ECN Forum Forums General Topics of the Trade General Discussion Area Welders: Hardfacing old drill bits?

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.