I would love to get some advice before I mess up again.I am trying to mill the following out of 1.125 in copper rod. the first time through I couldn’t figure out how to hold down the material so I shaped the octagonal on the belt sander, then milled out the bottom ( previous post) then this top slot was a problem. I assume I used a dull bit because it couldn’t cut a straight line. 1/8th inch bit, 7 mm/sec, 0.5 DOC. next time I will use a fresh bit and slow down the cut. additionally I will cut this first, instead of last.
when it comes to shaping the octagonal ( ~ 1 x 0.75 inches) I can shape it on the belt sander like last time, or the MPCNC. with the MPCNC, I can either mount the copper rod horizontal in a vice and flatten each face, or screw it down to the spoil board and try to shape the octagonal. what would you do?
thank you
The image seems to have gone missing, but I assume this is an accent piece for one of your knife handles (which I covet, although I have neither the space nor the expertise to warrant one). I am torn re: MPCNC vs. Belt Sander. If you have a slot already cut in the blank, you could use a flat pan-head screw (or two, to prevent rotation) to affix it to your spoil-board (or use the blue tape & super glue trick). Then you could cut the perimeter in one go.
But thinking about it… If you have 45 degree wedges, it’s dead simple to flatten the stock one side at a time. Figure out how much you’d need to remove, set up a job to flatten an area slightly larger than the projected surface area of any given face, then zero your bit to the copper blank. It’s already a conductor, so you don’t even need to hassle with the offset of a plate. Just make sure you’re zeroing to the crown of the stock. Then, as you rotate the stock, and you reveal the faces, they will register on your wedges (or jaws of your vice). Keep zeroing your Z axis, since you’ll be subtlety changing the height of the stock as you flatten one face and rotate it.
I tried flattening with blue tape as a hold down… I lost that piece when it fled across the room.
I think it would be very elegant it shape the octagonals on the MPCNC, but this is only rough shaping and the belt might make sense.
my current plan is to mill the internals first with the MPCNC, then rough shape the copper pieces on the belt grinder. I may flatten the rough cuts on the MPCNC.
once the roughly shaped pieces are epoxyed together, I will shape and polish everything.
PS I am running a knife giveaway on Instagram @bensbites. That would be the easy way to get one of my handles.
Can you clamp it in a vise, like you would on a drill press? If you’re short on vertical space, you could try to clamp it, and then clamp the clamp down.
It is a pretty small piece right? I would think super shallow passes would keep the load way down and it would cut better.
I have been clamping these down in a drill press vice, then clamping that to the guide rails. That has worked pretty well since the painter tape copper flying issue. I am pushing the vertical limits of my MPCNC. I am seriously debating raising the legs and using spoil board spacers when I need to cut short items.
I’ve been pondering this some more. For MPCNC, I’d be tempted to mill a longer blank (8-12") that you could then slice individual pieces off of as needed. That, of course, presupposes some vague “standard” for sizing, but if that’s a possibility, it could make things easier in the long run.
But now that I see the picture, and it’s a hole, not a slot, that makes things more… interesting. You would need to make a jig or two… Low-profile hold-downs… Not impossible, and possibly worthwhile, depending on the repeatability of the pieces. And they’d still require some hand-filing to square the inside corners (unless you’re OK with dogbones internal to the handle)…
Not sure what your vise looks like but you can get some cheap low profile vises that don’t raise the material up very much. I like mine. I mounted it on a square of wood that matches a hole in my spoil board so I can swap it in and out when I do metal.
I have not tried milling any metal, but I’ve used a “poor man’s” vice on my Lowrider a bit.
I use blocks and wedges to “clamp” some work pieces. I put the piece between 2 (or sometimes 4…) blocks, and then set a wedge in between the work piece and one of the blocks…a good rap with a hammer sets it pretty tight.
I have been using blue tape and superglue with wood no problem. I assume there is an important ratio of surface area taped down to milling force. When the first piece of 1/4 in copper flew off the mpcnc I am determined to use my drill press vice and clamp it in place.
Today’s update. I milled a 16x4 mm slot in the top of the copper 5 mm deep before the bit broke. 1/8 inch 2 flute endmill amazon cheapo running 0.25 DOC and 5 mm /sec. in the bottom side I was able to mill the same 1/2 inch hole x 15 mm deep as the previous attempt.
Tomorrow night I will use a drill press and files to connect the holes and shape this on the belt sander.
