3 Axis Foam Cutting Mill

3 - Axis Foam Cutting Mill - Part 7

Squaring and Screwing Around

The key thing that I know down to the pulpy marrow of my bones is that this rig has to be square, and I mean dead on 90 on all three planes.

As the square that's pictured is the most precise instrument that I own, it is the reference, unfortunately it's not large enough to run accurately the full length of the framing.

Luckily I still have one factory corner, and it's true to the square, I tag it with an "A" and all assembly is gauged against it. Also a base line is drawn to visually determine placement.

All the "test-fitting" is over, it's time to start to actually assembling with new screws and glue.

Initially I did drill 1/8" holes and used 2 1/2" screws, to my dismay there were still cracks in the MDF. To resolve this I upped the drill dia to 5/32nd" and reduced the screw length to 2" flooring screws. These screws have a wider thread that cuts deeper but has less parting influence.

All holes are filled with wood glue to aid in strengthening the bond. The cracks are also filled with glue and clamped as the screws are driven in.

After fastening all the sides while pushing, pulling and clamping, it was left to set-up for about 6 hrs. After I undid the clamps and removed the braces it stayed almost where it was set. There appears about 1/8" run-out over 14". If I try and square it to true I fear that the box will pop and I'll have 4 pieces again, only this time it won't go back together.

Here the mating face of the box is laid-up with glue, as I get ready to place it on the line that was drawn-out earlier.

Every possible joint, junction, point of contact and all of my finger tips is liberally coated with yellow carpenter's glue. If I was 6 yrs old, I'd have quite a snack on hand, but I was content to just peel it off and examine my finger prints in the glue.

Just before clamping down I tried one last tweak to gain absolute square, but it really didn't amount to much good. I'll have to adjust the X-Guides over to the Right, as the mechanism is critical, only you and I will know the frame is imperfect. During the 2 days it's taken to get to this point I must have listened to "Richard Feynman - Symmetry in Physical Laws.mp3" three times.

Half of these screws went into place before the clamps were loosened. That's a pile of screws and glue,

I used just one cordless drill for all pilot holes, counter sinks and driving the screws 3/4 of the way... each screw is hand tightened the last quarter to ensure that the hole isn't stripped.

This is the first of three coats of Automotive "Glaze Putty", being applied over rough joints and covering screw holes.

This is just like working on a car, actually easier, since all the surfaces are flat, and meet at a sharper corner than any that my S15 has.

I got some fixtures cast between sanding and skinning... more therapy...

I'm so glad I put in the holes for the guides, the rods just make it look like it may actually work.

This grey paint is automotive Hi-Build Primer. Even thinned 2.1 it finishes nice and just ties everything together. There are 3 or 4 spots that need more fill and a light sanding with 300 grit or finer will have this ready for a nice top coat. If not for the cost, I'd go for a durable enamel and bake it on.

The cast fixtures all need machining on the lathe, so while that's on-going, I'll plug away at the frame, and figure out what to seal this with.

In closing it seems quite sturdy and hopefully is over engineered structurally for the light duty Foam cutting that it is intended for.

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