Drilling Hardened Steel

[Stuartgb100]

I've about 100nr 13mm dia holes to drill in 6mm hardened steel.
Two questions please:
a) is milling in a pillar drill the way to go ?
b) are solid carbide bits the best bet ?
Thanks.

 

[Jameshow]

Pillar drill is best, and work out the correct speed.
Cutting fluid is recommended too.
Cobat drills at a minimum.
Night and day better than Hss.

 

[MikeK]

I used to work on safes and drilled lots of hardened plates to neutralize the locks. Carbide bits, and lots of them, were the first choice. Diamond hole saws were the next choice, depending on the type of hard plate. However, each diamond hole saw cost about the same as two dozen equally sized carbide bits and normally took longer to drill through the plate.

 

[Bingy man]

Good luck with that task , I made a knife handle for a friend and wanted to drill an additional hole but nothing I tried would touch it . It was an American made blade and all I achieved was to scratch the surface slightly. I even brought so called drill bits for hardened steel and no matter what speed I set or how much cutting fluid I applied I failed miserably.

 

[--Tom--]

Any idea on type of steel and hardness? If something like O1 worth checking if you could anneal the site of the hole with a torch, as tool wear will be high with that number of holes. For 13mm holes you’d be better off with a carbide tipped annular cutter in a mag drill.
If budget won’t stretch to that then solid carbide bits in stepped sizes. They’re brittle things so need a rigid set up and be prepared to lose a couple while you get a feel for the feed pressure.

Good luck, it won’t be a pleasant job

 

[Dibs-h]

Maybe ask a local'ish laser or waterjet cutters? The cost might not be as high as one might think.

 

[Setch]

Bosch multi construction bits with sharpened tct tips. They'll do it no trouble.

**edit**

Misread and thought you were drilling circa 13 6mm holes. 13mm is quite large, I think they'll still do it, but with that many holes you might need a few bits, or learn to touch up the edges with a diamond hone.

 

[xy mosian]

There have been a number of posts, sometime in history, about using bandsaw blades in frame saws. The problem of drilling fastening holes in the hardened steel has been tackled by annealing the steel before drilling. Some had success doing this by running a steel shaft, in a pillar drill, against the blade until friction caused localised heating, tell tale red spot and sometimes smoke. The spot produced was then soft enough to drill. Of course your work is much thicker than the average bandsaw blade, but the method may be woth looking at.
HTH
geoff

 

[--Tom--]

There have been a number of posts, sometime in history, about using bandsaw blades in frame saws. The problem of drilling fastening holes in the hardened steel has been tackled by annealing the steel before drilling. Some had success doing this by running a steel shaft, in a pillar drill, against the blade until friction caused localised heating, tell tale red spot and sometimes smoke. The spot produced was then soft enough to drill. Of course your work is much thicker than the average bandsaw blade, but the method may be woth looking at.
HTH
geoff

Part of why I asked steel type- if air hardening or hardened stainless then localised annealing isn’t really doable

 

[Limey Lurker]

Would it be worthwhile having the bulk of each hole removed by burning torch? The circumference wouldn't be any harder than originally: just a lot less to remove by drill than originally.

 

[Inspector]

You haven't said what alloy is being drilled? What the hardness is? Predrilled hole when soft and then finish sized after hardening? Clearance hole for a bolt or close tolerance hole for a bushing? An assembled part or individual pieces? Size of the part being drilled? Tolerances of size and positioning? Without knowing any of the above and perhaps more your best bet is on a CNC milling machine with flood coolant and carbide tooling. The CNC will control the feeds and speeds of the bit for maximum life and round and true holes. If the parts are more agricultural then manually doing it can work all be it at a greater cost in broken/worn tooling.

Pete

 

[Spectric]

If it is truly hard then you will not drill it, materials like Inconel and gauge plate.

 

[clogs]

I'd be using solid carbide BUT dont think the average pillar drill will have the stamina to do it.....
belt slip is the least of ur worries....
plus the biggest prob with carbide is it needd to be used in a very stable chuck/shaft assembly.....
Never seen a pillar drill without the shakes.....
that's what milling machines are for.....my mill has a 3hp motor and triple belt drive system plus a gearbox.....
plus 1 for lazer or watter jetting....

 

[Fergie 307]

I would also think solid carbide end mill on a milling machine. A drill will have too much slop to use and end mill, and if it is fairly hard it will eat up cobalt drills.

 

[PhilipL]

Spark erosion is a possibility. Model engineers sometimes build them for diy. Post on one of their sites.

 

[Bob Chapman]

I used to work on safes and drilled lots of hardened plates to neutralize the locks.

Mike, is that why you live abroad and wear dark glasses?

 

[xy mosian]

Part of why I asked steel type- if air hardening or hardened stainless then localised annealing isn’t really doable

Tom, thanks for catching that. Clearly I didn't think tthe problem through in my rush to try to be helpful.
geoff

 

[MikeK]

Mike, is that why you live abroad and wear dark glasses?

I have no idea what you mean. We never had this conversation.

 

[TPK]

I need to drill some holes through 3 or 4mm HSS. I wondered if I could soften the area to be drilled using a welder. Not given it a try yet and not sure if its suitable for thicker stock. Any thoughts on this would be appreciated.

 

[ChaiLatte]

I need to drill some holes through 3 or 4mm HSS. I wondered if I could soften the area to be drilled using a welder.

No.

Annealing HSS requires a controlled (specialised) process. It is one of the advantages of HSS over carbon steel, in that it will retain its hardness at elevated temperatures.

HSS will drill fine with a carbide endmill. All the advice above about ridgidity of setup applies. Either flood cool, air blast or cut dry with a few pecks to clear chips. Some sort of wishy-washy half drizzled on coolant will do more harm than good.

Another option is to silver solder the HSS to a piece of normal steel and then drill that.