PDA

View Full Version : Cobalt Drill Bits at Sears



deltaenterprizes
03-05-2008, 07:58 PM
I needed some cobalt drill bits for a job and it was suggested to try Sears and to my delight they had them!

Forrest Addy
03-05-2008, 08:23 PM
"Cobalt" drills once meant M42 HSS. I don't know what that means now that the markerts and huckster got ahold of it. M42 has greater hot hardness and abrasion resistance than M2 HSS usually used for consumer drills. M42 drills originally had thicker webs meaning it took greater thrust to make them penetrate and they were brittler meaning more of a chance of chipped edges and actual breakage particularly when free hand drilling.

The last time I looked at Sears offerings in "cobalt" drills they seemed like the real goods but were quite expensive at nearly double the price. If you're drilling stainless or allow steel they are a good choice. If you drill mostly kinder, gentler materials cobalt drills may be overkill.

deltaenterprizes
03-06-2008, 09:11 PM
I need to drill out a 1/8 roll pin inside a 1/4 roll pin.

BadDog
03-06-2008, 09:20 PM
Ehh, good luck, that's "spring" steel. That's a job for a carbide EM, EDM, tap burner, etc... Either that or some careful mechanical wizardry to coax it out. I don't see how drilling will ever get that.

Bill Pace
03-06-2008, 09:43 PM
Yep, youre about to ruin those brand new cobalt bits --- As Forrest pointed out about brittleness, one will probably shatter on contact with a roll pin ....

Thats gonna be a tough nut-----

BobWarfield
03-06-2008, 11:18 PM
"Cobalt" drills once meant M42 HSS. I don't know what that means now that the markerts and huckster got ahold of it.

It's like the jokes about very dry martinis where you just show the gin bottle to the vermouth bottle. You just show the bits a little cobalt but don't actually put any in!

Cheers,

BW

bighammer
03-07-2008, 10:49 AM
don't drill it,gap in pin can break any drill, stick a 3/32 or 1/8 welding rode tuit let ti cool & pull it .

cybor462
03-07-2008, 10:58 AM
Sorry wrong place

deltaenterprizes
03-07-2008, 10:14 PM
I already drilled it and removed it,the bits from Sears worked great!

airsmith282
03-07-2008, 10:50 PM
cobalt drills are not over kill by anymeans .. i prefer them and find the quaility of my driling jobs is far more accurate rounder and cleaner then HSS drills or titainium junker bits.. and are alot stronger as well in the same size when compared to other drills..

i also dont buy any drills from sears ..i go right to machine shop dealers i pay more but i get more for my buck and i get what i want..

sorry but iam a bit on the sketchy side these days after wasting alot of money on drills that are now nothing more then junk for drilling wood with.

Carld
03-08-2008, 12:14 AM
I can tell you for sure a good cobalt drill is the only thing besides carbide that will drill out hear hardened SS turbo studs.

BadDog
03-08-2008, 12:15 AM
I already drilled it and removed it,the bits from Sears worked great!
Sears bits drilled through a roll pin? Let me guess, Chinese roll pin, right? ;)

A good roll pin you hardly mark with a file, much less drill.

Bill Pace
03-08-2008, 09:21 AM
A good roll pin you hardly mark with a file, much less drill.

Thats certainly my experience with roll pins .... carbide em or grind em! Definitely never met one I couldve removed with a cobalt drill bit----

Being of Chinese origin may be the reason-----

deltaenterprises, what was the circumstances on these pins, were they in an import tool --or?

Your Old Dog
03-08-2008, 09:44 AM
It's like the jokes about very dry martinis where you just show the gin bottle to the vermouth bottle. You just show the bits a little cobalt but don't actually put any in!

Cheers,

BW

The guy who sharpens my saw blades says there is no criterion for what is carbide. He says it only takes a trace of carbide to allow you to advertise carbide blades. He pointed out that you can tell by the color of the carbide more than anything else. I "think" he said the better carbides were the ones darker in color.

deltaenterprizes
03-08-2008, 11:36 AM
The roll pins were in a shift lever on a transmission for a diesel injector pump test stand made 20 years ago for the US government. They required a roll pin inside a 1/4'' rool pin in the specs. A 20 ton press barely moved them,once the inner one was drilled out the other one came out easily. Sears was customers choice because it was close.
I posted this in case someone was in a bind late at night or on the weekend when supply houses are closed,like Friday evening and you want to do a job and finish it before Tuesday!