Dual diameter HSS bit.

Can't find one. A they available? I want to drill nearly 200 holes in corrugated iron, so something that will do it in one go would be good. I don't want a step drill bit. Something like a cross betwween a centre bit and a brad point bit. OD 8mm.

Reply to
Chris Bacon
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If they do, these people will have them. If they don't, they can make one to your specifications:

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Reply to
nightjar

De Walt "extreme" bits are like this (I have a set) and work very well in a drill press but are slightly aggressive in a hand-held drill

Reply to
nothanks

Very interesting. Have you tried them in thin (0.5mm and 0.7mm) sheet metal?

Reply to
Chris Bacon

Nice but £Ouch!

Reply to
Chris Bacon

Probably. When I first got them I used them all the time but found they were a bit too aggressive for general handheld use so, now, only tend to use them when their virtues are needed - they should be fine for your application. Although, TBH, for non-critical drilling in thin material I would use an auto centre punch and then go straight to a 4-facet drill of the right size. Whichever technique, I would have a piece of wood at the back if at all possible. If this is for cladding/roofing panels then use self-drilling Tek screws, they're the dogs danglies when driven with an impact driver.

Reply to
nothanks

You do get what you pay for though, which is quite important when drilling holes as part of a manufacturing business.

Reply to
nightjar

Two drills (one for each size drill you need)?

Reply to
Kevin Holohan

A bit tedious when doing 200 holes.

Reply to
nightjar

I might try one:

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This roof's being held down with hook bolts/Dowtys/Topats, I've got some TEKs but they're a bit long for stitching, will have to try and find some short stainless ones.

Reply to
Chris Bacon

Chris Bacon snipped-for-privacy@maildrop.cc wrote in news:sglnof$19h7$ snipped-for-privacy@gioia.aioe.org:

If truly cobalt then they could prove brittle, the Bosch extreme range (also avail at Sfx) with a similar profile may work out better.

Reply to
Peter Burke

Thank you. I had a look, could not find them. Got an URL? I might buy both...

Reply to
Chris Bacon

It says they are cobalt high speed steel (HSS). That is a steel with up to about 5% cobalt in the alloy mix.

Reply to
nightjar

Chris Bacon snipped-for-privacy@maildrop.cc wrote in news:sgm3f0$skp$1 @gioia.aioe.org:

Sorry it is the _DeWalt_ Extreme 2 Metal range, same tip as your linked product but no mention of cobalt in the description at DeWalt:

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DT5052-QZ (or DT5052QZ) specifies the specific range and 8mm size.

Huge potential for confusion as they have applied the 'Extreme' name to many drilling material ranges so finding "Extreme 2 Metal" is key. Many suppliers are showing stock photos of non-stepped drills too so more room for doubt.

One stockist here:

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or

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Cobalt (alloy) drills have amazing cutting power but are brittle and the slightest jarring (exit grabbing) or drilling misallignment can result in breakage with no warning. Better suited to drillng difficult or thicker materials in a drill press where things conditions are better controlled.

Reply to
Peter Burke

nightjar snipped-for-privacy@bignell.me.uk> wrote in news:ibKdnSLE9dLbJ7P8nZ2dnUU78W- snipped-for-privacy@giganews.com:

I think mine are about the same and I suffered a few breakages before I realised how fragile they were and learned to handle them care. I now only use them carefully in a drill press and on materials or thicknesses where they give a real advantage.

Reply to
Peter Burke

That sounds like M42 cobalt steel, which has a higher percentage of cobalt than the more common M35 grade. For really brittle drills, which only work with machine feeds, try solid carbide drills.

Reply to
nightjar

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