Trepanning tools, suggestions
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  1. #1
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    Anyone have any pointers on making an adjustable trepanning tool to cut holes 5 to 7 inches in diameter. Material to be cut is 6061, thickness 1/8 to 3/8. I've got beefy 50 taper machines to use this on so low speed operation is not a problem.

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    Are there holesaws that big? Not sure really but that would be my first choice. Maybe figure out how to make a large one from some heavy bandsaw blade (?)

    Next choice would be to drill a pilot hole, weld a bandsaw blade thru there...

    Trepan...kind of like a boring bar but has to have relief so the cutting edge is bigger than the shank plus some radiused relief...it gets to be a battle between the rigidity of the shank vs. the "form tool" cut of the cutting edge.

    However, I see you only have 3/8" thickness so I think you may come out in good shape.

    Those parting carbide inserts with a "U" shape that curl in the chip come to mind, but those don't have the radial relief...you might be able to do this with a HSS toolbit best for the relatively short depth of cut, just grind away enough to keep it from dragging.

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    One of the first jobs I did on my W&S #3 was trepan a 1/4" W with 1/4"R in bottom on a 5-3/4" D circle in 304 SS. Bought a Valenite tool for the job, worked great. Oh yes, had a 100 pcs to do.
    Harry

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    Matt,

    Basically I need rings 5.25" ID and 7" OD out of the afore mentioned .25 and .375 stock. I was thinking about making two cutter configuration to balance the cutting forces, and mount the thing to a shell mill arbor for mounting. I haven't found hole saws in either of those sizes. The bandsaw blade idea is not a bad one, but probably a lot of work. I am in a bit of a time crunch so I might just have to buy some tooling.

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    Here is picture of a trepanning setup cutting 3” diameter holes in 6061-T6 ½” thick aluminum plate on a 12” lathe. I used a Swiss made SPI Valcut trepanning tool with 6mm bit cutting speed was 70 rpm feed 0.0013 “ /rev Valcut uses the dragcut method in which the bit centerline is ~6mm below lathe centerline.

    http://i72.photobucket.com/albums/i1...repanning1.jpg

    Don Clement
    Running springs, California

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    That's what I would have in mind also. Just be sure to not stand in line with the part once the tool breaks through.(Even at 70 RPMs)

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    What I do is to trepan within a few mils of bottom of the cut, stop the machine then hit the plug with a rubber mallet. This eliminates the problem of the plug breaking the trepanning tool or flying out.
    BTW Travers, KBC carry SPI Valcut trepanning tools for both the lathe and mill. In the Travers 2007 master catalog new item brochure page 7, is an illustration of a Valcut trepanning tool model# 3000-5 for the mill that has both an internal toolholder and external toolholder set to cut different diameters on the same tool. Presumably one could cut large rings in one operation from aluminum stock.

    Don Clement
    Running Springs, California

  8. #8
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    Don,

    Thanks for that setup pic, can't ever have too many setups pics. I'll check into that valcut setup, which sounds exactly like what I am looking for.

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    Thanks for that setup pic, can't ever have too many setups pics. I'll check into that valcut setup, which sounds exactly like what I am looking for.
    I bought the SPI trepanning toolholder and several bits: one for OD cutting, one for ID cutting and one for grooving. The bits available from them for their holder are cobalt steel with a complex profile.
    Here are a few pix, from the PM archives:

    http://www.ibiblio.org/ecolandtech/m...nning_tool.jpg
    http://www.ibiblio.org/ecolandtech/m...hop/Valcut.jpg

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    Here is the page from the Travers 2007 master catalog showing SPI trepanning tools note the picture of the model #3000-5 with both internal toolholder and external toolholder on the same traneversal bar.
    http://www.travers.com/pdfshow.asp?p...&newp=Page+%23

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    Just a thought jkilroy,you say you've heavy 50 taper machines, I've done this before out of desparation and it worked fine.
    Cut squares and stack them with a couple of bolts on the inside waste on a rotary table, and chop them out with a long reach ally geom end mill, should do 4 .250's at a time and 3 .375's,

    Could be cheaper than buying (and waiting) for the tooling, those trepanner cutters seemed a bit pricey to me.......... but then lean manufacturing started in my shop!

    Sami

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    Hey LL, Nice picture of the SPI tool. How did my image get into the ibiblio archive? Am I famous now?

    Without heading down to the shop, I think the model of that tool is a 6000 series. Carbide and HSS inserts are available. Den

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    Sami,

    I thought about doing just that and I might for a few parts. But this is looking like its going to be an ongoing project so I need to get tooled up to do it right. I think I might purchase a pack of those cutting tools and build a lathe holder. Would it be ok to hold both bits and once at the proper spacing and then just make one plunge to cut the ring?

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    jkilroy, to be honest mate I dunno, suppose depends on how strong you make the tooling, I'd be thinking along the lines of plenty of wieght and maybe cast iron------- big truck flywheel?....... to dampen the vibes? but I'm getting right out of my depth here, I'd only be experimenting, though I've always found there's no substitute for weight.

    sami.

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    Hey LL, Nice picture of the SPI tool. How did my image get into the ibiblio archive? Am I famous now? [Big Grin] [Big Grin]
    Well, DENNH, if your metalworking resources have made it to ibiblio then they are definitely among the elite! You can rest on your laurels, you have finally made it!

    Actually, I read your posts in an earlier trepanning thread, d/l'ed them with pix into my own reference library on my computer. I use my website on ibiblio for gallery space for all sorts of topics I am interested in.

  16. #16
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    I bought two shop made tools at a yard sale. They had a round tool bar with a square hole on one end. used a 1/4" HSS tool bit held in with a set screw from the end of the bar. The tool bar had a flat milled on one side so it stayed in the main shank that is gripped by the chuck. Of course this set up can cut no deeper then the tool bit length minus the holder diameter.
    Bill D

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    I bought two shop made tools at a yard sale. They had a round tool bar with a square hole on one end. used a 1/4" HSS tool bit held in with a set screw from the end of the bar.
    I also have one of these, marketed as a circle-cutting tool sold in hardware sores. The circle-cutting tool is NOT the same as the Val-cut trepanning tool that uses a bit with unique geometry and cuts with the “drag cut” principal. I have cut hundreds of holes in ½” 6061-T6 aluminum plate from 2”-5” diameter with a Val-cut trepanning tool. The chip(s) come out as a continuous string with Val-cut. See: http://i72.photobucket.com/albums/i1...repanning1.jpg
    Val-cut trepanning tool eliminated the need for a series of hole saws and for me was cost effective solution to producing large holes.

    Don Clement


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