8mm for 3/8ths?

dieseldog69 · Feb 27, 2018

I ordered a new 11/32 twist drill to accompany the 3/8 NPT tap for a few little jobs but the tap has arrived but no drill bit, been to the hardware store and they don't have any 8.5mm drill bits (8.5mm closest metric to 11/32 imperial).

Question is, can I get away with 8mm drill bit or is that too much material for a mine thread tap?

jamesmartin · Feb 27, 2018

dieseldog69 said:
I ordered a new 11/32 twist drill to accompany the 3/8 NPT tap for a few little jobs but the tap has arrived but no drill bit, been to the hardware store and they don't have any 8.5mm drill bits (8.5mm closest metric to 11/32 imperial).

Question is, can I get away with 8mm drill bit or is that too much material for a mine thread tap?

if its a quality tap, cheap ones can snap

brianp38dse · Feb 27, 2018

A hardware store that hasn't got an 8.5mm

as James said, quality ok cheep

also depends on the depth and material you are tapping, file it out a bit and use some lube, forwards and back a bit gently does it.

wattfield · Feb 27, 2018

Are you in a hurry? Why not try ebay or mail order for the drill bit?

dieseldog69 · Feb 27, 2018

brianp38dse said:
A hardware store that hasn't got an 8.5mm
as James said, quality ok cheep also depends on the depth and material you are tapping, file it out a bit and use some lube, forwards and back a bit gently does it.

Hayling Hardware is awesome, they stock most things and have a really good selection of oddments, metric and imperial nuts and bolts, oils and fluids, it's a bit like B&Q/Machine Mart/Robert Dyas all rolled up into one, tapping the soft ally intake manifold.

wattfield said:
Are you in a hurry? Why not try ebay or mail order for the drill bit?

I ordered the tap and the drill bit together explicitly from the same supplier with the notion that they would come together, seems I was mistaken

jamesmartin said:
if its a quality tap, cheap ones can snap

Seems to be better quality than the Draper tap and die set I bought from Halfords years ago.

It's only soft ally so should go easy enough with a bit of care and cutting oil.

dieseldog69 · Feb 28, 2018

Drill bit turned up this morning, manifold has been washed up and degreased so will crack on and get it done when I get home, strange that they didn't pack the tap & drill together but hey ho, no drama.

Happy days

8mm for 3/8ths?

dieseldog69

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jamesmartin

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brianp38dse

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wattfield

AKA Dirk Diggler

dieseldog69

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dieseldog69

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