Drill bits

Ordinary HSS drills will suffice if really sharp, but cobalt drills are longer lasting. Drilling tubes is best done on a pillar drill and very carefully centred under the bit so that it is not deflected under pressure. It is essential to cool the workpiece during drilling or else it will become hardened and then it is near impossible to drill. My best results have been with cutting oil as a coolant, although water cooling can be effective. A medium drill speed so that it doesn't labour nor spin on the surface as though lighting a fire and enough pressure to maintain the cut, again to avoid building up heat. Once the variables are set up, proceed in a confident manner!

Good luck,

Rob.
 
High speed steel is OK but drill at low speed and do not allow the drill to rub, the drill must always be cutting otherwise the drill will blunt quickly and the stainless will work harden.

I have found if drilling with a hand drill speed of the cordless drills seem about right for drills up to about 10/12 mm dia, mains drills tend to be too fast or don't have a enough torque at slow speeds unless geared down.

A bench drill is best if you can take the work to the machine.

If you are drilling lots of holes learn to sharpen drills or buy lost. These drill sharpeners IMHO are c**p.
 
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As others have said, a simple cobalt drill bit.... I have just drilled some 8mm holes through the sides of the bow roller cheeks, in one go and for lubricant/cooling just ran a trickle of water over it whilst drilling.
Suggestion is not to centre punch first since this will harden the precise spot you want to start drilling.
 
I found Makita HSS bits at slow speed are absolutely superb but probably any high quality branded ones will do as well. Coated bits tend to be brittle and smaller ones snap easily unless everything is held super-rigid in a pillar drill. For larger holes, start small and then open it out by using successively larger bits about 2mm at a time. Wear tough gloves and whatever you do don't be tempted to wipe the swarfe away with your fingers ; it will cut you like a knife.
 
pessimist said:
I need to drill some stainless tubing and rather doubt that my cheapo bits will suffice. Suggestions?

Thanks,
Colin
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If you only have a small number of holes to drill decent hhs bits will do the job, but might not be much good afterwards

If you have more its well worth going for the cobalt bits

Very lightly centre punch only to avoid work hardening.

For the same reason drill slowly but steadily with cooling/lubrication.
 
Rogershaw said:
High speed steel is OK but drill at low speed and do not allow the drill to rub, the drill must always be cutting otherwise the drill will blunt quickly and the stainless will work harden.

I have found if drilling with a hand drill speed of the cordless drills seem about right for drills up to about 10/12 mm dia, mains drills tend to be too fast or don't have a enough torque at slow speeds unless geared down.

.
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Interesting. I'd wondered why I found it easier to drill metal with a cordless screwdriver and (presumably) cheap stick-in bits from Aldi/Lidl (can't remember which) rather than
with proper bits and an electric drill
 
What has not neen mentioned is that an ordinary electric drill say 600-800w tends to run far too fast for drilling stainless and if it does grab will stall the drill. A bigger drill say 1200-1600w will go slow eniugh and with enough torque to do the job. I have had very mixed results drilling stainless and when I started using a bigger drill it was a real revelation. My pillar drill although ot looked big and capable was still only a small motor which went too fast and was useless on stainless.
 
ahabdonal said:
What has not neen mentioned is that an ordinary electric drill say 600-800w tends to run far too fast for drilling stainless and if it does grab will stall the drill. A bigger drill say 1200-1600w will go slow eniugh and with enough torque to do the job. I have had very mixed results drilling stainless and when I started using a bigger drill it was a real revelation. My pillar drill although ot looked big and capable was still only a small motor which went too fast and was useless on stainless.
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A battery drill is often slow enough if the hole is say > 10m/m
 
I just use ordinary HSS drill bits. A pedestal drill will enable you to provide a lot of pressure to the bit. Mine pedestal drill has a slow enough speed by adjusting pulleys.
I use ordinary old engine oli or even WD40. If the job gets too hot the oil smokes a good sign that it is time to stop for cooling. As said high pressure slow speed and always cuting. If swarf stops coming off then stop drilling. If yopu have to use a hand held drill then do it in little bites so your arms can recover from exerrttion of the required pressure.
Larger drill bits can be sharpened quite easily with an oil stone. I just mount the bit in a vice point upwards and use the stone in my hands. Look very closely at the shape and cutrting angle of a good bit. It is far easier to sharpen a bit that is only slightly blunt as it is easy to copy the cutting angle wheras a very badly damaged bit is harder to emulate.
You can use a powered grinding wheel but there is a rsik of taking too much off in the wrong place and of overheating. good luck olewill
 
Don't forget that the speed is related to the diameter of the bit.The lager they are the slower the can be.So if you are starting with a small hole(I would) the small bit must go faster than the larger ones.It is important to keep the pressure up or the stainless will work harden .
I routinely drill stainless but my milling and drilling machine weighs 300kg so it is easy to apply a lot of pressure.Cobalt drill bits are worth the cost but you can use sharp HSS ones with cutting oil.
 
Having had problems drilling stainless with normal bits I bought some fancy Bosh ones for the next job, so much better I couldn't believe it.
 
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