A question for any of the EC who also happen to own welders.

Has anyone ever tried to hardface and re-sharpen a new surface to old drill bits? (Augers) I have about 20 old augers and a few self-feed hole augers that no longer have enough metal to re-sharpen. Wondering if anyone has ever done it, or if it worked out well?

I don't know about repair, but if you want a new bit to really last a long time try checking these guy's out. [http://www.diversifiedcryogenics.com/]

Mark,
Just a long shot, but wouldn't the heat from the fusion ruin the temper on the drill?.
Or even worse, bend the shaft from heat stresses?.
Just my $0.02 worth.
Alan Belson would be your man on this one, he knows about things metallic.

Cryo dont sound cheap, might be able to buy 5 new bits for the cost of re-tempering one.

As far as re-tempering during the weld - once the new metal is on, I can temper that new metal by a few quick dunks in the sink and be harder than the original metal. Twisting - good point, but doubt I'll notice it. I'm gonna give a few a shot this week end - I'll let you know......

"Hardfacing" is both effective, and a time-proved technique. The only real 'downside' is that you need to be able to grind a new point- without grinding through the new metal.

I believe that three things have made 'hardfacing' a thing of the past: the availability of cobalt steel (and coatings like TiN), the availability of carbide bits, and the affordability of bits.

Has anyone figured the cost of the actual hard-facing rods?.
You cannot use standard rutile rods to do this job.
Also, to build a surface up on a drill bit would take real skill.

Take TRUE hardfacing out of the equation, I'm looking to put some matierial back on there so they don't have to be tossed out. Nothing left to sharpen on most of them. Even mild wire would be harder than the steel that's not there anymore- really... And maybe harder that the steel that is still there? I just have so many bits that are past sharpening, and at 25-30 bucks each - thats money... And might take a few minutes each....

I had a short and stressful production job over 20 years ago TIG welding an assortment of cutting tools which were reground. Obviously there was no issue with hardness or temper, but I believe they had ovens. Anyway, like all metalurgy, there's a method to their madness.

Dave

e57 in all respect, what you are calling tempering ain't. The steel would have to be annealed first, which is heating the metal to about 1500 degrees, then slowly cooling in ashes or vermiculite; then, it is heated back to what is called critical temp. again, only a little higher this time, about 50 degrees above where the steel looses magnetic attraction, then it is quenched in a suitable medium such as oil, brine or water; then it must be tempered; that is, heated to about 400-450 deg. and allowed to slowly cool. Then you can file a new cutting edge. The problem is complicated by the 10,000 degree welding temp. causes there to be places on the new metal where it's so hard that a carbide milling cutter will shatter, so the idea of just welding a small amount of new steel on the end of a tool steel auger is, in reality, quite a difficult process. I wish I had a plan because I also have a mess of bits that are too worn to re sharpen again.

[This message has been edited by Almost Fried (edited 10-21-2006).]

There are some cyro places that are kinda cheap. The prices were low enough at some I checked out to make me wonder if the bit gets any treatment at all, or is the treatment being applied to the payee instead? I got interested in this stuff a few years back after discussions with a motorhead neighbor who sends brake rotors and all sorts of stuff to the mainland to get treated. I looked into starting up a treatment shop right here, cause there isn't one in this state, but found the startup costs to be too high for our low population to make it work.

The sort of auger I'm envisioning you have probably won't be exotic steel, so a weld built up with high carbon steel rods would be adequate, [if they can be got?]. Ordinary MS rutile rods are not hardenable, you need about 0.85% carbon content.

Using hardfacing rods, [such as 14% manganese], presents the problem of reshaping the cutting edges after welding, but with the right wheel, it can be done.
No heat treatment required, these steels either self harden or workharden at room temperature.

With carbon steels, after welding, cut the new teeth with a grinder - no need to anneal the weldment- raise it to bright red heat then plunge in water to get it hard. Test with a file to see how you did- it should be unfileable.
Don't overheat it! If you 'burn' the steel [white hot with sparks] you have a turbo paint-stirrer - the metal is ruined and unredeemable.
Tempering reduces the hardness [ reduces tendency to brittle chipping] and increases toughness [ but increases the wear rate ] so you need to know where to stop. Clean off any crud and oxide back to bright metal, enough to see what's happening, and heat slowly from well up the shank of the auger and watch carefully as the colors approach the tip. Don't worry about the rest of the auger just watch the tip. As the tip goes yellow/brown quench in water. Overdo the tip tempering to blue and you are back to a soft steel again!
One thing- you need to get both cutting edges on the auger the same, or it will cut a larger hole or be unmanageable.
Distortion is easy to avoid- heat the auger slowly and evenly, and plunge in the water vertically, not on the slant. If you do bend it with heat, temper it right out to light blue or dull red, belt it straight with a hammer and have another go! You can repeat hard/temper operations a few dozen times without harm.
Best of luck!

Alan

Alan (not a nay sayer) Benson, fantastic advice and oh so timely. I just did a few, and except for my first experimntal one, it went OK. The first got some burn though/undercut, (sacrificed!) but some adjustments fixed that, and the four I did after that got an 1/8" bead via carbon steel flux cored. (.035 very low voltage, med speed) Right on the edge. Then some grinding with 60Grit AL/OX on the grinder, bit by bit to keep cool. Just sharpened the bead only, so I have about 1/16" build up as an edge. It took a while, (The grinding, not the welding) but I have 4 usable bits now. I'll let you all know how long they last. (FYI carbon steel wire is a little pricey and hard to find in small rolls - but I can find other uses for it.)

Mark, glad the welding went well. Can do, that’s my motto… even if I fail, I’ve given it my best shot. My present project is casting a replica metal badge for the front of my new toy, a ‘57 Renault tractor. Over 100 hours in and I’m nearing success, with the final mould practically ready. Might post a few pics [ when I get outa the burns unit! ]- the process might be of interest in making replicas of obsolescent metal electrical parts.

Alan

Casting? What kind? I've been interested in sand casting lately - Love to learn how to do that, and not have a blob. However, it may be a while - some hobbies cost money and incure investment tools and time. The welding one has several projects in the pipe that will eat time and money for some time to come. Fence and gate. (Concentric circle paterns - still working on the design) And a BBQ and smoker. (Stainless dragon stove pipe - still building welding skills up before any attempt)

I still have an antique microwave (circa 1971) oven I won't part with (springwound timer lightning can't hurt). The pot metal latch broke some years ago. I super glued it back together and used that for a pattern to sand cast another one out of brazing rod material. It worked great. The trick is getting graded sand that will hold the shape. I used sifted beach sand. I made a crucible from a pipe cap welded to some #3 rebar and heated it over my MAPP torch while I tickled the brass in with acetylene. I had to clean the latch surface up a little with a file but it is still working 15 years later. My microwave detector says it is still sealing fine.

Mark, so as not to hijack this thread, I started a new one on castings.