Need to fix an eff up, can I fill a hole in cast iron with silicon bronze?

[benmychree]

One issue that has not been brought up is the likelyhood of cracking of the cast iron from concentrated high heat, a distinct possibility, better to explore other options, perhaps a steel plate sub base for the motor held onto the cabinet with flat head screws and tapped for the motor base???

 

[Nutfarmer]

Putting enough heat to braze or weld up the holes will most likely warp the bed. If it was mine I would tap the hole and plug it. If you have to drill into the plug lock it in place with a soft steel pin between the threads of the plug and the base metal. This will help to keep the plug from turning

 

[pontiac428]

If you can't pre-heat the bed in a furnace and re-grind it after the hot repair, it might be easier to plug, drill, and move on. It looks like it will be invisible. We all learn from boo-boos. It might make sense to set up a mag drill jig of some type to get your holes square and spot on if this is an alignment-critical assembly.

 

[Gaffer]

I think John's (@benmychree) solution of a steel plate makes the most sense given the working environment.

 

[mattthemuppet2]

definite no on the endmill in an electric drill, that would be a disaster.

If it were me I'd first try making some mild steel plugs (you could even use set screws), loctite or JB Weld them in and then grind them flush. Make up a 1/2" thick plate as a drill guide and attach that to your lathe base before redrilling the hole. It's way easy to get holes off center or angled, I've done it countless times. Another tip is to use some screw machine/ stub length drills, they're shorter and stiffer, thus less likely to wander.

 

[Bi11Hudson]

Any possibility of rotating the motor 15 degrees and redrilling the bolt holes??? Just a thought. . .
.

 

[WobblyHand]

I think John's (@benmychree) solution of a steel plate makes the most sense given the working environment.

Perhaps it does, but I don't understand the explanation. A simple sketch or something would be helpful for me to understand the gist of the idea.

 

[WobblyHand]

Any possibility of rotating the motor 15 degrees and redrilling the bolt holes??? Just a thought. . .
.

The opening in the lathe just allows the square stepper motor body through it. The plate is machined so the motor is inset into the plate to get the right pulley spacing. Can't get to my computer now to post the drawing.

 

[WobblyHand]

definite no on the endmill in an electric drill, that would be a disaster.

If it were me I'd first try making some mild steel plugs (you could even use set screws), loctite or JB Weld them in and then grind them flush. Make up a 1/2" thick plate as a drill guide and attach that to your lathe base before redrilling the hole. It's way easy to get holes off center or angled, I've done it countless times. Another tip is to use some screw machine/ stub length drills, they're shorter and stiffer, thus less likely to wander.

Need a longer drill bit to clear the chip pan. The drill chuck fouls the chip pan. The upper holes were done with stubby bits. They are not great but they are ok. It's the bottom two holes that are kicking my butt. The motor mount plate is 20mm thick steel. I was using the slots in the plate as a rough drill guide. Wonder if I could fit a small mag drill there. The plate is about 100*127mm.

 

[Flyinfool]

There will not be a lot of force on that plate in use. Since you need a very long drill to get past the chip pan, you definitely need to make up a drill guide plate. That is about the only way you will get the holes in the correct position and straight.
As for the holes you already have. Can you make the slots longer and then move both holes toward the center of the mounting plate by about a half inch or so, so that they miss the bad holes and you still have full adjustment range. Clean out the bad holes real good and fill them with JB Weld, no one will ever see them behind the stepper mounting plate.