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A friend has asked me to make her a bunch of 4" round drink coasters. I'm trying to figure out the best most economical way to do it. I made one this morning before work by just taking some flat stock and cutting it out on my band saw, but that didn't really produce a perfect circle even after a little sanding.

I'd thought about maybe getting a cheap lathe and turning a 4x4? I don't have any turning experience though and it seems a little on the dangerous side to try to round up a square piece of wood like that.

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    it seems a little on the dangerous side to try to round up a square piece of wood like that. It's not particularly dangerous, just more time-consuming. Usually it's a good idea to clip the corners of large square stock into an octagon before turning to save yourself some lathe work. – grfrazee May 11 '16 at 19:49
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    Maybe a 4" hole saw and a plug cutter for filling the pilot hole? You'd probably have to do quite a bit of edge cleanup though, and use a powerful drill to boot. – Doresoom May 11 '16 at 20:53
  • What tools do you have at your disposal? It'd make a difference in what you consider "economical". If you have a router, I can think of ways to do it that are different than what I'd suggest if you don't. – Charlie Kilian May 11 '16 at 21:22
  • I've got a router, table saw, miter saw, bandsaw, bench planar, drill press, and some handheld sanders, saws etc. although I considered getting a lathe for this. – confused May 12 '16 at 3:49
  • Have you considered slicing ~4" wide branches for this? If your friend didn't specify a perfect circle, this is an easy option that looks really good. – aaron May 13 '16 at 17:28
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Making things round is what lathes do. Turn a piece of wood and then use the band saw to slice off each coaster. You can rip a 4x4 into more of an octagon shape with the band saw to make it faster and safer to round it on the lathe.

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    That would mean the face of the coasters are the end grain, which might not be what OP has in mind. – Charlie Kilian May 11 '16 at 21:47
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    True, but it is a 4x4. You could cut 4" pieces and make any 4 sides of the cube round. – LeeG May 11 '16 at 21:57
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If you want to do this without having the end grain be the face of the coasters, here's a method you can use. It involves creating a template you can use with a router and flush trim bit to make copies.

First, prepare the work pieces that will become the coasters the same way you did before: using your bandsaw, cut a rough circle. Cut it a little big, maybe 1/16" - 1/8" larger than the final dimension of the coaster. You'll clean it up by tracing the template with a flush trim bit in your router.

To make the template, cut a 4" blank using a hole saw drill bit such as this one. Hole saws leave a plug of wood, but will also have a hole in the middle of the plug where the pilot bit cut through, which is why you can't just use the hole saw plug as a coaster directly. (Unless you're okay with your coasters having a hole in them! Perhaps it's a feature, not a bug!) Clean up any roughness on the edges by sanding. I would use my bench sander for this, but you can do it by hand, too. The template should be made out of something about 1/4" thick. Hardboard/Masonite is my usual go-to for this.

Next, you'll have to attach the template to the work piece. The standard way of doing this is by using double-sided carpet tape to tape the template and work piece together, but after you're done tracing the template, the carpet tape will leave some residue that you have to clean up, and more importantly you have to be careful the template doesn't move as you push against it with the router. WW.SE user Graphus suggested a better method of attaching the template. Take blue painters tape and put it on the surface of both the work piece and the template. Then superglue the two surfaces together. Unlike carpet tape, there is almost no risk of slipping, and no residue is left on the work piece after you've taken the painter's tape off.

Now adjust your router so the bearing on the flush trim bit will spin against the template. Route around the template, removing the excess.

Finally, pop off the template and remove the tape. You have a round coaster! The template can be reused to cut as many as you care to.

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  • not sure if it would work with a 4" cutter, but I've had success avoiding the pilot hole by using smaller sized cutters with the pilot bit removed. This requires the use of a drill press and clamping the work piece firmly in place. – Dave Smylie May 12 '16 at 1:47
  • @DaveSmylie - The hole in the center of Charile's hole-saw cut is just in the template so the pilot-bit hole doesn't really matter. – FreeMan May 12 '16 at 13:41
  • Are you thinking the router is in a router table, and then the bearing is close to the table face? – confused May 12 '16 at 14:26
  • You could do it that way. If you have a flush trim bit (where the bearing is on the end of the bit farthest from the router), then you'd have to orient the work piece towards the router table and have the template run along the bit. If you have a pattern bit (where the bearing is closest to the router), then you'd orient the template face down. It depends on what kind of bit you have at your disposal and/or prefer to work with. – Charlie Kilian May 12 '16 at 14:54
  • @FreeMan - sorry, to be clear, by using a decent quality hole-saw without the pilot hole, you negate the need to make a template and mess around trim routing. You can simply cut out the coasters directly using the hole saw (albeit with a small amount of sanding required for the edges) – Dave Smylie May 14 '16 at 21:26
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Since you have a bandsaw I think the simplest option for you here is a circle-cutting jig. You can throw together something small and basic for just this job, or with only a bit more effort build something more sophisticated which will deal with cutting circles of many different sized for many years to come. Either way you'll be cutting perfect 4" disks in no time.

