Need Help!- Tapping S.S.

[MikeZee]

Tapping 304 Stainless, 5/8 - 11 x 1.25 deep, blind hole. Need to do 120 holes - any clues???

[Shane123]

i have a few, dont know if its what your looking for tho......

on stainless, i like to drill the hole about 3-5 thou (.003-.005) oversized of what the chart says, have atleast a .03 chamfer before tapping. i like to use OSG elektraLUBE coated taps, and I use anchorlube on the holes for extra lubricity if needed. Anchorlube is a green paste and helps out tremendously. If your having chip build-up in the hole, you might have to run more depth passes like a peck cycle. I havent had the best of luck using spiral points for chip evacuation on stainless, and i hate it when i dont have much wall thickness around the tapped hole (example, 5/16-24 tapped hole in 7/16 diameter round stock).

you could also try thread milling i suppose....

[Boots]

I've had better luck with blind holes where you are limited to hole depth by going in after and hand tapping the hole with a "Bottom Tap". I know it will take a lot of time but is better than breaking taps. I've also used a mixture of cutting oil and Molly D.

[ctate2000]

Thread mill them. One tool should last 120 holes. Wayyyyyy better than tapping.

[MikeZee]

Almost done with the job, I actually drilled 1/64 oversize hole, power tapped about .8" deep, then finished by hand with taper, plug, finally bottoming taps to depth. Molly dee cutting fluid. i have 24 holes still to do - haven't busted a tap yet (knock on wood ).

[Boots]

Just how I would have done it......Glad to hear it's working for ya.

[djr76]

OSG VA3 Taps are specifically designed for stainless. I would of pecked tap all the way to the bottom with no need for the hand work. Otherwise thread milling would of been your best bet. Work smarter, not harder.

[Shane123]

Originally Posted by djr76 OSG VA3 Taps are specifically designed for stainless. I would of pecked tap all the way to the bottom with no need for the hand work. Otherwise thread milling would of been your best bet. Work smarter, not harder.

i agree 100% . i have a machine worth 100k, i aint gonna hand tap if i dont have to...

[MikeZee]

Finished. No busted taps. Thread milling not an option for me - manual equipment only. And "thanks" for the "work smarter, not harder" comment, that really gave me a boost - NOT!
I usually custom make prototype or small qty. runs. Took this job 'cos things were a bit slow at the time. Thanks for all replies.

[Boots]

Good Job !
A lot of people responding to these posts assume many things depending or their set-up not yours. So unless "all information" is provided you will get posts that do not relate to your particular set-up. But it is nice though that people do respond and try to help where they can. Free information and help is hard to come by when everybody wants $$ to share their ideas and or knowledge. These forums, albeit, a good source for info and help, take everything with a grain of salt and weed out the junk that doesn't apply.

[Shane123]

Originally Posted by MikeZee Finished. No busted taps. Thread milling not an option for me - manual equipment only. And "thanks" for the "work smarter, not harder" comment, that really gave me a boost - NOT! I usually custom make prototype or small qty. runs. Took this job 'cos things were a bit slow at the time. Thanks for all replies.

good job. sorry about the thread mill advice. you probably wouldnt have had that advice if we knew you were on a manual remember, better descriptions lead to better advise. but anyways, you should really look into the OSG elektralube taps if your going to continue to do stainless. 95% of our workload is stainless and its been a valuable lesson learned about using the right tooling for stainless.

[MikeZee]

I'm new in here, next time will provide more info. I wound up starting the hole (under power) with an Accupro three flute, spiral point tap. I only got one and it lasted thru' the whole job, although it was really "working" towards the end.