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robertspark

Drill Bits - Cobalt M35 ( 5% ) M42 ( 8% )

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hopefully this is not a repeat post as I did do a search before and found nothing on Cobalt bits other than Ti coated ones.

Anyone using cobalt bits? (not the coated ones, but the "solid" (alloyed) ones).

Anyone got any comments?

I've been trying to drill out some M12 10.9 bolts, and had a 1/4" bit that was doing well, until it broke as it snagged as it popped out of the bottom of the hole (I'd done about 4 out of 6 by this time).

Yes, I've read a few posts about dormer bits, but these posts were back in 2006 / 2008, was wondering if anyones opinion of the M35 cobalt bits had improved.

I guess I'm like most of you and have a box of drills of various parentage collected over the years, and try to weed out the butter ones can be hard in the age of internet purchases was wondering if anyone recommends them or are you still Dormer advocates and learning to sharpen them?

M35's (5% cobalt) seem fairly common and reasonable (25pc 1-13mm 1/2mm increments for £50), M42's (8% cobalt) seem mostly to be available from the US only.

thanks,

Rob

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Thanks Jeff, that was lucky, I nearly got a set of them yesterday

Si, I will probably end up sharpening them (to be fair it's practice, and I don't have an excuse as I'm all set up to sharpen them, must admit, I kind of struggle with the bigger sizes on a bench grinder (14, 17mm) .. I was wondering if there was much merit in using cobalt these days .. for the bigger sizes I tend to use incremental reamers given again I've god a box of those I've accumulated over the years.

You did a good post here on drill bit sharpening and there is the 2 nuts welded check method too.

http://forums.lr4x4.com/index.php?showtopic=5783&hl=sharpen

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I have bought and used examples of Cobalt drill bits from Taps and Dies.

They were absolutely amazing. I wanted to drill a 3mm hole along the length of a 1/4" x 12" piece of silver steel round bar. Having gone in ~20mm I reversed the drill bit, Loctited it in place, and now had a 3mm drill bit that could make 10 pilot holes (in 4mm steel) past a 6" obstruction.

I have subsequently wanted to drill two 2mm holes in a vernier calliper. The 3mm drill started well enough to convince me the task was doable. Having started the hole I tried a HSS bit, and another 'cobalt' bit. Both just polished the surface.

It was only when I went looking for a 'full set' that I realised the 'Taps and Dies' bits were 8% cobalt.

A 'full set' appeared to be a luxury I could not afford, so I looked for other suppliers.

Like you, I found several selling 5%.

Beals are a good price, but bits have to be bought in 10 per size.

I did think of making multiple sets and using them a Christmas presents to those family members who might appreciate them, but it was still a quality gamble as I hadn't actually used any Beal 5% cobalt bits myself.

In the end I was seduced by UKDrills (biggest supplier of drill bits on Ebay, or some such).

11 out of 10 for Customer Service, 3 out of 10 for product quality.

The 'cobalt' bit wouldn't touch the calliper I wanted to drill.

While the cardboard box said Cobalt, the tin said nothing, and the bits were only marked HSS.

I used 'contact the seller' through Ebay and said I wanted to return the bits, expecting to be given a Returns number.

I got an email asking if I wanted Credit or Refund, I asked for Refund, and it was immediately paid into the Paypal account I'd used for purchase. They never issued a Returns number, nor asked for them back. Although their system seems open to fraud, I've kept the bits, as HSS quality.

My order was for multiple bits, mostly 'cobalt', but the 'set' was the most expensive single item. I've not used UKDrills before, and won't again, but apart from the fact I have not got the cobalt bit I wanted, and so cannot complete that job, I think I'm about evens on the whole deal.

I've since seen this set from Sealey. Still only 5%, and does anyone go to Sealey for 'Quality' (rather than 'Ok for the price')?

On my experience, invest in Cobalt bits from Taps and Dies.

What do they say, the quality will continue to impress long after the pain of purchase has been forgotten? Something like that :-)

HTH

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Thanks David, much appreciated for your comments, insight and guidance.

