Broken Bolt Head - how should I fix?

[Luis Reyes]

Hi Everyone,

I have an old craftsman 6x48 belt sander that I bought used earlier this summer. The belt sanding paper was running left so I tried adjusting the bolt that holds the tension (which is what I think the limited instruction manual I have says to do) and the bolt head broke off. Is the only way to fix this by drilling a hole in the broken bolt and using a tap / extractor to get the screw out? I should mention the second picture looks like the bolt is kind of bent?

First picture is the broken bolt head. Second picture shows the tension at it's top and what I'm trying to lower to at least get the belt sandpaper off. The third picture is the still working right hand side of the tensioner.

Thanks in advance!

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[Tom M King]

Easiest "easy out" is a left handed drill bit. What is the diameter of the bolt? Easyouts work if something will come out easily. A left handed drill bit will get most anything else out. Since you probably don't have an Easyout, just skip straight forward to a left handed drill bit.

The left handed drill bit will drill a hole into the bolt, and then all of a sudden, and as if my magic, it will get to some critical point where it stops drilling into the bolt, grab, and the bolt will back out almost before you realize it.

We need to know what size the bolt is though. Left handed bits come in many sizes, and you only need one.

In the meantime, put some Blue Creeper, or some other penetrating oil on it while you're waiting for the bit to get there. I've had 100% luck with Blue Creeper. It may be nothing but Acetone and transmission fluid with blue dye in it, but it comes in nice little bottles with a needle applicator.

[Ronald Blue]

Is it seized in the threads or will it still turn? How large is it? The trouble with easy outs especially in smaller screws/bolts is that by the nature of how they work they often cause the stuck item to swell as they bite into the hole. What Tom said about left handed drill bits is true. Little tip with them. Drill a smaller pilot hole with a right hand drill bit. Then put the left hand in the drill and let it grab or bite into the metal. This will often times cause the broken bolt/screw to spin out. This also helps keep the left handed bit sharp because if it works you rarely actually drill with them. The other thought would be a nut over it and weld it if you have a welder.

[Steve Rozmiarek]

The easiest way to deal with broken bolts is to weld a nut on them. The combination of heating the bolt and giving it a new wrenching surface works quite well. Of course only works if you have a welder and can make a good weld. Hard to tell the scale in your pics.

[Luis Reyes]

The remaining part of the bolt is 5/16ths of an inch. It feels soft though as when I tried using locking pliers on it the pliers basically reshaped the remaining screw.

It wasn't seized earlier when I was turning it yesterday so should be able to come out. Just in case I did put some penetrating fluid on it last night so hopefully that help. I'll google a left hand drill bit now and try that as it sounds easier and better!

[Ole Anderson]

Did you loosen the locking bolt before trying to turn the adjusting nut? I have the same belt sander, I replaced the front locking bolt with a knob. I leave the rear adjuster in a fixed position until I change belts to a different production run (slightly different length).

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[Luis Reyes]

Looks like we do have the same one! The locking bolt was likely tightened (I actually don't know but knowing how clumsy I can be it probably was) when I was trying to turn the adjusting nut as I lost track after a while of what I had tightened and what I hadn't tightened. It's completely my error as I'm not too familiar with the machine yet. I haven't had to change the belt sand paper yet.

Does the adjusting nut come right out? I noticed afterwards there's a small screw inside that nut.. what does that do?



Did you loosen the locking bolt before trying to turn the adjusting nut? I have the same belt sander, I replaced the front locking bolt with a knob. I leave the rear adjuster in a fixed position until I change belts to a different production run (slightly different length).

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