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Input (thread type) in Crosslide nut , Colchester Student 1800.

pippaman

Plastic
Joined
Dec 27, 2023
I just bought a Colchester Student 1800. It has the double wedge crosslide nut. It had not an excessive but annoying 1mm backlash. The wedges are almost driven completely and i could add some spacers to drive them further as the nut still has some meat.

Point is the fix will be temporary and i was trying to understand what kind of thread it is (metric version of the lathe). At first glance it seemed the thread on the shaft was rounded over from wear , but the back lash is the same at the very fist and very end of the travel, and the threaded shaft is identical at the very end and beginning. So its either a rounded thread profile, or i don't know its a whitworth thread worn? (but perfectly worn along the whole travel?) And it would be a withworth thread in mm pitch? As the pitch is 2.5mm / 5mm in the diameter on the dial.

Do you have any idea what i may do down the line? Machine a new shaft in metric trapezoidal? But again i'm fairly convinced the shaft is ok, but i can't find any kind of tap or insert small enough to single point thread eventually a new nut.

Quite a conundrum, sorry for the wall of text. (i'll take a picture of the thread so you can judge)

Thank you very much
 
Alright hahahaha thanks
Yeah I know sounds mean but really ... you bought the thing to make stuff. You don't know enough yet to worry about the lathe. Just make stuff.

Brass, aluminum, stainless. Make stuff that has to fit. Find out about materials, sharpening cutters, different threads. Drilling and reaming holes. Make parts for whatever your hobbies are. Learn how to use emery cloth and other tricks when necessary. Then come back in a year and see if you really care about a little backlash in a colchester student.
 
No not mean don't worry. I'm quite seasoned for a young machinist. I was cleaning and seeing whats wrong on the machine, and i was thinking about the future what might happen i have to rectify and what was the best approach.
 
Pitch is metric obvious Probably LH spindle
If it needs replaement I would go Tr14x2.5 or thereabout
Buy a tap on Aliexpres or Alibaba
These taps are super for bronze
Eighter turn the spindle or use a piece of rolled allthread
Good enough if you use a DRO

Peter
 
Pitch is metric obvious Probably LH spindle
If it needs replaement I would go Tr14x2.5 or thereabout
Buy a tap on Aliexpres or Alibaba
These taps are super for bronze
Eighter turn the spindle or use a piece of rolled allthread
Good enough if you use a DRO

Peter

Hello thanks for the answer. Yeah i found taps but i can't find allthread, 2.5 is not a supported pitch it seems so i guess i'll need to turn a new leadscrew eventually. I found a picture online of a new colchester metric leadscrew and it look very much like a square profile. Mine then must be pretty cooked being so round i suspected a knuckle profile (along ALL its lenght thought, thats why it boggles my mind)

Thanks again for the tip.
 








 
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