How do you get perfect rounded corners using a router?

[funster]

I have a print that requires me to put an interior hole in a part. It requires all four corners to be rounded to a 1" radius. How do I do that without having to buy a 1" drill bit and then having the router do the straight part?

Also, on a different part, I am required to have all four exterior corners rounded. How do I do that? Is there something on the market that will work? I looked into the "route a corner", but it is unsuitable for a 1" radius. An earlier post mentions the "radius guide" from Woodhaven, but I was unable to find it on their website. Any help would be appreciated. Thanks!

[Noons]

funster apparently said,on my timestamp of 23/01/2005 7:08 PM:

Drill a suitable hole in MDF, then use that as a template guide for your router? You may need to work out a proper diameter for the hole depending if you're using a bearing bit or a template guide bush, but it will do the job.

[Dave]

One option for both would be to make (or buy) a router trammel which would give the router a pivot point.

I would make a template for the interior hole by using the trammel for the corners connecting them with straight cuts as required. Use the template as a guide for a pattern bit to cut the actual interior hole. Make the template large enough to get a couple of clamps on it that don't interfere with the router.

For the exterior corners, again make a template with the trammel and use a pattern bit. For these radii cut as much of the corner off with saw as you can. Make very light cuts with the router. This type of operation can catch the wood and cause large chip out. That will make you think bad things.

Suggestion, go buy some 1/2" MDF and keep it around for template stock. You can buy a lot of MDF for the price of most store bought templates.

[George]

That's it. Make your inside and outside templates for guide or pattern routing. Choose anything round to draw the sections and file/sand to the line unless you have a good selection of hole saws.

[Unisaw A100]

Sometimes with woodworking you just have to break down and buy the tools and machines required to do whatcha wanna do.

Otherwise everybody'd being doing it.

UA100

[Wes Stewart]

|I have a print that requires me to put an interior hole in a part. It |requires all four corners to be rounded to a 1" radius. How do I do |that without having to buy a 1" drill bit and then having the router do |the straight part?

I think that if I wanted a 1" *radius*, I'd use a 2" *diameter* Forstner bit.

Or use this:

||Also, on a different part, I am required to have all four exterior |corners rounded. How do I do that? Is there something on the market |that will work? I looked into the "route a corner", but it is |unsuitable for a 1" radius. An earlier post mentions the "radius |guide" from Woodhaven, but I was unable to find it on their website. |Any help would be appreciated. Thanks!

[Bob Schmall]

1. Remove the word "perfect" from your vocabulary. Just flush it out of your brain.
2. For the inside hole, buy a hole saw and 1" bit. Should be about for both, and you'll have the saw next time, just add other bits as needed.
3. As for the outside, see #1 first. Then use a saber saw, band saw or router to carefully cut the corner just outside the line you've (yuve, Don) drawn with a compass. Then sand/file to the line. If it ain't close enough to within 1/100, see #1 again.
4. Relax--part of the satisfaction in the hobby is knowing that what you do is mos def not machine made.

Bob

[CW]

A 1" drill bit would give you a 1/2" radius.

[Edwin Pawlowski]

You can use a 2" dia round over bit. Hold the pice on edge to make the 1" radius. If you are not willing to buy a drill bit, I doubt that you'd spend $40 for the router bit though.

Another way is to marke them with a pencil, cut the rough part with a jig or bandsaw, then finish on the belt sander. Youjust put one edge against the belot and rotate the piece until you are parellel on the other edge and it will blend in perfectly.

[BillyBob]

Even though I have a router and template set, there are some things I just won't use it for. It takes a lot of set up time to do small jobs. Unless its something that just has to be near - perfect, I might use hand tools instead. Its amazing how much you can do with a good half-round rasp and some sandpaper and a coping saw. A small drum sander bit in the drill press is also handy for shaping.

Bob

[John]

Many wood working catalogs have router corner TEMPLATES (for outside AND inside curves) and after years of jig saw/bandsawing, I went with the templates. Gives really GREAT results and totally repeatable and identical

Same templates work on BOTH situations

John

[funster]

Thanks Everyone for the advice.

I just love workshop gizmos, so I'll probably get the template from Woodhaven. (I couldn't find it on their website until someone attached a link here).

Woodworking drill bits are much more reasonably priced as compared to metal working bits.

Just go to McMaster.com and you'll see that you can spend up over $70 for a high end metal cutting 1" bit. So, drilling out the interior rounded corner is an option.

I just got back from Home Depot and I was going to split with $30 or so for a template bit from Porter Cable. Since they keep the expensive stuff locked up and no sales help anywhere, I didn't bother. Then I went into their aisle which contains birch plywood. Man that stuff was warped!! Anybody know where to get quality 3/8" thick birch plywood? This is for a homebrew computer controlled engraving machine, so warped won't work. So far it's in the "gather the materials" phase. See

for more info if you'd like.

[CW]

Mcmaster has just about everything, including the highest prices around. It pays to look elsewhere.

[Edwin Pawlowski]

Keep in mind that a 1" radius corner needs a 2" bit.

HD is a crap shoot on the quality. I hot a beautiful piece last week, but I've walked away empty a few times. For your needs maybe a Baltic birch ply would be better. Try a wood dealer rather than the big box stores.

[George]

WOW! And to think, the best-quality holesaws run ten bucks or less. Seems you could do a lot for 70 bucks.