Who makes really tough HSS drill bits?

[Greenheart]

Last month I asked a Scotsman working in a French DIY store, why some of the drill bits sold there were eight times the price of others. (This sounds like a joke; sorry, it isn't.)

He said the cheapies were Chinese and won't last; the costly ones were French and much better kit.

I readily paid the extra and I wish I'd bought them in all sizes. Today I bought 'superior' grades in three sizes here in the UK, but one has already snapped and the point of another is rounding-off.

Is there a manufacturer I should look for? I'm drilling 10mm-thick stainless steel. It's slow work and the ubiquitously-available Chinese bits are sadly inadequate.

 

[Avocet]

I've always been fond of Dormer drill bits. I also have a set of cobalt steel bits (Screwfix's own) which are very good.

 

[VicS]

Dormer is one of the names i was trying to remember. Presto is another good one IIRC

For drilling stainless steel you need cobalt steel bits.

 

[nigelmercier]

For drilling stainless steel you need cobalt steel bits.

And not cobalt coated ones, these are the proper ones: http://amzn.to/1q3HxxQ

 

[Rigger Mortice]

I've said it before and feel a bit sheepish doing so again, but I've found the drill sets from Lidl's to be the best I've ever had.
I bought a single drill for SS a sometime ago and it cost more and wasn't as good as a full set from Mr Lidl

 

[Greenheart]

Thanks gents, the keyword seems to be cobalt...that's definitely one for my next trip to Ebay/Amazon.

I've heard that drilling-oil can help - both by cooling and by cleaning the bit's cutting edge. Any points of view on this?

 

[prof pat pending]

You really want silicone carbide, but they are easy to chip

There's a knack to cutting stainless.

You mustn't let the material work harden as you cut it. Don't even centre punch to mark the start point.
Keep you drill speed low and your cut rate as high as you can, if you feel the drill going off sharpen it or get another, don't keep going.

....and use plenty of cutting fluid

 

[Richard10002]

I drilled some holes in my 4mm grab rail last year. The cheap HSS bits I had were useless. The Dormer drills I bought went through easily and remain sharp.

 

[William_H]

You really want silicone carbide, but they are easy to chip

There's a knack to cutting stainless.

You mustn't let the material work harden as you cut it. Don't even centre punch to mark the start point.
Keep you drill speed low and your cut rate as high as you can, if you feel the drill going off sharpen it or get another, don't keep going.

....and use plenty of cutting fluid

+1 Lots of pressure slow speed. I use engine oil. As soon as it starts to smoke you know it is all too hot or drill is too blunt. Stop. Large drills are easy to sharpen if you just look closely at the shape and angle of the cutting edges. olewill

 

[Greenheart]

Thanks for these contributions. I just bought a little cordless drill, partly because it doesn't have the fixed, very high running speed of 240v drills I'd seen at similar prices.

What exactly is cutting fluid?

 

[prof pat pending]

I just bought a little cordless drill, partly because it doesn't have the fixed, very high running speed of 240v drills I'd seen at similar prices.
What exactly is cutting fluid?

Depending on the grade I think you are going to stuggle to get through 10mm of stainless with a cordless.

Cutting fluid is usually a mix of soluble oil and water, it acts as a lubricant and a coolant
As mentioned above, engine oil will work, but I'd go for something a bit thinner

 

[prv]

Depending on the grade I think you are going to stuggle to get through 10mm of stainless with a cordless.

Depends on the cordless. I'd back my 18v Li-Ion Makita to do it. The 12v NiMh, perhaps 50/50.

Pete

 

[penfold]

Thanks for these contributions. I just bought a little cordless drill, partly because it doesn't have the fixed, very high running speed of 240v drills I'd seen at similar prices.

What exactly is cutting fluid?

In this context cutting fluid is something like Rocol RTD liquid or compound, which is designed to improve finish and the life of cutting tools. Diluted cutting fluids aren't really appropriate for this job. Going through 10mm of stainless with a cordless drill will be a test of man, machine and drill bit, but a good quality bit and cutting fluid will get you there eventually, perhaps after a change of battery and an aching shoulder and arm.

 

[DownWest]

What exactly is cutting fluid?

