Cast Iron and galling bolts

[AllThumbs]

I am putting a VFD on my 8x12 lathe. This means a 3 phase motor needed to be mounted. After removing the old motor, I marked holes to be drilled and tapped into the cast iron for the new motor mount. I was playing with the position of the new motor to get the belts right, so that involved tightening and loosening the 1/4 - 20 bolts a few times. In no time two of the 3 bolts were stuck in thier tapped holes. One bolt I got out but the threads were stripped, the other bolt eventually broke off. Pissed me off.

My question is why did the bolts gall up in the cast iron? I thought cast was pretty forgiving that way. Yes, I drilled and tapped plenty deep. I can only think I didn't blow the crap out of the blind holes causing the cast dust to get trapped in there, siezing it all up. Thing is all was well until I tried to remove the bolts. They went in all the way with no effort.

I ended up drilling and tapping all new holes and greased up the 1/4 - 20 socket cap screws (ofter making sure all the cast dust was removed) and now all is well.

I'll put some photos in the machine modifications section once I am done this mod.

E

 

[zeusrekning]

May be an ignorant question but you weren't using stainless fasteners were you?

 

[d-m]

I think you have answered your own question. More than likely it was some cast matter from the taping operation. The best way I have found is to use your can of brake cleaner with the straw all the way in the bottom of the hole blast it and draw it out. Then use your blow gun wile it is still wet and you will have a clean hole. It wouldn't hurt to put a bit of antiseze to the bolts before installation.
Dave

 

[AllThumbs]

May be an ignorant question but you weren't using stainless fasteners were you?

No, standard SHCS.

E