Should I be scared to rigid tap 4-40 in stainless?

[PGW Steve]

Stuff is 416SS which machines pretty nice, about a 36C hardness. I have 130 pieces with one hole to tap in each and I would like to avoid doing it by hand. I was going to try at around 500rpm even though the book says 2700 or so just so there might be less timing issues with stopping and starting the spindle. I'll apply some Butterfield tap lube to the hole for each one. Any tips you guys can share is appreciated.

 

Thanks in advance,

 

Steve

[Guest]

Use a coated tap and rollform the thread

 

 

I tend towards Moly-dee in SS

[Span]

Moly-Dee! 400-500 rpm

[robk]

Have no fear grasshopper. Do it in here every day in 420ss. Never had much luck with roll taps that size though.

Prior to tapping we go oversize when pre-drilling @ .098 dia. drill . For taps we use OSG List 313 taps. We slow the RPM's down to 300.

[robk]

... oh yeah, coolant only. No additives to contaminate the coolant.

[chris m]

Roll tap 4-40 in 36 Rc 17-4 all the time with OSG ExoTap NRT [P/N# 14050020] and use a 2.550MM carbide tap drill. I run 341 RPM and tap with coolant only.

 

416 is pretty decent stuff so you should get your 130 pieces without even breaking a sweat

[Randy Morton @ Clem Industrial]

At my last shop I would use just regular HSS taps for doing that. We tapped 316, 416 & 17-4 H1150 constantly. Never had any issues.

 

Do as RobK said, drill over size .005" - .008" over.

[Kevangel]

quote:

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Butterfield tap lube

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that stuff "rocks" totally...when I was shopping for a machining center salesman took me to other shops to look at a machine they had sold and one of the comments on ridgid tapping was this shop had problems on breaking small 6-32taps and the solution was to run them "fast"...I was use to power feeding in bridgeport and they said run them at 1000 rpm?? been awhile, just stored that away in my brain.

[PGW Steve]

Okay guys, thanks for the tips and confidence boost!! Sometimes it is weird to try something like throwing a 7 ton machine at such a wee tap when I break them by hand. I've done 4 so far and I using 320 rpm, a #42 drill against the recommended #43 for a bit oversize. The Butterfield tap lube seems to work, but based on the recommendation of you guys I called Castrol and found a local distributor and got them to bring me in a bottle to try. I do a bit of titanium tapping here so that might be the cats rear. I've had terrible luck with using coolant for tapping as I'm using Valenite VNT900 synthetic. I hate stinky coolant and went that way but have issues with poor tapping performance, especially on aluminum.

[HEAVY METAL]

+1 i've also had better luck runnin at higher rpm with very small taps. i think a low rpm torques the tap too much for small taps

[GVM]

No problem, OSG form tap at 700 rpm Blaser coolant. Need to watch your drill size.

[kinglouie V]

anyone see what happens to a form tap in 316?

[Bruce Caulley]

quote:

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anyone see what happens to a form tap in 316?

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Yep, runs like a dream. We roll all our stainless here. A 4-40 we would run at at least 2000rpm with the coolant concentration a little higher than normal 8%-10%. We use Hocut 795B coolant and use a variety of different taps. Hahnreiter and Titex work well. We have also been trying Iscar's (YG1) new taps, but haven't given them a good enough run to comment on performance yet.

 

We also don't have the luxury of going slightly oversize on core diameter, so I know this is achievable without doing so. If the core isn't in limit then the parts are scrap

 

Bruce

[Guest]

quote:

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anyone see what happens to a form tap in 316?

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I agree with Bruce, taps fine.

 

I have found the harder materials actually tap better when you rollform.

[cadcam]

Roll taps all the way. I am with you guys the cut taps just don't hang.

[chris m]

quote:

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I have found the harder materials actually tap better when you rollform.

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over 36 - 38 Rc the tap guys really start to cringe but I roll tap anything I can possibly get away with

[toolall1]

Moly-Dee! 250-300 rpm

great stuff for stainless. agreed span.

drill it a little over. 75 % probability of thread is adiquit.for a class 2 fit

so you end up with 68% 72% thread .the go gauge range still should be within specs.

life is to short

[chowquoe^]

Are any of you using Moly-Dee on medical components, material is 17-4 S.S.