Joined: Aug 2017 Posts: 1,987 Threads: 90
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Location: Ripon
I try to use new, unused bits for drilling stainless. A blunt tip is worse than trying to drill with a matchstick IMHO. A light lube such as paraffin or WD40 and I've found that steady fairy heavy pressure on the drill helps. I agree that a pillar drill is almost essential. Once a drill bit has failed it is only fit for the bin as it will have been heated inadvertently and so lost its temper and the S/S will be so hard that you may need a point grinder to finish the hole. (by which time I will have lost my temper as well)
Joined: Jan 2022 Posts: 76 Threads: 19
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Location: cambridge
Car type: A7 special 34
You need to make any drill cut not rub. Rubbing greats the heat and takes the edge off the drill. Goinig in with a smaller pilot hole helps as does relieving the drill point. Good quality cutting oil is a must as well. The force required to make much above a standard 5mm diameter drill cut its own hole in a bit of 316 will be on the limit of pressure you can apply with a hand drill.
Joined: Sep 2017 Posts: 216 Threads: 29
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Try Rotabroach mini cutters, very good indeed, plus CT 90 lubricant.
Arthur
Joined: Aug 2017 Posts: 1,987 Threads: 90
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Location: Ripon
At £377.00 for 10 they need to be good! You also need to have a lot of holes to drill to justify that sort of outlay.
Joined: Aug 2017 Posts: 745 Threads: 13
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Ok Folks,
An addition to this Boring thread.
Having had to drill lots of 316 Stainless over the years.
rule 1 sharp drill start with pilot drill and open out as needed.
rule 2 slow speed most electric drills run too fast ( I use a decent cordless )
rule 3 use proper cutting fluid
rule 4 use a lot of pressure on the bit
A pillar drill on slow speed is the best tool ( Apart from using a milling machine )
Normal HSS bits are fine to use
Split point drills are very good.
As mentioned before when you cut stainless it work hardens so overheating the work or the drill bit is bad news.
Often you will find a sweet spot of drill speed and pressure and it cuts nicely, you then pull the bit out for a rest and then when you go again it is really hard to start the cut again.
I spend a few years drilling into 25mm round 316 tube to countersink and tap to 4BA I broke less taps using a cordless drill to drive them than with a tap wrench.
Joined: Aug 2017 Posts: 17 Threads: 0
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Boat building, I used a hand cranked drill with a flywheel on top. I would drill slowly and could apply good pressure and I drilled up to half inch holes with it. I had a power drill but the hand crank drill was as quick. Bruce
