How to cut a slot inside a C-channel side?

[dml66]

I need to cut a 1/2" tall, 0.01" deep slot along both sides of a 5" piece of aluminum C-channel, looks like this:



My thought is to acquire a 1/2" cutting height straight router bit and do this on the router table.

The piece would ride legs-down against the fence, first one side, then rotate it 180°, run the other side.

Ideas for other approaches welcomed!

Thank you,

 

[talvare]

Looks like you'll need to use something like a T-slot or Woodruff key cutter. Something like this: https://www.mcmaster.com/products/t-slot-milling-cutters/
I can't picture how you would use a "straight router bit"
Ted

 

[brino]

I'm not sure I understand your sketch.
You seem to have those slots drawn on the inside of the channel sides, not the outside......

Do the holes go thru the channel sides or are they blind?

You say the channel is 1/8" thick so 0.125".
Is the slot 0.100" deep? (leaving a 0.025" thin wall?)

If it is a thru slot with dimensions 0.500 x 0.100 inch, then you'd need a pretty small diameter router bit.
I might pre-drill at both ends of the slot first with a drill bit the same size as the router bit.

....but I'm not sure that I understand this properly.

Brian

 

[extropic]

Either your graphic is not to scale or you wrote .1" but meant .01".

The best way is to relieve a standard end mill to create enough clearance to side cut your slots.

Something like this.

 

[dml66]

The slots are on the inside of sides. Good catch on the 0.1, it's really 0.01" deep

I flipped the image to (hopefully) better illustrate how I'd use a router. The fence would be set 0.115" off the router bit cutting edge.

 

[Eddyde]

I think it will be difficult to get precision with the router setup, also it could dangerous. Do you have a mill?

 

[dml66]

I think it will be difficult to get precision with the router setup, also it could dangerous. Do you have a mill?

I don't have a mill at this time. I agree, using the router could be dangerous.

There isn't a requirement for super precision in this case; the theoretical amount to remove on each side is 0.009" but that doesn't account for fitment oddities that may show up. I'd take tiny amounts off, try the fit, and so on.

 

[francist]

I think I might go at it the other way around. By that I mean have the C-channel with the open side “up” and run the router spanning both of the open legs. I think I’d like that better because:

a) I can clamp the C-channel firmly to some sort of bed (even if it’s only a straight piece of plywood or something) that can in turn be secured to a workbench;

and b) the router can be run against the inside faces of the channel and not be pinched between a fence and the workpiece (I never like that).

It would mean that you’d need to come up with a pilot bearing the right diameter to give you your 0.010” depth but that may not be that difficult. Either on its own or by using a commercially made bearing along with a shim strip of appropriate thickness stuck to the inside face of the channel. If things go sideways during the cut, your bit remains free and has room to come out of the cut into the open core of the channel.

That is if understand the objective correctly.

 

[extropic]

It is very dangerous to set the fence at .115" as you stated. That way, any unexpected movement of the workpiece will result in a deeper cut, or worse.

Instead, put the fence against the opposite leg of the channel and back up the other leg (being cut) with a hand held 2x4 to minimize deflection.
You should be holding (manually) the workpiece against the cutter. Do not trap the workpiece between the fence and the cutter. The workpiece (at a minimum) will loose that fight.

A straight flute router cutter (zero helix) will beat the hell out of the workpiece, but for .010" DOC, if that's all you got . . .

 

[m1kemex]

Cutting inside features is always difficult with rotary tools as you need space for the spindle holding the bit. Those neck grindings do exactly that.

I'd say, this is the kind of job a shaper / planer excels at. Since you're removing very little soft material, maybe some jig holding a wood chisel could work? It won't be fast, but no risk of hurting yourself.

I'd prioritize my own safety over speed and routing metal by hand definitely doesn't sound like safe.