drilling stainless steel

[johnnyboy]

Some info for those who might be interested!

Drilling stainless steel - type din 1.4301,  thickness of plate, 10mm, hole size 5mm, drill speed 800 rpm, hand feed, very good quality tungsten carbide drill bit.

result: 7 holes then failure.

problem: definately need flood coolant on this. drill speed to high?  With careful feed and flood coolant should be no problem...

to be continuted!

cheers,
Johnnyboy

[Lew_Merrick_PE]

JohnnyBoy,

OK, I do not recognize the DIN 1.4301 alloy designation except to assume that is something similar to the US ASTM 301 type stainless.  My best guess is that, like ASTM 301, the material work hardens.  (1) Coolant/lubricant -- a clay dam filled with coolant/lubricant (call it 15-20mm ID X 25mm tall) should make things better.  I really like the Tapmatic Gold lubricant.  (2) 800 RPM does not sound terribly high for a carbide drill bit and slowing it down a bit should not hurt, but that is a guess.  It is more likely a matter of insufficient feed (301 work hardens when taking light cuts) and/or minor damage to the cutting lips of your bit catching up with you.  I regularly hone the cutting edges of a drill when working in 20X or 30X type stainless.

Does this help?

[philf]

Drilling stainless steel - type din 1.4301,  thickness of plate, 10mm, hole size 5mm, drill speed 800 rpm, hand feed, very good quality tungsten carbide drill bit.

result: 7 holes then failure.

problem: definately need flood coolant on this. drill speed to high?  With careful feed and flood coolant should be no problem...

Johnnyboy

johnnyboy,

I don't know din 1.4301 either but I think 800 rpm is about the right speed for HSS. For carbide you should ideally be 3 to 4 times faster (2,900 rpm) and a feed rate of about 230mm/min. (According to the GWizard feeds/speeds calculator.)

As Lew says, pussyfooting with low feeds and speeds can lead to work hardening with some materials.

Phil.

[johnnyboy]

Thanks guys. Equivalent grade 304ss - trust me a wasn't pussy footing!
I will get another couple of tools and do some tests - coolant will be the key
Here I believe! Then I can safely increase speed.

Thanks, Johnny

[Arbalist]

Something similar happened to me. I had to anneal the piece to continue and went through ok with a fresh 6mm bit at 500 rpm.

[johnnyboy]

When i get some more drill bits I will test and report back. 303ss is like butter by comparison...

[Jonny]

G304 aint bad just need decent drills and get a feel for it cutting.
G316S11 can be a bitch, again with decent tools quite doable.
G303 easy

Point being they don't make drills like they used to.