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cutting circles in 1" plate

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  • #16
    I have managed to cut a couple of 'wheels' from plate using my lathe.

    I fix the plate to the backplate on the lathe then drill the centre hole and use a piece of all thread as a 'drawbar' to fix the centre firmly to the backplate, the edges of the plate are already firmly afixed.

    Then I use a trepanning tool to cut the wheel out.

    N.B. It is important to have both the centre 'wheel' and the offcut edge firmly fixed to the backplate to avoid disaster at 'breakthrough'.

    A layer of sacrificial plywood saves my back plate from disfigurement!


    • #17
      First question is are you sure the application requires steel? Would delrin work? Second, how do you hold them in that lathe to clean up? Half and half? I make 8" sheaves for a stock product of mine often. Its not cheap, but you can buy slices from bar from McMaster-Carr as well, to sizes much larger than 6".
      James Kilroy


      • #18
        Originally posted by jkilroy
        First question is are you sure the application requires steel? Would delrin work? Second, how do you hold them in that lathe to clean up?
        I faced mine using external chuck jaws and trued the edges with the 'wheel' on an arbor.


        • #19
          Originally posted by Abner
          I figured as much, I just get tired of the clean up.
          Pulleys mainly for cable and odd mechanisms so sheaves wouldn't work.
          I should just go buy some 5-6 in shaft for the bigger ones.
          I do cable sheave sizes up to 18" OD on a regular basis.The ones up to 12" I buy from a metal service center,cut from round bar.They can saw and deliver as many discs as I need for not much more than I pay for the steel plate it would take to make them myself.Plus there is no hard skin.

          I use-

          The best part is I can get any alloy I want,for pennies more with no nasty torch scale to waste tooling on.

          The 12"+ sizes I have laser cut,much,much less slag than gas or plasma and much cheaper than waterjet.An additonal benifit is any spokes,or bearing bores can be programed and cut at the same time and need only slight cleanup for preess fits.
          I just need one more tool,just one!


          • #20
            Trepanning looks like the better option if I want to do it myself.I have both a mill and a lathe. If I don't want to buy trepan tooling I could use my lathe.

            The cutter shape - any details? looks like it would be easy to get vibration.

            I like the idea of buying discs, I guess I will have to get off my wallet
            Last edited by Abner; 12-11-2010, 07:49 AM.


            • #21
              An easy but slow way----

              Is to use a holesaw. Put blank in chuck, centre drill, then hold holesaw in tailstock chuck, drill centre hole, put lathe in backgear, cut half depth of holesaw teeth, withdraw, tap holesaw with chuck key or small hammer so that the swarf in the teeth falls off or/ and brush teeth with disposable paint brush, put a few drops of cutting oil on if cutting steel and repeat until about half way through, reverse the part and repeat until you are through. IF you go all the way through the blank you cut out may wedge very firmly in the saw, if you reverse it it will fall out easily, dont ask why, I really do not know! If you are gentle even cheap hole saws will work well, it MAY speed things up if you grind off every other tooth. If you try to take too deep a cut you will BREAK off some teeth and maybe jam the saw very firmly into the work. Some machinists have told me this is not a " proper" procedure but it works for me. Regards David Powell.


              • #22
                You should ge able to make your own trepan tool for the mill. I'd think you could make one with some large rod stock. You'll want to make sure it is rigid and well secured and fairly balanced. Run it at real low RPM until you are sure it is working well. I think you can make your cutter bit out of 3/16" or 1/4" round drill blanks. I'm not sure what cutter geometry would work well but you could experiment. Something tells me you would want to back grind your cutter so that it has clearance like a lathe parting tool does.

                A guy I know turned a small diameter trepan tool on the lath out of O1 and then hardened it with a torch. I think it was for making 1" discs. It kind of looked like a hole saw but with 2 large teeth and was alot more rigid. You really only have to harden the two teeth and then temper them and grind to sharp.

                Edit: Toolguy already suggested it, but a rotary table can make these cuts with an endmill. If your stock is precut (bandsaw) to be just above your size you only have to cut off the corners.

                Last edited by KEJR; 12-11-2010, 02:39 PM.


                • #23
                  I read about making your own holesaw using sections of bandsaw blade attached to a suitably sized disc. I have tried that in a small way and it works. One difference between that and a regular hole saw is that you can have a lot less teeth in the workpiece, so with reasonable pressure, each tooth gets a proper bite into the steel. Also there's way more clearance in the kerf because you'd only have sections of toothed blade and not a full hoop.

                  I don't see my experimental tool right now, but I believe what I did is drill and tap around the edge of a metal disc, then grind a slot in both ends of the bandsaw blade sections. The bolts hold each section in place, putting the curve in them as they are bolted on. That makes them align properly and the teeth have the same type of clearance that they did in use as a bandsaw blade.

                  I have made several types of trepanning tools over the years, most of which are a single cutter on the end of an arm, basically. To balance the forces, you could start with a piece of bar, length to suit the diameter of the hole you need to make, then round each end and attach a blade section to each end. The bar is mounted to the mill spindle in whatever way it can be made rigid. You could machine a recess in a metal disc such that it would be a close fit to the end of your spindle, then use a drawbar to keep it there. The piece of bar would be fixed to the disc, possibly being threaded through along with the disc for the drawbar. In my case, this has resulted in the most rigid tool mounting method, better than using a morse taper adapter. In one case I used both a short tapered stub and the recessed disc to fit my spindle.

                  In any event, this bar with two cutters will be evenly loaded when cutting, so the possibility exists for smoother cutting action. The bandsaw blade sections that you bolt on are replaceable, so it's basically a matter of getting your attachment method figured out. Drilling the blade sections is not usually an option for me, but grinding a slot in each end is easy. When the length of each piece is right, and the depth of the slots is right, the fit can be very close. You should be able to find bandsaw blade sections without too much trouble- a local shop gave me a few pieces which were either leftover from making up blades, or pieces from where they had damaged a blade and it couldn't be used on their machine. Either way, you basically get new teeth, or at least perfectly usable teeth, and probably HSS of a good grade.

                  Depth of cut will obviously be limited to the width of the blade material less the bar thickness. You would probably have to make sure if you turn the material over you can center it again so the cuts meet. You also have the option of grinding away some of the teeth from each blade section to leave an appropriate number of teeth for the best cutting action with the available torque from the machine.
                  Last edited by darryl; 12-11-2010, 03:22 PM.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                  • #24
                    Just noticed there's one of the multi-tools for sale used here:
                    Nice guys to deal with. Been to their shop many times.


                    • #25
                      If you have a mill, a hole saw works great up to 6" and 1" thick. Sawing a plate that's more than about 1/8" thick requires a couple of holes to allow the swarf to fall out. Put the hole location so that its OD intersects with the kerf of the hole saw, either inside the circle or outside, depending...