Frame Material

[elogicca]

Would Rectanglar Extruded Aluminum Bar 1/2" x 3" be ok for a 20"x20" mill?

Could i go thinner?

Thanks

[Ken_Shea]

Thicker, Yes, Thinner No.

Ken!

[WhiteTiger]

Mill, no... router, yes. That's assuming that you'd be properly mounting your linear rails on the bar, which would effectively increase the material depth and decrease extreme fiber loads and deflection.

The 1/2 by 3 loaded on the 3" axis should be more than enough for any sensible router work, I'd think. Add the rail thickness and your deflections the other direction should be minimal as well.


Tiger

[cbass]

Originally Posted by WhiteTiger Mill, no... router, yes. That's assuming that you'd be properly mounting your linear rails on the bar, which would effectively increase the material depth and decrease extreme fiber loads and deflection. The 1/2 by 3 loaded on the 3" axis should be more than enough for any sensible router work, I'd think. Add the rail thickness and your deflections the other direction should be minimal as well. Tiger

Tiger,

While I agree that the aluminum will suffice for a router, the rails will provide almost no structural support for the frame. Despite the fact that they are steel, they have a very small cross section. Rails are for motion, not for structural support!

Carlo

[WhiteTiger]

Hmmm. Seems to me that rails are by definition structural support members. They are, after all, rated largely by their load carrying capacity.

Had a quick refresher look around, and the lightest duty units I could find were the techno model 1 rails which would add just under an inch (24.5 mm) of aluminum to that 1/2 plate. THK's smallest I found offhand was a 5mm thick stainless steel rail which would not be an inconsequential addition when figuring beam moments for lateral loads on that plate.

Any way I look at it, the rails add to the total.


Tiger

[elogicca]

How about using hss steel? 1/2" by 3"

[elogicca]

Ok just did some checking, 3"x3" 1/4" Ibeam extruded aluminum for the frame how would that be?

[pen25]

for 20x20 i would think heading over to the 8020 store on ebay would prob net you better results. plus simplifies building.

[Geof]

Originally Posted by elogicca Ok just did some checking, 3"x3" 1/4" Ibeam extruded aluminum for the frame how would that be?

This is a much better choice than the flat bar. It will be stiffer than the flat bar in both directions but not that much heavier because the cross section are is not much larger.

[elogicca]

Well, I opted for 2" square steel tube .100" wall, this thing seems solid