Drilling SS question.

[Hoohaa]

I need to install a new bow roller which will involve drilling 4* 3/8 holes in the SS plate shown in the pic.
I was hoping someone could tell me the right way to do it. ie. Pilot holes, punches, decent drill bits, drill speeds ect.
The main problem I am facing is doing while the boats on the mooring, We could lug a large generator out to the boat. Not easy but doable or the preferred option is just to use a good cordless drill. So. what are the tricks to getting it right the first time? Its going on the Port side.

Thanks. Jeff

Attachment 55889

[40 South]

Slow speed, pilot holes increasing in size and cobolt tipped drill bits. Let the drill do the work, don't apply too much pressure.

[Bash]

Decent bits? Absolutely--figure on one per hole with the plate in the photo. Colbolt is best.
Drill speed? Sloooooow.
Oil? Oh yeah.

A good strategy would be to drill one hole per day. No more, no less. The more you rush a job like this, the longer it takes.

[daddle]

Slow RPM. As much pressure as you can apply. Use some heavy oil. Put your shoulder into it.

Do not let the bit spin at high speed even for an instant as the steel will harden. Keep the material cool. You want big fat curly chips. Not filings. 4 Turns per second of the bit is plenty.

I would drill a 1/8" pilot hole. Them the 3/8" hole.

Buy new drill bits.

[Hoohaa]

This is gold. Thanks for the quick responses.
So, should I drill it in 2 or 3 goes, increasing the size each time? Which might save the larger drill bit or should I just bight the bullet and buy new bits for each of the holes, don't mind either way, which ever works.
Jeff

[Hoohaa]

What's the good oil?

[40 South]

Drill in 3 or 4 stages. Cobolt drills are much better than regular high speed steel drill bits for SS. Buy new drill bits as you have several holes to drill!

[geoffh]

I use 'Rapid Tap' heavy duty cutting fluid, it is a small yellow can 4fl oz or 118ml.It has worked well for me , drilling or cutting threads. Cheers

[daddle]

Old motor oil is good enough. Thread cutting oil is better. Found near the plumbing threading dies in the stores.

[Stumble]

We have actually found that the best oil for cutting/drilling is actually extra refined olive oil (the 'not for human consumption' if possible). It's basically free, and when it drips into the water you don't have a problem with the coast guard.

As mentioned, slow speed, lots of preassure, and sharp cobalt bits FTW.

[FlyingCloud1937]

All of the above, with one caveat. YOU NEED A HIGH TORQUE SLOW SPEED.

With-out the high torque drill motor slow speed won't have the cahonas.

So we are talking a good 1/2 drive Milwaukee, and a bat drive won't have it. So bring the portable ac gen.

Use a good cutting oil that won't smoke at less then 800F. Like the finest eeextra V olive oil. Cobalt is a must, slow and drill press weight, plus motor torque

Lloyd

[Wotname]

What the others said about low speed, high torque and as much pressure as you can muster.

For lube, I have tried heaps but find good old dishwashing detergent among the best - and it is easy to clean up afterwards.

[irwin37]

Its funny how many different ways there are, I always drilled stainless with lots of force looked for the best drill bits, lots of oil, and was told once started never stop as the stainless will harden when it cools. I hated drilling stainless.

This year I spoke with a machinist I know and he said drill in lots of steps starting small and work your way up, don't force it but let the drill do the work. He stated that most people apply way too much force which will dull the drill bit right from the start.

Drilled half dozen 1/4 inch holes in 1/4 inch SS last week using some every day bits I have had be using for years and a battery drill and no oil. Started holes 3/32 pilot and worked my way up in 5 steps, did not push hard at all and was surprised that each hole was done in a matter of minutes.

Learn something new every day. Carefull with the small bits, they brake easily.

[Cotemar]

Drilling Stainless Steel,

Stainless Steel can be nasty to drill. Put on safety glasses. Just use sharp ordinary high speed steel drill bits in a hand drill. Bring extra bits, as you will need them. If you want to step up, use split-point cobalt steel bits. Start with a punch on your location, then use a drill half the size or smaller and work your way upto the final size drill.

Success is enhanced with good lubrication and keeping the drill cool. Slow down the spindle, to between 150 to 400 RPM and when you bring down the drill, drive it home forcefully.

The material tends to work-harden. Slow drill speed , and steady firm pressure on the drill to make it CUT, (never hesitate) so it will not scrape its way through. A spiral chip coming off that drill is better than making dust-sized particles.

Once the SS work-hardens your pretty much done, as only a carbide drill will get throught it at that point.

[HopCar]

The only thing I have to add to the above is that Cobalt bits are much easier to break than regular HSS bits. Use a drill press if you can, have lots of spare bits if you can't. Keep the drill straight.