CNC Tapping - Help

[weaston]

I would like our cnc mills to do our tapping. Currently cnc does a pretap, operator then finishes the tapping by hand.

When he attempts to tap the hole on the cnc, taps break...

He is using rigid tapping canned cycle (G84). Through hole (16mm stainless steel). M12 Tap with a 10.2 predrilled hole.

Any suggestions to overcome this problem???

Thanks

[GaryCorlew]

With stainless you have to use slow rpms and lots of coolant, you do not want it to get hot at all. What grade of stainless?

[DareBee]

Is the rigid tapping cycle not G84.1?

On my machine I would break taps using G84 without a compression holder.

It may be as simple as using a different brand/style of tap, that should be an easy hole to tap.

[jetski]

I would check with a tool supplier like OSG and see what they advise for speeds, feeds, and coolants. They make taps for different material and know how to run them. Use the free information from their tech support. Most suppliers want to look like heros and sell product at the same time use them. Have fun.

[psychomill]

I'd open your hole up for stainless as well. I assume you're tapping a M12 x 1.75. Your hole size should be a 10.25. For steel, I usually go to 10.3 or 10.35 even. And your minor Ø will still be good....

[cadman]

You can't do synchronized tapping with a regular tapping cycle. You will break taps. On some machines it is an option and some it is standard. look through your documentation and list of G codes available for your machine. You should find something there that will tell you if you can indeed perform rigid tapping. Good luck.

If you have an Okuma you need to change the tapping cycle parameter to synchronized.

[Genguy]

We had some rigid tapping problems recently.
I found it helpful to test on a soft material like wood. If it taps perfect threads in wood without shredding it, you know the machine is doing it's job properly.

[ajl6549]

What type of machine is it? On a Mazak g84 is the code for rigid tapping and the machine must be set in g95(i.p.r.) as well. Also other machines require an "E" word for the feed and this would be the number of threads per inch instead of the pitch etc. Anyway there are many different type of comands for tapping.

[davereagan]

Stainless steel can be amazingly difficult to tap, especially 316. 304 and 316 don't even measure on the Rockwell C scale of hardness, but they are harder to tap than 35-40 Rc carbon or alloy steel. I wouldn't use flood coolant to tap any stainless but 303, which is sulfurized and makes beautiful chips. I would use a high vanadium spiral pont tap with Tap Magic w/EP extra or even their extra thick formula. I used the extra thick with a spiral flute Vega Tin coated XHP tap and did (160) 1/2"-13 blind holes 1" deep in 316 stainless
(7/16" tap drill). I tried the first hole with flood coolant and it made an awful squeal. The regular Tap Magic was good, but I used the extra thick formula just to be sure and only 100-120 rpm. Many feed and speed charts for drills, taps and endmills don't distinguish between 304 and 316, but try running 316 at the 304 speed and you'll be in trouble in a hurry. So after this big sermon, what grade are you cutting? Tap brand? I would drill it to 10.4mm Every little bit helps to reduce tapping torque.

Dave

[weaston]

Thanks for reply. we were tapping 304 stainless. 100 RPM with coolant. Tried twice, the sprial flute (SOMTA) tap broke and the spiral point tap (FEW) got stuck in the job. (Shavings sort of welded in the hole between the flutes). The tap can rotate in the hole but we can't get it out because of the shavings.

[davereagan]

Weaston,
Did you use the 5UA1200? Below is a link to that page. Are you using a soluble oil at 10% or stronger or is it synthetic? Either way, I would use a heavy duty tapping fluid and turn the coolant off. Solving these problems can be difficult, but satisfying when you get it fixed. You may want to check the Z backlash on your machine using an indicator with the Manual Pulse wheel. If it is within .001", you should be fine.

Dave



http://www.somta.co.za/thr/5ua.htm

[greg b]

stainless steel is a rotten material to tap at any time, in our brigeport i use a floating tap holder, you may like to try a 3 or 4 flute straight conventional tap,use no coolant and apply a good quality tapping paste and try around 60rpm good luck greg b