Thread: Drilling out broken bolts
05-12-2010, 08:34 PM #1
Drilling out broken bolts
Whatever this yellow stuff is, it is tough.
I had two PTO mounting bracket bolts break. I could not get enough heat into the case with my propane torch even with 40 some minutes heat. Doing it again I would consider putting the block in the oven.
I tried cutting a slot in the exposed bolt and went after it with a hand held impact driver. The bit broke. I ended up drilling the bolt out. It was set up square on my drill press. I started with a 1/16th ish bit, and only drilled 1/16th deep. I dragged the hole to the center of the bolt using a carbide dremel bit. Then progressively worked up to the minor diameter of the bolt. The bit would bind and pull the threads out, but some was pulled out by hand as a long spring. On the first bolt I was well centered and after cleaning with a tap, it is good to go. The other hole was slightly off and the bolt is loose when threaded in. I am going to drill that out and re-tap for next size up in english.
I have never had much luck with easy outs and couldn't get heat to this. I keep reading suggestions for welding something to the bolt and the heat of welding softening the loctite. I think that would have been the only way here.
05-12-2010, 08:45 PM #2
I have a left hand drill index with extractors that work well--some times the drill bit works by itself. However, these sets are spendy.
You may just want to install a Heli-Coil. If you go this route, drill-out to appropriate size, tap to appropriate size and install Heli-Coil. Works like a champ and is better than new as the threads are not aluminum any more. You can purchase this at NAPA and you can keep the correct threads.
05-14-2010, 08:51 AM #3
Have a good welder build up a bead on the sheared bolt(s) heads. The weld heat will break down the LT,, then work the sheared bolt out by gripping the weld matl. with a Vise-Grip pliers.
Run some beeswax around the area while hot--the wax will wick into the threads and make removal easier.
Tough Break (pardon the pun)
Best of Luck to you---for this delicate job
PS: Lock-Tite *may* sell some type of chemical which breaks down that Yellow hybrid sealant as well.
05-14-2010, 08:55 AM #4
05-14-2010, 01:03 PM #5
- Join Date
- Nov 2007
I much prefer heli-coil if there is enough meat left around perimeter of hole,I use mapp gas instead of propane to heat areas that have large amounts of aluminum which acts as a heat exchanger and you cant get it hot enough with propane,also before drilling I level bolt with dremel,then using a center punch pop a divot in exact center of broken bolt,if you miss exact center ,center the pilot with dremel.If you drill you want to be in exact center.Also if bolt is a little loose,you usually can go to std thread size the closest thats bigger than the metric you removed.And for worse case yet if no room for helicoil,then heat and fill hole with a alloy rod such as HTS-2000. aluminum melts at1200+ degrees and these rods are harder and also melt at only 730 degrees,you can then grind,drill ,tap etc. as you want.They cost 70.00 a pound but are well worth it.They do not require flux only a first pass of heat then brush with a stainless steel brush then weld it,you can use it for anything from fixing a cracked exhaust manifold(it expands without cracking with the aluminum)to even welding up a .005 thick aluminum can,I have used them for both,hope this helps>Marvin PS. that yellow factory loctite requires a lot of heat like red loctite!
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