BSW vs UNC

[Dr S]

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?

[woodypup59]

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

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

[Oneball]

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.

[GraemeC]

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.

[Dr S]

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

[GraemeC]

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.

[Dr S]

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

[Exminiman]

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

[Polarsilver]

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.