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Drill bits

Started by woody1, September 28, 2008, 11:32:16 AM

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woody1

I am installing window gaurds on my cabin to make it a little harder for someone to break in and get shot. I was drilling 5/8'' rebar with hss bit...Ya right. So, this morning I went over to Tractor Supply and bought a couple Cobalt bit. WOW !! What a great bit. They are sure the bits to buy.
Woody
If you don't want to row, get out of the boat !

Rocky_J

I've had great service using the DeWalt branded drill bits with the pilot point tip. They are made in Germany and are very hard steel.

logwalker

Rebar is made from scrap and can have some very hard areas. I haven't tried those cobalts. But I will. Are they coated or an alloy of cobalt? Joe
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

sprucebunny

The only bits to buy are a cobalt alloy ... 8%, I think.
You can wind them right into heavier steel . They start to get a little pricey as you get up over 3/4" but way worth it  8)
MS193, MS192 and an 026  Weeding and Thinning. Gilbert Champion sawmill

cheyenne

Cobalt is a form of tool steel & holds an edge longer & better than hss. Also takes heat better.....Cheyenne
Home of the white buffalo

Dave Shepard

I've also had good luck with New England Twist Drill split point bits, pricey, but they work really well.

Rebar trivia time. The markings and numbers on rebar mean something to someone, probably bridge builders. Rebar actually has to be of a specific makup in order to be used in an engineered application. If it's hard in one spot, it'll be hard everywhere. Because it is of an unknown (to me), alloy, I avoid using it in place of mild steel in blacksmithing work. It usually doesn't like to be pounded on. ;)


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

jesse

cobalt bits work good drilling stainless steel

Gary_C

Quote from: jesse on September 28, 2008, 11:53:06 PM
cobalt bits work good drilling stainless steel

Sharp bits work well in stainless also. Dull bits will make stainless near impossible to ever drill in that spot again.

That same principle is true in other steels as well. If you start with a dull bit you can work harden the steel so that it may be extremely difficult to ever drill again in that spot.

Any of the types of drill bits will work if used properly. That means the bits are sharpened properly for the material you are drilling and run at the correct speed for the size. These specialized drills like the cobalt bits will usually just stay sharp longer. You may better spend your money on a good drill bit sharpening unit.

And no matter how expensive the drill bit, if you do not hold the drill steady while drilling, you can easily chip the cutting edge and no amount of sharpening will make it cut right till you grind the point back past the chip.
Never take life seriously. Nobody gets out alive anyway.

logwalker

I friend showed me how to drill Stainless once. Basically when you start to drill you push at a pretty good clip and don't stop. He explained that the chip coming off carries the heat away form the workpiece. Of course you have to have good sharp bits and the right coolant. Joe
Let's all be careful out there tomorrow. Lt40hd, 22' Kenworth Flatbed rollback dump, MM45B Mitsubishi trackhoe, Clark5000lb Forklift, Kubota L2850 tractor

woody1

Any of the types of drill bits will work if used properly. That means the bits are sharpened properly for the material you are drilling and run at the correct speed for the size. These specialized drills like the cobalt bits will usually just stay sharp longer. You may better spend your money on a good drill bit sharpening unit.

Gary,
I respectfully disagree. I used sharp hss bits, cutting oil, slow speed on a drill press. Dulled the hss after 1 hole. Cabolt, saw deal, 20 holes and still good.
Very respectfully,
Woody
If you don't want to row, get out of the boat !

little Bark

Quote from: woody1 on September 29, 2008, 10:45:49 AM
Any of the types of drill bits will work if used properly. That means the bits are sharpened properly for the material you are drilling and run at the correct speed for the size. These specialized drills like the cobalt bits will usually just stay sharp longer. You may better spend your money on a good drill bit sharpening unit.

You hit the nail on the head w/ your first sentence Gary.  I have no idea of how many 1,000's of feet of holes that I have drilled in the years that I cranked handles for a living.  I only ever had two kinds of drill bits in my tool box.  A full drill index of HHS Cleveland Twist drill bits and a few carbide bits to get a broken tap or drill bit out of a hole.  Here is a link to a chart that may prove helpful.  IMO if you are just doing general shop work and not running high speed production your wasting your money on the fancy stuff.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=2&PMCTLG=54

Rebar  is some tough stuff.  I have no idea what material it is made from but I do know that it is made by a forming process
and any time that you compress the molecules you get a tough piece of steel. 
Always use the rite tool for the job.

okmulch

I use cobalt drill bits all the time. I have noticed that they seem to be a little more brittle than others, of course that could just be the user. :)
Rotochopper b66 track, #2 Rotochopper b66 track, woodmizer lt40, CAT 277b, CAT 268b, CAT 287c, CAT 277c, CAT299d2, CAT299d3, CAT 299d3, Volvo 70e,volvo70f, volvo90f

SPIKER

as a side note to above drilling S.S. or anything else and you get some work hardening, use a punch (center type) to crack the hardened surface under where you want to drill, this will break through the surface and let it cut.

I agree with most, a good HHS bit is fine for pretty much every thing, harder materials that few will need or use is what the cobalt & carbide bits are for.   Stainless or not regular good bit can will cut it with the bit being given a chance (sharp & right speed for material and bit size)

mark
I'm looking for help all the shrinks have given up on me :o

arj

http://www.baddogtools.com/cat.php?id=2
Try baddog drill bits, they really work. You can drill through a
fill if you want to. Very pricey, but they will replace any that
break for FREE. You can send them back, or take them to a
show they are at, and just swap for new.
                                                                 arj

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