Problem with Bosch Orbital Sander

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MysteryMan

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Hi

I have a Bosch PEX 115A Orbital Sander and this has worked fine for years (occasional use only!)

Just lately when I use then after a few seconds the bolt holding the backing plate in place works loose and the plate un-attaches itself! Not a pleasant experience.

I re-attach and make sure the bolt is nice and tight, but, same thing happens as soon I apply any pressure to the pad. It may be a total coincidence, but, have just started using a new batch of pads (fairly cheap off eBay!)

I can fire up the sander without making contact with wood and this seems to spin fine with no signs of getting loose - it seems like it is the pressure from applying to wood that is causing the problem.

Anybody any ideas what could be causing this or what part, if any, needs replacing?

:?:
 
topconker":2v15wd95 said:
Try putting a star washer behind the nut, that should stop it loosening.

Thanks for suggestion.

Now this is going to appear to be a very dumb question, but, where should the star washer go? :roll:

At the moment I have the bolt and a plain washer - should it go between those or between the plain washer and the backing plate?

See....told you it was dumb!!!!!

Update - have worked it out and does, indeed, seem to do the trick - marvelous!

Thanks again :D
 
I doubt a star washer will do it in this case: they rely on a solid but soft-ish metal surface under the bolt head to grip well. I'd guess in this case the new pads are too squashy and you can't nip up the bolt enough. I suspect a star washer will just cut a bigger hole in the pad, around the bolt, if it does anything at all.

Squib's suggestion of Loctite is the first thing I'd try. There are several versions - try one that explicitly allows dismantling -- better than finding you've locked the bolt in immovably. And if the design permits, it's probably worth replacing any Pozi or Phillips headed bolt with either a Torx or Allen headed one: the Loctite will make it harder to undo, and you will want to do that several times (at least), and probably in a hurry when it interrupts your work. Something that can't slip or easily chew up is the way to go.

Finally, Loctite (proper) is cyanoacrylate-based. It will work, but will also be a pain to clean out of the female thread after a few repeats. Running a tap down will do it (probably). As an alternative you might try something like ordinary lacquer, as that will easily dissolve in meths. The disadvantage is that you may need to do it up then wait for the solvent to flash off before going back to work.

Annoying problem - hope you get a solution.
 
Loctite or superglue on the thread, but it sounds like it's something else to me if it's just started happening regularly.
 
Graham Orm":af0ayeyn said:
Loctite or superglue on the thread, but it sounds like it's something else to me if it's just started happening regularly.

Will try the Loctite and hope you are wrong! :wink:
 
My sander has an allen bolt to hold on the head and always had blue loctite type compound on it so was hardish to remove.
having replaced the head the other day, which I have to do every year, it was looser so re loctited it.
As an idea I am trying an abranet intermediate velcro pad so when it wears I shall replace that rather than the whole head.
 
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