Drilling Stainless

[Burdekin]

i have some wee stainless machine screws I need to drill out but not having much luck with my normal drill bits, what’s good for drilling stainless in small sizes?

 

[Paul.]

Cobalt drills, sit down when you look at the price of decent ones though.

 

[Burdekin]

Cobalt drills, sit down when you look at the price of decent ones though.

Thanks.

Much swearing today. Think the screws are the wrong type and either locktighted in or cross threaded.

 

[Ashley Burton]

What I've heard many of times is use a sharp bit, Drill slowly, Use good pressure & try to keep the stainless as cool as possible.

 

[Paul.]

For drilling and tapping stainless I use Rocol RTD, either paste or fluid, again not cheap but if you do any amount of work with stainless is well worth having on the shelf.

 

[Hitch]

Decent bits are a must really. Decent pressure, and a slow speed.
Are you drilling them with a pistol drill?
Ive found cobalt bits drill well, but dont like any sideways force.

Stainless screws in stainless holes/nuts by chance? Probably galled up.

 

[jerrytug]

Yes to above..keep the pressure on, if the bit is turning in the hole without cutting you can work-harden the job, making it very tricky to get through. Been there done that

 

[Burdekin]

Decent bits are a must really. Decent pressure, and a slow speed.
Are you drilling them with a pistol drill?
Ive found cobalt bits drill well, but dont like any sideways force.

Stainless screws in stainless holes/nuts by chance? Probably galled up.

No in mild steel. Someone has replaced the steel screws with stainless and don’t really sit in properly, so either cross threaded or glued in. I thought the remaining steel ones might be a problem but with some spray on them cam straight out.

 

[Richard.]

Cobalt bits ain’t too bad a price if you just get a few smaller ones which is all you’ll need to drill out screws. Dormer a777 being my favourite.
Chances are you’ve made them really hard now by wrecking your other drills trying to get through them so you may even struggle to get a cobalt to bite. Go in with a very small bit to start and hope the very centre of the screw is still soft enough to pilot.
Don’t go mad on the pressure apply just enough to keep the bit cutting. Lots of people think you need to put loads of force on when drilling stainless but it does more harm than good. Too much will either bust the bit or blunt it quick and again make it rub and make it hard. Work hardened stainless steel can be so hard that in a lot of cases you simply need to anneal it to get it to cut again. I don’t like the fluid too much for drilling I find it a bit runny and not as effective as the compound for staying where you want it. The fluid is best for turning

 

[brightspark]

rocol rtd for me every time and smells nice or templars temaxol it stinks though but if you get it free who cares

 

[Hitch]

Used CT90 for sometime now, even at work (99.9% stainless steel fabrications) I prefer it in the squeezy bottles, much thicker than that in the aerosol cans.

 

[brightspark]

I have some rocol that I thin down with white spirit and dab some on with a squeezy bottle

 

[Burdekin]

Ordered some bit, all got a bit expensive for some wee screws.

The screws are 6-40 UNF so assume the stainless screws that are tight maybe 3.5mm. That tested my eyesight with the thread gauge.

 

[Paul.]

Run them nice and slow and use some cutting fluid, they are quite brittle so don't press hard and risk flexing the drill, I have a chuck that fits a cordless screwdriver which runs very small drills quite nicely.

 

[Richard.]

rocol rtd for me every time and smells nice or templars temaxol it stinks though but if you get it free who cares

It’s all I use now.
The compound is mega cheap really a small tin lasts for years.
I do fly through the rtd liquid much quicker on the lathe.

 

[brightspark]

It’s all I use now.
The compound is mega cheap really a small tin lasts for years.
I do fly through the rtd liquid much quicker on the lathe.

I bought a gallon tin from farm sale for a tenner will last me till I die

 

[ajlelectronics]

Cobalt bits. Be careful when choosing, the cheap ones are Cobalt COLOURED.

 

[slim_boy_fat]

or glued in

Worth trying the tip of a soldering iron on them, just in case?

 

[Burdekin]

Worth trying the tip of a soldering iron on them, just in case?

Good idea for the remaining screws...

 

[MattH]

I’d be reaching for the left hand bits for this job.
Better to wind the screw out than drill all the way through.