Colchester Bantam 2000

[needleworksParticipant @needleworks]

The play in my cross slide is starting to really annoy me now so I reckon it's about time to replace the nut, or the screw, or both if that's what it needs. I assume it's going to be an acme thread, but on measuring, I can't decide if it's imperial or metric !

I have measured it at 14.2 mm x 2.5 in metric, on the imperial side it measures .559 x 10 tpi.

Has anyone previously done this fix that could give me some advice?

Thanks in advance guys

[needleworksParticipant @needleworks]

[Mick B1Participant @mickb1]

.559" is 3 1/2 thou down from 9/16. My guess is imperial.

[Mike PooleParticipant @mikepoole82104]

Does the scale on the handwheel not give away the pitch?

Mike

[needleworksParticipant @needleworks]

Posted by Mike Poole on 18/02/2018 19:13:10:

Does the scale on the handwheel not give away the pitch?

Mike

On the Bantam you have the luxury of both, pull the dial out it reads metric, push it in it reads imperial.

[needleworksParticipant @needleworks]

Posted by Mick B1 on 18/02/2018 19:08:48:

.559" is 3 1/2 thou down from 9/16. My guess is imperial.

I thought of 9/16, but I can't find a left hand acme tap 9/16 x 10 tpi anywhere on the net

[Chris Evans 6Participant @chrisevans6]

Look for leadscrew makers on the net. Plenty about I bought a 1 metre length of 16mm left hand screw and matching nut very cheaply from Automotion Components. A bit of simple machining to cut the threaded part of the original screw off and spigot it onto the remaining part secured with a roll pin and a dab of Loctite. If the pitch is correct don't get to hung up about the diameter if replacing the nut. I got enough to make three cross slide screws and a nut for around £50/60.

[Pete RimmerParticipant @peterimmer30576]

Posted by needleworks on 18/02/2018 20:07:34:

Posted by Mick B1 on 18/02/2018 19:08:48:

.559" is 3 1/2 thou down from 9/16. My guess is imperial.

I thought of 9/16, but I can't find a left hand acme tap 9/16 x 10 tpi anywhere on the net

You won't and it probably wouldn't help you anyway. IIRC the Bantam cross slide screw is a 2-start thread. .100" pitch but 5tpi lead.

[Mike PooleParticipant @mikepoole82104]

Posted by needleworks on 18/02/2018 20:03:40:

Posted by Mike Poole on 18/02/2018 19:13:10:

Does the scale on the handwheel not give away the pitch?

Mike

On the Bantam you have the luxury of both, pull the dial out it reads metric, push it in it reads imperial.

Ah that makes life a bit more complicated.

Mike

[Deleted AccountParticipant @deletedaccount69088]

Posted by Chris Evans 6 on 18/02/2018 20:35:57:

Look for leadscrew makers on the net. Plenty about I bought a 1 metre length of 16mm left hand screw and matching nut very cheaply from Automotion Components. A bit of simple machining to cut the threaded part of the original screw off and spigot it onto the remaining part secured with a roll pin and a dab of Loctite. If the pitch is correct don't get to hung up about the diameter if replacing the nut. I got enough to make three cross slide screws and a nut for around £50/60.

I was wondering was there any centres on the leadscrew or whatever they are called to accurately place the bar between two centres?

[EmgeeParticipant @emgee]

You can easily confirm the pitch of the leadscrew by fitting a Dial gauge between the tool post and a chuck mounted rod, do 1 complete revolution of the handwheel and read the gauge, you will have to take up any backlash before doing the test revolution.

Emgee

[Chris Evans 6Participant @chrisevans6]

As I recall there are no centres in the replacement lengths of leadscrew. The threads are formed by rolling and I have found them to be very accurate. I simply cut off the required amount and held it in a 5C collet to turn the ends to suit. I made two cross screws and nuts from what I bought and still had enough over to make a third screw. After 5 or 6 years of regular use there is still no play in the first one I fitted so the spares are still on the shelf. I did add an additional oil point to lubricate the screw a bit better than original design.

[Deleted AccountParticipant @deletedaccount69088]

Posted by Chris Evans 6 on 17/10/2020 12:56:30:

As I recall there are no centres in the replacement lengths of leadscrew. The threads are formed by rolling and I have found them to be very accurate. I simply cut off the required amount and held it in a 5C collet to turn the ends to suit. I made two cross screws and nuts from what I bought and still had enough over to make a third screw. After 5 or 6 years of regular use there is still no play in the first one I fitted so the spares are still on the shelf. I did add an additional oil point to lubricate the screw a bit better than original design.

thanks for the information. The collet idea would seem to solve the problem of centering things.

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