Simple Way to Rout Big Circular Holes Without Template?

[Steve H Graham]

Every so often I make a large round hole (ten to twelve inches in diameter) for a speaker enclosure. It's a pain. I came up with my own method.

I mount a long piece of 2 x 2 across my router table, with the ends clamped on spacers so the 2 x 2 is above the table, high enough so the work can fit under it. There is a hole that goes through the 2 x 2. I run a screw through this hole, down into the center of the wood I'm cutting. This allows me to turn the wood in a circle over the router bit. The screw acts as a pivot.

I rout up halfway through the wood, turning it as I go, until I have a shallow circular slot. Then I remove the 2 x 2 and turn the wood over so the slot faces down. I raise the cutter so it goes all the way through the wood, and the bearing at the bottom of the cutter presses against the inside of the slot. This way the slot works as a guide, and I get a very nice round hole.

Is there a smarter way to do this? I know I can save a piece of wood that already has a hole in it and use it as a template, but I'm wondering if there is a simpler way, when I don't have a template handy. I know I can get a rough, nasty hole with a jigsaw, but that's not satisfactory.

The thing that makes it complicated is that you can't just make a circular piece of wood and use the piece it came from. To do that, you have to have some kind of anchoring device in the center of that wood, and once you get most of the way around the circle, the outer part of the wood will wobble due to decreased support, and you may get gouges and problems. The circular part, which is useless, will be fine, but the rest of the wood will be scarred up.

[Mel Fulks]

If you are using the typical two flute straight router bit ,switch to 1/2 inch diameter single flute . Process will at least be faster.

[Bill Huber]

I have only done it one or two times but this is what I did.

Cut the MDF to the finished size, then with turners tape I put a few strips of it on the back of the MDF.
Now the whole thing is pressed to a scrap piece of MDS.
Using the circle cutter attachment to my router base, you can make one or buy one, I set my bit to just go though the MDF.
Set the router up for size circle and make about 3 cuts with a 1/4" spiral bit.
Then pull the MDF off and then do it again for the next one.

I am sure there are many other ways to do it but that was the way I did it.

[Joe Scharle]

Make or buy a router circle jig. Put your material on a suitably sized piece of rigid foam. Double stick tape it if it wants to slide around. Rout your circle in 1/4" passes, leaving the cake in the groove! The cake will keep the router from jumping or bumping when the final half inch is cut away. Let the router come to a stop before moving anything.

[Stephen Cherry]

A pin router can have this job done faster and better than you could imagine.

CR Onsrud 2003 is a light industrial quality inverted pin router that can sell used for less than a good pc router and lift. Maybe 500 dollars. I bought mine, which was used very lightly, for 900. The big problem with them is that cnc routers have taken over most of their market.

check at 2:40
https://www.youtube.com/watch?v=TI18ZWaG1_c

[Steve H Graham]

I think this is the most intelligent way. I don't know why it didn't occur to me that the approach I was using would work just as well with a jig, as long as I only went halfway through on the first pass.

[Steve H Graham]

Okay, now that Joe has provided the answer I should have seen myself, can anyone recommend a circle jig that will do 12" circles, at a reasonable price?

Right now I'm throwing a speaker cabinet together. First time I've used my 90° clamps. Pretty cool! I didn't realize they don't press the joints together, but it's still a whole lot better than my previous efforts with bar clamps.

[Jim Matthews]

Try Parts Express for the Jasper jig.

No reason you couldn't make this yourself, with a piece of masonite.
If the dimension is always fixed, you just drop a nail in the center of your desired hole
and draw the router through 360 degrees.

I've done this with the Jasper, and you won't believe the amount of dust this throws off.
Have a vacuum handy, if you can.

[Steve H Graham]

That was the nice thing about the router table. It sucked most of the dust out of my life.

[Mort Stevens]

it didn't occur to me that the approach I was using would work just as well with a jig.

While a router circle jig will work, a template is a far better solution in the long run, and it sounds like speaker cabinets are something you do quite often. Since speakers sizes are pretty much standard (3", 4", 5 -1/4", 6-1/2", 8", 10", 12", 15", and 18"), so 10 templates made of 1/4" tempered Masonite will cover just about anything you may encounter (you are keeping the templates you make aren't you?). Assuming you're making these speaker openings in solid wood, I would rough cut them with a jig saw leaving maybe 1/8" proud of the line then use the router+template to just clean up the edge... not only is this faster than (making 2-3 passes) with the router alone, but it will produce a cleaner opening and also keep the router bit sharper a little while longer. FYI I've made a few speakers enclosures over the years too. :)

[Steve H Graham]

Well, if I had made templates instead of using the holes I made...

Here's an irrelevant question. Is there any point in adding screws to hold this together? My natural tendency is not to trust glue, but common sense tells me this thing is not likely to fall apart.

I put the butt joints together and held them in place with clamps until the glue set. Then I added these 2x2 pieces.

270060

[Joe Scharle]

Okay, now that Joe has provided the answer I should have seen myself, can anyone recommend a circle jig that will do 12" circles, at a reasonable price?

Right now I'm throwing a speaker cabinet together. First time I've used my 90° clamps. Pretty cool! I didn't realize they don't press the joints together, but it's still a whole lot better than my previous efforts with bar clamps.


