boatbuilder
Well-Known Member
sorry, screwfix cobalts are crap . go to a prpoer engineers suppliers. And expect to pay at least double,
drilling stainless steel
- Thread starter owen
- Start date
Gin
Well-Known Member
Absolutely right- cobalt by far the best, handles the job well.
pandos
Well-Known Member
I have drilled S/S thousands of time at work (304) and on the boat (316).
I generally use water as a coolant.
I think using a lubricant reduces the bite that the pressure is meant to achieve.
Have a cup of water handy dip the bit in it regularly or if horizontal pour some on the workpiece.
Heat really is the enemy.
Usually the drill bit can be touched up wit a rub of an angle grinder, but in reality it is broken bits rather than wornout bits that is the problem, this is especially so when using pilot holes.
Relativly slow speed, plenty of pressure, cup of water, reasonable bit.!!!
I generally use water as a coolant.
I think using a lubricant reduces the bite that the pressure is meant to achieve.
Have a cup of water handy dip the bit in it regularly or if horizontal pour some on the workpiece.
Heat really is the enemy.
Usually the drill bit can be touched up wit a rub of an angle grinder, but in reality it is broken bits rather than wornout bits that is the problem, this is especially so when using pilot holes.
Relativly slow speed, plenty of pressure, cup of water, reasonable bit.!!!
owen
Well-Known Member
thanks for the replies. one of the bits i used is marked as "Cobalt" so there must be different qualities of cobalt. does anyone have a named bit maker i can buy and has anyone an online toolshop that they can recommend.thanks in advance
savageseadog
Well-Known Member
Another source for cobalt drills id a bodyshop or bodyshop suppliers. They are used for drilling spot welds on car bodywork and are 6 or 8mm only and an unusual drilling tipp.
peteandthira
Well-Known Member
Agree about water. My SS expert said lubrication is unecessary- it's cooling it wants. He keeps a hose pipe pouring water on the job all the time, but watch it if you're using a mains drill or your hair may well stand on end!
alan8376
Well-Known Member
My mate who works on Jet engines sent me some of the weirdest looking drills for SS I have ever seen!
Avocet
Well-Known Member
I've used mine plenty of times on stainless with no problems!
Sailfree
Well-Known Member
From a previous post I bought a set of Cobalt drills from Screwfix- definately the cheapest. They are part of Kingfisher group so same products as B & Q.
Have not tried mine yet but believe that everything is made in china today only the labels are changed to protect the innocent!!
Have not tried mine yet but believe that everything is made in china today only the labels are changed to protect the innocent!!
TheBoatman
Well-Known Member
BINGO - Just what I was thinking - SDS is a drill holding method and nothing to do with drilling speed. It's like saying drill useing Morse taper drills not parallel.
Peter.
Peter.
Graham_Wright
Well-Known Member
As a condensate of the (good) advice;- there is no problem drilling SS with ordinary HSS drills.
The cost of these to my company (I get around 50% discount) varies form £3 for 10mm jobber drills down to £7.00 for 10 off 5mm jobbers. Just pop into your local tool merchant. We have drilled around a thousand 6.1mm diameter holes in 316 SS 6mm thick with the same HSS drill without sharpening (although this was with coolant and machine driven).
You didn't say what size the bolt was but it is difficult achieving sufficient pressure for any thing over 8mm with a hand-held drill. For large diameters use a pilot drill but no bigger than around 30% of the eventual diameter (otherwise you will just burn the corners of the final drill).
The use of a lever to achieve the necessary force can make a dramatic difference and most drills have a recess on the handle where you can lodge such.
As has been observed, once the drill point overheats, you have probably lost the battle. I have found that a solid carbide drill, a carbide slot drill (or maybe a masonry drill but is needs to be sharpened first) can occasionally recover the situation.
If you think it is overheating, STOP IMMENDIATELY!
If you can't find a supplier of HSS, send me a stamped addressed jiffy bag, and I'll give you a selection. (Pm me).
The cost of these to my company (I get around 50% discount) varies form £3 for 10mm jobber drills down to £7.00 for 10 off 5mm jobbers. Just pop into your local tool merchant. We have drilled around a thousand 6.1mm diameter holes in 316 SS 6mm thick with the same HSS drill without sharpening (although this was with coolant and machine driven).
You didn't say what size the bolt was but it is difficult achieving sufficient pressure for any thing over 8mm with a hand-held drill. For large diameters use a pilot drill but no bigger than around 30% of the eventual diameter (otherwise you will just burn the corners of the final drill).
The use of a lever to achieve the necessary force can make a dramatic difference and most drills have a recess on the handle where you can lodge such.
As has been observed, once the drill point overheats, you have probably lost the battle. I have found that a solid carbide drill, a carbide slot drill (or maybe a masonry drill but is needs to be sharpened first) can occasionally recover the situation.
If you think it is overheating, STOP IMMENDIATELY!
If you can't find a supplier of HSS, send me a stamped addressed jiffy bag, and I'll give you a selection. (Pm me).