I am building something where I need a very specific length of 2020 extrusion (632.9mm, ideally) and I want to have nice clean and square ends on the extrusion. I have a Shapeoko Pro with SMW fixture plates / vises so work holding should all be solid and I’m comfortable cutting aluminum stock. I’m thinking of:
rough cutting to about 637mm with a hacksaw
securing on the Pro with a vise near (~ 5-10mm) each end, supported on parallels
running a series of contour cuts on each end to get to the appropriate length (leaving 0.1mm of stock) with a conservative DOC of 1mm
running 2 full depth cuts at +0.05 and =0.00 of the final dimension
Does anyone have experience trying to clean up a crappy cut in 2020 extrusion and/or any feedback on what I am thinking of doing vs. what I want to accomplish?
This is not a cnc solution but if you have a chop saw you can cut aluminum with a carbide blade. You might get a better result. Make sure your chop saw is set up with the blade square to the bed of the saw and the fence is perpendicular to the saw blade. After cutting you will have to use a file or sand paper to clean up the fuzzies.
So if your piece is long enough to try cutting one end to see how it works. Just dont try to cut to final dimension without seeing how your saw performs. Be sure to wear proper protection because the chips will fly.
@gdon_2003, are you saying that you’re not offering a CNC solution or that my goal doesn’t want to have a CNC solution? If I’m wrong in thinking the CNC should do this well, why? If you’re suggesting using a chop saw instead, I was actually afraid that the RPM of my miter saw would be too high and even with an aluminum blade I would either get a bad cut or a dangerous cut. Is that a worry?
I have cut aluminum on a miter saw with a wood blade no problem. Just go a little slower thru the cut.
I would also say this is possible on the cnc, just would take longer. How thick is this extrusion? Im thinking you might need an extended mill.
Just like the miter saw option having it perfectly square is up to your machine setup. Does 1 inch really cut 1 inch on your machine, is the spindle perfectly square, do you align the piece 100% square to the machine, etc.
The best tool for the job would be a metal cutting chop saw but not too many woodworkers have them.
I have cut aluminum on my table saw and my Dewalt miter saw.
Your 2020 material is quite solid/dense and if you do not take your time you can damage your blade. All wood cutting blades have a different rake, carbide thickness and set designed for wood and when these blades are used on aluminum you can chip the carbide or worse break off a tooth and send it flying into something you don’t want damaged.
If you plan on cutting a lot of this material or you may be doing more in the near future purchase a blade designed for aluminum for the machine you will be using it on.
Using a table saw or a chop saw you will want to move slowly and smoothly when making your cut. Use goggles and a face shield along with long sleeve tight fitting tee shirt to reduce the amount of shavings that will impact your arms.
A better option if you are making just a few cuts is to go to a metal shop or a metal supplier and have them make the cuts for you.
You can cut your extrusion many ways. When a carpenter only has a single tool a hammer everything looks like a nail to him. You can certainly cut it on the CNC but you can also cut it on a chop saw with a carbide wood blade. The only issue with a cnc is the long time to design, setup and execute. With the chop saw you are through in a few minutes and a few more with clean up. I have cut a lot of aluminum with a chop saw. It is not my favorite thing to do but if you can mark it accurately you can cut it quick and easy. As Mike Lange suggested cut slowly and have the piece clamped down. Most miter saws have a clamp with them.
Yes you can cut it on the CNC but if you just want to cut it and not make a big production a chop saw would certainly work.
A lot of people buy a chop saw, take it out of the box and start cutting. You need to verify that the saw is set 90 degrees to the deck and the fence is 90 degrees to the blade. A simple machinist square can be used to set up a chop saw. Be sure to calibrate the degree scale on both the left and right and the angle scale is calibrated. Most saws that come out of the box are like a hand grenade, close but not all that accurate. Since you want to get a square cut just check the saw before cutting. The added benefit is when you cut wood it will be accurate as well.
edit - I also found this to be pretty essential to avoid the teeth clogging up whilst cutting 10+mm thick plate and softer aluminium
Although it smells weirdly like bacon…
Or I would think that the OP could use the SO Pro to walk down the end of the 2020 with an aluminium cutter with at least 20mm flute length in shallow cuts, probably won’t leave a super finish but it will be dimensionally pretty good, if, and only if the SO Pro has been calibrated well by the OP.
I just tried a quick test where I trimmed a random v-slot I have which has a badly cut end (hacksaw without a miter box). I setup the CNC to trim it to 490mm and the CNC operation went without issue, it didn’t need any deburring (the cut was quite clean) and according to my square the ends are good and square. It looks like 490mm with my measuring tape.
I would say that this is definitely at least as accurate as I could cut it with a crosscut sled on my table saw and more accurate than I’d be able to cut it on my miter saw.
It is definitely slower though! I would estimate about 10 minutes (setup and cutting time). If I wanted 4 extrusion to be exactly the same length, I would put all 4 in the vises and cut them and feel very confident about the result.
The biggest surprise was that it’s non trivial to clamp the v-slot in the SMW vises. There is surprisingly little flat face on the sides of the v-slot. I ended up 3d printing a spacer that raised them up such that I could clamp both halves on the side at once.
Next stop is to get an aluminum cutting blade for my table saw and see how that works. After more research, that does seem like a very viable way of cutting aluminum and would be very convenient when cutting bar stock for the CNC.
I bought an aluminum cutting blade for my table saw and, of course, it is definitely much faster to cut than setting up the CNC but not as much as you’d think if I have to swap blades (twice) for a single one-off cut.
The cuts seem to be of about the same quality (the CNC was quite clean). The precision is roughly the same but much more work to get to the same precision with the table saw with careful measuring and setup. However, with a good stop block, you can get a lot of pieces to the same size much more efficiently with the saw.