Question about using M10X1.5 thread chaser.....

[HuskyMan]

on the 1984 300DT, using M10X1.5 Lang tools thread chaser to clean up threads in the passenger side motor mount arm. I placed some Kroil oil on the chaser; the chaser goes easily about 1/2" into the threads. At that point, I need to use a wrench and it becomes harder to turn the thread chaser the further I go.

I backed it out because I don't want to ruin anything. I then carefully measured the actual M10X1.5 bolt in a new motor mount and it looks like I need to chase the threads another 1/2" or so.

Question; if I keep turning the chaser can it damage the threads? I read on the Lang website that if it gets difficult to turn the bolt a turn, then back out a turn then go back a little further, etc.

[Diseasel300]

If it's binding up, the threads are probably already damaged. I prefer to use a T-handle when driving taps or chasers down damaged threads. It keeps the torque perpendicular to the hole, a wrench has a pretty significant sideload/orbital motion that can destroy the threading.

[tangofox007]

Originally Posted by HuskyMan

Question; if I keep turning the chaser can it damage the threads?

If it's too hard to turn, you can break the chaser off. You don't want to do that.

[MCallahan]

Use a T handle tap wrench to keep the chaser straight and to avoid breaking off the chaser. As said, break that off in the hole and your life will immediately suck beyond compare. It's harder than any drill you can get your hands on. Only solution is a tap disintegrator (electric discharge machine) or a carbide endmill (can't hold it with a hand drill because it will chip and break, too).

[HuskyMan]

Thank you for the replies, unfortunately I do not have a T handle so I used a 1/2" wrench to turn the chaser. I sprayed lubricant in the hole and on the chaser before beginning. I worked it clockwise half turns, then back counter-clockwise then clockwise again until the chaser went as far as it could.

I then used a large 2"X4" board to manhandle the engine to force the motor mount into the correct position. I then placed high quality blue thread locker on the M10X1.5 bolt. I left the 6mm allen top bolts loose, which allowed me to move the motor mount into position to insert and tighten the M10X1.5 bolt from below. The M10X1.5 bolt went in smooth as silk!

All appears well, this morning I am starting on the driver's side motor mount which doesn't appear to have the thread issues the passenger side did.

On another note; I am thinking when the original M10X1.5 bolt slowly worked its way out, it stretched the threads.....

BTW, where can I purchase a T-handle that will work on these metric thread chasers. Funny enough, it took a 1/2" SAE wrench to turn the metric thread chaser......weird.