Steve, a circle jig can be whatever is on the floor as long as it's as wide as your router base. But I find 1/4" plexiglass to be more convenient to use, as I can see what's going on. The picture below shows a Bruce Wrenn router docking station. The great thing about connecting your router to your jig this way is, the router goes all the way around the circle with it always facing you. The cord doesn't twist, the DC hose stays connected and you never have to take your hands off of the handles. You can use the template guide on wood or plastic, of course.

http://www.ncwoodworker.net/pp/data/1582/Bruce_Wrenn_socket1.jpg

[David L Morse]

Steve, a circle jig can be whatever is on the floor as long as it's as wide as your router base. But I find 1/4" plexiglass to be more convenient to use, as I can see what's going on. The picture below shows a Bruce Wrenn router docking station. The great thing about connecting your router to your jig this way is, the router goes all the way around the circle with it always facing you. The cord doesn't twist, the DC hose stays connected and you never have to take your hands off of the handles. You can use the template guide on wood or plastic, of course.

http://www.ncwoodworker.net/pp/data/1582/Bruce_Wrenn_socket1.jpg
GENIUS!

My current circle jig (such as it is) will get a 5/8" hole drilled in it and I will never have to remove a baseplate again!

[Greg Hines, MD]

For your second query, I would definitely use screw, probably pocket screws, without the corner blocks. With them, it should be strong enough,though I would probably still use screws. For your former query, if you are doing this more often than once, I would make a template, or router trammel. Mine is made of a scrap of 1/2" plywood, with a 1" hole in one end, and a series of screw holes down the center line. I use a 1" OD collet and then a spiral bit with it, usually a 3/8" bit.

If you are looking for a good trammel design, Norm Abram did a very nice one on the New Yankee Workshop. He routs a slot down the center line, so it could be used for any diameter. I have not needed this fine level of adjustment, so I just drill another hole as I need it.

Doc

[David L Morse]

Every so often I make a large round hole (ten to twelve inches in diameter) for a speaker enclosure. It's a pain. I came up with my own method.

I mount a long piece of 2 x 2 across my router table, with the ends clamped on spacers so the 2 x 2 is above the table, high enough so the work can fit under it. There is a hole that goes through the 2 x 2. I run a screw through this hole, down into the center of the wood I'm cutting. This allows me to turn the wood in a circle over the router bit. The screw acts as a pivot.

I rout up halfway through the wood, turning it as I go, until I have a shallow circular slot. Then I remove the 2 x 2 and turn the wood over so the slot faces down. I raise the cutter so it goes all the way through the wood, and the bearing at the bottom of the cutter presses against the inside of the slot. This way the slot works as a guide, and I get a very nice round hole.

Is there a smarter way to do this? I know I can save a piece of wood that already has a hole in it and use it as a template, but I'm wondering if there is a simpler way, when I don't have a template handy. I know I can get a rough, nasty hole with a jigsaw, but that's not satisfactory.

The thing that makes it complicated is that you can't just make a circular piece of wood and use the piece it came from. To do that, you have to have some kind of anchoring device in the center of that wood, and once you get most of the way around the circle, the outer part of the wood will wobble due to decreased support, and you may get gouges and problems. The circular part, which is useless, will be fine, but the rest of the wood will be scarred up.

I've built a few speaker cabinets over the years and currently prefer the use of a template. I can cut holes for all of the drivers as well as marking or drilling holes for the mounting hardware.

I use Bill's method for cutting holes in the template except I use screws instead of tape, a few extra holes in a template are of no concern.
270084


Well, if I had made templates instead of using the holes I made...

Here's an irrelevant question. Is there any point in adding screws to hold this together? My natural tendency is not to trust glue, but common sense tells me this thing is not likely to fall apart.

I put the butt joints together and held them in place with clamps until the glue set. Then I added these 2x2 pieces.

270060
For plywood cabs I use rabbet joints with glue and staples for the sides. If the backs are non-removable I set them into rabbets with glue and staples. For removable backs (does anyone still do this?) I add 1x2 cleats to the sides. A recessed front goes into dados in the sides. For a flush front rabbet either the sides or the front depending upon the desired look. There's really no need for the corner blocking with rabbets and dados.

For subs add stiffeners to the back and, depending on aspect ratio, to the sides. Try to keep shapes and dimensions random. If the front panel is much more than 30% larger than the driver some stiffeners will help there too.

[Bruce Wrenn]

GENIUS!

My current circle jig (such as it is) will get a 5/8" hole drilled in it and I will never have to remove a baseplate again!I came up with this when I was cutting ribs for round front desk. The ribs had both and inner and outer radius. By using hole for bushing, I didn't have to have two trammels, just move the router to the other radius.

[Myk Rian]

No reason you couldn't make this yourself, with a piece of masonite.
+1. Easiest, and cheapest. Done it many times.

[Steve H Graham]

I had what I think is a bright idea. I am planning to put a 2" hole in the center of the board. Then I'll mount it on the rotary table on my milling machine and use an end mill to cut a half-depth slot to use as a guide for the router. Follow up with the router table, and I'm done. Hope nothing flies across the room.

[Myk Rian]

Ever hear of Murphy, and his laws?

[Steve H Graham]

Murphy and I go way back. But he must be drunk, because he didn't make it today. Some photos. I'm sure there are other people here who count machine tools among the items they could not resist buying.


270121270122270123