Yikes! I'm embarrassed that it has taken this long to get back to this project. Currently preparing to machine the base casting. In Harold Hall's article he spent a fair amount of time describing how he machined the awkward shaped and sized base casting. He ended up moving it several times and made compromises in the sequence of machining steps.
In thinking this through - HOW will I machine this on my little Atlas MF - I decided to machine this on an angle plate and use endmills. So, I started the fixture plate:
This model illustrates a 12" wide, 4-1/2" deep on the base by 10" high welded steel fixture plate. The plate is 3/8" thick 1018.
The fixture will be split into two pieces, 6" wide each - so that I can slide the fixtures into appropriate support areas and slide the base around correspondingly. This split feature will allow me to get clamps in the middle of the base and hold things securely. You can't see the split in the model.
Back view. The four straps are 3/8" x 1-1/2" x 8-1/2" high - spaced 4" in between straps.
Drilling holes in the 4-1/2" x 12" plate to bolt it to the table during machining. These will be used during machining when the fixture is in use as well. It should be obvious looking at this and considering my plan to make two fixtures that that I will cut this plate across the width to make two 6" wide bases. For now, we will machine it as one piece to keep everything aligned and true.
Next step is to bolt the plate up to the table and square it up. Then I milled a flat area where the vertical plate will be welded.
A couple of things to take notice of. The cutter is a 2" diameter, 3/8" wide side milling cutter. There is not a lot of clearance between the arbor spacers and the workpiece - limiting the travel on the table to either side of the arbor. No good. My solution was to grind down the tops of the socket head cap screws. You can also see if you look closely that there is some chatter/finish problems on the left side of the cut. I'm not to worried about the finish, as I'm going to be welding in this area anyway.
I didn't fully realize it at the time, but I was slowly stripping the table nut underneath using the full travel of this machine which explains what was going on with the finish to some extent. After I replaced the nut
(which you can read about here) I flipped the part and milled some deeper grooves where I will weld in some 3/8" keys to the bottom of the fixture, this will allow me to drop the fixture(s) onto the table. Finish cleaned up nicely.
Prior to this part of the job, I cut the straps and verticals to length and deburred with a file. Here is a quick clip of the Miller's Falls saw cutting the verticals.
View attachment IMG_6849.MOV
The alignment of the saw is not great and it doesn't cut straight. So I had to clean up the ends and square them up on the mill.
This was prior to the lead nut stripping and this was the first time I've put a couple of hours into the machine - I'm sure the power feed didn't help the lead nut either.
Anyway, more pics to come later!