Drill Vs tap size ?

[Tom Morookian]

I tried searching the forum and archives with no luck.

Anybody got a chart of drill size to use for each tap size?

[texas webb]

google should do it for you.

[PeteVS]

Here's a link...
http://www.newmantools.com/tapdrill.htm#inchlink

[3quarter32]

Give this a try. You can enlarge them in about any picture viewer.
Lee

[paul2748]

Most taps I have seen has the the drill size on them.

[ken ct]

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Those are good charts have a couple of them,but they dont give them out anymore.ken ct.

[rgtharley]

Do yourself a huge favor, and buy a copy of the machinist's handbook. It has everything you'll ever want or need to know about metalworking and materials. It is not a cheap book, but worth every penny. (just my two cents!)
Bob

[BillM]

A simple formula for tap drill size is nominal diameter minus thread pitch. For example; 1/4-20 is .250 minus -1/20 or .050 = .200" , or a number 7 drill which is .201. This also works with metric sizes.

[Dale Fairfax]

The proper name is Machinery's Handbook.

Originally Posted by rgtharley

Do yourself a huge favor, and buy a copy of the machinist's handbook. It has everything you'll ever want or need to know about metalworking and materials. It is not a cheap book, but worth every penny. (just my two cents!)
Bob

[19Fordy]

Originally Posted by rgtharley

Do yourself a huge favor, and buy a copy of the machinist's handbook. It has everything you'll ever want or need to know about metalworking and materials. It is not a cheap book, but worth every penny. (just my two cents!)
Bob

I bought mine "used" in the college bookstore in 1967 and still have it.
I imagine it's been updated since then.

[Tom Morookian]

Wow, I sure "screwed" (that up) trying to copy th spreadsheet.

Here's what I meant


Coarse threads

Screw/bolt TPI Drill Size

in 64ths
#8 20
#10 20
1/4 20
5/16 20

3/8 20
7/16 20
Drill size
Fine threads in 64ths
#8 32

#10 32
1/4 26
5/16 26

3/8 26
7/16 26

[Tom Morookian]

Screw/boltin 64th'sDiameterTPIDrill SizeDrill in 64'sSize 3/16120.1875200.17812511.4 1/4160.25200.237515.2 5/16200.3125200.29687519 3/8240.375200.3562522.8 7/16280.4375200.41562526.6 1/2320.5200.47530.4What I'd like to haveScrew/BoltTPIDrill SizeTPIDrill SizeSizeCoarse(in32 or 64th)Fine(in32 or 64th)#4na#62026#82026#102026 3/162026 1/42026 5/162026 3/82026 7/162026 1/21626

[PeteVS]

One formula that no one's mentioned deals with "Number Size" screws, such as a #10-24 screw or a #6-32 screw. The major diameter of the screw thread (actually just a little more than what a screw would measure) is (THREAD NUMBER x .013) + .060.
This yields: #0 screw is .060", #1 screw is .073", #2 screw is .086", #3 screw (they do exist) is .099", #4 screw is .112", #5 screw is .125", #6 screw is .138", #7 screw is .151", #8 screw is .164", #9 screw is .177", #10 screw is .190" and #12 screw is .216".

[Karl Wolf]

I put a caliper on the tap, where I think the thread depth is ok...
Use this to go thru my drill index... Sometimes it's suitable to ream the start end of the hole to make it easy to start the tap... Can make a guide by drilling a wood block- makes it so the tap goes straight...
Karl

[rgtharley]

Originally Posted by Dale Fairfax

The proper name is Machinery's Handbook.

So sorry to mis represent the bible of the trade, but I guess since I got my Journeyman Certification in 1979, my memory has faded a bit. Besides, any online search for anything close to that will bring up the right links.