Small corner round overs, big problems... Any way to do this out of the machine?

Hi guys I have a customer who uses round corners on a lot of parts. This time its some fairly big 1/4" aluminum plates. 14 x 18 inch. Needs 0.078 rad all around, Both sides of course. Going to be tricky to hold this flat enough to get corners looking good. Just a couple parts, hard to justify complicated fixtures and stuff for small jobs like this. Part has a bunch of holes too so vacuum table not easy either.

Is there any way to do this afterwards with a router or router table or something? Even if i had to sand it a little bit after to blend might be fine. With a tool something like this? https://www.toolstoday.com/media/catalog/product/4/9/49494_1.jpg

Will this work on aluminum or is there any other options that will make this easier?

I don't see why it wouldn't. If it's just a few, you could do it with a trim router if you don't have an appropriate-sized router table. We do this a lot on polyethylene, which is softer, but we're putting on a bigger radius. We machine the part on the CNC mill, then add radii with a trim router (the 18V cordless Ryobi is pretty handy)

Hi mmurray70:
Yep, that's exactly how I would do it too.
One small thing I typically do if cosmetics is more important than geometry; I soften the two corners of the cutter where the radius meets the cylinder and the radius meets the end face of the cutter.
It only takes a thou or two of rollover and the edges of the routed shape will be pretty much indistinguishable from the surfaces of the part unless you seriously fuck up your depth settings or your part is curled like a banana.
I use the broken sliver of a phenollc diamond wheel I trashed years ago...it's 320 grit as I recall; but you can use a very fine diamond file too.
A couple of quick strokes under the microscope and all is good.
Make sure you preserve the relief on the cutter when you do this.

You just want to kiss it to dub away the dead sharp corners on the cutter...no need to stone on a honkin' big radius.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Oh yeah, I forgot to add: don't try to take it all in one bite in aluminum...it'll bounce all over the place and look like shit.
I always did it in two bites and made the second bite only a couple of thou.
A trick that has worked for me is to put clear packing tape under the router base to lift the cutter off a twitch and then remove it for the final pass.
Also I like stick wax smeared on the part before routing and I like climb cutting the finish pass...but do hang on tight to the router!

MC

I actually do this fairly frequently for one line of parts that are similar to what you describe. We get them waterjetted. I bought a cheap generic variable speed router and mounted it upside down on a platten like a spindle moulder. Use a bit with a guide bearing*. Works fine. No machining involved.

*edit - just like the one you linked!

Ok awesome, was hoping it might be as easy as this.

Anybody have suggestions on a decent router thats nice and rigid with decent height adjustment, something that might not be too disappointing for a machinist to use?

implmex said:

Hi mmurray70:
One small thing I typically do if cosmetics is more important than geometry; I soften the two corners of the cutter where the radius meets the cylinder and the radius meets the end face of the cutter.
It only takes a thou or two of rollover and the edges of the routed shape will be pretty much indistinguishable from the surfaces of the part unless you seriously fuck up your depth settings or your part is curled like a banana.

Click to expand...

Several companies offer radius cutters that are ground like this. It leads off on a 5 degree angle or something instead of being perfectly tangent. Makes it much more forgiving. Im talking milling cutters though, not router bits.

I guess if I do it on the router with a bearing I could try doing that mod myself. Thanks for the tip.

I just use a Dewalt trim router and pretty much do this on all our aluminum plate jobs, turns out great.

If you want to do it in-machine for automation’s sake, Harvey Tool makes flared corner rounders that make these blends easier. But if the parts don’t need to be accurately cut (IE straight, flat etc.) a handheld wood router would be pretty easy with a firm hand.

The little Makita trim router is very nicely made, pretty much all metal where it counts.

Ok if you guys are using handheld units I might try this milwaukee one: https://www.homedepot.ca/product/mi...cordless-compact-router-tool-only-/1001510585

Nice metal base, looks like it has decent depth adjustment, I can bolt on my own flange or mount it to a table if i want to, and I have bunch of M18 batteries here already. Think this will be ok?

mmurray70 said:

Ok if you guys are using handheld units I might try this milwaukee one: https://www.homedepot.ca/product/mi...cordless-compact-router-tool-only-/1001510585

Nice metal base, looks like it has decent depth adjustment, I can bolt on my own flange or mount it to a table if i want to, and I have bunch of M18 batteries here already. Think this will be ok?

Click to expand...

Can't open that page for some reason, but this is the one I bought.

Silverline 264895 DIY 1500 W Plunge Router 1/2" 1500 W UK : Amazon.co.uk: DIY & Tools

Not quite the cheapest piece of shit I could find, but pretty close to it. I didn't want to ruin a good tool by misusing it. To be honest, I've not (yet) ever wished I bought a better one for this purpose.