Through slot in aluminum tube

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jwmelvin

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I have some 2x2, 3/16" wall, aluminum tube, in which I'd like to cut some 3/8" wide by ~8-12" long, longitudinal slots through both walls (to allow the tube to slide along its length and then be fixed in position by a bolt through the slot). I could mill the slots in two setups, working from each side; I have a 2-flute cobalt end mill I could use.

But I'm considering whether it's worth it to buy a long end mill and cut the slots in one go, reaching through the width of the tube to cut the far wall after cutting the close wall. This is a long stickout for the tool, but it would save a lot of time as compared to two setups with the associated effort to align the slots.

As potential end mills to use, I'm thinking of: YG1 JAG98911 (reduced shank for clearance as it reaches through); YG1 JAG97941 (straight 2" LOC); or Helical Solutions 46255 (similar to the first, reduced-shank YG1).

I appreciate any thoughts or guidance you may have. These are just clearance slots for clamping bolts, so no precision to speak of. If I cut in two setups, I'd want the slots aligned to about 0.010" across their width, which seems reasonably easy with an edge finder.

My mill is a PM-30MV.

-jason
 
You could use a long end mill or maybe spot drill and drill through holes at either end of the slots with a jobbers length drill bit. Mill the slot in the top side, flip it, and use the drilled holes to locate the ends of the slots for the second side.

Bruce
 
IF the slots are centered on the tube and you set it up carefully for the first one with a stop to set the starting point, this will all be done in one setup. You will mill the slot flip the tube over and mill the other side and they will line up perfectly.
 
Yes the slots are centered so you are probably right it’s just better to save the $50 extra tool and use a stop to make flipping the tube an easy operation.

I like the locating through-hole idea too, thanks.
 
I use an edge finder on both sides to center a piece of work. If the tube dimensions are uniform, you can just flip for the second cut. If not, you can just find the center as for the first side.
 
If you were off-center, you could still flip it and still be very close. Just keep the same side of the tubing to the fixed jaw when it's flipped. Theoretically, you'd be spot on. Yeah, takes time to flip the part, just a matter of spending the cash or spending the time.

Bruce
 
My only advise is to do it without a vise.
Nestle the tube in a t-slot directly in the table and clamp it down to the table.
This will avoid any pinching of the slot by a vise as you're cutting the slot.

Since your slot is 8-12" long you could put a temporary clamp (or two) in the middle and move them as you cut the slot.

-brino
 
I guess one of my questions is: if I were to buy a long end mill, would that be a reasonable approach, or am I likely to have issues with chatter, etc. anyway such that the from-each-side approach would be better?
 
Long end mills flex, so I only use them when the job calls for it. I'd indicate off of the stationary end of the vise, set the Y for the centerline of your work piece and lock the axis, set a work stop, then go go go paying attention only to x travel for slot length.
 
jwmelvin said:
I guess one of my questions is: if I were to buy a long end mill, would that be a reasonable approach, or am I likely to have issues with chatter, etc. anyway such that the from-each-side approach would be better?
Click to expand...

I have tried this before and I did experience serious chatter. Maybe I just wasn't doing something correctly, but this has been my experience.

Ted
 
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