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Trepan a big washer?

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  • Trepan a big washer?

    I need to make seven large washer-like disks. About 230mm (9") OD and 150mm (6") ID. Material is 3mm (1/8") 316 stainless.

    I was thinking of using the lathe faceplate or a rotary table, but then I thought about trepanning it on the mill as it would be easier to set up. I've got a slightly overbuilt indicator holder for a fly cutter head that I could use. The indicator holder is 1" square.

    So what do you suggest? Faceplate, rotary table or trepan? Carbide or HSS? I've got a carbide face grooving tool that I could use.


  • #2
    Faceplate.
    Using measurement instrument holders for machining is a total no-go, even if it's overbuilt. Just the idea!

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    • #3
      Second vote for faceplate. Would consider trepanning 230mm stainless disk on a mill only if your mill is super heavy monster(at least the tool taper is promising)

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      • #4
        Mill is one of these https://www.machineryhouse.com.au/M585D

        Not a super heavy monster, but probably more rigid than a BP as the head doesn't nod. Weighs 1.7 tonnes.

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        • #5
          Hi,

          Yeah, I would do a face plate too. Your mill is a bit better than a Bridgeport, but it's still going to be pissed at you.
          If you think you understand what is going on, you haven't been paying attention.

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          • #6
            No, I don't think that machine is going to be good enough Seriously, I'd have some reservations about trepanning at that size in stainless to begin with. I'm in the faceplate camp- I'd probably band saw them out roughly, then mount on a faceplate and turn out the center disc, then re-mount using the center hole so you can turn the OD. Just my thoughts on it-
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #7
              I would rough it out first with a plasma cutter and use the mill to drill a center hole. Then I'd put on the lathe faceplate and put the part against a piece of MDF against the faceplate with pieces of kraft paper between. Hold it there with a live center in the tailstock. Now you can either turn it to size or trepan, your choice. Either way you can dig the cutter right into the MDF, no damage to the faceplate or part.

              After you get the OD finished you can put the part in a 4-jaw carefully and trepan the inner hole.

              metalmagpie

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              • #8
                Thanks all. No bandsaw or plasma cutter here. Any concerns about only clamping it from the outside, cutting the ID, then cutting the OD? The minimum distance between slots is about 200 mm (bigger than the ID of the part).

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                • #9
                  I would go with the faceplate. Clamp the blank with some sacrificial material behind it. Grind a narrow trepanning tool.You want a lead angle on the tip of the tool so the side facing the part breaks through first. Cut the hole first, then the OD. Be prepared for some excitement when the tip of the tool breaks through.

                  You might consider fastening the blank to the sacrificial material with glue or double sided tape. That could prevent material from shifting when the tool breaks through. Less excitement that way.

                  edit
                  Better yet screw the sheet to the backing inside the 6" dia. Several screws. Cut the outside first, then the inside. You might want to consider drilling and tapping some holes in the faceplate inside thr 6" dia. to better grip the sheet.
                  Last edited by Illinoyance; 03-28-2019, 11:54 AM.

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                  • #10
                    Why not rotab on the mill with a backer board? Sounds real boring to me compared to the potential "excitement" of the other methods.

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                    • #11
                      Use the more rigid machine. And depends on speed you want to be around 50 rpm if not using carbide..
                      1/8 is pretty easy cut, even if you got to widen the cut

                      But if you have a place nearby that plasma cuts, you can often get it cut very cheaply , no real setup..

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                      • #12
                        Perhaps not the best choice for this exact job, but the usefulness of hole saws for this sort of thing needs to be considered. Since I made a decent arbor for hole saws (in the shop made tools thread) I've been able to make large washers with less effort.

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                        • #13
                          Lookup an SPI trepaning tool. I bought the bit from them and made a holder. It is angled in a way that it doesn’t chatter at all.

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                          • #14
                            Stop messing around--get them laser cut...
                            Keith
                            __________________________
                            Just one project too many--that's what finally got him...

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                            • #15
                              Originally posted by garyhlucas View Post
                              Lookup an SPI trepaning tool. I bought the bit from them and made a holder. It is angled in a way that it doesn’t chatter at all.
                              This

                              I'm betting your curious as how the trepaning would work. I would go for it, if i were you.

                              I know I'm curious.
                              John Titor, when are you.

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