Drilling stainless steel

[NSN]

I am working on a project and will have to drill 8 holes in 8-18 stainless steel. The stock is 3/16" thick. I have good equipment .. drill press, machinist vise, sharp drill bits, etc. The holes will be

13/32" in size.

Shall I drill in one step or start with a pilot hole and enlarge. If the latter, what drill sizes should I use?

All suggestions appreciated.

Thanks

Norm

[Greg O]

Consider buying a step drill, Unibit is one brand name. Start with a pilot hole, 1/8"-3/16" or so. Sharp, (new), drill bit, lots of pressure and slow speed. Stainless work hardens so if you use a dull bit, you may never get a hole drilled in that spot. Greg

[Mark]

Cobalt bits. Don't even think of using HSS.

Start at 1/8" and work up in increments. The fact that you're using a press will make it much easier.

Also, do not attempt to hold the stock by hand.

[Ross Mac]

I would make certain to use a good entry material, well clamped to the stainless steel. This way the burrs will be on the entry and not on the finished product. As far as what material to use for this....just pick something close in hardness to stainless and maybe 1/8" thick or so....Make a few test holes in scrap if you aren't comfortable with the setup....good luck...Ross

[Darren]

HSS is OK to use. Start with a center drill if you have one, or a split point drill about 3/16" . If using a drill bit, start by pecking the material until you get it started. Use a speed of approx. 950 rpm.( cutting speed times four divided by the drill diameter ). Then you can go to the

13/32 drill bit and use approx 500 rpm. If your drill is sharp the burr will be minimal as long as you don't let the material get hot. Be sure to use a cutting oil, it will make things alot easier.

Darren

[Steve]

I would buy 2 carbide drill bits. 5/32 and 13/32. If you attempt with HSS slow with lots of coolant.

[NSN]

THANKS to all who replied. I have a new set of titanium nitride coated HSS drill bits. I used a 3/16 and 13/32 with plenty of coolant and a slow speed. EASY !!! The stainless was type 303 and not very hard.

Having a heavy duty drill press (30 year old Rockwell) and a good vise helped. My drill bits seem to have tolerated the drilling quite well and remain sharp.

FYI: I got the bits from Harbor Freight. Over the years I have found that their drill bits and "good" screwdrivers are as good or better than my USA stuff (I do have a set of SnapOn screwdrivers for comparison).

Norm