Drill bit for stainless steel.

[james.d]

I need to drill through stainless steel, I bought 2 drill bits (5mm)  locally and was assured they would be fine but didn't work and only left a tiny pin size dent.

I see people recommend cobalt, titanium or HSS as being the best drill bit.

I'll make the trip to Homepro, but 

could any let me know which to get for a one off job of drilling two holes. This will be the only time I'll need to drill through stainless steel.

Thank you.

Edited January 8, 2021 by james.d

[CharlieH]

For info:

 

 Cobalt (HSCO) is considered an upgrade from HSS because it includes 5-8% Cobalt blended into the base material. This is a great option for drilling into harder steel as well as stainless steel grades. Carbide (Carb) is the hardest and most brittle of the drill bit materials. 

 

source: https://www.grainger.com/know-how/industry/metalworking/kh-which-drill-bit-does-the-job

 

 

[Kwasaki]

Global house have high quality steel drill bits, I guess Home-pro should to..

Sounds like you were sold drill bits for wood.

 

[Dumbastheycome]

I would suggest drilling a pilot hole with a 2.5 mm bit first. Drill rotation speed  should be  kept low .

Stainless  steel is notorious  for "work hardening " as it is  drilled so is important  to drill as  hard and slow as  can. HSS bits  will blunt  quickly .

Edited January 8, 2021 by Dumbastheycome
explainer

[DaLa]

Try a good quality (??) 2 or 3 mm drill bit first. And remember twice the speed , half the feed.

 

(Dumbastheycome beat me too it)

Edited January 8, 2021 by DaLa

[james.d]

Thanks all, I'll go for cobalt hsco and also get a smaller 3mm for pilot hole.

And use a low slow speed 

 

Thanks again.

 

[VocalNeal]

29 minutes ago, james.d said:

I bought 2 drill bits (5mm)  locally

 

If we knew where "locally" was we might be able to help. 

 

Std. drill angle is about 118 deg. whereas for stainless or hard steel you need 135 deg.

[james.d]

2 minutes ago, VocalNeal said:

 

If we knew where "locally" was we might be able to help. 

 

Std. drill angle is about 118 deg. whereas for stainless or hard steel you need 135 deg.

Thanks Neal,  l got them in Saimai at the local ironmongery.

 

The 135 degree is something else for me to check.

 

Thanks.

 

[86Tiger]

It is not only about the bit.

 

To be successful drilling stainless you must use a good cutting fluid, very liberally, as in keep the stream flowing on point of contact while bit is turning.

 

One bit can make many holes if you keep it cool with cutting fluid.  Once the bit gets over heated may as well be using a tooth pick.

[VocalNeal]

Also keep the pressure on. If not cutting the drill or the steel will just burnish. Losts of coolant. If thin stainless gate or..... then not too much problem.

[shaemus]

Some Good avdice here.

 

What thickness is the material you are drilling?  is it 204, 304, 316?

 

Make sure you get a decent punch and get a decent start so you bit doesn't wander, Set you drill on slow and high torque, use a constant pressure and keep the bit perpendicular, you can use water to keep things cool. you can make a little dam using blue tack or similar if you workpiece is horizontal. Heat is the killer here

 

Dont breath the smoke that comes of the stainless as this will contain hexavailant chromium which is very bad for you. I  spent half a day in an induction for a job once that was using all stainless electrical ladder. so we had to go through that.

 

If your bit does start smoking or first starts screaching  then your bit is cooked

[fredob43]

Most S/S shops have the correct Drill bits. When they did my S/S they gave me a couple of drills just in case I wanted to drill anything. As others have said start with a small one and progress up.   

[mogandave]

As someone else said, you likely ran the drill too fast and burned the tip.  

 

The big advantage of the 135 deg bits is that they are typically ground with a split point which allows for much easier starts and much less “walking”.

 

How thick is the material? I would not bother with a pilot hole (5mm is already pretty small)  unless the material is thicker than 3mm AND you are using a drill press. 

 

Low speed, push hard, use coolant.

[liddelljohn]

Use a slow speed  , use cobalt bits and a pilot hole  and use a cutting lubricant to cool the bit