Have a question about tapping 303 stainless steel. This is the first time I've worked with 303 and everything went great at first. I drilled a hole and then milled the bottom flat. Then I started to thread (3/8-24) with a taper tap. It was more difficult than usual. I skipped using a plug tap and went straight to a bottoming tap. It really bound up! Not from an occasional chip or tough cut, but it seemed like it would stick to the 303 (even backing out)! I used standard cutting oil and the taper tap didn't stick like the bottoming tap.

Is it a low quality bottoming tap (USA HSS, but hardware store variety)? Is it because I skipped the plug tap? Do I need special cutting oil, or is 303 just hard to tap and I should be using a different type of tap (or some combination of the above)?

Thanks,
AR

of the St/St alloys tend to gall badly when you work them. There are some tapping fluids that are formulated for working St/St, MSC and most of the big tooling suppliers carry them. I would however use a plug tap before going to a bottoming tap,
especially in St/St.

I found that I used a plug tap after all, not a taper tap, so I didn't skip the plug. I guess I will try a different cutting oil. I have some Tap Magic around that I've never tried - I'll give it a try and see if that helps.

Thanks,
AR

Believe it or not, it works like magic for tapping stainless !!

quite a while back I was talking to an old, really old machinist and he claimed for some jobs the only lube that would hold up for some jobs was LARD! john

I had tried just about everything over the years to surface grind aluminum, but it was always a pain. The shop I am at now, that taught me about crisco, had another trick for the stuff......... you microwave it, and soak a surface grinder wheel in it. Not the whole wheel, just run it slowly by hand through a trough of the stuff heated to almost boiling, and let it wick up into the wheel. Then, when it cools, it will not fly off the wheel, ANd it will prevent galling and heating up that is common with grinding aluminum. Of course, painting a thin coat on the surface you are grinding helps as well, that can be done in the original thick, "natural" state....
One note, when we do this on fixture bases, (large), we use a wet grinder (larger!), but again, just a crisco soaked wheel, no coolant. BUT.... when you are done, you must clean everything, and it helps to put down newspaper first as well. Shop vac all the residue out, or it will cause your coolant to "turn" in a few days, as in.... rot..! If you clean the machine well, this is not a problem...

a manifold for spray booths and thread Stainless Steel for the job.
Tapping drilling and cutting SS we use Ridgid 74012 and apply pressure dont be wimppy push and turn at the same time

Has worked for me in all types of steel. Best I have used.

smells like bacon grease.

Hello,

You have probably already gotten over this problem. But, I use Tap Magic Xtra-Thick, this works for metals up to 45 rc. The poor quality tap probably had a lot to do with your results. But I would also look at the hole size produced by the tap drill as well. If you could, try and go as large as the thread tolerances will allow for the use of the thread(decrease the percentage of thread, but don't go below 50-55%, only do this if the thread isn't for a pressure vessel). There might have been some "work hardening" of the material also if your drill was dull or just created too much heat (rubbing not cutting). Hope all is well!!