Carver clamps - thread type?

[Munkul]

I'm refurbish a carver machine vice, it needs a new CSK for the bar retainer clip and also a new pressure screw. They are 5/16-18 and 7/16-14 respectively, however, I can't work out if they are UNC or BSW.
Can anyone help?

 

[8ob]

The countersunk screw may give it away, unc and bsw have a different countersink angle.

Bob

 

[Munkul]

Ah, cool, I hadn't realised that. I THINK then the CSK is a Whitworth with a 90 degree countersink angle, as opposed to a UNC with an 82 degree angle. But I can't measure it properly.

Anyway I've ordered a screw and hopefully its right, I've decided to modify the clamp and drill/tap out to metric, as the old threads are crazy worn, and make a new pressure screw from a caphead.

 

[Rrobson]

Unc and whitworth have different thread angles too, unc being 60 degrees and whit 55 degrees so if you’ve got a thread gauge or can grind an accurate 55 degree you can use that to determine the form

 

[Munkul]

Unc and whitworth have different thread angles too, unc being 60 degrees and whit 55 degrees so if you’ve got a thread gauge or can grind an accurate 55 degree you can use that to determine the form

That was why i asked. On worn and knackered threads, it's anyone's guess as to whether they used to be 55 or 60 degrees... I personally can't tell with a thread gauge anyway.

 

[8ob]

That was why i asked. On worn and knackered threads, it's anyone's guess as to whether they used to be 55 or 60 degrees... I personally can't tell with a thread gauge anyway.

On the smaller sizes it makes no difference, I quite often substitute smaller whit bolts with unc on older kit just to make servicing easier. Saves hunting out the whit spanners/sockets, keeps it all on the af spanners.

Bob

 

[Munkul]

On the smaller sizes it makes no difference, I quite often substitute smaller whit bolts with unc on older kit just to make servicing easier. Saves hunting out the whit spanners/sockets, keeps it all on the af spanners.

Bob

I have been known to not care in the slightest in the past... interference fit it is

 

[frank horton]

whit and UNC is near enough the same up to 3/8ths diameter......

 

[grim_d]

I have been known to not care in the slightest in the past... interference fit it is

Yep, if the TPI matches then in it goes. Very rare the tolerance on the threads is small enough to make any difference

 

[RichardM]

Give them a call and ask, they may even send you a couple of new screws FOC.

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