Tapping in stainless 304

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tcncj

Cast Iron

Joined

Dec 15, 2016

• Feb 25, 2020

• #1

I need some help with tapping some M4 thread in a part.

Material: Stainless 304

The thread goes 30mm deep
Thread size: m4

How should I tap it?
Peck tapping? Tapping it in one go?

I don't do allot of stainless.
What I did was tap the thread 10mm deep. And do the rest by hand. But due to my lack of expierence with stainless...I didn't knew it would work harden and will break taps.

 

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BT Fabrication

Titanium

Joined

Nov 3, 2019

Location

Ontario Canada

• Feb 25, 2020

• #2

tcncj said:

I need some help with tapping some M4 thread in a part.

Material: Stainless 304

The thread goes 30mm deep
Thread size: m4

How should I tap it?
Peck tapping? Tapping it in one go?

I don't do allot of stainless.
What I did was tap the thread 10mm deep. And do the rest by hand. But due to my lack of expierence with stainless...I didn't knew it would work harden and will break taps.

Click to expand...

if you are worried, use a ton of coolant with a good sharp tap. I personally like spiral taps when cutting that deep.
or you could thread mill it being how small it is and about 7.5xD

 

Dupa3872

Stainless

Joined

May 1, 2007

Location

Boston Hyde park Ma.

• Feb 25, 2020

• #3

Form Tap it. You will be happy you did.

We need to know more information about how you are doing this and what type of machine is being used. Manual Mill ? CNC Machining Center ? Rigid tapping available ?

It always help people to assist you if you give them as much as possible.

Good luck !

Make Chips Boys !

Ron

 

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tcncj

Cast Iron

Joined

Dec 15, 2016

• Feb 25, 2020

• #4

Hello

It's on a VMC (with rigid tapping)
Coolant is at 10%
Form tap can go in without pecking?

 

B

BT Fabrication

Titanium

Joined

Nov 3, 2019

Location

Ontario Canada

• Feb 25, 2020

• #5

short answer. yes.

 

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tcncj

Cast Iron

Joined

Dec 15, 2016

• Feb 25, 2020

• #6

3 of my tooling suppliers don't have a roltap which can go so deep.
The ones with a reduced shank which can go so deep, are normal taps.

 

Bobw

Diamond

Joined

Feb 8, 2005

Location

Hatch, NM Chile capital of the WORLD

• Feb 25, 2020

• #7

Blind or thru? What is it for?

Many moons ago there was a part that I made quite the # of times. 5:1 or so
deep blind hole in 304. But all it did was hold a stupid little thing that
could have been glued in, no force on it whatsoever, it just needed to be there.

It was also way down in a narrow slot.

So I drilled for a form tap, and tapped as deep as I could on the machine with
a standard form tap, and then by hand finished out the bottom 2/3rds of the
hole with a cut tap by hand(drill).

A cut tap in a form tap hole is REALLY EASY.

*Disclaimer: This wasn't a "Too Print" critical thing. It was more of a
cosmetic, reverse engineered thing.

 

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SND

Diamond

Joined

Jan 12, 2003

Location

Canada

• Feb 26, 2020

• #8

Good cutting oil, coolant is garbage for tapping stainless by comparison.
If its a through hole spiral point that can push the chip out the other side works great, otherwise form tap if they're fine with that.
If its just a few parts I usually just tap about 2xD on the machine then finish by hand if I want to be 100% I won't be leaving broken taps in there.

 

B

BT Fabrication

Titanium

Joined

Nov 3, 2019

Location

Ontario Canada

• Feb 26, 2020

• #9

SND said:

Good cutting oil, coolant is garbage for tapping stainless by comparison.
If its a through hole spiral point that can push the chip out the other side works great, otherwise form tap if they're fine with that.
If its just a few parts I usually just tap about 2xD on the machine then finish by hand if I want to be 100% I won't be leaving broken taps in there.

Click to expand...

for a form tap, yes oil is much better for lubricity

 

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Scruffy887

Titanium

Joined

Dec 17, 2012

Location

Se Ma USA

• Feb 26, 2020

• #10

BT Fabrication said:

for a form tap, yes oil is much better for lubricity

Click to expand...

+2. I form tapped thousands of holes in 304 and to make things worse, 304 rolled thread acme shaft. Normal flood coolant. Very low tapping speed gave best tap life and setting tool life parameters was key. I thing 40 minutes was max before tossing them. Quarter 20.

 

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DanASM

Hot Rolled

Joined

Mar 11, 2019

• Feb 26, 2020

• #11

Form taps will work great with oil coolant in SS. I guess you have to find one with enough relief on the shank to get your depth. Never peck anything in SS.

 

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tcncj

Cast Iron

Joined

Dec 15, 2016

• Feb 26, 2020

• #12

Thanks for all the useful information!


My tooling rep says...get a tap with a reduced shank and you can tap it as far as it can go (without pecking).
I don't want to scrap the parts, and talked to the customer.
They agreed to tap the hole from both sides only 10mm deep. So that's no issue for a normal tap.