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Drilling holes in stainless


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I have to drill 4x 10mm holes in some 3mm stainless, I managed some 5mm pilot holes no problem, then one 10mm hole and then the drill bit melted :blink: Bought a new HSS bit today and that doesn't even make a dent and is now blunt :angry: The first one, that worked at least briefly, was titanium coated (yellow) so does that really make a difference?

What's the best way to drill SS, bearing in mind I am doing this upside-down in a puddle with a B&D hand-drill...

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Apparently a good quality sharp HSS bit with oil and slow speed will drill stainless. They heat up really quickly and that's what blunts the drill. I bought one of those indestructable 10mm drill bits for some stainless plate and it went through with no problems at all - it just cost me £48! :o

Les.

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What's the best way to drill SS, bearing in mind I am doing this upside-down in a puddle with a B&D hand-drill...

In general to drill stainless slop on some coolant, don't have too fast a drill speed but keep the pressure on and don't stop. If you back off (which people often do with pistol drills) the cutting surface will have work hardened and it will be almost impossible to start cutting again without a special drill as detailed above. Only use a pilot drill of a size equal to the flat 'tip' of the larger drill if necessary, smaller is pointless and larger defeats the object.

AndyG

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It might, if posible, be better to remove the upside down stainless plate, drill it with lubricant then put it back on!

Hmm, the stainless is part of the rear x-member and it's not coming off :rolleyes:

Cheers for the advice guys, hopefully tomorrow I can get it drilled if the rain holds off a bit <_<

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I have to drill 4x 10mm holes in some 3mm stainless, I managed some 5mm pilot holes no problem, then one 10mm hole and then the drill bit melted :blink: Bought a new HSS bit today and that doesn't even make a dent and is now blunt :angry: The first one, that worked at least briefly, was titanium coated (yellow) so does that really make a difference?

What's the best way to drill SS, bearing in mind I am doing this upside-down in a puddle with a B&D hand-drill...

With regard to the 'yellow' drill bit - there is a lot of "fake" titanium tools around. Just because a drill bit is yellow does not guarantee the quality of the material. Maybe a bit like those 'orange' products which have been mentioned in another thread....

And maybe I am being a bit pedantic, but actually you do not want the drill bit to be _titianium_ coated, as titatium is a rather soft metal (around 40-44 Rockwell C).

The correct titanium coating is actually a titanium alloy, which is applied to a softer base metal by micro welding. The coating can be either titanium carbide (TiC), titanium nitride (TiN) or titanium-carbo-nitride (TiCN). The two first are yellow-ish coloured, where the third is black-coloured.

TiC, TiN and other such coatings are extremely hard and brittle materials. TiN coatings has been tested to - in some instances - hardness above 2,000 kg per square millimeter, which roughly translates to about 85 on the forementioned Rockwell C scale.

I have a full set of TiN coated drill bits, and the perform absolutely brilliant in both mild steel, hardened steel and stainless steel.

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Carbide tipped drills are the best you can get. I'm an engineer in the food industry and everything is made from Stainless steel, if you take your time a good "Dormer" HSS drill with the correct coolant and at the right feed and speed will cut through anything.

It makes it a bit more awkward when it's upside down.

Trev

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