mk1-forum.net

I’m making a manifold. I’ve got a BSW tap is that close enough to UNC to be useful? Or do I need to be proper?

Different thread angle, same tpi up to 7/16".

So you may find the fixing tight, depending on tolerances.

I wouldn’t. I used a 3/8 BSW tap by mistake a couple of weeks ago and the bolt just feels loose. Has done up alright but I don’t like it.

I have UNC if you need to borrow them.

Is the manifold you’re making not steel? If so I’d be using UNF studs.

Cheers Graham, it is indeed steel. Can you tell I don’t know what I’m doing yet

UNF will give you more thread engagement as I’d assume the steel plate isn’t very thick.

for reference, Maniflow manifolds aren’t tapped - they have a clearance hole and then you can either use bolts, or still use studs but with nuts on both ends.

Given the tight squeeze a nut and bolt combo would probably work best... hmm food for thought

In case it helps, have found these guys really good for the odd tap, can also get the correct size drill, which is the bit I often struggle to find
https://www.tracytools.com/taps-and-dies/UNC-taps

As i remember that Whitworth & UNC threads have the same thread pitch up to 1/2inch ..making Half Inch Threads not interchangeable as Whit / UNC have differing pitch.
Suggest whatever you do the tapping hole size needs to be correct .. before any Thread Tapping is done.