CNC Tapping Stainless Steels

[lowdowncoyote]

Greetings All,

Looking for information and experiences tapping small diameters (under 1/4") in various stainless steels, Carpenter Project 70, AISI 316, AISI 303, 440C, etc. What tap brands, geometries and techniques have been led to success? Every tap manufacturer seems to sell a $38.00 magic bullet and I can attest by my bucket of broken shanks that not all high-performance taps are created equal.

 

[jdj]

Taps that are specifically for those materials, of course, made by Guhring, OSG and Emuge should do you right.

 

[dandrummerman21]

I've had great luck with tapping 303, 304, 316L, and 17-4PH stainless using roll/form taps. Cutting taps should work fine for thru holes (get spiral point taps for that, they push the chips thru the hole), but with all the issues I've had with blind holes and cut taps, I don't even try cut taps anymore. They say that spiral flute taps should bring the chips out, allowing you to go deeper with it, but they all seem too weak to last (I've not tried any "high performance" spiral flute taps AFAIK)

Just make sure you dial in the correct diameter starting hole for your form tap, so you don't end up with a minor diameter too small or too large. Sometimes I have to ream a hole, just to keep the minor diameter within spec, after tapping.

(I've never roll tapped a size under M4, so not sure how things work when it gets that small. I'd imagine it would be OK)

 

[Neslob660]

I've had great luck with tapping 303, 304, 316L, and 17-4PH stainless using roll/form taps. Cutting taps should work fine for thru holes (get spiral point taps for that, they push the chips thru the hole), but with all the issues I've had with blind holes and cut taps, I don't even try cut taps anymore. They say that spiral flute taps should bring the chips out, allowing you to go deeper with it, but they all seem too weak to last (I've not tried any "high performance" spiral flute taps AFAIK)

Just make sure you dial in the correct diameter starting hole for your form tap, so you don't end up with a minor diameter too small or too large. Sometimes I have to ream a hole, just to keep the minor diameter within spec, after tapping.

(I've never roll tapped a size under M4, so not sure how things work when it gets that small. I'd imagine it would be OK)

Great info, Dan. This is more or less the same conclusion I've reached about tapping stainless. I prefer BALAX form taps over all. Their tech support is excellent as well.

Brian

 

[Mydrrin]

I prefer Nachi, they also have a semi form tap. For a VMC form tapping is great on most any kind of stainless.

 

[lowdowncoyote]

I have had great luck using Balax form taps as well. Stellar performance down to 0-80 and UNM sizes. The steam oxide coating is a must. 0-80 in 6AL-4V titanium was a nightmare before we were turned onto the small Balax form taps. JI Morris grinds small diameter instrument taps (spiral point, plug, and bottoming) which work great for hand tapping or chasing operations, I have struggled to get the spiral point taps to run well in the CNC.

I think I have broke off just about every brand of spiral flute tap made. Every once in a while I will get one to run, usually OSG, but not with the reliability I would like. I think my record is 150 ea. blind 6-32 holes in 316 with a single spiral flute tap at a 70% thread using oil and floating tap holders. Typically my experience with spiral flute taps has been to snap them off at retract in the first hole.

In low volume work I tend to prefer cut taps because I can often get the thread quality I am looking for quicker than fiddling with various form tap limits and drill diameters, excluding the time it takes to EDM out the first broken spiral flute tap of course. I also contend with many thin cross section parts were form tapping could cause undesirable distortion or thread witnesses.

@Mydrrin- I will have to look into the Nachi line. Thanks for the recommendation.