gauge plane (which could be either below or above the face of the spindle) to suit the spindle bore and nose detail of the machine to which it was fitted.

It is reasonably easy to find 5-3 sleeves, which provide a known reference: https://www.rdgtools.co.uk/product/5-3-morse-taper-sleeve/

If the taper of the one you have is correct, but it is just too big, you can clock up a male taper to suit its ID in a four jaw, put the sleeve onto it and turn it down (it may need a CBN insert as the sleeves can be hard).

Find someone with the same lathe and a bush and obtain some rough dimensions - big end approx., small end approx. and overall length. That would tell you from where it has been sliced on an infinite cone of the appropriate Morse angle.

 

[6ply]

It may be based on the taper per foot of a standard Morse taper but with a different gauge plane (which could be either below or above the face of the spindle) to suit the spindle bore and nose detail of the machine to which it was fitted.

It is reasonably easy to find 5-3 sleeves, which provide a known reference: https://www.rdgtools.co.uk/product/5-3-morse-taper-sleeve/

If the taper of the one you have is correct, but it is just too big, you can clock up a male taper to suit its ID in a four jaw, put the sleeve onto it and turn it down (it may need a CBN insert as the sleeves can be hard).

Find someone with the same lathe and a bush and obtain some rough dimensions - big end approx., small end approx. and overall length. That would tell you from where it has been sliced on an infinite cone of the appropriate Morse angle.

I've got a 5-3 sleeve, several actually. Yes, I could turn this down and have done so before, but I'm surprised it is not a standard size. Thanks for your suggestions.

 

[Martin-Sy]

CVA and Monarch 10EE are both short Jarno 12.
Colchester Bantam and Chipmaster are MT4.5. i don't know if the Student is the same.
Which version of Student is it?

 

[6ply]

CVA and Monarch 10EE are both short Jarno 12.
Colchester Bantam and Chipmaster are MT4.5. i don't know if the Student is the same.
Which version of Student is it?

I'll see if I can find out.

 

[Martin-Sy]

I'll measure up the Jarno 12 later. That will at least let you know if that's what you've got.

 

[Pete.]

If youndo happen to have a Jarno 12 I want one. Failing that I could re-grind a suitable MT one as the angles are very close.

 

[Martin-Sy]

Here's my CVA one:

And a very rough sketch:

As you say, they are difficult to measure accurately. The length in the sketch is the overall length rather than the taper length.
Note only 2MT internal (like the tail-stock on most CVA's).

 

[6ply]

Here's my CVA one:

View attachment 488709
And a very rough sketch:

View attachment 488710

As you say, they are difficult to measure accurately. The length in the sketch is the overall length rather than the taper length.
Note only 2MT internal (like the tail-stock on most CVA's).

Thanks for that. I'm at work now and can't confirm the dimensions but I believe the adapters I have are larger. I may have a go at grinding one down in due course. I have a mandrel I can mount between centres.