Practical Machinist and other such forums a number of the users advocate 8% (M42) bits, but always with the caveat of from a quality supplier.... the problem in the UK is we are flooded by far east imports so choosing a "quality supplier name" can be difficult.

The problem is being a backyard mechanic (well this isn't my day / paying job) .... I like many others I guess don't buy many drills and tools etc, so it's a bit of a minfield because many many are listed as cobalt when in fact they are HSS, on the practical machinist site, someone stated that when you sharpen a cobalt bit you will get red sparks.... great, bit late though when I've just forked out for a set and the seller is not going to be too happy getting them back with grinding marks on them and a buyer saying they are not cobalt!

I saw the clarke ones (machine mart) , and I've seen "silverline" ones, albeit all are listed as 5% and I guess remain of questionable chocolate box quality unless someone's had some experience. Hence Jeff's comment above was most helpful regarding Clarke / Machine mart ones .... although did I expect anything else considering they were cheap.

I've bought from UK drills before and they've been ok, albeit I was only drilling a few oddball holes (17mm) and after a blackeye (another story....) I tend to ream out all larger bore holes than 12 / 13mm when it's in anything other than wood / ali and not being done with a holesaw. ( lesson learned the "Nige" way.... won't make that mistake again, but I'll probably make one of the million other potential ones though)

Taps and dies look good, albeit at £140 for a box set of 19 1-10mm in 1/2mm increments + VAT..... I'd still be keen to see if anyone's got any good experiences at the chocolate box ones (silverline Irwin sealey etc) as the taps and dies ones are ~3x the cost

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Why not consider Tungsten Carbide hard plate drill bits...Very similar to a masonary bit, but the tungsten carbide tip is ground to a very sharp edge.

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Why not consider Tungsten Carbide hard plate drill bits...Very similar to a masonary bit, but the tungsten carbide tip is ground to a very sharp edge.

That set from Triple X trading looks good...................

Seriously though, I bought some cobalt bits from Toolstation of all places. I dont know the content, but they were cheap, and they sell individual sizes. I needed to make some holes in a 3mm stainless plate and they went through no problem at all.

Probably not a lifetime investment, but if you only want them for one job.....................

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I use Dormer drills and taps, at work and at home Cobalt and regular, for the following reasons, however Swiss tech are doing some nice kit as well.

1 I order them

2 I lke them

3 they do lots of different types for different applications

A couple of points to be aware of

harder drills are more brittle, be careful when breaking through, they will chip/break

use cutting fluid apprpriate to the material being drilled

learn to sharpen drills, they do not last long drilling harder materials, or buy yourself a Darex,

one angle does not suit all materials or drills (buy yourself a machinery's handbook)

most cobalt drills are ground split point, pilot drilling is not needed on smaller sizes (caveats apply depending on material and drill set up, thats where experience comes in)

keep your weight on when drilling bolts, if you spin the drill and it gets hot, game over

when your really in the s**t break out the stellite drills and melt your way through.

Cheap drill bits are cheap drill bits, for a reason.

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.....

Cheap drill bits are cheap drill bits, for a reason.

This I agree with, however not all expensive drill bits are expensive for the right reason ;)

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I just use cheap bits - mostly Winzur-Wurth - and accept that I have to sharpen them occasionally. I've been using the same set for 14 years now (some of them are getting a bit short!). The disadvantage of coated bits is that if you sharpen it, normally the material under the coating is as soft as a carrot and will not hold an edge. Non coated are the same all the way through and can be re-sharpened until the flutes are gone!

Si

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I was very impressed with some cobalt franklin drill bits I bought from ebay. don't no about drilling out 10.9 I cant remember doing it but I probably did at one point also they were 5% m35 I will see if I can drill out a 10.9 or 12.9 at work on Monday.

Just had a though after posting the above I have a set of snap on extractors and it has some very good left hand drill bits in the set wonder what they are made of? they have defiantly drilled out a 10.9 and possibly a 12.9 I did blunt a couple on a bolt in an engine block that another fitter had roasted a few times and hardened it but nothing would touch that.

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