I used 1/2" drill rod for a shaft...and it broke.

Had a repair job kind of back-fire on me. A guy gave me this old cheese grater to fix.

The main body of it was a cast aluminum. You clamp it onto a counter-top to use it. It had a cylindrical stainless grater inside that you turned with a hand crank.

It was broken when he gave it to me. The crank was missing and however it attached to the SS grater, some kind of shaft that goes through a bronze bushing in the housing...was also missing.

The diameter of the bushing (I.D.) was 1/2", so I bought a piece of 1/2" rod...I'm not sure if it was "drill rod" or cold-rolled and cut off a small piece for the shaft. TIG -welded that to the grater part and used a cast aluminum pulley on the outside for a hand-crank (held to shaft by set-screws).

Well...I'm not sure why...but the shaft broke...my weld stayed 100% intact, but the shaft broke very close to the weld...into two pieces.

Defective material? Heat from welding weakened it? Did I use the wrong material? Any ideas? Thanks.

It is always so tempting to use O-1 or W-1 as repair shafting. If you weld any of the high carbon steels they become very brittle. I am sure your weld was fine, its the base metal that became hard and snapped. Sometimes you can anneal the area but its not worth the effort. Just use some low carbon steel and it will work like a champ.

Drill rod is tool steel. Great for little widgits that need to be heat treated and maybe precision ground after.

Not worth anything for welding, fixing things or trying to make strong parts.

John

I would have told the man that it was for show only. The fool probably took it home and tried to grate 10 pounds of cheese in one shot.

Any fool can bust something. Probably took you longer to fix it than it did for him to break it.

Charge him full price next time and see how long it takes him to break it again.

If you still have the shaft, either the broken one or the stock you used, you can test it easily. If you have the shaft that broke, try to file the end that broke. If it's hard, you know it was drill rod or similar. If you only have the stock piece, saw off a thin slice and heat it red hot with a torch and quench it.
Than stick that piece in a vise and smack it with a hammer. If it shatters, don't use it for welding unless you anneal it afterwards.

Most any material containing more than 25 Carbon points is considered nonweldable. The weld transition zone (HAZ) will be harder than hell and about as brittle. Stick with shafting material (HRS, CRS, etc.) and you'll have no problems. Be happy it wasn't part of a school bus with 40 kids on board

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Barry Milton

i have seen wire rope welded together (thats a 1095 steel) to reeve wire through a 12 part block when changing out wire on the drum of a 700 ton derrick. the welder who did it used a 7018 and said it was the dumbest thing he was ever told to do, surprised the hell out of him when it held. point being sometimes unweldable materials can be made to stick just long enough to get done what you need them to do. no, the welded part wasn't used for lifting.

I've had customers come with a broken shaft that they "upgraded" to drill rod or tool steel. I send them to a guy that does only tool steel welding. He does a furnace preheat and aneal. It works because the tool steel is now soft. He also charges several hundred bucks. Depends on how bad you want it.

as most blademakers and blacksmiths and many welders can tell you-the weld heat transition zone and the alloy transition zone are both critical points for strength and all other characteristic transitions. the weld heat action changes the weld filler, and both parentmetals. annealing the finished part in something as simple as a toasteroven after welding canlower the resulting hardness and really draw the temper way down if you heat to high enough temp. check the knifemaking boards for better info, they do this all the time, for change of the performance characteristics in the high-hardened areas mostly, which sounds like the problem here. also- dont use air-hardening steel, waste of $ and its the wrong steel to use. W-1 or O-1 works fine when annealed down and if you need to- you can reharden the portions you want hardened for cutting edges etc. steel is always just ,well - steel. it all has some heat -affected characteristics and welding always changes that. keep it in mind. doing things the right way yuo can weld W-2 tool steel to spring steel to S-7 and have then all do their jobs properly, they have to be welded, annealed, and heat treated to the proper FINAL state,which is not always the pre-welded state. once the heat treat is understood, you can use a lot of diff steels for many uses. its all just tools of the trade in the maintenance on a shoestring projects.