If I am tapping a hole in an alloy casting (to bolt the stubaxle assemly inplace)

What would be the prefered thread? UNF or UNC?

I know UNF for suspension pivots is a bad idea as they work loose...


But in an alloy casting... is UNF too fine?

yep, your suspicions are right, unf too fine. Metric coarse would be my first choice, followed by unc

quote:

---

Originally posted by tegwin



But in an alloy casting... is UNF too fine?

---

So if I am looking at an alloy casting that takes some studs...

Logic would suggest that the thread in the casting would be UNC...... but the thread on the other end of the stud that takes the nut should be UNF? Would that be "normal" on a british car?

Not exactly like this... but you get the idea:


The nut is DEFFINATELY 5/16UNF.... I am not sure what the other end of the stud should be.... I have a nasty mismatch of buggered holes in my upright :s

[Edited on 12/5/09 by tegwin]

[Edited on 12/5/09 by tegwin]

dunno, could be whitworth, but unc and whit are bloody similar anyway at smaller sizes

quote:

---

Originally posted by tegwin
So if I am looking at an alloy casting that takes some studs...

Logic would suggest that the thread in the casting would be UNC...... but the thread on the other end of the stud that takes the nut should be UNF? Would that be "normal" on a british car?

Not exactly like this... but you get the idea:



[Edited on 12/5/09 by tegwin]

---

unc at one end and unf at the other is a standard exhaust stud on just about every old british car I have had the pleasure to bust a knuckle on.

I am surprised at your comment about unf threads working loose - they are the standard on aircraft bolts now.

Thats weird... thought I had better check...

The stud "5" in that drawing is 5/16UNF both ends... I have a bag of them in the garage


I am missing three studs on my upright... all the holes have been chewed out to UNC....

I dont know if its a bad idea to remove one of the other good studs and check to see what the holes "should be".... How does one unscrew a stud without buggering it up?

In the 1960s UNF was the normal choice for any part subject to vibration because they don't work loose. If fact they are bloody impossible to get off because the thread becomes choked up with rust.

Threads into alloy should always be a coarse thread --- UNC, metric coarse or good old Whitworth.
Apart from flank angle Whitworth and UNC are more or less the same except in a couple of sizes whre the tpi is different (ISTR 5/16" dia is one).



[Edited on 13/5/09 by britishtrident]

quote:

---

Originally posted by tegwin
Thats weird... thought I had better check...

The stud "5" in that drawing is 5/16UNF both ends... I have a bag of them in the garage


I am missing three studs on my upright... all the holes have been chewed out to UNC....

I dont know if its a bad idea to remove one of the other good studs and check to see what the holes "should be".... How does one unscrew a stud without buggering it up?

---

The studs marked '5' on your drawing ARE 5/16 UNF... and they shouldn't have done it like that, as they pull out, most people retap them to UNC when they are doing a restoration (unless the studs won't come out, in which case they get left!), If you are doing those then I strongly suggest that you find a local triumph specialist for advice, as they are very easy to bugger up entirely and not that easy to get hold of in good condition..... not saying don't do it - but get some proper advice before - if you haven't anywhere close, a chat with Colin at CTM engineering (google him) would be a good start.

Chris

That would make sence..

Where can you buy UNF/UNC studs?

quote:

---

Where can you buy UNF/UNC studs?

---