Drilling and Tapping Q's (1 Viewer)

[Morse_FJ40]

I need to drill and retap some holes in my raingutter. Is there a formula to which to need to adhere to. Tapp size- drill size??? thanks
Ryan

 

[slickrock]

the tap will tell you the drill size on the package. For every full turn with the tap, back it off 1/2 turn. then one turn and back 1/2 turn to get a good thread. (some even say 3/4 turn back, but I have had good luck with 1/2 back)

 

[mpetersrx7]

This should help.

http://www.engineersedge.com/tap_drill_chart.htm

 

[jim45r]

This is a handy chart that has both metric and american standard:
http://sosnick.uchicago.edu/tap_drill_size.html
The American side is kind of whacky (like our measuring system) with fractions, wire gauge numbers, and letters, but the metric is pretty clear.
Here's another:
http://www.kramerusa.com/DrillTapChart.htm

And here's a handy chart I stumbled across from a public school in madison:
http://www.madison.k12.wi.us/toki/teched/codrills.htm

 

[rusty_tlc]

USe tap oil, Tap Magic or even 3-in-1. You will save a lot of taps.

 

[Blue77FJ40]

Don't forget to use compressed air to clean up your work and bits. Watch yer eyes when you do that! Usually, I place a cloth over the hole to trap the debris while I shoot the hole with air.

For mobile pieces, I love to use my drill press adapter that permits me perfectly vertical taps. The drill press keeps the tap verical while I hand tap the piece. Sweet. Got mine at MSC.

 

[andrewfarmer]

A good rule of thumb for (most) metric sizes is to downszie the drill by the thread pitch - ie M8x1.25 drill 6.75mm, M6x1 drill 5mm