What’s the secret to drilling stainless steel?
Posted: Fri May 20, 2016 10:15 pm
by Bacon8tor
I’m working on the wing spars on my Onex and having a heck of a time updrilling the stainless steel outboard pivot plates, W18-15. Granted it’s thick stock but sometimes even new high quality bits just spin, dull, and make no progress. Sometimes a bit will smoke a little then get through. I might get two or three holes with that bit before dulling. I’m using high speed and cutting fluid. Is this normal? Should I just plan on a new bit for each hole?
Re: What’s the secret to drilling stainless steel?
Posted: Fri May 20, 2016 10:19 pm
by fastj22
slow speed. don’t let it get hot. Getting hot only work hardens the stainless steel and makes it harder. Same thing for drilling out stainless rivets.
Re: What’s the secret to drilling stainless steel?
Posted: Fri May 20, 2016 10:30 pm
by wlarson861
In order to drill stainless steel you need to use a Cobalt bit. Nothing else will cut the stainless steel or titanium in the gear legs with any degree of success.
Re: What’s the secret to drilling stainless steel?
Posted: Fri May 20, 2016 11:04 pm
by pchuckie
I don’t have experience drilling SS on aircraft parts, but tons of experience drilling SS shower surrounds. Like previously mentioned, slow speed and good bits. Most people drill holes way to fast and way to much pressure.
Re: What’s the secret to drilling stainless steel?
Posted: Fri May 20, 2016 11:21 pm
by Bryan Cotton
Slow speed, high pressure, oil.
Re: What’s the secret to drilling stainless steel?
Posted: Sat May 21, 2016 12:29 am
by mike.smith
Like REALLY, REALLY, REALLY slow speeds! A snail’s pace.
Re: What’s the secret to drilling stainless steel?
Posted: Sat May 21, 2016 9:14 am
by DCASonex
Along with slow speeds, make sure bit keeps cutting. Stainless Steel is such a poor conductor of heat that very localized high temperatures can quickly develop, both hardening the Stainless steel and damaging the bit. Use of light pressure, thinking it will save the bit, does just the opposite. New sharp bits will cut with less pressure. In general, for most all materials, not just SS, 135 degree spit point bits are good for first holes, but the old standby 118 degree bits are better for enlarging holes as they are less apt to grab with pressure.
David A.
Re: What’s the secret to drilling stainless steel?
Posted: Sat May 21, 2016 9:49 am
by Bryan Cotton
Here is a short video showing the slow speed.
https://youtu.be/8zfjsZKSmuY
Re: What’s the secret to drilling stainless steel?
Posted: Sat May 21, 2016 9:12 pm
by sonex892.
DCASonex wrote:Along with slow speeds, make sure bit keeps cutting.
David A.
David makes a good point with this. If there is no metal spiraling out immediately, something is wrong. Stop or it will get hot real quick. If it is a new bit and you are going slow. Not using enough pressure is most likely the problem. If you have heated the metal you can expect to throw away every new drill used to fix that hole.
Using the correct technique and cutting fluid I used to get 50 to 100 uses from 1/8" bits in stainless electrical cabinets. Pilot drilling requires more pressure than updrilling. Just never get it hot
Steve
Sonex 892
Re: What’s the secret to drilling stainless steel?
Posted: Sat May 21, 2016 10:27 pm
by paulonex
plates on the onex wing joint are made of 4140 to my understanding and are not SS
Having said that the drilling comment in general are correct
Note 4140 has corrosion resistance properties, but is not classified as a “stainless steel”