Drilling in 60HRc

[Martin DowingParticipant @martindowing58466]

I have few solid carbide TiAlN coated spot drills (90deg.)

Are these suitable to crossdrill a hole in hardened bar, 60HRc, (of course a little flat will be ground to aid start of the hole).

If so, what speeds would be suitable for 3-4 mm spot drills @ 60HRc job?

How many holes each drill could produce before call for regrinding or retiring?

Martin

[Martin DowingParticipant @martindowing58466]

[Brian WoodParticipant @brianwood45127]

Hello Martin,

As no-one else has ventured a suggestion, I can report that I have drilled holes in hardened steels with masonry drills using a diamond sharpened tip. Whether you can still get them in the size you talk about I don't know and the life before needing sharpening is not very long.

Slow speed, heavy loading on the drill and coolant should get a result

Regards Brian

[David George 1Participant @davidgeorge1]

Hi Martin I have had poor results drilling in this hardness steel what material is it as if it is a tool steel you win probably not succeed but if it is silver steel or GFS you may but I have resorted to spark erosion at this hardness there may be someone near you that can spark out a hole using a copper electrode. Also what depth are you drilling.

David

[Chris Evans 6Participant @chrisevans6]

Sometimes it is doable but I can tell you from experience broken carbide in a job is a bugger to spark erode out. If it is a through hole try and find a wire eroding company that has a start hole machine and get the hole wire eroded. They will be able to hold a very good size.

[Martin DowingParticipant @martindowing58466]

Material is a ground bar for linear bearings of Cf53 steel, 8 mm diameter and induction hardened to depth of 0.8 – 1 mm. So it is really a deep case hardening.

Specified hardness is 60+/- 4 HRc. Crossdrilled hole would be through.

@Brian – Thanks for hint. Will try it – cheap enough.

@David and Chris – I have to look around for someone with spark eroding facility.

Martin

[SamsarandaParticipant @samsaranda]

Recently had to open an 11.2 MM hole to 12 MM, the object in question was a quick change tool post, it was hardened steel, not sure what hardness but bloody hard. I tried 12 MM cobalt drills but gave them up after wrecking 3, then found that a 12 MM diamond core drill as sold by Arceurotrade managed the job not quite like a knife through butter but at least it made it through. I would suggest that you probably will need some sort of diamond cutting tool.

Dave W

[John ReeseParticipant @johnreese12848]

Drill through the case hardening using a carbide die drill. Turn the shaft 180* and drill through the case on the other side. Use HSS drill to drill out the remainder.

[Chris Evans 6Participant @chrisevans6]

Now we know it is linier shafting you will be fine with your small flat and drill to start the hole. I would not use the spotting drill to go all the way due to lack of any side relief.

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