Help with planers gearbox

[Joe Wood]

I'm replacing the gasket and I've never gotten inside a gearbox before. I have the cover off and was able to get the two top sprocket bolts off but the bottom sprockets bolt, when I try to turn it the chains move!

how do I stop the chains from moving as I loosen the bolt? I tried jamming a piece of wood in there, and also tried holding it with a gloved hand.

[Andrew Gibson]

If you have an impact driver with a socket adapter it should take care of it in short order. If you don't have any info in the instructions, you may be able to put a piece of wood in and raise the table to chalk the feed rollers to add some resistance. The small sprocket is giving you the most mechanical advantage over the rest of the transmission.

[Joe Wood]

Right on Andrew!

[Joe Wood]

This is terrible! I put the new gasket in, then the cover, and managed to strip out the bottom right bolt, no idea how but it just spins in the hole, now what can I do, tap out a larger hole?

[Malcolm McLeod]

Look at the depth of thread in the hole. It may be that the bolt only engaged with 3-4 threads in the hole - and damaged them. If the hole is deeper, and hopefully tapped to near full depth, then all you need to do is get a slightly longer bolt (~1/4"?).

If this fails, look for a Heli-coil thread repair kit (IIRC this is trade name, so there may be others). You drill the hole larger and tap it with the provided tap, then install an insert whose ID restores the thread to its original spec.

Edit - On option 1, if the hole is deeper than the thread, or can be drilled slightly deeper, then you could get a bottoming tap and extend the depth of threads to allow a longer bolt. ...Looks like 1/4-20 in the pic, so maybe $3-$5 for the tap and a #7 bit??

[Jerry Bruette]

Joe, is it possible that the bolts are of different lengths and maybe you have a long bolt where a short one should be and the last bolt is a short one and you're trying to put it in a "long" hole? Hard to believe that you stripped out a hole in cast iron without knowing that it happened. If the hole is truly stripped out I'd try to repair it as Malcolm stated by tapping it deeper if you can or I'd use a "keensert" type insert. You can google keensert for illustrations and suppliers.

[Bill Dufour]

You could take the bolt to the hardware store and match it up with a English size bolt of slightly larger diameter but about the same thread pitch if there is something close. Or tap it out to the next up metric size with the same thread pitch. If these will not work do you can helicoil or fill with JB weld and retap. There may not be enough wall thickness to drill and tap oversize for a bolt or helicoil.
Consider installing a stud with jb weld.

[Ken Fitzgerald]

Do a search on "How to install a helicoil".... after installing the proper helicoil, you could use the same bolt or one of the same size. There are a bunch of videos showing the step-by-step procedures.

[Bill Dufour]

Timesert is also a good brand

[Joe Wood]

Some great Info guys! Fingers crossed it's a short bolt in a long hole, I'll know tomorrow!

[Joe Wood]

OK, I was able to get longer screws as the holes were pretty deep and threaded all the way :-) Put the cover back on, filled it with oil and noticed a leak from the lower shaft seal, so it wasn't the gasket after all!