Safety question: mill as saw?

I do it all the time. The inside piece can come up and go flying. Make sure there aren't any chips underneath to keep it from dropping and feed slowly when the part is about to break loose. Randy

Is the latter

another alternative is to use a large diameter hole saw to remove the bulk of the mateiral. Costs are generally about 10$ for the adapter/hoilder and 10$ for a given size saw. 2 good US brands ar Morse and Starrett. One trick is to drill a smaller hole in a corner that the saw blade will cross to allow the swarf to exit easily. I have used this up to 1 inch thick steel. Deeper saws are available and you can drill the pilot hole through so you can saw from both sides.

GmcD

I've done this many times, too. I've never had the mill toss things very far (more than a few inches). One thing to remember, a large cutter turning slowly will be more inclined to throw things than a small cutter turning fast. And roughing mills are more inclined to throw things than a finish mill. A friend of mine (a master tool and die maker) keeps handy a piece of plywood with a handle on it that he holds up like a shield to deflect flying "stuff" (mostly because he doesn't like getting hit with hot chips...).

The big hazard with cutting a chunk out of the middle of a piece is that, if the chunk is too big with respect to the remaining metal, the work can bow and come out of the vise. This is usually MUCH more exciting than what happens to the piece you cut out...

The basic rule in using any machine (any tool, for that matter) is to think about what you are doing and, if you know an operation is hazardous, or just aren't too sure, take the necessary precautions to protect yourself, the machine and the work IN THAT ORDER. Far too many injuries (and busted machines) result when something happens and someone makes a grab for something trying to salvage the work.

Jerry

I'd mount the piece to the mill table with the bolt(s) going through the part to be removed. Put a piece of 1/8" plywood underneath when you do this so you don't cut the table of the mill. Plunge in one corner and go around the edge of what you want and one pass will do the whole thing. The big piece will pop up when you have the cut done and really won't go anywhere.

-- Why do penguins walk so far to get to their nesting grounds?

Jerry,

Funny, I did something similar just today: used cardboard to deflect wood chips from the cross-travel ways.

:) Back to the serious, I will keep that in mind. In this case, the work will be too large for the vice, unless I attach something to it and in turn put that in the vice. By the time I get that right, it will be easier to remove the vice and use clamps.

Good advice - thanks!

Bill

Bob,

Up? It seems that it would fall, or is the plywood under it too?

Do you see any harm in bolting both pieces? Well, probably bolting the throw-away (no harm drilling through it to do so) and clamping the "keeper". The hole is near a corner of a fairly large piece (15x20 inch or so), so it would cause trouble unless it is held in place.

Thanks!

Bill

Bob, that's not a very good way to go about the job unless the opening desired is just a rough cut, and size or finish aren't critical. It always leaves a sharp point the radius of the end mill, and generally a ragged cut with chip welding, even when well lubed.

What works best is to clamp the part to the table, then open the window undersized, leaving enough material for some finish passes that permit sizing and locating the window properly. By measuring and marking the dials, you can machine a close tolerance window easily, with a decent finish in the window by taking the last cut by climb milling. That pass should not be much of a cut (a few thou) , so you don't have problems with the cutter self feeding.

Setting the part on parallels is better than using a (wooden or other type) spacer, for it permits chips to clear the cutter by dropping through the slot as it develops.

Harold

Clamp it to the table, with a thick piece of something sacrificial under it. Plywood, MDF (which I usually use cause its flat)

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner