Basic question: How would you make this cut?

Z

Zoltan

Active User
Registered
So I'm very new to the world of milling, and I just have a mini mill.

I have an 8x4 piece of steel which is 1/8" thick, and I want to mill an edge of it flat. I originally clamping it on top of a pair of 123 blocks and tried running the end mill down it's edge, but it wasn't giving me a good cut. Before I start blindly trying other things, I'd like to ask to see how you would do it.
 
1/8" might be your culprit as it is thin enough to induce vibrations and is hard to hold rigidly enough to get a clean cut.

I think your procedure is basically good, you just need to tweak it a bit to add rigidity to the work piece, depending on what you have available you can try to following:

1. bring the workpiece edge to be milled closer to the 1-2-3 blocks to leave less material hanging off in mid air
2. clamp the entire workpiece to a sacrificial substrat and clamp both directly to the mill table - make your cut into the substrat which will keep the 1/8" workpiece more secure and less vibrating.

there is always the - change spindle speed and feed rate to reduce chatter.

what rpm and feed rate are you using?

do you have a picture showing your current setup for this cut?
 
Side milling is the best way to machine a large, thin part like that. If the surface finish is poor, make sure the end mill is sharp and rotating the proper direction (don't laugh, it's been done). Also make sure you are running the end mill at the proper rpm, four times the cutting speed (100 for steel) divided by the diameter of the end mill. For instance, a 1/4" end mill cutting steel should be run at 1600 rpm. You might also try taking a light clean up cut (.005") by climb milling for a better finish. Just make sure to snug the table lock up a bit when doing so.

Tom
 
Yes, all of the above and... make sure you do a conventional cut and not a hill climb cut.


Ray
 
Nothing wrong with a spring pass or light cut in climb cutting, just put a little lock drag on the moving axis.
 
Also, use a straigh mill, because helical mills tend to lift the part and induce the chatter, a slot cutter with straight teeth will work fine, a reamer, held close.
 
It seems like it should be easy, but I have found that what you are trying to do (mill thin mild steel sheet) can be a real PITA. I would recommend getting some sacrificial pieces of wood (plywood, or mdf, mdf is great because it is demensionally accurate, though it doesn't do too well with coolant...). Put your piece on top of the mdf/plywood, then put another piece of mdf/plywood on top like a sandwich. Make sure that there is not too much steel protruding from the wood, just a little more than you are going to cut, and really, it can be less, because that mill is going to cut through it like nothing compared to the steel. Now clamp the sandwich to the table with some strap clamps.

If you have access to straight flute cutters like Syaminab suggests, those should be great for cutting sheet, but I don't tend to keep those on hand. If you do a bunch of sheet goods, they would be a good investment, I can't seem to find a supplier that carries a variety recommended for steel though, most of them seem to be intended for aluminum/plastic/composites.
 
You must log in or register to reply here.
Back
Top