There are many many variations on such a jig, here's one:

Circle-cutting jig

This is from this article on Fine Woodworking: Circle-Cutting Bandsaw Jig.

The text suggests "To avoid a center mark on the stock, attach a sacrificial surface to the underside of the workpiece with double-sided tape." In place of the double-sided you can also use the tape & superglue trick previously plugged by Charlie Kilian, or hot-melt glue if you prefer.

If you'd prefer to see a few more styles before going ahead with making it here are a few additional versions:
Techniques to Cut Circles With a Band Saw on The Family Handyman.
How to Cut Perfect Circles on a Bandsaw on Startwoodworking.com.
Super simple bandsaw circle jig on Instructables.

Note: most of these jigs can be fitted to a router table to allow the router (fitted with a straight-cutting bit) to do the same cutting task. This should result in a smoother finish requiring much less final sanding.

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  • I will add that it will probably take some practice to get nice circles with this jig. I made one for my band saw and the first (only) half-dozen or so circles didn't come out so well. They required a fair bit of work to smooth out some nicks. Of course, the jig may not have been constructed as well as it could have been, and the 10-year-old that was "helping" me (they were for his project) probably wasn't the smoothest operator in the world... – FreeMan May 13 '16 at 14:21
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I would recommend one of three things which will depend upon the tools you have.

  1. Use a 4" hole saw with the pilot bit removed

    • If you have a drill press this option would work well. If not you need a powerful corded electric hand drill (with a stabilizing handle) and steady hands. Be warned that there can be a lot of torque if the bit binds up in any way so be careful not to break your wrists.
  2. Use a lathe to turn a 4x4 as you described

    • This method is safe, but time consuming and expensive if you have to buy a lathe.
  3. Use a wooden rod with a 4 inch diameter.This could be something like a fence post or a tree. Make straight cuts along the rod at the height you want the coasters to be.

    • This is a fast method and safe, but reduces the wood choices.
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    Not quite sure how but I think option 3 needs to be reworded – Matt May 14 '16 at 3:25
  • #1 by hand would be a nightmare, and grossly unsafe to boot. Getting the cut started cleanly would be horrible, and the subsequent drilling not a whole lot better. – WhatRoughBeast Feb 14 '19 at 23:40
  • #3 is a great answer. I was about to offer it myself. Go into the backyard and find a tree branch with a 4 inch or slightly greater diameter. Clean off the bark, then slice 1" wafers from it using the bandsaw. Dry them in your oven on low heat for a few hours till they get down to <10%, then sand them to the desired thickness and finish with food-safe resin so they can survive the moisture from glasses getting placed on them. – Henry Taylor Feb 22 '19 at 4:03
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I was hoping that you might have a disc sander, but you didn't mention one. However, if you have a table saw you can mount a sanding disc on it and it will function as a small one (but big enough for your purpose.) Once you have that, you'll also need a piece of plywood that measures 4 or 5 inches wide and a couple inches longer than the distance from your saw blade to the far edge of your miter slot, and a piece of scrap hardwood at least as wide as your miter slot, slightly shallower than the slot, and as long as the width of your plywood piece.

Cut a rail to a little less than the width of your miter slot (so that it fits in the slot with about 1/8 inch of play left) from the hardwood scrap and mount it to the bottom of the plywood so that the plywood's edge, when the rail is placed in the slot with its edge pushed against the close side of the slot, comes close to the sanding disc's face (1/8 is probably close enough.) Drive a finishing nail straight into the plywood so that while in the close position the nail center is 2" from the sanding disc and approximately centered on the plywood jig. Snip or grind off the nail so that it protrudes about half the thickness of your coasters from the surface. This is your circle-sanding jig for the coasters. Note that the pin is less than the thickness of the coaster, allowing you a "show" side with no center hole. My illustration's not to scale, but I hope it shows the concept adequately, didn't want to spend all afternoon on such a simple device :)

Top view of jig in-place on table saw Now, mark the centers and 2" diameter edges of the coasters on your workpiece(s) on the non-show side (bottom). Make a hole in each rough coaster at its marked center ON THE MARKED (non-show) SIDE with the same size finishing nail as you used for your jig pin, deep enough to accommodate the protruding pin fully. Cut close to the circular edge line but not quite up to it with your bandsaw. Your cut should be at least 2" from center at all points, yet not by more than the 1/8" of play in the jig. This should be easy enough to attain, and will allow you to place the roughed coaster on the jig when away from the disc, and when the jig is snugged up to the close edge of the slot the disc will make contact. This is how you finish the coaster: you place the coaster on the jig when in the far position, then move it into the close position and gradually turn the coaster on its pinned center to work the edge into a perfect circle. You can probably scoot your fence over to the right-edge of the jig to hold it in place in the close position while sanding. Be sure to keep a hand on the coaster at all times when sanding, as you don't want it flung away. Complete the finishing by breaking the sharp edges with sandpaper, roundover router bit, or whatever.

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