Circle cutting advice

[Jerome Hanby]

So, as long I feed from the correct direction I shouldn't worry about the disk getting jerked out of my hand and flying through the shop?

Jerome, if you use the bit with the bearing at the end of the bit, not toward the shank, (actually a flush trim bit) and use it in a router table, the bearing will be on top, as is the pattern piece, and easy to see. If you were using the router hand held, I would want the true pattern bit with the bearing on the shank end of the cutter. Both ways makes the cutter further away from you. Jim.

[Greg Hines, MD]

Another way to do it would be to use a spiral saw and circle guide. 3/4" MDF would probably need 3 steps to go the full depth, but it would leave a nice smooth line, and would be repeatable.

Doc

[Phil Thien]

I saw that post. At the moment, my router table is cast iron and the only way I could see to mount the pivot was on an "auxiliary" table top that I could clamp to the table. The way my router adapter mounts to my Craftsman CI extension, I loose a little height and I wasn't sure I would have enough to clear the aux table and the 3/4" mdf I'm cutting. Sounds like a good excuse to buy a long, guided spiral bit!

The pivot actually goes IN the workpiece, and the jig on TOP of the workpiece, so the design will work on any router table.

HOWEVER, I don't think it is the optimum design for cutting small holes.

I use a wing cutter from time to time and purchased a new bit for mine (on eBay) that uses carbide inserts (same kind used on a jointer/planer). They take a long time to dull. It came in a little kit. If you're interested, check out eBay #330224254890

[Jim O'Dell]

So, as long I feed from the correct direction I shouldn't worry about the disk getting jerked out of my hand and flying through the shop?

Not sure I'd go that far. The circle cutting I have done is in some 9 X 9 squares of 3/4" melamine covered particle board. I put a screw at each corner into a sacrificial layer on my make shift work bench. I also put 3 screws in the circle I was cutting out (scrap for me, I wanted what was left for blast gates). Nothing moved for me that way. But I was using a router circle jig and holding the router in my hand. I have not tried it on the router table. If I was to do it on the table looking to keep the disks and discard the rings, I'd probably try to rig a second point that would ride on the template piece so that I had 2 points of contact about 90 degrees apart. I would personally be a little leary of doing it on the table. But then the circle jig on the router worked so well for me, I'm comfortable with using it. YMMV. What ever you do, go slow. If it doesn't feel right. STOP AND DO IT ANOTHER WAY!!! Jim.

[Wayne Cannon]

I would recommend a router with a simple circle jig (e.g., the Jasper 400, or simple home-made equivalent) over a template-based solution or any drill- or hole-saw based approach. It is faster to set up for each piece than a bandsaw jig and will make a much smoother cut. If you cut them all from a single piece (or a couple of pieces) of material, you won't even have to cut out blanks.

I made about 20 circular recesses in plywood (for holding bottles) yesterday using a router with a simple circle jig for 5" and 3.5" dia cuts and a Forstner bit for 2.5" cuts. Frankly, the router was quick and almost as easy as the Forstner bit and left a much cleaner cut. The biggest pain was inserting the center/pivot pin, since it is under the router base at those diameters.

Because of the dust-collection hose and power cord, it was easier rotating the work underneath the router than rotating the router. Were I to do it again, I would consider putting a lazy suzan under the work (one was two feet from my elbow, but I didn't think about it at the time).

[Mike Heidrick]

Jasper Jigs are awesome for circles - holes and discs. They are a speaker enclosure builders best friend.

Good idea on the lazy susan. I may have to try that out sometime.

[Lance Norris]

I have used this little doohicky-thingy to cut multiple circles at a time with my bandsaw. I use double sided tape and cut 10 circles at a time. It came with my Jet stationary sander. I dont know what its called, but is available through Jet. It goes in the miter slot, but wont work in a slot that doesnt have a groove.

[Lance Norris]

Its here:

http://woodworking.jettools.com/Part....aspx?BDID=385

Item #42-45. Jet calls it a circle gauge.

[Mick Zelaska]

I built a jig for cutting circles on my bandsaw that Norm made on one of his shows. It cuts perfect circles ranging from a few inches to several feet in diameter pretty much as fast as you can turn the material on the jig. You can check it out here:

http://www.newyankee.com/getproduct.php?0101

[Rick Thom]

I saw a plan for this recently and what they did made a lot of sense.
Fisrt layout your 'circles' on the mdf and using a dp, bore all the center holes for the shaft.
Next cut out the circles to rough shape but slightly oversize.
Load all the blanks onto the rod and glue them together. Several of them had thru pins that ensured when the rod turned, the blanks did too.
A jig was fashioned (4 sided box open on the top and bottom) and the rod was let into the 2 ends so that it straddled the open center area.
A makeshift crank was afixed to the end of the rod so that it could be rotated by hand.
A channel jig was made on the top of the open box so that a router could be positioned directly over the center line of the shaft and so the router could travel from one end of the box to the other.
A router, equipped with a straight-cutting bit, was placed in the guide channel and the bit lowered to just contact the blanks. The rod is cranked and the router bit removes all the excess making the blank perfectly round. As each blank is completed, the router is slid along the guide to the next blank and it is cut. Sort of like a lathe where the router does the cutting rather than a chisel... When you are done, the mfd blanks are perfectly centered on the shaft and absolutely smooth from end to end.
Not a difficult concept at all. Hope this explanation makes some sense to you.

