Seeking Drilling Parameters for Stainless Steel 401

[hallowed]

Lately I have damaged tens of drills and wasted hours developing a job in Stainless Steel 401!

Here are some of the job specs:
Material: Stainless Steel 401
Hardness: 32-35 HRC
Hole dia.: 2.0 mm
No. of holes: 5,230

Has anyone been through this before?
Would really appreciate any suggestions from anybody here regarding the SPEED, FEED, DRILL MAKE for this job.

Thanks!

[azmachinist]

How deep are the holes?

What are you using to spot the holes with?

Is this a rigid set-up? Very rigid as in "rock-solid' This will determine drill material.

Need a little more information.

I would say your looking at using carbide and you need to establish tool life.

Post back more about the exact application we are looking at here.

Regards

R.J.

[mattstawicki]

hallowed,

Need more info. First, are you sure it's 401ss? I've never heard of it. Looked through all material books, even did a google search, and can't find anything on it.

Is this Stainless Steel plate, or bar?
What kind of machine are you using?
Oil/coolant type?
What type of drills are you currently using? (rpm, feed?)

Matt

[hallowed]

Thanks for you replies guys!

The material is indeed SS 401 and the holes are to be dug on a circular sleeve abt. 200 mm in dia. Hole dia.- 2.0 mm & Hole depth - 20 mm

Attached is a pic of the mounted job if tht helps.

Let me know.

Thanks!

[mattstawicki]

hallowed,

Saw the picture........Merry Christmas!

Looks like you're doing it on a VMC with a 4th-axis. Also doesn't look like you're spotting the holes. That could be part of the problem.

If you're using a split point, and starting out really slow, you could be work hardening the material. You can also run into a problem with the drill walking. Still can't find any info on 401ss, but if it's anything like 316L, I run a part that has a 10-32 rolled thread. Use a #16 (.177") dia. drill @ 1800 rpm, and a .0015" ipr feed. That works out to 83.4 sfm, and 2.7 ipm.

Granted, your drill is half that size, so you have to reduce that feed, but I would think that you could maintain that sfm. For a 2mm drill, that works out to 4046 rpm, and I'd get that feed down to no more than .001 ipr, in fact, you may want to keep it at about .0007" ipr. I can get wimpy at times - especially when working on something where I stand to loose a lot of money if things go wrong. That .0007"ipr works out to 2.83 ipm. But this is what I'd do in 316L.

20mm is pretty deep for a 2mm drill, and given the fact that you're drilling from above, you have to lift the chips out of the hole. You also have to be careful not to feed too slow or you'll work harden the material. You ought to be able to drill at least 3x the diameter for the first peck, and then probably have to back off to 1.5x the diameter for the next peck or two, 1x the diameter for the next one or two, and you will probably have to back off to .5x the diameter for the remaining pecks.

Like I said, I can't find anything on 401ss, but my initial thought, if I was trying to run it, was to run it somewhere around 50-60 sfm., with a .0007ipr. feed. With the .07874 drill, that would be between 2425-2910 rpm's (in which case I'd probably try 2700 rpm), and the feed in IPM would be 1.89.

What rpm are you using now?
Feed?
Are you spotting? (maybe I can't see it in the picture)
What kind of drill are you using? (I use Nachi Cobalts in 316L)
I see you're using toilet water. Have you tried increasing the concentration?

Matt

[azmachinist]

I am unable to find anything on this 401 Stainless also. I have searched everywhere. I also registered at this Steel database website and they have no record of it. http://www.key-to-steel.com/ I registered for the demo and It shows nothing for 80,000 steel entries. Are you sure it is not 410 stainless? I can not even find anything that is made from it.

Regards,

RJ

[Mitsui Seiki]

Use Dormers carbide drills.The shortest drills you can find.

[hallowed]

Guys,

The material is indeed SS410 and NOT SS401 as mentioned before :|
My mistake. Sorry for all the confusion it caused.
I can vouch that at least the job description is correct

Any suggestions for SS410?

Thanks again for all your replies!

[kalmah]

Your material isn't easy to cut (25%Cr, 19% Ni): GOOD LUCK.

Use SUS drill (in HSS) from Nachi-fujikoshi. It produces only short chip in austenitic stainless steel !!!
FOr this reason, pecking cycle isn't requiered until a depth of 4xD.
Cutting parameter:
Vc = 20m/min (3200 RPM)
Vf = 150 mm/min
Drilling in one time

Why ??
All competitor drill (in carbide or HSS) without oil hole produce long chip in super austenitic stainless steel. Long chip => chipping and pecking cycle required.

[hallowed]

Thanks Kalmah!

Never used Nakamichi before although heard a lot about it.
Will give it a shot and let you know if that works..

[kalmah]

http://www.nachi-fujikoshi.co.jp/eng/new/pre/020422.htm

Here is the link.

I've tried in 316 and 904-l stainless steel. Great performance.