Are there rules about how far out you can hold material blanks?
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  1. #1
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    Default Are there rules about how far out you can hold material blanks?

    I have some parts, made from 3/4 x 2-1/2" 1018 cold drawn steel. Saw cut about 6-1/4" long has some work on both faces and one end.

    hb44ct4.2.1-1.jpg

    It has a step down on both faces, and is designed to have a removable cap.

    I want to hold it in an Orange delta4 vise. I think if I hold it on the "cap" side, I could drill and mill bore the bore, rotate on 4th axis, mill the end, rotate, mill the other face, rotate, mill the 4th edge. Mill a 1/8" wide by 1/8" deep groove on each face and then use that on band saw to separate.

    My question then, is how much do I need to hold onto to help stability. I have to think this thing is going to want to sing.
    Will it hold it square enough in the vise to use the 3/4 bar, or would I need to use 1" thick bar and machine every surface?

    Or would it be better to get 3/4 bar, but maybe 1 inch wider for the delta 4 to really grab onto. I dunno, just looking for ideas before I go too far down the wrong road.

  2. #2
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    I treat it like bar stock for a turning operation. You can pretty much go crazy up until 3XD sickout. Slow it down a bit, but otherwise pretty confident until 5XD stickout. Anything over 5XD and you are going to have to be careful, or possibly figure out a way to support it.

    .750 x 2.50 x 6.25 is right at that spot where it's going to start to get hairy. Step it up to 1.00in thick, and you are back in the comfort zone.

  3. #3
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    I'm not exactly sure how you'll be holding it, but I'd prefer to stay with stock that matches the part thickness. If there's an area that you could put even a small 60* divot into the center of the outboard end and use a tailstock support to stabilize it, you should be set.

    I've kludged tailstocks if I've not had one on hand, so don't let not having a bespoke TS available stop you if the basic idea will work for you. Just a tiny divot/center will stop the part from ringing.

    Even pressing a center into the end of the stock firmly (no divot) can work, so you could do the end trim after the rest of the machining is done and remove the mark from the center at that time. It would need an M0 and moving the tailstock back, of course.

  4. #4
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    It depends on how much cutting force you wish to use. There are no hard fast rules, like everything, it just depends...


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