[Rob Will]

I would assemble oversize blanks on a shaft and true everything up as an assembly.
As Rick suggested, a box style router jig or perhaps in a metal lathe or pattern maker's lathe.

Rob

[Jerome Hanby]

That sounds a lot like the rig in Hylton's Router Magic book.

I saw a plan for this recently and what they did made a lot of sense.
Fisrt layout your 'circles' on the mdf and using a dp, bore all the center holes for the shaft.
Next cut out the circles to rough shape but slightly oversize.
Load all the blanks onto the rod and glue them together. Several of them had thru pins that ensured when the rod turned, the blanks did too.
A jig was fashioned (4 sided box open on the top and bottom) and the rod was let into the 2 ends so that it straddled the open center area.
A makeshift crank was afixed to the end of the rod so that it could be rotated by hand.
A channel jig was made on the top of the open box so that a router could be positioned directly over the center line of the shaft and so the router could travel from one end of the box to the other.
A router, equipped with a straight-cutting bit, was placed in the guide channel and the bit lowered to just contact the blanks. The rod is cranked and the router bit removes all the excess making the blank perfectly round. As each blank is completed, the router is slid along the guide to the next blank and it is cut. Sort of like a lathe where the router does the cutting rather than a chisel... When you are done, the mfd blanks are perfectly centered on the shaft and absolutely smooth from end to end.
Not a difficult concept at all. Hope this explanation makes some sense to you.

[Jerome Hanby]

My bandsaw miter slot doesn't have the grove, but your reply does bring to light that I'm an idiot. While my bandsaw doesn't have the depth of cut to handle 10 at a shot, I could easily handle 5. Looks like I'm building a bandsaw circle cutting jig!

I have used this little doohicky-thingy to cut multiple circles at a time with my bandsaw. I use double sided tape and cut 10 circles at a time. It came with my Jet stationary sander. I dont know what its called, but is available through Jet. It goes in the miter slot, but wont work in a slot that doesnt have a groove.

[Kim Spence]

I purchased a wing cutter from Woodcraft for my drill press. Set it up this Weekend to cut some 5-1/16" circles out of 3/4" MDF. The First circle cut fairly well (but slow!) and I had to flip the blank to finish the cut. I tried cutting a second one and it didn't cut well at all. I'm assuming the MDF is hard on the steel cutter. Since I need to make 30 or so if these things, I'm thinking this wing cutter is not going to get the job done.

For what its worth, though I think your bandsaw circle jig is a fine idea, the circle cutter you describe above should cut MDF just fine. I just used mine (also from Woodcraft, likely same one as yours) to cut 3/4 MDF last night and it cut quickly and cleanly all the way through. I'd say somewhere between 5 and 10 seconds to cut the hole.

I think the problem you're having may be due to the cutter not being inserted with the right orientation. The first time I used my circle cutter I experienced something similar - very slow cutting, burning, etc. Orienting the cutter correctly made a WORLD of difference. If I remember right I think the directions that come with it were either incorrect or the picture was very misleading.

Yes, MDF will be hard on the steel cutter, but when set up properly I think it will cut MANY circles (dozens) before needing honing. I've used a diamond touch up stick to hone mine in the past.

[Jerome Hanby]

That reply hit home. I couldn't relate the diagram to the actual cutter and made my best guess, evidently a wrong guess.

Can you describe how it should be oriented?

For what its worth, though I think your bandsaw circle jig is a fine idea, the circle cutter you describe above should cut MDF just fine. I just used mine (also from Woodcraft, likely same one as yours) to cut 3/4 MDF last night and it cut quickly and cleanly all the way through. I'd say somewhere between 5 and 10 seconds to cut the hole.

I think the problem you're having may be due to the cutter not being inserted with the right orientation. The first time I used my circle cutter I experienced something similar - very slow cutting, burning, etc. Orienting the cutter correctly made a WORLD of difference. If I remember right I think the directions that come with it were either incorrect or the picture was very misleading.

Yes, MDF will be hard on the steel cutter, but when set up properly I think it will cut MANY circles (dozens) before needing honing. I've used a diamond touch up stick to hone mine in the past.