Cloudy: Try Thermolock, Or Bolt It Down To A Block Of Wood Through The Hole In The Square Part. As Far As Engraving It Just Be Very Carefull To Maintain The Proper Angle Of the Face Of The Graver To The Cut.
Hi, Cloudy.
I have engraved quite a few cap nuts to get the feel of those compound curves. They're a lot smaller than your plane part so if you get the hang of them, the plane part should seem easy, I would guess. I seldom comment but while I'm at it, let me compliment your work. I've been noticing and appreciating and enjoying.
However you attach it (doo,glue,screw), attach it to a longer than usual stick that is more or less exactly the shape of the object. Having your plate raised above the jaws like that will allow you to get access to the lower extremities of the dome, where your block would have blocked you before
This is a job for Cylinder Blocks! For your benefit, I took apart my own Lie-Nielsen low-angle block plane. As you can see in the photos, I just screwed it down to one of my Cylinder Blocks (the new 2.5"D size), using a big pan-head wood screw and a nylon washer to prevent marring the part. If I were actually going to engrave it, I'd put a big glob of thermo-loc or jett-sett under the 'knob' to hold it all steady. If you really need to tip it way over to work on the back end, I'd recommend using a short chunk of Cyl. Blk (so the flat section of the bronze part is hanging out in mid-air) and mold the glob of plastic under the 'knob'- first plugging the screw hole with wax, a short 1/4-20 screw stub (like a set screw), or cover it with tape or something. After it cools, lift off the bronze part and use the mound of plastic as a guide to drill about a 3/8" hole thru the block at the correct angle. Then use a 1/4-20 bolt or screw from the bottom to solidly anchor it to the block. Have fun!
Get yourself a fairly large diameter dowel 1" + flatten a spot on top of the dowel for you part to sit on. Either glue or screw the part to the dowel. Clamping on the round will allow you to turn the part side to side very easily to work around that curved surface. A cutoff piece of staircase handrail would probably work fairly well too. Just don't use handrail that is too flat on top. You want something pretty round in order to get the ability to clamp it in vrious positions.
Glad you responded Mitch. I was actually looking to see if you responded because I knew about your cylinder blocks,and knew this would probably be a good application for them.
i use junk wood, turned on my wood lathe to about 2" dia. depending on the object i may use a rasp to create a flat spot on top. about the same idea that ray suggested. hot melt glue does the trick.
Personally I'd stick/screw it to a block but make sure the block is exactly the same width as the metal or when you move down the radius the block will get in the way of the graver making it impossible to cut cleanly and continuously.