Author Topic: Tapping 6 mm threads in 304 stainless  (Read 5700 times)

Online smiffy

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Tapping 6 mm threads in 304 stainless
« on: April 17, 2016, 03:23:37 PM »
   I need to tap 6 mm threads in 12 mm 304 stainless and I have 180 holes to tap .
  So the question is what is the best tap ,straight flute or spiral .I would also like to use a tapping head .
   What speed to run at and best tapping compound to use?
   Thanks Mike

Offline Will_D

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Re: Tapping 6 mm threads in 304 stainless
« Reply #1 on: April 17, 2016, 07:12:49 PM »
I have been tappping 3,4,6 mm into 303/304 using the Swiss-Tech spiral taps.

I start them in the mill at very low speed, allow them to cut say 4 mm (this is for blind, 8 or 10 mm deep holes) of thread and then finish by hand.

I am sure that a tapping head would be even better.

These taps are designed for machine use. Normal straight flutes are NOT! They produce 3 ribbons of swarf like what a drill does (well they only do 2) that clears the tap and the hole. Straight taps produce chips that need to be backed off and even removed after only a few mm of depth.
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Offline sparky961

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Re: Tapping 6 mm threads in 304 stainless
« Reply #2 on: April 17, 2016, 08:56:12 PM »
I'll assume the holes are tapped through, not blind. There are distinct differences either way.

If you can find a name brand 2-flute spiral point machine tap or three, you shouldn't have to fight with it. Run fairly slow, like 50 to 100 RPM. This is slower than the SFM works out to but will give you better control. Drill slightly oversize if you can, giving you 50 to 60 percent thread. Studies show the loss in strength is negligible. Use a rigid clamped setup with positive alignment of the previously drilled hole to avoid flexing the tap. RapidTap cutting oil works well for me in this locale but any decent cutting oil should give similar results. Run the tap all the way through as far as you dare before reversing to push the chips out the bottom of the hole. Reversing before fully cutting off the chip can bind and break a machine tap, unlike a hand tap that's me and to reverse often.

 Definitely avoid spiral flute taps unless machine tapping blind. They are the weakest of the lot.

Offline Jonny

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Re: Tapping 6 mm threads in 304 stainless
« Reply #3 on: April 18, 2016, 06:58:39 AM »
Assume drilling and tapping in a mill on centre.

I generally use the coloured ring taps either red for hard materials, yellow or blue for aluminiums, never tried the green. Having used each colour I would say the red works best powered in and out the job on aluminiums or the blue against whats recommended.
http://www.ebay.co.uk/itm/M6-x-1-0-SPIRAL-POINT-RED-RING-M-C-TAP-DIN371-EUROPA-TOOL-TM27160600-NEW-BOXED-/200922962861?hash=item2ec7f11bad:g:ajgAAOSw~CRTrWKV

Green never tried for softer materials than red
http://www.ebay.co.uk/itm/M5-x-0-8-SPIRAL-POINT-GREEN-RINGED-TAP-EUROPA-TOOL-TM31300500-NEW-BOXED-A7-/201284713657

Plenty of cutting oil.

Online smiffy

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Re: Tapping 6 mm threads in 304 stainless
« Reply #4 on: April 18, 2016, 04:04:48 PM »
Thanks for the replies I will buy a selection of different taps and see how they perform .
                       Thanks Mike

Offline sparky961

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Re: Tapping 6 mm threads in 304 stainless
« Reply #5 on: April 18, 2016, 04:05:46 PM »
I generally use the coloured ring taps either red for hard materials, yellow or blue for aluminiums, never tried the green.

Just a heads up - check the intended application for the tap, not just colour. There is no standard that can be relied on.

304 SS isn't hard, but it quickly work hardens is your speed is too fast or feed too light. Turn as slow as time allows and feed as hard as machine and tools allow. A generalization, of course, but not far off.

Offline ieezitin

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Re: Tapping 6 mm threads in 304 stainless
« Reply #6 on: April 18, 2016, 05:02:42 PM »
Smiffy

Spiral taps sure are the tits but 180 holes is a project worth planning out. Give thread-forming taps a look...( a form tool tap) they are more expensive but are very unlikely to snap or dull on the right conditions like spiral or regular taps... they make a Tin coating for stainless which is forms with ease.

They thread better and the threads are formed harder and sharper due to work hardening with the added benefit of no mess with chips so you don't have to clean out the holes, they do not adhere to the regular pilot hole size charts so you need to find out what the correct size to drill first for that size tap. Power tapping will be a doddel and if you are in a blind hole the plug can be finished off by hand at 6mm. one tap is probably capable of doing all 180 holes. They leave a double peak on the thread which looks a little funny but its a part of the process.

Hit these cats up they make an outstanding product, Also somewhere in the website they show a little video on how these taps work.

http://balax.com/browse-products?category=7


Hope this helps brother.... Happy tapping.

Anthony.
If you cant fix it, get another hobby.

Offline krv3000

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Re: Tapping 6 mm threads in 304 stainless
« Reply #7 on: April 18, 2016, 05:38:26 PM »
hi just my bit I wont go it to the maths but drill your taping hole 1 two 2% bigger for stainless

Offline j1312v

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Re: Tapping 6 mm threads in 304 stainless
« Reply #8 on: April 19, 2016, 09:57:28 AM »
 I normally go 0.1 bigger or more on the drill and it helps quite a LOT...that gives aprox. a 65% full thread the witch is a small percent less stronger as a 75% thread as per the standard formula.

Offline DavidA

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Re: Tapping 6 mm threads in 304 stainless
« Reply #9 on: April 19, 2016, 02:06:52 PM »
I did a lot of tapping of stainless steel when I worked at the chicken factory.

I always used a 5.2 mm drill and 'food lube' as a cutting fluid.  Never broke a tap in five years.

Dave.

Offline krv3000

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Re: Tapping 6 mm threads in 304 stainless
« Reply #10 on: April 19, 2016, 04:07:06 PM »
brill

Offline sparky961

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Re: Tapping 6 mm threads in 304 stainless
« Reply #11 on: April 19, 2016, 04:34:07 PM »
I did a lot of tapping of stainless steel when I worked at the chicken factory.

I always used a 5.2 mm drill and 'food lube' as a cutting fluid.  Never broke a tap in five years.

Dave.

"Food Lube" .... makes me think of greasing the chicken before it goes through the machine.

A little pet peve of mine is seeing people drown the tap in cutting oil.  This is usually unnecessary and wasteful.  As long as there's a film, and enough that it doesn't get hot and all turn to smoke, you've got enough.  Anything that drips, runs or flies off the tool isn't doing you any good.  Many coatings help by being somewhat porous and keeping an amount of oil near the tool's surface.