Chevy tune up

I made some progress on the Chevalet this week, although not all of it is wood related.

First off, I got the “saw support arm” completed.  This is the three pieces that support the gimbal and saw frame.  Once I’d wrapped up the adjusters last weekend it was just simple stuff — cut the tenons that fit into the vertical and horizontal adjusters, and add the mounting bolts.

The mounting bolts were a bit interesting.  There is a 3/8″ bolt that goes through the adjuster slot into a hole in the end grain of the horizontal support.  It needs a nut on the end.  The simple thing to do would be to carve out a big hole so I could reach in and put the nut on the end of the bolt.  Instead I decided to chop a mortise just the size of the nut so I could drop it in place, and the walls of the mortise would keep it from spinning when I tighten it.  That meant I had to be pretty accurate in drilling the hole into the end of the horizontal support, and in laying out and chopping the mortises.

It turned out to be pretty simple really, I just had to pay attention to what I was doing.  I figured out the “clamping depth” — how far in the nut needed to be — and knifed in a mortise just big enough for a square nut.  Then I figured out how deep it had to sit to engage the bolt coming from the end.  I set a blue tape depth stop and drilled out most of the waste.

Mortise knifed in.  The next step is to use a drill to remove the waste, then chop out the rest.

Mortise knifed in. The next step is to use a drill to remove the waste, then chop out the rest.

That just left chopping out the waste, and paring the fit so the bolt would drop to the right depth.  I didn’t want to have to force it down, and risk it getting stuck!  The repeat for the other end of the support.

Nut mortise done

Nut mortise done

That completed the horizontal frame assembly.  Mostly.

Mostly-done horizontal support assembly

Mostly-done horizontal support assembly

Why “mostly”?  Well, attaching this to the frame I’ve built so far required figuring out the length of the vertical riser and where it hits this horizontal member.  All of this to ensure that the saw frame ends up in the right place relative to the clamping jaws.

Unclear on what I’m talking about?  The saw hangs from a gimbal mechanism that pivots on the two knobs in the picture above.  The saw blade has to end up in the right location, or the saw won’t work, and I’ll just have a large pile of expensive firewood.

So I pulled measurements from the blueprints provided by Patrick Edwards, and modeled all of the parts so far in SolidWorks.  I adjusted the layout for the joinery and the length of the vertical riser until I got the parts in the right location, and then printed out some plans that match the parts and materials I’m using.

CAD Layout

CAD Layout

In theory, I just need to do two joints to complete things to match my model.  That shouldn’t take me more than an hour or two, but I spent probably two hours measuring blueprints and re-creating parts in CAD to know where to cut everything.

Once that’s done I need to make the seat assembly, and the saw frame.  I don’t have enough wood for the seat assembly, and I think I’d like to do that next.  The parts I’ve built so far won’t stand up without the seat assembly, and I’m worried about cutting the joint for the saw frame.  It’s essentially a giant finger joint, but it’s too big to cut on the table saw, and I’m not confident enough in my hand sawing to be able to saw it.  I guess I can do some practicing.  Or maybe do it on the bandsaw.

Now I just need to catch up with the CAD model...

Now I just need to catch up with the CAD model…

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