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Premium Member
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283 Posts
Discussion Starter · #1 ·
Hey Guys,

I need to tap a hole to fit a 1/2" x 18 bolt, but nowhere seems to sell taps this size. Have I got a really odd size bolt or am I not looking in the right places for a tap?

Ta, Ady
 

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Semi Proffessional Prat
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3,489 Posts
What's it off. UK or US?

Just had a look through my bible, and it's none of the usual ones.
Any chance you could drill and cut a new thread such as M14?
 

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Premium Member
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283 Posts
Discussion Starter · #6 ·
Hi V8Ian,

1/4 NPT makes sense as my bolt size measurer would only go half way up the thread in the 1/2" hole. It's an American throttle cable with a threaded bolt attached. How do you tap out a tapered thread or is the tap the same diameter through it's whole length?

Thanks.
 

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1,844 Posts
NP & NPT, or it may be NPT & NPTT, cant remember, National Pipe,& National Pipe Taper, then it may be National Pipe Thread, and National Pipe Taper Thread, havent had time to check my boxes of taps yet.
 

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3,238 Posts
it might be 1/4 npt, that is about 1/2" and 18 tpi. im sure i have 1/4 npt taps in the workshop, i will have a look in the morning, could pop one in the post for you to borrow (cheaper than buying one just for one hole). all it will cost is the postage and a donation to charity.
 
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