1/2 NPT tap drill bit

[chrisT]

I read that a 1/2 NPT tap requires a 45/64 bit, but I am finding that bit a little hard to come by. Anyone have any tricks to get this done or a good source for this bit?

[Fluxion]

Thats a really odd size to find. An 11/16" drill is just 1/64th under what you need and should work fine for your tap. You could also go witha 0.7092" (18mm) bit, its only 0.0062" bigger. Both of those are easier to find. I buy a lot of my tooling for my business from Enco here is a Link to the drill bit pae with these bits listed.

[douggiestyle]

most tool shops that sell the taps also sell the appropriate bit sizes. usually, they could be out or be a lousy shop. im lucky i have three great shops less than a mile from my home.

[douggiestyle]

are you tapping plastic?

[douggiestyle]

^^

[dattack]

I use 11/16" wood spade bit. It's easy to come by and cheap.

[douggiestyle]

Originally posted by dattack
I use 11/16" wood spade bit. It's easy to come by and cheap.

thats what i would suggest if tapping plastic.

[chrisT]

Thanks for the replies, its exactly the advice I needed. I am taping 6" OD 1/4" cast tube for a kalk reactor.

[checkinhawk]

a hole saw would be best on the pipe.odds are you will crack the pipe with a spade bit.also put something inside the pipe to keep it ridgid.cut a 3/4"thick wood disk that fits snug inside the pipe,then place the disk under the center point of the hole to be drilled.this will keep the pipe from blowing threw on the inside and chipping.

[BruiseAndy]

When using a holesaw you also can try going backwards so you dont get tearout when you punch through. Melts the plastic though so it may screw up the diameter.

[checkinhawk]

never a good thing to melt through the sheet or tube.just use a good holesaw and backing plate.

[douggiestyle]

hole saws melt plastic.

spade bit, brand new, nice and sharp. slow speed easy pressure and hold tubing tightly, i suggest a vee jig to hold the tubing nice tight.