Circle Cutter

[Greg in Maryland]

I am considering one of those circle cutters that attach to a drill press to cut a bunch of large circles -- 3 to 6 inches in diameter.

How clean is the cut when using one of these? Also, anything to watch out for or consider when purchasing?

Thanks.

Greg

[whitecobra]

The biggest thing to remember is to run it SLOW
I use one now and again for special sized holes they work fine

The "blades" break but other then that the holes are clean enough and the results are not usually obtainable any other way when you need a strange sized hole

Dr D

[LarryG]

+1 on Dave's comments. Mine is made by General, which is one of the brands of budget-but-decent carpenter's/woodworker's tools. I think I paid maybe ten or twelve bucks for it at Lowe's.

In addition to a slow spindle speed, clamp your workpiece down SECURELY and keep your hands and clothing well clear. Wing cutters are pretty scary just watching the things run ... definitely not something you want to have a fleshy encounter with.

[jziegler]

I bought one at Woodcraft last summer to cut some speaker cutouts. It worked well and cut clean holes. That said, they can be dangerous. +1 on Dr. Dave and Larry's comments about the low speed. Use the slowest speed on you drill press. I used a speed ~200 RPM I think. Also, some places sell the cutters with two different size ranges, so make sure you get one that covers all the sizes that you need.

Jim

[LCHIEN]

One of these, I presume (one shown from Sears' website, probably made by General).
Also variously called a circle cutter, beam cutter, fly cutter, wing cutter.
Follow all the precautions that Dr D, and Larry suggested.

If you are going to 3-6" then I really strongly suggest RPMs not in excess of about 250 RPM. Many drill presses won't go this slow! The ones with two pulleys (not three) generally only go down to around 600 RPM, which I would think is too fast for this kind of bit at that diameter. The 12- and 15-speed DPs with three pulleys of 4-5 steps each often go down to the 200's of RPMs.

Be safe, clamp and watch out for that swinging beam, it'll reach out and grab ya.

[Greg in Maryland]

Thanks for the responses. I'll will be very careful with the speed and other pitfalls as suggested.

I am not sure my drill press can go slow enough for one of these. I'll check before I buy or use one of these circle cutters.

Cheers!

Greg

[Tom Miller]

...and be careful. (Or did someone already mention that?)

Random points:

If you want a wood circle, it'll have a pilot hole in the middle.

These cutters make good holes, too, but you need to orient your cutter differently than for a circle.

You can have a good circle, or a good hole, but not both. (At least, not without further work.)

...and be careful.


Regards,
Tom

[LarryG]

I am not sure my drill press can go slow enough for one of these.

General and Lee Valley both specify a maximum speed of 500 RPM.

Tom raises a good point about the pilot hole in the center of the cut-out disc. I took your OP to mean you wanted holes, not discs, but now see that it could go either way.

[LCHIEN]

General and Lee Valley both specify a maximum speed of 500 RPM.
...

I would think the maximum speed depends in part upon the location of the cutter. Set for small circles (like 1-2 inches) you could cut higher RPMs
but for larger circles (like 3-6") you would use less than the maximum because the linear velocity of the cutter itself would be much higher (proportional to the radius).

Most 2-3" cutters like rosettes, big forstners etc recommend 200-300 RPM range on a D.P. I wouldn't think you could turn a circle cutter set for 3" much faster.

Aside from cutter tip velocity, you also have an un-balanced assembly spinning around and the end of the beam spinning around at its maximum length no matter where the cutter is.

I think the safe RPM is the biggest concern I'd have.


Between 2- and 3 inches I use a 1-1/2 to 2.125" inch forstner and a few passes with a router equipped with rabbeting bits and flush trim bits to enlarge the holes perfectly. Ask me if you need more info.
Once it gets past about 3 inches I start thinking about a router and circle jig.

[GregW]

I'm not sure what type of project you're working on, but I've cut circles and holes that size (3-6") a lot quicker, neater and safer using my router instead of the fly cutter.

Greg

[sweensdv]

According to WOOD Magazines Drill Press Speed Chart the recommended RPM speed for circle cutters is;

1½" - 3" circle, 500 RPM's for softwoods and 250 RPM's for hardwoods
3¼" - 6" circle, 250 RPM's for both softwoods and hardwoods
1½" - 6" circle, 250 RPM's for acrylic

[Slik Geek]

I've got the General, and I have been very pleased with the quality of holes. I carefully honed the cutter, following the tips in an issue of ShopNotes from a couple years ago. And I always run it at the lowest speed possible on my drill press.

I've had better results with the cutter than with a router. (Perhaps my router template moved slightly under load?)

[Greg in Maryland]

Again thanks for all the comments -- you've given me a lot to think about.

I am just thinking through building a set of building blocks and a toy box as a gift for a nephew. The set has lots of squares, rectangles, arches, arcs, triangles, pillars, wheels, and other shapes I need to fabricate. I am going to use hard maple and other woods. I am trying to find a way to cut arches, arcs and other round shapes without too much hassle, waste and cost.

Certainly, my band saw would be fine for all this -- presuming that I can get the thing tuned correctly, learn how to use it properly, and cut cleanly, and, and, and ...

Alternatively, a really gigantic forstner big bit will do the job, but precious wood would decorate the floor. Besides, these bits cost a small fortune.

As luck would have it, my drill press can go as low as 380 rpm so this tool might be a option. It sounds like these cutters are fairly inexpensive, so I can give it a try. If it isn't stable or scares me too much, I can go always go the bandsaw route.

Thanks.

Greg

[GregW]

I've got the General, and I have been very pleased with the quality of holes. I carefully honed the cutter, following the tips in an issue of ShopNotes from a couple years ago. And I always run it at the lowest speed possible on my drill press.

I've had better results with the cutter than with a router. (Perhaps my router template moved slightly under load?)

with the router I would use a pivot pin hole in the sub base instead of a template...or just a board with a series of pivot pin holes for each radius that you want to cut at the proper distance from a 3/4" hole for a guide bushing. This would also work good for any arcs or arches that you want to cut...

[Gary L]

Check out my post in tool reviews regarding the Jasper Circle jig.

They make a smaller one perfect for your projects.

Gary