Colchester Student - new to me.. Help finding parts/blueprints maybe?

Hello all. Tasmanian here.

I have recently purchased a Colchester Student MK1 round head model (I think lol).

I believe it was an ex school model, so it has its fair share of "apprentice marks". Its old, with a lot of character marks on the non sliding surfaces from years of (ab)use, however the slideways seem quite good and the total runout on the spindle taper is just less than 0.01mm (4 Tenths).
The machine was absolutely filthy so I went about and began slowly taking things apart and cleaning them.

I removed the drive shaft and the leadscrew then took apart the apron. Inside was many years of gunk and chips which I cleaned out. After cleaning and degreasing and re-oiling all of the parts I put it all back together. It appears that the Half-Nut is very worn and four rows of thread have been broken off. The shaft from the top of the halfnut has snapped in half previously but someone has drilled and tapped from the top to make it one piece again with the use of a single socket head cap screw. It works for now though.

The issue I'm currently facing is the surfacing/sliding selector. My lathe has the sliding lever type, where there are two slots to select from either cross slide or saddle feed. On reassembly, the cross feed engages okay, but the saddle feed (sliding feed?) does not.
The problem is that the holes that the selector uses to ride on the driveshaft (and pivot from) have worn into quite the oval shape. So when trying to engage slide feed, the small worm gear wont reach the handwheel gear and the selector wont lock into its detent.

Its interesting to me that this was manufactured this way, as the original cast surface was used as a bearing surface for riding on and pivoting on the drive shaft. I would have thought changeable bronze bushings would have been used to avoid this inevitable wear problem.
Anyway, I'm guessing that its the reason for the "knock off" type apron design.

So..
My thoughts on fixing this issue would be to find the original centre line on the casting, then somehow fixture and bore larger holes to accept consumable bronze bushings to be pressed in.

I have two questions:

1) Does anyone have any drawings or original measurements of the selector bore holes?
2) Is my above thoughts a good way of going about this "fix"?

If I cant find any measurements or drawings I reckon I'll just estimate it and try my best

Any help would be great,
Cheers from Tasmania
PN

Must say ,Ive seen every kind of wear in these lathes ,but never the feed detent holes oversized enough to cause problems......I dont recall why ,but the more load comes on the feed,the tighter the levers seem to lodge in the detents...The worn half nut is common ,and the leadscrew is also likely worn beyond use too(in parts)....These lathes have a very weak threading system.Good used spares would be a forlorn hope.The leadscrew can be repaired by swapping end for end,a new halfnut will need to be made..

I used to recommend a company called " Nobilla " in Stevenage for Colchester lathe spares. They are a company that sells " pre-owned " and brand new spare parts. I always found them very helpful and cheap regarding price. I say " I used to " because it's about 5 years since I last dealt with them and another poster on here recently said they were no longer cheap.

In my experience they will have the spares you need and they might even have the drawings.

Regards Tyrone.

john.k said:

Must say ,Ive seen every kind of wear in these lathes ,but never the feed detent holes oversized enough to cause problems......I dont recall why ,but the more load comes on the feed,the tighter the levers seem to lodge in the detents...The worn half nut is common ,and the leadscrew is also likely worn beyond use too(in parts)....These lathes have a very weak threading system.Good used spares would be a forlorn hope.The leadscrew can be repaired by swapping end for end,a new halfnut will need to be made..

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Turns out that I'm a bit stupid as I found that the half nut selector needed a few degrees adjustment so that the feed disengaging lever would clear. (The lever that stops one from engaging the half nut and the feed at the same time) it was out by only a few degrees but after changing that the feed now engages as it should.

You were very correct about the worn holes. lol.
I agree with the statement that the threading design isn't the best, but at least I've got a gearbox with metric and imperial threads so that's a bonus. I will try to make a new half nut down the track if I can. The leadscrew its self looks to be in good condition but I havent taken precise measurements yet so..

On a positive, I did cut my first thread while mucking around today. Doesn't fit any nuts but the thread form "looked" ok.

Thanks for the reply

Tyrone Shoelaces said:

I used to recommend a company called " Nobilla " in Stevenage for Colchester lathe spares. They are a company that sells " pre-owned " and brand new spare parts. I always found them very helpful and cheap regarding price. I say " I used to " because it's about 5 years since I last dealt with them and another poster on here recently said they were no longer cheap.

In my experience they will have the spares you need and they might even have the drawings.

Regards Tyrone.

Click to expand...

Thanks for that Tyrone, I'll check them out - cheers mate.

PhatNOB said:

Thanks for that Tyrone, I'll check them out - cheers mate.

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They buy up used " Colchesters " either for cannibalizing for spare parts or re-building. I've bought brand new gears and bearings off them as well as used. It all depended on what the customer wanted to pay.

Regards Tyrone.

Tyrone Shoelaces said:

They buy up used " Colchesters " either for cannibalizing for spare parts or re-building. I've bought brand new gears and bearings off them as well as used. It all depended on what the customer wanted to pay.

Regards Tyrone.

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Hi Tyrone, I got hold of Simon from there and he has lots of them.
He quoted me a delivered price which is expensive but not bad compared to any of the other prices I’ve seen about.
Thanks very much mate!

Oddly I had used this model for a 6 month period of time, in a hydraulics shop. I thought the machine was a very good one. I was warned the threading mechanism was "tricky" but didnt find a problem, as usual in hydraulics the thread most cut was 12tpi.
I was looking for one recently, all I could find were too worn, another indication they were good machines.

The leadscrew is slightly unusual ,in that it is fine pitch ,but coarse lead,and that puts a deal of load on the fine teeth of the halfnut(singular-there is only one).....Another problem is the ease of getting swarf and chips jammed in the halfnut threads,causing partial engagement,and causing wear ledges to form ,so that even after cleaning the nut,it doesnt engage fully.Also takes the edge from the leadscrew thread.