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Misery drilling firewall

blaplante

blaplante

Well Known Member
ok I must be missing something. I've been trying to drill the firewall just to get the 3/32 holes for the slider supports. So two holes drilled, two bits dulled and one broken! Right. After the first hole (one bit dulled, one broken) I read the internet and found I should use a Cobalt bit and slow speed and a good bit of pressure.

Followed that advice and got a second hole drilled. That drill is now so dull it won't drill aluminum.

At one bit per hole, this is not looking good.

I've searched the forums... found nothing? Maybe my old RV-6A kit has special super stainless? The answer? 357 Magnum hole starter? [Kidding] Advice?
 
good quality bit, center punch where you want the hole, slow speed with Boelube or cutting fluid, lots of pressure. If you go with a high speed and let the drill spin without cutting, the stainless heats up and work hardens.
Very sharp when it breaks through, so avoid the temptation to run your finger across the back side of the hole.
Bill Brooks
Ottawa Canada
RV-6A finishing kit
 
I found that drilling the SS firewall goes better when you oil the bit. I even used some high temp wheel bearing grease on the tip of the bit. A unibit helps too.

blaplante said:
357 Magnum hole starter? [Kidding] Advice?
Click to expand...

Maybe .17 HMR for the smaller holes :D
 
When drilling steel of any sort, ditch the air drill. It simply spins too fast, and if you do get it to go nice and slow, there's not nearly enough torque. Try a battery-powered, slow poke of a drill, lube the bit before/during each hole, go nice and slow. 1 bit should last a good many holes, maybe even the whole firewall.
 
blaplante said:
ok I must be missing something. I've been trying to drill the firewall just to get the 3/32 holes for the slider supports. So two holes drilled, two bits dulled and one broken! Right. After the first hole (one bit dulled, one broken) I read the internet and found I should use a Cobalt bit and slow speed and a good bit of pressure.

Followed that advice and got a second hole drilled. That drill is now so dull it won't drill aluminum.

At one bit per hole, this is not looking good.

I've searched the forums... found nothing? Maybe my old RV-6A kit has special super stainless? The answer? 357 Magnum hole starter? [Kidding] Advice?
Click to expand...

Bite the bullet and buy what the professionals use.....Trefolex cutting compound. This stuff is extremely effective for drilling stainless steel....also truly amazing on steel and in fact all metals.

I use it all the time for serious drilling operations. A small tin will last forever. I wouldn't be without it

PS. Forget about the boelube for steel or stainless.

So there's the answer for stainless (in fact all steels). Slow drill speed, high pressure, sharp drill...and Trefolex. You'll thank me !!! :D
 
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ss drilling

ok dont flame me but a friend of mine thats a IA told me he had to drill hundreds of holes in a ss shield and an old timer told him to geta fresh clove of garlic and run bite in clove and then drill hole he said it cut like butter if anyone tries let us know
 
If you cant find the prior lube recommendation,

get some Castrol Moly-Dee. Same supply houses will have this. Messy, but good. Very low speed and very high pressure. Have band-aides nearby;)
 
Reassuring

Thanks guys. I'm relieved to learn that I'm not the only guy turning nice sharp drill bits into tiny butter knives. Cutting stainless is a pain...

Rob
 
Let me just add..... Center punch and start with a small bit and step up. And do lube and go slow.................. slow enough to see the flute on the bit. Don't let off of the pressure.

A uni-bit does work great for larger holes after a small pilot hole.
 
keep it Cutting

As a machinist for something over 30 years, I?ve drilled literally thousands of holes in stainless, all the advice given above is good, but a trick (that has been mentioned but without enough emphases) is to KEEP the bit cutting. One revolution without making a chip, and you?re done. With small bits like a 3/32, you can turn it fairly fast (maybe about 1/3 to ? the speed you would use for aluminum) as long as you KEEP it cutting. A lot of the heat will come off in the chip, and that will help keep the drill bit temps within reason. So, use a good cutting fluid, and KEEP it cutting.
 
I'm glad this thread came up - I'm working on my engine mount right now too.

Is boelube even worth using in this application? I'm finding that I'm pushing nearly as hard as I can for several minutes and its just wearing me out. It seems like not enough lubrication on the bit to sustain that long of drilling. I have been stopping after several minutes and reapplying boelube to the bit and maybe thats my down fall.

If I were to use a cutting oil, would I apply that just once at the beginning?
 
Get some cutting oil and apply it to the bit. Drilling through the firewall should take seconds. Any longer and you created too much heat. The pilot hole is the critical one. up sizing the hole will be easy because the bit has something to bite into.

1.... center punch..... gives the bit a place to bite.
2.... small bit first
3.... cutting oil on bit..... why do they call it cutting oil? Use cutting oil.
4.... apply firm pressure for the bit size
5.... SLOW!!! drill speed... use cordless drill motor.
6.... SS firewall is thin.... this will be over in seconds.
7.... increase bit sizes in small steps to finished size......... use a uni-bit for holes over 1/4" is best.
8.... now you can talk about how easy it was to drill SS.
 
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Clarification - I'm drilling through the engine mount holes as a drill guide per instructions. There is already a pilot hole there, which is 3/16" big and need to drill to 3/8". There is probably around 1/4" thick of steel to drill through. Going to buy another new bit and some cutting oil and give it a try.

RV10_Plans_sec46-pg02.jpg
 
Why not purchase six 3/16 id. X 3/8" od. bushings and see how far off the existing holes are from the motor mount. My first pass would be with the 3/16 through a bushnig with the motor mount as a guide only after it was bolted in place with 3/16 bolts and bushings in all holes that are lined up to start with.

Remember, the SS firewall is only 26ga (.0187) after that the remaining hole will be through mild steel and will cut really nice.
 
turbo super rv-10 said:
ok dont flame me but a friend of mine thats a IA told me he had to drill hundreds of holes in a ss shield and an old timer told him to geta fresh clove of garlic and run bite in clove and then drill hole he said it cut like butter if anyone tries let us know
Click to expand...

Good for vampires and SS...who knew! :D
 
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