Drilling into 316 stainless steel with 0.0472 hss tin covered step drill bit

I'm going nuts trying to drill into 4mm of 316 stainless steel plate with a Gurhing Step 1.2mm (.0472inch) drill bits.Using a multiple drill system or gang drill system to make multiple holes at the same time.

I'm busting bits because I know my feed and speed are just crap.

The machine is limited to 2500 rpm or slower
It's feed is controlled by a dial that looks like a dimmer switch so has to be done by watching it go down and timing it.

Any old school suggestions would be great.

2500rpm because you cannot reach recommended 40sfpm
.0008-.0012ipr
peck 100% drill dia

use powdered metal drills and avoid pecking

2500rpm because you cannot reach recommended 40sfpm
.0008-.0012ipr
peck 100% drill dia

use powdered metal drills and avoid pecking

The easiest way is to get drills specifically designed for this purpose. Such drills contain cobalt, they are easy to find in any store, although they cost more than usual. Usually, a small diameter drill is first taken, the first hole is made, then the diameter of the drill gradually increases until the desired hole diameter is reached. Stainless steel is most easily drilled with cobalt drills, they are stronger due to their composition and blunter than usual, they can even be drilled at high speeds. This will reduce the resource of the drill, but in everyday conditions, if you need to drill just a few holes, you most likely will not even notice it...

CadCamSam's feed range is about right for cobalt or HSS drills won't matter much because your speed is so slow.. 135 deg for sure either way.

To dial that feed in just do the math.

Middle of range. 0.001" IPR

2500rpm X 0.001 = 2.5ipm

If you're total travel is 1/4", adjust that dial until the down part of the cycle takes 6 seconds.

Your rpm is way too high, I work with 316 SS everyday of the week making hydraulic fittings and for HSS we stick to cutting speed of 12-15m/min which works out at 954-1192 revs and a feed of 0.004 to 0.006 thousand per rev. Also we peck hss about every 120 thousand.

Quote:

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Originally Posted by npage84

Your rpm is way too high, I work with 316 SS everyday of the week making hydraulic fittings and for HSS we stick to cutting speed of 12-15m/min which works out at 954-1192 revs and a feed of 0.004 to 0.006 thousand per rev. Also we peck hss about every 120 thousand.

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npage I think you weren't paying attention to the original post or your calculator or both. For starters, when does 15m/min equal 1192 revs on a 1.2mm (0.0472") drill. How about 3979 rpm which he can't reach anyway? The feed suggested is a mile high too. 6 thou per rev on that tiny drill? Are you punching or drilling? :-)

Want a do-over? You must have missed something.

Quote:

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Originally Posted by the_gentlegiant

npage I think you weren't paying attention to the original post or your calculator or both. For starters, when does 15m/min equal 1192 revs on a 1.2mm (0.0472") drill. How about 3979 rpm which he can't reach anyway? The feed suggested is a mile high too. 6 thou per rev on that tiny drill? Are you punching or drilling? :-)

Want a do-over? You must have missed something.

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Ahh 1.2mm Drill, sorry I seen 4mm and got that stuck in my head. What I have seen done is a dremel in a tool post for tiny drills

Quote:

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Originally Posted by npage84

Ahh 1.2mm Drill, sorry I seen 4mm and got that stuck in my head. What I have seen done is a dremel in a tool post for tiny drills

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Ha-ha... I figured a person working daily with the material in question knew what they were talking about and had simply slipped up on the facts. No harm done.

Quote:

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Originally Posted by npage84

Your rpm is way too high, I work with 316 SS everyday of the week making hydraulic fittings and for HSS we stick to cutting speed of 12-15m/min which works out at 954-1192 revs and a feed of 0.004 to 0.006 thousand per rev. Also we peck hss about every 120 thousand.

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Ditto. In my experience (and seems counter intuitive with stainless) slow the RPMs and increase the feed. You need to get through the material before it work hardens.