Best lubricant for cutting SS?

[Flying Scotsman]

Hoping to finish up the right wing in the next couple of weeks and get started on the fuselage, and the first task involves messing with the stainless steel firewall. I ordered some new bits that are more suited to drilling SS, but also want to make sure to use a good lube on them while drilling. Any suggestions?

 

[adburhoe]

anything will do.

You can buy cutting oil. Straight cutting oil is petroleum based, but the water miscible fluids that many machinists use are mineral or vegetable based. Unless you are doing high production, and pushing cutting tools to their limits, just grab some vegetable oil from the kitchen, or use a squirt of motor oil. It'll do the trick.

 

[gasman]

Use a sharp bit and drill SLOW..... and good pressure. If the bit stops cutting, the SS will harden and the cutting will stop. Use cutting oil and don't let the SS get hot! A UNI-BIT works great. How slow? Slow enough to see the flute come around.

 

[terrykohler]

I believe you can purchase Boelube from Aircraft Spruce in both liquid as well as solid form. Stainless is difficult to cut without the proper lube due to the abrasive properties of the alloying elements. As already mentioned, drill slowly with continuous pressure. If the bit starts "chirping", it's already toast. Replace immediately as a dull bit will only contribute to additional work hardening of the surface you're trying to drill. Watch the burrs and edges, they can cause a lot of damage.

 

[yakdriver]

Good Unibits and Boelube are a great combination. I did all my firewall holes with one Unibit and it is still going strong. Don

 

[Jeff R]

I had good luck with regular drill bits, a unibit and Boelube. My biggest issue was that the breakthru metal was super sharp. My blood is literally on my firewall! It is also more difficult to deburr. What takes a turn or two on aluminum takes a lot of cranking with SS. Also, even though it is difficult to drill, the thin material makes it easy to produce undesired dimpling with the drill bit. I mean, if you apply a lot of pressure, the metal will dimple inward, and it is a pain to file it down. Of course, the thin metal is easy to dimple with dimple dies, too.

 

[mike newall]

If you end up with sharp burrs on the other side, use a Dremel with either a sanding drum or the edge of a reinforced cutting wheel - lightly dress the spiky bit and it cleans it off a treat.

 

[Mike S]

Back in another life, I was a machinist for Garrett/AirResearch.

Made jet engine innards. I worked with lots of exotic materials.

We used various cutting compounds from Houghton .

You might see if there is a distributor in your area that can get you a small batch of the correct fluid for Stainless.

Good luck.