Thread, drill and clearance Chart

[neillarson]

For us that don't work in the metal machining world, this chart is of great help. At least it was to me.

http://www.physics.harvard.edu/servi...HREADCHART.pdf

[BigSki]

Thanks for the link, this is a good to use as well.

[Duuuuuuuude]

What, no metric system?

[roglum]

good info, thanks. might help in the day to day as well.

[Charlie-III]

Originally Posted by Duuuuuuuude

What, no metric system?

Nice, but doesn't cover the small stuff we use..... try this.... http://www.engineersedge.com/manufac...rill-chart.htm

[Manning]

Originally Posted by Duuuuuuuude

What, no metric system?

Metric tap drills size is easy, just subtract the pitch from the nominal size. Done.

[Charlie-III]

Originally Posted by Manning

Metric tap drills size is easy, just subtract the pitch from the nominal size. Done.

Good point, I frikkin forgot that......

[roksloski]

I found that an 1/8" clearance hole for a 3mm is too big...

[Duuuuuuuude]

Originally Posted by Manning

Metric tap drills size is easy, just subtract the pitch from the nominal size. Done.

Yet another reason to love the metric system.

[Manning]

Originally Posted by Duuuuuuuude

Yet another reason to love the metric system.

Darn straight. Much easier to deal with. Stupid 'merican inch pound system......

[M1tch]

when i was an apprentice many years ago the best reference for threads and other machining know how was the Zeus book of tables. plastic coated flip book. i still have my 1976 edition somewhere

http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=310187580240

someone has converted them to PDF format here

http://www.green-oval.com/data/zeus.pdf

[losikid]

here's the chart i use

http://www.physics.ncsu.edu/pearl/Tap_Drill_Chart.html

[M1tch]

i like that...... a lot

[sim]

Originally Posted by neillarson

For us that don't work in the metal machining world, this chart is of great help. At least it was to me.

http://www.physics.harvard.edu/servi...HREADCHART.pdf

I looked at the chart and the clearance drill sizes might be loose on some of those smaller screws. A 4-40 screw will rattle about inside a 1/8" hole for sure.

[SMR 510RR]

Originally Posted by losikid

here's the chart i use

http://www.physics.ncsu.edu/pearl/Tap_Drill_Chart.html

This is the best one that I have found. It lists different tap drill based upon material, none of the other tables posted have that information. Very important when you are trying to tap an 0-80 hole .500" deep in Stainless Steel!

[Reflection]

Originally Posted by SMR 510RR

This is the best one that I have found. It lists different tap drill based upon material, none of the other tables posted have that information. Very important when you are trying to tap an 0-80 hole .500" deep in Stainless Steel!

Very true. Allot of times at work, material, tolerances, and application plays a part in what size hole I drill for a threaded hole. What style of tap also plays a big part in what drill I use.

[slappomatt]

0-80 .500 deep in SS is easy. Don't bother even trying lol.

[Charlie-III]

Originally Posted by Reflection

What style of tap also plays a big part in what drill I use.

You are likely referring to rolled threads vs. cut threads. Rolled is better, but not found often.
Then again, you could be referring to straight flute vs. spiral flutes......

[Reflection]

Originally Posted by Charlie-III

You are likely referring to rolled threads vs. cut threads. Rolled is better, but not found often.
Then again, you could be referring to straight flute vs. spiral flutes......

We typically use rolled threads (form taps) when taping a smaller size like 3mm or #6 and smaller...in aluminum. Can't do that in steel, stainless or anything hard. In hard material, a hole a few thousandths bigger will be allot easier on your taps. Using spiral flute cut taps help in hard material since they pull the chips out of the hole instead of pushing them down into the hole. From my limited experience, the chips coming off the tap in the hole is what breaks allot of taps.

[Charlie-III]

Originally Posted by Reflection

We typically use rolled threads (form taps) when taping a smaller size like 3mm or #6 and smaller...in aluminum. Can't do that in steel, stainless or anything hard. In hard material, a hole a few thousandths bigger will be allot easier on your taps. Using spiral flute cut taps help in hard material since they pull the chips out of the hole instead of pushing them down into the hole. From my limited experience, the chips coming off the tap in the hole is what breaks allot of taps.

Yep, I used to do thousands of #10 rolled threads in aluminum in a machine shop. Much better thread than cut.
As to chips breaking taps, having them go to the bottom of a blind hole can bind the tap & break it.
Not backing the tap off to break chips can be as bad (in 3/4-1 turn, back 1/2 turn.....).
Bending taps also breaks them off.

Funny story....one place I worked, we ordered TiN taps for a job, our purchasing dept bought HSS taps & had them sent out for Tin coating. They couldn't figure out why we were pissed when they came in.