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Thread: Circles?

  1. #1
    Join Date
    Oct 2015
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    Australia
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    Default Circles?

    I had a need to cut a circle today.
    So, I made a really simple jig, just a nail in a board really.
    Placed my blank on it and started to cut.
    However, the blade just wanted to pull itself off to the side.
    Brand new 6mm blade, 14" 'generic' saw.
    I gave up on the jig and cut freehand, which wasn't perfect, but due to the operator, not the blade trying to turn left.

    Any ideas what I did wrong?
    Tension? Guides? Jealousy because I glanced at a newer model at the show yesterday?



    Russ

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  3. #2
    Join Date
    Apr 2016
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    Kyabram, Victoria, Australia
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    Default

    From my limited experience I found tension to be my problem. Though jealousy can never truly be ruled out can it?

    If you haven't already, watch the Alex Snodgrass youtube video on how to setup a bandsaw correctly. I learnt heaps and have watched it several times.

  4. #3
    Join Date
    Mar 2008
    Location
    Hobart, Tas
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    Default

    Russ, I can do circle-esque with just the bandsaw using the method you've described. To get a smooth, consistent circle however, I've always had to clean it up with a router using a circle jig which operates on the same principle as the bandsaw jig.

    Also depending on the diameter you're cutting, I find a wider blade produces a better result. As in, if a 10 mm blade can cut the required radius, I use a 10 mm blade, not my 6 mm one.

    I'm keen to read the responses to your post though. Perhaps I can get a better result with a change in setup or technique too.

    Lance

  5. #4
    Join Date
    Aug 2014
    Location
    Wentworth Falls, NSW
    Posts
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    Default

    It also depends on the size of the circle, the width of the blade and the amount of set on the blade (or in other words the width of the kerf). The kerf does not change much though.

    My bandsaw manual has a chart to work out the size of circle you can cut with different blades.


    No plug for Laguna intended although very happy with my saw.

    Bruce


    Sent from my iPhone using Tapatalk

  6. #5
    Join Date
    Oct 2015
    Location
    Australia
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    Default

    So it looks like I didn't need to change the blade. Circle was 250 diameter.

    I'll try increasing the tension.

    And I must work through that setup video. Something else on the list.
    (when I bought the saw, allegedly 'set up by a professional [emoji1787]), the guides were adjusted so that the back bearing pressed on the side of the blade, I was warned against touching the tension because "its exactly right", the blade length marked on the door was 30mm too long, and it was as blunt as. Wouldn't cut pine, in fact couldn't. So who knows what else the 'professional' did. Forgot to ask what profession was claimed. Maybe one of the older professions... [emoji848]
    (and was advertised as having 'tap handles' fitted as a 'quirky upgrade....)

    Still a great purchase, good price and very handy in the shed...



    Russ

  7. #6
    Join Date
    Nov 2011
    Location
    Sutherland Shire, Sydney
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    1,174

    Default

    Your problem may be related to the alignment of the pivot point in relation to the front of the bandsaw blade. The cutting edge of the teeth must align with the centreline of the pivot point. If the pivot is forward or back of the teeth, the blade will not cut freely and the circle will not be true.

    There are heaps of designs of jigs with an adjustable pivot point on the net. It is well worth making one if you are likely to be cutting variable diameter circles.

    Alan...

  8. #7
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    Oct 2008
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    Leopold, Victoria
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    Default

    Totally agree with Uncle Al, the location of the circle centre point should be in line with the front of the teeth. If you have the centre point in front of the teeth tips it will push the blade away and you get a larger circle and if it is behind the tips the blade will get pushed towards the centre so you end up with a smaller circle than you wanted. The circle also will not be round in either case. A 250mm circle should be pretty easy to achieve as I can cut circles as small as about 40mm dia with a 6mm blade.
    Cheers,
    Dallas

  9. #8
    Join Date
    Feb 2016
    Location
    Canberra
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    Default

    Using a simple circle jig that is adjustable is the way to go. I'll find a picture of mine and post it up.

    I make wheels for carts, 100mm diameter. I use the 6mm blades from Gregory Machinery, because they are hyper aggressive and have a huge offset. All other small blades are way too fine.

    A big offset is needed so the back of the blade doesn't touch the edge of the circle. It it does touch it will guide the blade all wrong.... it will bind up and give you hell.

    I've also found to get better cuts is to have the centreline of the circle slightly behind the blade.

    The wheels are cleaned up on the belt sander with a similar jig.

  10. #9
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  11. #10
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    Feb 2018
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    Shepparton
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    Default

    I agree with Uncle Al if you haven't set up correctly which sounds like your problem you will find the blade will run off.

  12. #11
    Join Date
    Aug 2004
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    Newcatle
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    I sympathise Russ. I have never been able to get my 16" H&F bandsaw to run true no matter what I adjust.
    Now I cut freehand like you would with a scroll saw.

    A jig for the router is my choice for good circles and I have made and bought several jigs that all work well.
    Scally
    __________________________________________
    The ark was built by an amateur
    the titanic was built by professionals

  13. #12
    Join Date
    Jul 2009
    Location
    inverloch
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    464

    Default

    Hi Scully, I have found this you tube vid pretty good. I might help you sort your bandsaw problems

    YouTube

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