Spindle Speed for tapping 1/4-20 holes.

[lerman]

Soak the tap in lye. (Use powdered lye drain cleaner). Lye will attack the aluminum but not the steel. It took a few hours to get the aluminum off a mill I had messed up.

Ken

Originally Posted by JPMach Check machinery's handbook for tap drill sizes for form taps. I highly recomend form taps or spiral point two flute tap for thru hole in aluminum. Alot of the other guys on here have great success with tapping around the speeds you said you tried, personally I tap 1/4-20 thru aluminum at 2500rpm and I haven't broke one yet. I've got around 110 holes on one form tap and it still looks as good as the day I bought it. I usually just have the flood coolant on but around every 20 holes or so I will coat the tap with a dry graphite film spray, I don't know that it does much after the first 1 or 2 holes but it can't hurt. With form taps though just be sure you have the right size or a hair bigger hole drilled for the tap as a hair under will cause problems, I already coated one 5/16-18 tap with aluminum- not pretty. Also with form taps use a 90 deg spot drill and run it down far enough so that the tapped hole will be chamfered when all said and done, as the form tap displaces material, with no chf on top they will quite often roll material up above the top of the hole. JP

[JPMach]

Originally Posted by lerman Soak the tap in lye. (Use powdered lye drain cleaner). Lye will attack the aluminum but not the steel. It took a few hours to get the aluminum off a mill I had messed up. Ken

Holy #$%^& that worked. I just tryed that with a tap I hap lolipoped and in like 3 minutes it was completly clean of aluminum.

Thanks for the tip, I knew lye was powerful stuff I just never thought of applying to machining before.

JP

[M-man]

Try a MTX tap... 2632 Rmp and calculated to last for 76585 holes..

[Geof]

Originally Posted by JPMach Holy #$%^& that worked. I just tryed that with a tap I hap lolipoped and in like 3 minutes it was completly clean of aluminum. Thanks for the tip, I knew lye was powerful stuff I just never thought of applying to machining before. JP

Two hints; 1, you will dissolve almost as fast as aluminum so keep it off your skin;2, the bubbles coming of are hydrogen so don't do this near a source of ignition including electric switches.

[tobyaxis]

Doesn't anyone like MollyDee?

[peter.blais]

Just bought MEpro a week ago... Money VERY well spent.

[gbowne1]

I'm tapping 1/4"-20 UNC through holes in 6061-T651 plate. It's a hanson and whitney plug 2 flute G8 tolerance. I've used mist coolant and I have tried 2 of the slowest speeds I have on my mill. One I broke one tap, the other was hard on the tap but didn't break. I liked tapmagic too.. which I tried at my friends' shop.

I'm using a tapholder and tap collet setup in a NMTB 40 holder.

I have to drill 5/16 holes in the plates.. they are tooling plates I hold small parts on.

Greg

[JPMach]

Some how I wouldn't think breaking 1/4-20 taps would be much of a problem with 5/16 holes
I think you have the wrong drill size there unless that is for something else alltogether.

JP

[gbowne1]

They are different holes in the plates for an entirely different purpose. They hold 5/16" pins for indexing a hole in a part.

Greg