Tapping 304 Stainless

[rc]

Hello,

 

We are getting into bottom tapping alot of 304 stainless steel 2-64 thru 6-32. The machine has rigid tap. We have checked feeds and speeds, went with a bigger major diameter for drilling. We have tension compression holders coming in on Monday to try out but the bottom taps break right away. A plug tap will work fine except that we cannot achieve the correct depth because of the lead on the tap. Any suggestions?

 

Thanks,

rc

[Rekd™]

Are you packing chips down the hole? Try form taps, or high spirals to pull the chips out

 

'Rekd

[gcode]

Try OSG VA3 bottom taps.

Another trick I've used in 304 is to drill the hole undersized and line bore it to the maximum allowable size with a ground to size endmill.

304SS work hardens easily.

The endmill straightens the hole, and removes any work hardened material from the drilling operation.

Another thing you must do, especially in small tap sizes is do a program stop before the tapping cycle. Make sure there are no chips in the holes and apply a good tapping fluid.

The EPA has banned most of the good tapping

oils so I can't make a recommendation there.

Its been a few years since I tapped any 304SS and I don't know what's legal anymore.

 

I think in the long run, you may find it more economical to tap the holes by hand with a Procunier tapping head. Don't even think about a Tapamatic. In my experience they are complete junk.

[TheePres]

CHEAT!!!

on drill depth

[crazy^millman]

I would look at a hypro modifed bottom tap or the emuge tapes designed for hard materials. The form (Roll) tap would be my first choice also on that small of a size. I would also look at using a good tap fluid on the holes also.

[HEAVY METAL]

I don't know what tap drill size your using but you can go with as little as 50 % thread height for ss steal and still have sufficient thread strength. I.m using an osg high sprial tap on some 304 ss 1/4-20 about 60 % thread height. 548 holes still going strong.

[Kevangel]

Tapping fluid from Union Butterfield (ashville,NC) I buy mine from E.M. Wick in Dayton, Ohio phone# 1-937-293-5330 The bottles I buy are 2.5" dia. X 7" tall. I think it was only $25 for case of 6? several years ago CHEAP...It is THICK, clear,oderless? It Works!!, taps in a Bridgeport that (hand-tapping,center guided) that will not go in with anything else , will start cutting again in stainless. Never have seen anything else even close. I use it for all steels, except aluminum. I am so amazed to never see it in catalogs. Yet an old toolmaker in Denver turned me on to it 23 years ago, he had used it at Cobe Labs and still had a little bit left.

[Harryman]

Form tap. OSG, Balax. Heavy sticky oil.

 

Gcode's suggestion to clean up the holes is a good one. Drilled holes work, but if you're running the drill too fast and it's wearing, that HSS is sticking to the sides of your holes and will kill a form tap.

 

Save the money on the holders. Return them. Rigid works.

 

Are you using Mazatrol? There's a parameter that I lovingly refer to as the Snap Tap Parameter, that adds a few turns to the depth you've programmed. Set it to zero.

 

For drilling 304 with HSS, we really like Viking/Norsman Super Premium drills.

[chris m]

If you have rigid tapping as you said:

 

1) Trash the tension / compression holders

 

2) Keep the drill RPM low and peck it short to avoid making the hole harder to tap

 

3) I would use OSG Exotap NRT roll taps with the TiCN coating. The HyPro is a decent tap and much less expensive [$8 vs. $20] so you could start there also with the TiCN coating but I think you'll find that in some apps you just need to spend the $$.

 

We run a job all of the time [running right now actually] that is a #4-40 roll-form thread .300 deep blind hole in 17-4PH stainless heat-treated to 32Rc. It is not unusual to tap 900 holes with the same drill and tap using coolant only, no program stops, no oil [oil is a coolant killer]. I am using a Guhring parabolic jobber drill, TiN coated [658 series] running 30 SFM with a .100 peck and the Exotap NRT TiCN coated at 10 SFM.

 

It ain't super fast but it runs and runs and runs and runs....

 

C

[rc]

Thanks everyone for all your help!

[chris m]

Bump

 

Where'd you end up with this?

 

C

[Chris Rizzo]

I think that Tapmatic should be renamed "SNAPMATIC" . I threw our's across the shop (on purpose). I'm sure it's still snapping many a tap in it's new shop...THE JUNKYARD!