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Thread: Circle cuting

  1. #1
    Join Date
    May 2002
    Location
    NL
    Posts
    1,389

    Question Circle cuting

    I have to cut out several 7 7/8" cirles in 3/4" mild steel plate.
    I saw somewhere a guy cut circles on his bandsaw with a subplate on the table and a dowel pin in the subplate.He would drill a hole in the centre of the square that he was cutting the circle out of and place over the dowel pin on the subplate on the bandsaw table.Then turning the square,he cut out the circle.
    Only HE was doing this with wood.
    Think it would work in 3/4" plate
    These DO NOT have to be perfect.
    please visit my webpage:
    http://motorworks88.webs.com/

  2. #2
    Join Date
    Jan 2004
    Location
    Arlington TEXAS
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    380

    Post

    Motorworks,

    Unless you have the plate already, why not just have them cut from 8" rod stock at the local metal supplier ?

    If I had to do it out of plate, I'd use the rotary table on the mill.

    I would think you could use a bandsaw if you had the blade vertical too. It can, is and has be done in 3/4" wood on a wood bandsaw.

    FWIW
    Lenord

  3. #3
    Join Date
    Jan 2003
    Location
    On the Oil Coast,USA
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    Post

    3-15/16" radius means 3/8" wide blade,yes you can do it,I have done it,just be sure that the bottom of the tooth gullet is exactly on the centerline of the the guide pin,otherwise you will be cutting cams.
    I just need one more tool,just one!

  4. #4
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    Post

    weird, how'd you arrive at that blade width? Did you calculate it as a chord length? I've seen that calculation done, but don't remember it.

  5. #5
    Join Date
    Jan 2003
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    2,807

    Post

    lynnl,

    Don't the band saw blade catalogs have this info, minimum radius for blade widths, etc.?

    IMO, unless the poster has a very heavy duty saw this is not going to be an easy thing to do, especially in 3/4" stock.

  6. #6
    Join Date
    Jan 2004
    Posts
    782

    Post

    I would use my torch with a circle cutting attachment.

  7. #7
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    Post

    DR, maybe you're right...I may be thinking of a chart(s) I've seen. Of course they (charts) would probably have originally been derived from calculations of the chords of the corresponding arcs. Maybe with an emperical fudge factor thrown in.
    And, as has been pointed out before, radiusing the back edge of the blades help to make the turning cut, if you're cutting near the limit for the blade width.

  8. #8
    Join Date
    Jan 2003
    Location
    On the Oil Coast,USA
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    Post

    Its in nearly every catalog that sells blades,every bandsaw thats intended to cut circles and it really helps if you have two Doall,two Tannawitz and one Grob bandsaw
    I just need one more tool,just one!

  9. #9

    Post

    I would put a 7 7/8" drill bit in my drill press and go at it.

  10. #10

    Cool

    Derek13:

    Make sure you're using a 7/78" hole saw bit, not a regular drill bit. Frankly, on a 1110v circuit, only a Sears drill press would have the necessary horsepower. I believe Sears can get about 75HP out of 15 amps.

    George

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