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
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