7

I have seen videos related to cutting circles on a table saw. I would love to try this but I am hesitant to make a jig that, to me, seems to be extremely dangerous. Here is a video of Matthias Wandel using his jig to cut a rabbet into the circle, which seems like it'd be even scarier.

How does one make this jig and do so safely? Are there any gotchas that should be considered when executing this jig?

  • It would be helpful if you included a link to one of the specific videos or jigs for complete context. – rob Apr 23 '15 at 16:06
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    Just added a link to Mathias Wandel's video about making a cyclone where he uses his circle jig to make a rabbet in a circle. – Peter Grace Apr 23 '15 at 16:17
  • Reminds me of how you can make elliptical grooves on a table saw. Instead of rotating to make a circle you push the stock through at an angle. You have to start with a shallow depth of cut and increase small amounts until you have the desired contour. – Phil Apr 23 '15 at 17:18
  • Jimmy Diresta just made a video which has exactly this "problem" and his solution at 8:55. youtu.be/UKWIZM9aI5Y?t=8m55s I would still probably use one of the other methods that have been mentioned though. – Daniel B. Aug 19 '15 at 16:46
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Take a sled and add a pivot as far away from the blade as you want your radius. (riving knife and guards can remain in place)

As preparation rough cut your piece on the band-saw.

http://woodgears.ca/bandsaw/cut_outline.jpg
source

Then put your piece on the sled and attach it to the pivot. Clamp it down to avoid the piece rotating while you are cutting and make a cut. Unclamp, rotate, clamp and cut again; rinse and repeat until it is round.

To get it perfectly round while not rotating the wood against the blade is nearly impossible. The last passes would require very accurate turns.

Instead if you have a motor and some shaft and bearings handy you can attach you can attach a pully to the wheel and work on it like a lathe.

enter image description here
source

The main advantage of this last step is that you are turning the wheel on its own axle so even if you make a mistake when mounting the bearings/putting it on the shaft you can true out the wobble.

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    Yes alternatives here are most likely the way to go as I have never seen the situation where a table saw was the go to tool for doing this. – datUser Apr 24 '15 at 19:28
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I'm of the same mind, Peter. All the plans I've seen require removal of too much safety equipment.

There are too many other tools that would suffice- from a band saw for smaller circles to a jig saw or router on a commercial or shop made trammel for large ones.

e.g.

Band saw- band saw circle jig

Or router.. Router circle jig

Or for a jig saw..

jigsaw

  • 1
    I used a band saw jig to cut some circles, and it wasn't easy. I might not have made my jig particularly well, since i was under pressure from the frigidity 6 year old to hurry up and help him get his Christmas presents made. I'd still prefer that to the table saw, though. – FreeMan Apr 23 '15 at 16:35
  • Agreed. A friend of mine has a novel way of doing it- he has a pivot point on a box that fits on the corner of his workbench. He pulls the band saw over close to the bench and sets the casters on both so that neither can move. He pops the box (which is tall enough to make the box surface and band saw table coplanar) on the bench and locks it in with a vise. That provides a fixed pivot for the saw. – TX Turner Apr 23 '15 at 16:50
  • @Freeman some bandsaw circle-cutting jigs are better-designed than others. It's also important to use an appropriately-sized blade and have your bandsaw tuned properly. – rob Apr 23 '15 at 17:02
  • Umm... that wasn't supposed to be frigidity ... – FreeMan Apr 23 '15 at 17:18
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What I think makes most of such jigs dangerous is that they allow rotation of the work piece while cutting. That is not a safety issue per se, but at the begging of the process, the work piece is not a circle at all which makes it awkward to work with.

Here's what I suggest

  1. use a sacrificial board like a table saw sled, this will become the "jig", but it really is just a sacrificial board
  2. Put the circle-to-be board on top of it, mark the center (depending on the desired radius) and place is accordingly (there should be the a distance between the blade and the center as big as the desired radius)
  3. Screw the upper board to the sled. Position the screw at the center of the radius
  4. Add a second screw. This one locks the upper board from spinning around.
  5. Feed that into the saw. This is not different from any other two board being securely connected. It's just "one thicker board".
  6. Pull back, unscrew the second screw, rotate the top board a bit, srew the second screw back in. Go to 5. until you have a sufficiently round work piece.

These are just my thoughts. I do not have a table saw.

I agree with TX Turner that other tools might be better suited for this task or will be much safer to use.

  • If your degree of rotation is sufficiently small, and your "2nd screw" placement accurate enough, you can make a donut! :) – FreeMan Apr 23 '15 at 16:33
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Trying to cut finished circles on a table saw is about as unsafe an idea as I can think of. The reason that the Wandel setup works is that the rabbet is not much deeper than the tooth depth on the blade. This means that any wood fed into the blade at an angle encounters teeth and gets cut.

For any cut deeper than the tooth depth, this invites disaster. Wood which is fed into the body of the blade at an angle will do one of two things: if the blade is moving downwards, the wood will burn due to friction and the piece will stall - if the blade is moving upwards, the piece will be picked up and thrown.

Neither is a good idea.

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    A deeper cut can be accomplished by a series of shallow cuts. – Caleb Apr 26 '15 at 20:13

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