Fixturing Round Stock

[totalhack]

Crazy idea. Use square stock and clamp it with your pitbull clamps. Do the threaded portion, then screw it into whole to do the top. Slightly more material to remove but makes fixturing a lot easier. Mill won't care whether it's making round stock round or square stock round.

Thanks for the response, this actually sounds like a good idea to me. I already have more than enough mitee bite clamps for holding square stock and I don't care about the slight increase in machining. I could save some coin by using the clamps I already have and I like the thought of that very much.

Just thinking out loud here because I haven't done it myself.

Make two sets of soft jaws for your chuck. If the parts are as small as they look, the jaws could probably be quite a bit wider than your vise. Machine one set of jaws smooth to hold the raw stock. In that set of jaws, machine the boy side of the part. After you have finished the whole batch, machine a set of soft jaws by thread milling the jaws to hold the boy side of your parts, half in each side of the jaws. Thread them down and snug up your vise and complete the girl side of the parts. I don't think you are going to get 20 parts per cycle start but depending on the size, you could probably get 10+.

Thanks for the input. I already have a set of 7 inch soft jaws for my 5 inch vise and I did not like the results. It could have very well been my technique but closing the vise tilts the parts slightly which throws off the chamfers on the OD and of course everything else but the chamfer's were the only thing you could visibly see. Also the parts are 1 inch in diameter so I can't fit as many into the soft jaws as I would like.

[rlockwood]

I've forgotten most of the requirements of this job, but pit bull clamps really still don't do a great job if faced with holding incredibly tall parts. I'd probably make a block with a bunch of V's around the periphery, drill/tap a hole on each side of all of the V's, then make a bar clamp to span them. High part density, low material cost, V won't be perfect on the first op, but round stock is actually quite consistent on diameter, and the second op would repeat to the first quite well. Make two, and make them so they attach to a main fixture that stays put in the machine. Then you can load one up while the other runs, and the swap when it stops just takes a few seconds.

Keep in mind that when you place more parts on the table, more get ruined when something goes wrong. I'd suggest at minimum installing a simple switch as a tool setter and using it to verify tool length (and as such, breakage) once in awhile during the cycle.

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[totalhack]

I've forgotten most of the requirements of this job, but pit bull clamps really still don't do a great job if faced with holding incredibly tall parts. I'd probably make a block with a bunch of V's around the periphery, drill/tap a hole on each side of all of the V's, then make a bar clamp to span them. High part density, low material cost, V won't be perfect on the first op, but round stock is actually quite consistent on diameter, and the second op would repeat to the first quite well. Make two, and make them so they attach to a main fixture that stays put in the machine. Then you can load one up while the other runs, and the swap when it stops just takes a few seconds.

Keep in mind that when you place more parts on the table, more get ruined when something goes wrong. I'd suggest at minimum installing a simple switch as a tool setter and using it to verify tool length (and as such, breakage) once in awhile during the cycle.

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The parts are 1 inch diameter and 1.33 inch tall. I only need about .625 above the fixture plate for either side to machine what I have to machine.

I have heard others want to do what you are suggesting as far as a way to check tool breakage. Do you have a link to a write up on the subject? I don't currently have tool height setter but I do want one. I would be curious to see how you go about checking the tool length in the middle of a program and either continue working if the length is good or pause if the tool is broke. I'm usually in the same room when I machine parts just like to be doing something more productive than watching the machine so usually if I have a tool break I can hear it and I walk over and stop the machine.

[rlockwood]

So if attempting to hold them from the bottom, you'll have roughly a 20:1 lever acting against the clamp.. At the least, bury the part so that only slightly more than your .625 needed extends above. I don't actually run Mach3, but the idea will be the same. You'll use the switch to set length in the first place, this is fairly well documented and easily implemented. Then write a small subroutine that establishes the current length as a variable, checks that variable against the tool offset, and if the two numbers differ by more than some tolerance, fails.

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[sansbury]

This isn't a situation where I'd be too worried about tool breakage. When tools break it is for very specific reasons: dullness, too high feeds or speeds, problems evacuating chips, insufficient lube, or collisions. You're milling cheese metal, watch the first cycle and make sure chips are clearing well, use flood, sharp tool, you should be fine. When I break tools it is almost always on the first part or because of a crash because I didn't think things through enough.

[rlockwood]

This isn't a situation where I'd be too worried about tool breakage. When tools break it is for very specific reasons: dullness, too high feeds or speeds, problems evacuating chips, insufficient lube, or collisions. You're milling cheese metal, watch the first cycle and make sure chips are clearing well, use flood, sharp tool, you should be fine. When I break tools it is almost always on the first part or because of a crash because I didn't think things through enough.

Things do change when running unattended, but if you're close by enough to hear it break, odds are you'll limit the damage.. Planning on nothing going wrong seems to ignore Murphy's law.. Everyone has a plan until they get punched in the face.

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[sansbury]

Yeah, if you're trying to run lights out or something I agree, anything can and will eventually happen. I just wouldn't look at this as a job to worry a lot about. A lot of people run long jobs like this without breakage detection and do fine. If you wanted to be extra cautious, add a 10-second pause here and there to give you time to hit the big red button if SHTF before you scrap too many parts. I do agree that if you were going to leave for an hour you'd want extra protection.

[Zbuilder]

Get some CE (canvas) or G-10 (FR-4). Ebay or any plastics supply house. Get some steel to make some long steel jaws for your vise. Cut some soft jaws the same length & wide nough to mill some holes in the soft jaws wioth the vise closed. Place a 1/16" spacer in-between the soft jaws before you close the vise. Mill some pockets the same dia. as your stock rod by whatever spacing you can get away with.(a 1.250" spacing can yield 4 pcs in 6" long jaws, etc). Set up another vise, same size jaws but with holes to match the finished diameters milled in the 1st vise. Make the program to mill the top half of your parts in the 1st vise, jump up for clearance, then mill the parts complete in the 2nd vise. 2 station setup.