A soluble oil that one mixes at around 3% with water. Aparently they have some very clever mixes for specific uses.
I never drill SS with a hand drill unless desperate. Slow speed and pressure are the key (as William H says) plus lots of coolant. I halved the lowest speed on my pillar drill (extra pulleys) to drill a load of 50mm holes in 6mm SS. It considerable extended the life of the hole saws from OMG to acceptabe.

The old 'suds' soluble oil was reputed to be the cause of testicular cancer with machine operators (leaning over lathes and stuffing rags in overall pockets) The stuff I use is a sort of bio product. But writ big on the container is 'Do not freeze', so I keep it in the house in the winter.

I find that decent HSS drills work fine, keep 'em sharp. The old Eclipse sharpener (best investment ever, but only found on e-bay now) is ace for honing new drills and slightly worn ones. The better drills from Brico Depot ( B & Q ) are good

 

[Heckler]

Last month I asked a Scotsman working in a French DIY store, why some of the drill bits sold there were eight times the price of others. (This sounds like a joke; sorry, it isn't.)

He said the cheapies were Chinese and won't last; the costly ones were French and much better kit.

I readily paid the extra and I wish I'd bought them in all sizes. Today I bought 'superior' grades in three sizes here in the UK, but one has already snapped and the point of another is rounding-off.

Is there a manufacturer I should look for? I'm drilling 10mm-thick stainless steel. It's slow work and the ubiquitously-available Chinese bits are sadly inadequate.

I wanted bits to drill stainless. I did a search on ebay, dormer ones came up, a couole of quid each. I bought them, they work, slow speed, oil, and heavy pressure, knife thru butter!
They are designed for stainless with a "quicker" spiral and different angle on the cutting bit. They look like ordinary steel drill bits otherwise!
S

 

[Heckler]

Thanks for these contributions. I just bought a little cordless drill, partly because it doesn't have the fixed, very high running speed of 240v drills I'd seen at similar prices.

What exactly is cutting fluid?

Just use a bit of engine oil, dont get fixated on cutting fluid! As someone else said, if it starts to smoke, stop and put a bit more on.
S
PS 55 years of maintenance experience!

 

[trthebees]

+1 Lots of pressure slow speed. I use engine oil. As soon as it starts to smoke you know it is all too hot or drill is too blunt. Stop. Large drills are easy to sharpen if you just look closely at the shape and angle of the cutting edges. olewill

+1 for williamH and prof pat pending. I had to drill about 2,500 holes,10mm diameter, in 10mm SS making replacement drain covers for a hospital. Grade 304. Ok, I used a pillar drill. But the technique was moderately slow drill speed, probably about 300 rpm, loads of pressure and get on with it without hesitation. I used Rocol grease-like cutting paste....I can smell it now, lovely... and Dormer HSS drills. Straight in with the 10 mm, no pilot. I seem to recall I got about 30 holes before resistance or excess blueing or rear breakout indicated I needed to resharpen. It was like drilling cheese up to that point.
I know the above doesn't help when using a hand drill, and can't see your diameter in the posts, but I would be shoving hard, trying to maintain a steady slowish speed, and feeling what the drill is doing. Cutting paste is best, but if you've only a few holes, it can be expensive.

 

[bigwow]

I take my jobs to the local machine shop where they stamp out any holes, less stress

 

[Graham_Wright]

Dormer is one of the names i was trying to remember. Presto is another good one IIRC

For drilling stainless steel you need cobalt steel bits.

In my factory we have never used cobalt drills. We probably drill 10,000 holes of varying sizes in 304 and 316 stainless per year using HSS drills by Guhring, Trojan or Dormer (now Sandvik). Currently we are producing a batch of components for Morgan Cars requiring a 16mm hole (which has a 6mm pilot). Admittedly this is on a CNC lathe with loads of coolant.

Stainless steel is a poor conductor of heat and work hardens very easily if that heat is not removed.

As others have said, slow speed, loads of pressure, a fluid to remove the heat and stop the minute the going doesn't "feel right". If you don't stop, you will probably not be able to complete the hole without solid carbide.

 

[sailorman]

+1 Lots of pressure slow speed. I use engine oil. As soon as it starts to smoke you know it is all too hot or drill is too blunt. Stop. Large drills are easy to sharpen if you just look closely at the shape and angle of the cutting edges. olewill

a 3m/m pilot hole first to remove the centre of the 10m/m hss bit, then slow & cold with lube & a sharp bit. i have never used cobalt