The starting point for milling was ensuring my mill was perfectly level, as measured on the bed of my trammed vise. I used a machinist’s precision level, and got it spot on. Then, I put a length of 80/20 in the vise and supported by the stand on the other. I used my machinist level to level the stand to the vise and perpendicular to the vise (stand leveled in all directions). It was a fussy and time-consuming process, but necessary for high quality results.

Now, it’s time to mill. I started by coating the extrusion ends with Steel Blue marking fluid. I used it to monitor the cutting process so I didn’t remove any more material than necessary. I used a 2 flute. 4” cut length. HSS end mill. HSS tends to be sharper than carbide and sometimes works better than carbide on aluminum. This may make machinists cringe, but after removing the marking fluid, I made 2 more passes at the same setting to ensure the end was cut square. Long end mills defect some. The extra two passes removed the slight additional material occasioned by end mill deflection. Yes, I know this causes rubbing and can be tough on tool life. However, it was that or accept that the ends would not be as square as possible. I went for square.

Here are some photos of a 1530 angle brace vise showing the marking fluid and its being milled off.







You get a sense of how far off from 45 degrees the ends were. Note the makeshift work holding with angle plate and 1 2 3 blocks. I set my vice up at 45 degrees, but the body of the vice was in the way of cutting. I could have used the vise, but I would have needed to extend the extrusion out from the vise farther than I liked. Setting up the angle plate to 45 degrees worked fine.

After getting the ends milled square, it was time to measure to get all like pieces the same length. I made comparative measurements to determine which piece was shortest. Then, I used the shortest piece as the part to measure against to determine how much needed to be removed from the rest. On the long pieces, I put an outrigger on my support stand and added a hard stop. That way, I could zero my DRO to the desired ultimate length and cut each piece until I reached zero. Sounds good in theory, but it didn’t work in practice. I found that the stop flexed, and no matter how careful I was placing the stock in the vise and moving to the stop, the results were inconsistent. Failing the use of a hard stop, I resorted to cutting the measured amount each piece was too long. This is where the blue tape came in. I wrote on the tape how many thousands need to be removed for each piece.

Assembly next. I did not take photos until I got the legs and braces on and cross pieces going in.

Here is a photo of the frame with the first cross piece in place. Linear rails, the gantry and stock for gantry mounts/interface plates are on the floor under the frame.




Here is a closeup photo showing some aluminum angle temporarily bolted to the extrusions. I used the angle because there is quite a bit of wiggle room when assembling 80/20. The angle ensures that sides and tops align properly. 1. Attach the angle, 2. tighten the connectors, 3. remove the angle, and 4. final tightening of the connectors.




Here is a photo with a Woodpeckers precision 45-45-90 triangle clamped to the extrusions. I clamped it for photo taking purposes. I was gratified to find that everything went together perfectly square. Square ends make square frames.



You will note the angle supports hanging out in the air. I had to put them in place on the legs before adding connecting pieces. I quickly found that if not perfectly positioned, they will cause the upper frame members to flex up or down, if only by a few thousands. I decided to get the frame assembled and then
finalize with connecting the braces.

Here are additional pictures as the frame went together.