Will it degrade the strength?
Need help with Hitch bolts
- Thread starter RepoDevil
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Malleus
Far west of Siegen
Not at all. I'd suggest being very careful about drilling the bolts out, though. It's unlikely that you'll get the drill in the center of the bolt, which means that the tap drill will run out through the threads somewhere. Also not the end of the world, but not desirable. I've stopped trying to drill out rusted bolts in frames and have resorted to a carbide burr on my Dremel. It takes the same amount of time, and I can control exactly what I take out and when.
Just carve out most of the bolt and when it gets thin enough you can unwind the rest with a pair of needle nose pliers. Run a tap through the weldnut and you're set.
If you decide to drill it out, use a center punch first. That way, you'll get the drill at least close to the center of the bolt. Step into the drill sizes by 1/16ths or 3/32nds until you get to the tap drill size. You really don't want to do this in one or two steps; you'll wind up breaking the drill and they don't drill out as easily as bolts. Carbide drills are also a big help, but the small ones break very easily. I usually start with 3/32" and move up from there.
This will leave an untapped area the size of the tap drill which you will then run a tap through to cut the threads. Don't exceed the tap drill size, or the threads won't have enough bite. The tap drill size is the nominal size, minus the pitch. So, for a M12x1.75 you need a 10.25-mm drill. A 13/32 drill will also work.
Just carve out most of the bolt and when it gets thin enough you can unwind the rest with a pair of needle nose pliers. Run a tap through the weldnut and you're set.
If you decide to drill it out, use a center punch first. That way, you'll get the drill at least close to the center of the bolt. Step into the drill sizes by 1/16ths or 3/32nds until you get to the tap drill size. You really don't want to do this in one or two steps; you'll wind up breaking the drill and they don't drill out as easily as bolts. Carbide drills are also a big help, but the small ones break very easily. I usually start with 3/32" and move up from there.
This will leave an untapped area the size of the tap drill which you will then run a tap through to cut the threads. Don't exceed the tap drill size, or the threads won't have enough bite. The tap drill size is the nominal size, minus the pitch. So, for a M12x1.75 you need a 10.25-mm drill. A 13/32 drill will also work.
mudgudgeon
Resident galah
Drilling and tapping an existing M12x1.25 out to M12x1.75 will definitely downgrade the thread strength.
If you can drill and extract the existing built and then retap to M12x1.25 would be a better option
Flank
American by Birth, Texan by the grace of God.
Alternative option:
Drill the frame member bolts out entirely, and add a 1/4-1/2" piece of steel behind it with some captured nuts, pass the bolts through the frame member to the new beefed up piece?
Drill the frame member bolts out entirely, and add a 1/4-1/2" piece of steel behind it with some captured nuts, pass the bolts through the frame member to the new beefed up piece?
