Rounded corners?

[ffingers]

So I feel like I have searched high and low but can't find a simple way (if there is one) on how to round of the corners of a piece.

What I want to do is to curve the edges of my cab and CP....just a very slight radius for the t-moulding to run around. I saw something about templates, etc, but nothing definitive. I know I could cut the corners at 45s and sand them into a nice rounded edge but I just feel there has to be a better way?

So for all of you who round the corners off, how do you do so that you have a consistent, smooth corner???

[bungy]

I found something round with a radius similar to the size I needed and traced it onto my pattern where the straight edges of the corner were tangent to the circular object.  You can use a coffee can, coffee mug... I used the top of a maglite flashlight.

I started out by cutting all my edges with sharp corners and then went back with the maglite and traced curves over the corners and then put a drum sander in my router on low speed and rounded them off.  Was a lot easier that I expected.  Get some scrap and try a few corners.

Obviously with inside rounded corners, you'll have to leave extra material instead of cutting it sharp first.

[Epyx]

There are a few different options...

You can use a jigsaw and then use a flush trim bit to "copy" the curve on the 2nd piece.  Or you can use a template...either one you make yourself or something pre-made that has the dimensions to make it "router friendly" to do the curves with a flush trim bit.

[ffingers]

yeah, i understand the idea of tracing out the rounded portion using some sort of template...my concern is actually making it rounded...

i guess i could freehand it with a jig and sand it out, but i keep thinking there is a better way....
i also understand the flush bit as well and had planned on doing my second side of the cab with it, so i know i only really need to worry about 1 side....

so the best bet is to work hard and make a rounded template i guess and use that???

i have some weird angles on my cab so it might have to all done by hand which will be a pain

[Franco B]

Copied from another thread.

In regards to putting the radii on I find its best to make a template and then use a flush trim bit to follow the profile. For a radius you just need something round to follow. You could saw/file a radius on a bit of scrap material and then screw/stick that onto your sides corners and then use your flush trim bit.

For perfect circles/radii, especially larger ones I make templates on a lathe. Obviously you may not have access to one but another thing you can do is to use something like a tin can. They come in many different diameters and you should be able to find something to suit your needs. If you cut the top section of the can away leaving the base and about 1/2" of the side you should be able to screw this to your cab (or to a scrap piece to make a template) and then follow the cans side with the routers bearing.

Also keep in mind when routing you want to remove as much material before hand before using the router, especially on thicker material. 3mm (1/8") is more than enough.

[bdjou]

for my cocktail cabinet, I used a rotozip with a circle cutter adapter and made a template on 1/8" masonite. Then I used my router with a pattern bit to make the cuts. I think the key is to make a template out of materials that's easy to cut and sand down.

[LilMikey]

For my curves I used a jigsaw to get very close and a palm sander to smooth it out.  Second piece was templated.

[gryhnd]

I do the "find an object and trace" routine as well. However now I work on a piece of scrap, tune it as noted above by others, clamp to my work and use my router with a flush trim bit on it. Perfect copy every time.

[Franco B]

Just another thought, If you make a termplate its always a good idea to hang on to them for future use. You never know when you may need one and it will save you making one again.

[markronz]

I am looking to do the same thing actually.   I searched on the internet for a template.   I couldn't find much, but I did find one site.   Do you think that something like the templates here would work?
http://routertemplate.net/circle.html

Specifically the "Medium Convex:  Overall size 11½ x 9” one"?     It seems to me that this is the sort of thing that you could clamp onto the bottom of the wood, and then maybe use a flush bit on my router to follow along the pattern.   Making sure that the little roller on the bottom of the router bit runs along the template.    Does that seem right to everyone?  And if so, are there any negatives to using something like this that you can think of?

(Also if anyone knows of a cheaper template, I'd appreciate a link as well!)

[Franco B]

What kinda size radius/circle are you trying to route?

As before I would suggest using a round object to trace/follow or if you want something more precise or larger you could buy or [build your own circle cutting jig] to either route the radius in position or to make a circle to use as a template.

[Knave Jack]

If you know the radius (or diameter im easy) you want, i can laser cut some acrylic for you to use as a jig. The hard part for you is deciding how you want to clamp it down.
KJ

[gryhnd]

...you could buy or [build your own circle cutting jig]

Face palm

Excellent suggestion there. I had to build a circle jig much like yours for cutting my Pacman inlay template.  Now that I have that jig, I would use it for creating corner templates too.

[markronz]

If you know the radius (or diameter im easy) you want, i can laser cut some acrylic for you to use as a jig. The hard part for you is deciding how you want to clamp it down.
KJ

\

Thanks very much for the offer!   I think I am going to try to use something circular to make my own template first.   I'm not terribly experienced working with wood, so if I can't do it or something I will be in touch.   

[Knave Jack]

No problem. We have lots of scrap quarter acrylic at the moment. Its a very ugly brown, but that doesnt matter for a jig.

[markronz]

Is a "jig" the same thing as what I've been calling a template.   Sorry, I know that's probably a n00b question...

[Knave Jack]

Yep, i tend to use the 2 terms interchangeably. In this case its a rectangle with rounded corners. 4 different sizes of radius, with enough room to clamp it down and still use the router with a piloted straight cut bit (edge trimming).

[Franco B]

A jig is generally a work or tool holding device. I wouldn't personally call a router template a jig.

[Knave Jack]

A jig is generally a work or tool holding device. I wouldn't personally call a router template a jig.

You are absolutely correct. 
I should be more carefull with my termonology.

[MB]

How thick should a template generally be to work nicely with a router?

[Franco B]

6mm-12mm (1/4"-1/2") should be ample for use with most flush trim bits. All you really need is enough height for your bearing to run on the template. I always make sure my router is set so it overlaps the templates by 1-2mm to make sure the full side of the material is cut.

If I am making something to repeat several times I normally make a template out of 6mm MDF as it is easy to work and then use that template to make a 6mm thick acrylic template. I do this as MDF can compress slightly when you run a bearing over it again and again and you end up with a slightly inaccurate template towards the end. This can be minimised with an MDF template by just leaving a fraction of material to remove (~1mm) so that you hardly have to apply any pressure onto the template with the bearing. I prefer to make acrylic templates though as compression is never a problem and they are less likely to get damaged in storage/use etc.

If you are using a pattern bit to counterbore/recess a piece you will most likely need to use thicker materail for the template. I normally use 18mm (3/4") with a patten bit cutter height of 1/4" to start with. If your cutter height is longer you will need a thicker piece of template material or spacers between the work piece and template to allow the bearing to run along the template whilst the cutting edge makes contact with the work piece.