Drilling cast iron

Jim,

Have you considered NOT drilling at all? I have used "soft jaws" on a blacksmith's post vise which were simple "J" bent pieces of steel plate that slip over the top of the vice jaws to protect the work piece. You may be able to create a wooden version of this that can wrap around the top or sides of the vise and then use a couple of screws to hold the wood faces in place. It looks like there are plenty of recesses on the back of the vise jaws for the bolts/screws to lock into.

Hope this helps, Paul

From behind with something like a hard wood if you can...

Standard drills at Approximately 10% faster than steel RPMs but much less thrust... Just pull the handle easy on your drill press and let the bit do most of the work. Very little downward pressure is needed. You can run at the same RPM as steel (3/16" around 1500 RPM) and barely pull that handle to drill a few holes like this.

If you had LOTS to do, there would be a faster way... But that's not needed.

Oh look at that! 3/16" it is...

Counter bore some holes in the wood liner and install a few rare earth magnets. This way you can make different jaw liners.

Wilton sells fiber and rubber jaw liners that work well. They attach with magnets and stay put pretty well.

I have drilled CI castings and I have always used normal drill bits. Well, maybe not normal, there are Chicago Latrobe with split points.

I doubt you need anythings special for a small shallow hole.

My Darex manual mentions using 90 degree points and double angle drills which I have not heard of before. Should I consider making a set for CI use?

chuck

If grabbing at breakout is your problem you drill from both sides. Set your stop for .050 breakthru and flip the part. See:

wws

hone drill edge just enough to take the sharp edge off, a slight flat, could be a little negative.

use no oil, a little kerosene would be okay.

sjm1.pitt

Glue your wood to some soft copper sheeting which has been cut to "hang over" the jaws on the vise.... Ken.

The biggest concern is if the iron is chilled. If it is, it will be very difficult to drill. Free machining cast iron is gray in color, although it could have a tough "skin", which is a shallow layer of chilled iron and sand on the surface. If it's white in color (inside), the chance of drilling it is very small due to hardness.

For the small amount of work you're facing, a standard HSS twist drill should work fine. Gray cast iron can be drilled dry, thanks to the free graphite in its makeup.

Harold

Grind the drill's cutting edge a bit negative on its front face so that it drags and scrapes the iron off rather than digging in and lifting it. This also applies to turning cast iron; the tool should have a downslope on its top surface. Cutting dry is best.

Dan

Rare earth magnets - very clever, I hadn't thought of that.

Thanks

Jim

If you can avoid drilling, do so, the magnet idea is good. Otherwise, I've just used good, brand-name split-point bits with no problems. If you get a chilled spot, you're going to have troubles and Asian castings seem to have those. One hole will be like drilling pine, the next will shuck the flutes off the drill. The only way to avoid chilled spots to to anneal the casting and that's not going to be easy to do without damage on a completed part. It should be done during manufacture, but it costs money, so it's not one of those things that gets done on import items that sell to a price.

Stan

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