Tapping 2-64 is Stainless steel

[Froneck]

I'm designing an item and largest tap size I can use is #2 and with limited thread depth I selected 64tpi in 304SS. It is a blind hole but I'm only doing 2 holes at this time. I do have a new 3 piece set by Morse. I've tapped a lot of holes but none as small as #2, I've done quite a bit of #3. Cutting to the bottom of a blind hole is not a problem at this time, I don't mind removing the tap after 1 thread to clean out the hole. Later if I do quite a few of the item I'll spend the $$ on high end spiral flute bottom gun taps. My concern is not to break a tap not speed. Any suggestions?

 

[Milland]

Tapping by hand or CNC? If CNC, I'd try form tapping with a dab of the most slippery tap lube I can find. On the tap, not in the hole - don't want to set up a hydrolock situation.

Spiral flute taps will be weak at this size, I'd be clenching non-stop using them even by hand. In that case use a gun with the tip removed, then a ground-to-full-thread gun to finish.

 

[Froneck]

I'm putting the holes in with a Jig Borer. But I'm hand tapping. Thread depth is short, only .090. Tap alignment is with top thru hole and .250 gap. I do use Castrol Moly Dee. I do have OSG spiral point (Gun) taps. I too thought spiral flute taps were weak but tapping 12mm X 25mm deep blind hole spiral flute bottoming spiral point taps made from powdered metal by OSG was recommended. I was surprised to see them cut great in 304SS taping under power with friction clutch tapping head. About 50 holes and still going in Engine lathe.

 

[Milland]

In that case, carry on. Not a lot of experience with PM taps, but if they're working one can't argue.

 

[Leg17]

What kind of stainless?
Some of it can be quite a bear to tap.

 

[Froneck]

I did say 304 in the first post. I've tapped quite a bit of 304 down to 3-48 and never had a problem but never as small as #2

 

[eKretz]

If you have a handle on alignment there's not much more we can give you other than a "good luck." It sounds like you should be fine, having done similar size holes before. This comes down to more of a feel thing when you're doing holes this small by hand. Know when it doesn't feel right and quit while you're ahead. Check for misalignment or switch taps.

 

[TKassoc]

#2 in stainless shouldn't be bad with sharp taps. I find that hand tapping down at that size works best with a shop made holder for the tap. I use a bit scrap rod stock in the 3/8" range to reduce my leverage for more sensitivity. Drill a reasonably close fitting hole and glue the tap into the rod. For speed use UV cure superglue and a quick heating with a propane torch will kill the bond and make the shank of a broken tap pop out for re-use.




This is a M1 and a 0000-160 tap for reference. At this point I haven't broken an M1 in a year or so...my record on 0000-160 in 304 stainless is not so good and I've gone to custom threadmills instead.

 

[Milland]

my record on 0000-160 in 304 stainless is not so good and I've gone to custom threadmills instead.

Whaa? You can get a threadmill for 0000-160?? Is joke, yes? It would need a negative shank diameter (well, almost).

 

[FredC]

Another way to drive small taps. The guides have a ball under the O-rings to keep the taps from dropping out when used on a CNC mill (My small mill does not have spindle reverse). The knurled wheels have a set screw and I grind a small flat on the tap for a nonslip drive.

 

[FredC]

Whaa? You can get a threadmill for 0000-160?? Is joke, yes? It would need a negative shank diameter (well, almost).

Some people are magicians. I am impressed.

The smallest threads I have ever milled are 3-56.

 

[TKassoc]

Whaa? You can get a threadmill for 0000-160?? Is joke, yes? It would need a negative shank diameter (well, almost).

Quite real. The WhizCut ones are stocked in the US but didn't have enough reach for me so I also got some M0.3x0.8 imported by Mikron too. They run decent but not amazing. They're one hell of a lot better than taps you can get at that size which only seem suited to free machining brass in watch mid-plates.

 

[Milland]

Good 'eavens. I'll check into those, thanks for the info.

 

[DanASM]

I have to tap 2-56 threads in 303 and grade 5 titanium soon. Those PM form taps from OSG work wonders for me in 316 SS (5-40). I never tap under 4-40 threads, but this is done all the time by others. Its not like it cant be done.

Good Luck

 

[MaxPrairie]

Some people are magicians. I am impressed.

The smallest threads I have ever milled are 3-56.

I have some 2-56 threadmills from carmex. I am sure they go smaller still.

 

[BugRobotics]

I know you mentioned you are cut tapping and if it's working cool but here is another vote for form taps. I form tap 4-40, 2-56 and 1-64 in 17-4 quite a bit. Granted 17-4 is nicer than most 304. I use a Procunier tapping head. Once you get a feel and get your hole size correct it's a pretty stress free process. Splurge for the nice coatings for your specific material. I've had great luck with OSGs offerings but a bunch of companies offer great stuff.

Not sure what your using for lubrication but I've found that stainless likes Anchorlube. It seems like the waxiness seems to help keep the stiction down.

 

[Rollerman]

Old fashion Tap Magic, not the "New and Improved" stuff.
Old Tap Magic is magic, new stuff is not!

 

[eKretz]

Old fashion Tap Magic, not the "New and Improved" stuff.
Old Tap Magic is magic, new stuff is not!

*Schwing!* Good luck finding it though.

 

[SigurdACVW]

I'll start off by saying I have never tapped any stainless that small, only DME #2. I hand-tap those little 2-56 holes for the slide catch screws. Plain HSS tap, Mobilmet 766, 1/8 turn at a time, bench block drilled for the tap and clamped to the workpiece.

 

[Froneck]

Item I'm tapping is similar to a .531" wide U. sides of the U are .141", opening .250". .089 (#43 drill) thru one side, might use #44 drill, tap will probably cut a shallow thread. Use 5/64" solid carbide spotting drill as center drill on other side of .250" wide gap. Drill #50 maybe #49 as deep as possible in .141" thick other side but can't be thru. Thru hole on one side will act a tap guide. I plan to make a "Tap Wench" as seen in Joe Pieczynski's videos. He's tapping #1 with a thick knurled washer. I do have the complete set of Starrett 91 tap wrenches and another that looks exactly like a 91, has no name or number on it, is only 3" long but is too big for a #2 tap. I've broken a few 3-48 taps with it. But I've used it on 100's of 3-48 tapped holes. Yes I do have some old Tap Magic with Triclore I keep hidden for special tapping and have Moly Dee.