# Replacing damaged half nut on a Colchester Master Mk2 Lathe



## metalman133 (Jan 13, 2015)

Hi everyone,
I'm new to this forum and this is my first post. I have a Colchester Master Mk2 lathe (US fellow users would call this a Clausing, but I'm in the UK). It's a square head model, 13" swing and 36" between centres. I need to replace the half nut and have no idea how to go about getting at it, never having done a job like this before. I have a replacement half nut ready to fit.

Is there anyone on the forum with experience of this? I need to know thinks like Do I remove to cross slide? Do I dismantle the apron? etc (and if so, how?)
Any helpful suggestions would be very gratefully accepted.

K


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## mike (Jan 14, 2015)

How you doing metalman133
I have just recently acquired a 21" Colchester 8001 series lathe, the square head type at 100" between centers and have taken the apron off and took out the half nuts just to clean and change the seals around the feed shaft pinion. I am not sure if your lathe being smaller would be much different, but it was pretty easy on this one. I did take the saddle off, first by removing the hold downs that have the adjustable gibs under the bed for the saddle. I did have the apron blocked up for support, then removed the lead screw, feed screw and the third shaft end block at the end of the bed. then I slide the apron off, I did have to remove the feed shaft since the key-way did not go all the way through the length of the shaft. If your 13" is anything like this one once you have the apron off like I said I changed the oil seals around the feed screw pinion, just because I would get a drip of oil here and there. I took the half-nut off and other pieces just to clean and scrub. I put it all back together in no time. I hope this may help you. BTW anyone out there with a 21" or 17" Colchester 8001 series I am looking fort some parts and the 21 and the 17 have a lot of the same parts Mike


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## metalman133 (Jan 15, 2015)

Hi Mike, thanks very much for your guidance. I'm going to give it a go once the weather warms up a bit. We are just above freezing here, and my workshop is not heated. Insulation and heating will be on the list of jobs this year, with any luck.

Thanks again,

K


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## Chiptosser (Jan 15, 2015)

There is a person in Texas, that deals in Colchester lathe parts.
If you do a google search, his name will pop up. 
Parts are not cheap by a long shot.


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## metalman133 (Jan 19, 2015)

Hi Chiptosser,
I have managed to get hold of a new half nut, so it's just a case of knowing how to fit it. You are certainly spot on when you say parts are expensive. I'm hoping nothing else breaks.

K


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## Colchester lathe man (Feb 22, 2015)

mike said:


> How you doing metalman133
> I have just recently acquired a 21" Colchester 8001 series lathe, the square head type at 100" between centers and have taken the apron off and took out the half nuts just to clean and change the seals around the feed shaft pinion. I am not sure if your lathe being smaller would be much different, but it was pretty easy on this one. I did take the saddle off, first by removing the hold downs that have the adjustable gibs under the bed for the saddle. I did have the apron blocked up for support, then removed the lead screw, feed screw and the third shaft end block at the end of the bed. then I slide the apron off, I did have to remove the feed shaft since the key-way did not go all the way through the length of the shaft. If your 13" is anything like this one once you have the apron off like I said I changed the oil seals around the feed screw pinion, just because I would get a drip of oil here and there. I took the half-nut off and other pieces just to clean and scrub. I put it all back together in no time. I hope this may help you. BTW anyone out there with a 21" or 17" Colchester 8001 series I am looking fort some parts and the 21 and the 17 have a lot of the same parts Mike


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## Colchester lathe man (Feb 22, 2015)

Chiptosser said:


> There is a person in Texas, that deals in Colchester lathe parts.
> If you do a google search, his name will pop up.
> Parts are not cheap by a long shot.


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## Kiwi (Mar 2, 2015)

I'm in the process of doing my 6 1/2" master roundhead as the half nut didn't work  so on removing the apron as said before remove the shafts first  I found my halfnut in ok condition it seams to me that it is the apron lead screw bearings that are worn


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## Kiwi (Mar 5, 2015)

Just got the master back together only to find the worn bushes not to be the problem I am thinking someone has replaced the halfnut cam with the wrong cam or the wrong halfnut or it is installed incorrectly and I repeated it but this I doubt
With the engagement lever up the half nut sits a long way off the lead screw in this position the cross feed lever will engage as it should  when the lever is moved down to engage the lead screw it doesn't to get it to engage I have to remove the lower lever stop then it will engage the leadscrew If I slide the lever off the splines  after the lead screw is engaged and slide it back on the splines with the lever stop in place ,when it is lifted back up the leadscrew disengages but the cross slide lever is locked out so either the half nut  or the  cam is wrong does anyone know if these parts are the same in each model colchester


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