Stripped thread hole repair question

[muddy42]

What I wish is somebody would tell me the trick to getting the hole drilled straight. Doesn't matter much on a screw hole. But, on a bar stud if you are off angle just a little the cover won't fit.

Fair question, this is important. Take your time. Get the saw dismantled as much as possible, no handle, covers or starter mechanism. Then mount the saw on a wooden board, you can chock it and clamp it, place a drill in the hole you are trying to bore out - check this is square to your drill press or use spirit level.

Its called a bottoming tap if your looking for one.

I regularly break taps so i just keep and regrind a broken one flat

 

[ZeroJunk]

Its called a bottoming tap if your looking for one.

He just grinds one flat on the end is what he is saying.

 

[ZeroJunk]

Fair question, this is important. Take your time. Get the saw dismantled as much as possible, no handle, covers or starter mechanism. Then mount the saw on a wooden board, you can chock it and clamp it, place a drill in the hole you are trying to bore out - check this is square to your drill press or use spirit level.



I regularly break taps so i just keep and regrind a broken one flat

I need to get a better drill press. I did a TS420 over at my brother in laws shop and I cut wooden wedges and everything else.. LOL Should have been on the three stooges.

 

[singinwoodwackr]

Droll p

What I wish is somebody would tell me the trick to getting the hole drilled straight. Doesn't matter much on a screw hole. But, on a bar stud if you are off angle just a little the cover won't fit.

Drill press and a 3-axis vise

 

[singinwoodwackr]

Fair question, this is important. Take your time. Get the saw dismantled as much as possible, no handle, covers or starter mechanism. Then mount the saw on a wooden board, you can chock it and clamp it, place a drill in the hole you are trying to bore out - check this is square to your drill press or use spirit level.



I regularly break taps so i just keep and regrind a broken one flat

 

[ZeroJunk]

How do you mount the power head in your three axis vise ?

 

[singinwoodwackr]

The hole was so badly augered out it was quite a pain to get a centered hole drilled at all. Trick is not to let the drill blow out the side of the case.
I wound up carefully using a 6mm die grind bit to get a half way round hole then tapped to 1/4-20.
I threaded a piece of 1/4" AL rod and ran it all the way down and JB'd it all in place.
Next step will be to drill/tap for 5mm bolt.
We'll see...
Filled in some badly worn spots as well.

Will machine it all down tomorrow and see what happens.

Is this Husky orange paint available?

 

[singinwoodwackr]

How do you mount the power head in your three axis vise ?

Haven't had to try that yet. So far just a cylinder. I made up a bunch of shims to get this case halfway square to drill. I gave up in drill bits as they kept wandering and used the die grinder...easier to control.

 

[stihltech]

Use a tube with a square end. I use one of the seal installers I have for bar stud helicoils. Side cover fits well afterwards.

 

[ZeroJunk]

Use a tube with a square end. I use one of the seal installers I have for bar stud helicoils. Side cover fits well afterwards.

OK . I think I get the picture.

 

[Husky77]

Haven’t tried braising cuz I’m afraid I’ll melt the magnesium
i have, however, drilled, tapped in a 5/16” or 8mm bolt, secured it with JB weld and then drilled/tapped for 5mm/.08 and done well In a cylinder…muffler bolt hole.
am in the process of repairing a very bad top cover bolt hole in a 372. Stay tuned…

have you seen magnesium burn????? look into it before even thinking of putting a torch near it

 

[singinwoodwackr]

have you seen magnesium burn????? look into it before even thinking of putting a torch near it

Jr Hi chem class

 

[singinwoodwackr]

ugly but functional

 

[Armosh]

ugly but functional View attachment 1141290View attachment 1141292

Nice work! I have not got the hang of fixing stripped holes like that yet. I can deal with just stripped threads but twice now I've run into the hole just being wallowed out conically, the hole is more egg shaped and oval than round. I think I'm just going to start blue loctiting every last damn screw

 

[fields_mj]

I regularly break taps so i just keep and regrind a broken one flat

I've always done the same thing with broken or dull taps. Having said that, with regards to heli-coils and the like, it's worth noting that a bottom tap still has a slight taper to the last couple of threads. Its less taper than a plug tap, but its still there. It shouldn't cause a problem, but be aware that the end isn't actually square like it would be if you ground the end off. If I'm putting heli coils in a blind hole, I start off with at least 2 taps, with one being a plug tap. I prefer for the 2nd to be an actual bottom tap because that 1 to 1.5 threads of taper does make it a lot easier to cut those last threads where as an absolutely square corner puts all the cutting force on the leading tooth making it harder to cut, and easier to break. When I'm done, if I'm concerned about it, I'll grind the bottom tap square and go back one more time and cut the very last thread. The only time I went to that much effort was when I was putting inserts in to the engine block on my '83 Ford 1710 tractor. Most of the mounting bolts were loose and the threads were wallered out. It was bad enough that the vibration would wear out o-ring seals on part of the hydraulic system ever 8 to 12 hrs of operation. I installed the longest helicoils I could get, and was thankful that I didn't poke through anything while drilling. Since cast iron threads aren't really the strongest, and the diesel engine on a utility tractor is prone to experience a fair amount of vibration, I wanted every thread I could get and I wanted all of the torque to be going into the clamp force. I've checked them a few times since, and they've stayed tight. Now I get about 24 hrs of use before having to replace that o-ring. Not ideal, but I only gave $2K for the tractor with the loader, so I'm not going to complain too much.

 

[fields_mj]

I wound up carefully using a 6mm die grind bit to get a half way round hole then tapped to 1/4-20.

FWIW, if you can get the work piece secured adequately, I've chucked an endmill in my drill press to make a round hole again, and then followed that with the appropriate size of drill bit to get the final diameter. The end mill is way too stiff to deflect or walk, but it will certainly throw your work piece around if it can. High rpm with a very slow feed rate seems to be the trick. Easier to do on an actual mill, but it can also be done with a drill press. I don't think it can be done with a hand drill though.

 

[singinwoodwackr]

FWIW, if you can get the work piece secured adequately, I've chucked an endmill in my drill press to make a round hole again, and then followed that with the appropriate size of drill bit to get the final diameter. The end mill is way too stiff to deflect or walk, but it will certainly throw your work piece around if it can. High rpm with a very slow feed rate seems to be the trick. Easier to do on an actual mill, but it can also be done with a drill press. I don't think it can be done with a hand drill though.

Exactly. The tough part is getting what you need drilled completely secure.
I’m usually too lazy to spend the time needed to do this . I did it on a 350 cyl, muffler bolt hole…and it turned out great. I have another to do so will repeat the process. There is no way to do it with hand tools.

 

[SteveSr]

What I wish is somebody would tell me the trick to getting the hole drilled straight. Doesn't matter much on a screw hole. But, on a bar stud if you are off angle just a little the cover won't fit.

I put the tap in a drill press with the belt disconnected, level the target on the table and start the tap by hand by turning the chuck. Once the tap is started straight loosen the chuck and continue as normal.

 

[lone wolf]

What I wish is somebody would tell me the trick to getting the hole drilled straight. Doesn't matter much on a screw hole. But, on a bar stud if you are off angle just a little the cover won't fit.

https://www.mcmaster.com/products/tap-jigs/

 

[ZeroJunk]

https://www.mcmaster.com/products/tap-jigs/

They used to send me catalogs that were 3 inches thick. Doesn't tell me what to buy.