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Hello All.  I am getting ready to make some radiused sanding blocks and fretboard glueing cauls using the router pendulum method.  I have on hand some MDF, Baltic Birch ply, and 3/4" flat sawn Red Oak.  No matter what I decide to use, I will laminate it up to get a nice thick piece.  So,  what do you think will be my best bet for stability and wear?  The oak will hold up the best but stable enough?  The MDF is very stable but not so tough or stiff.  If I cut the outer skin of the baltic birch will it stay pretty stable?  My first choice is the birch but I do wonder about removing that outer veneer.  Anyway, I would love for you to chime in.  Thanks.

MDF or the new moist resistant MDF. Birch Ply microscopicly move in the direction you don't want and could separate plus if you do not have a good source for the top grade birch you are likely to run into voids when routing out the bowl

I'd make a doubled up (like you mentioned) 1-1/2" MDF block. Cut your radius and than seal it with some varathane or what have you.

It will than be very stiff and should remain true to its form once sealed.

If you had some 1" hard maple, I'd use that to. I love maple for hard sanding blocks.

What ever you choose, make sure and seal it to combate humidity changes.

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I have some corian sink cut outs I was thinking of using. Profiling will be interesting and they are 3/4" thick. I'll report how that works out.

Peter

I decided to use the MDF.  Like you say Rod, it'll be 1 1/2" thick so it should be stiff enough.  Does anyone have any pics or ideas for a router pendulum?  Specifically I am wondering about supporting the router weight and keeping everything stiff.  Also wondering about using a 4 penny nail or 1/4" pin for the pivot.  I want to run the whole thing vertical instead of horizontal like I've seen others do. Any ideas for me?  Thanks.  

If you're looking for something which'll never change shape, get a brick of acrylic or corian and use that. I cut blocks out of spare acrylic when I need 'em.

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I came up with something.  Havn't tried it but I'm sure it will work well enough.  You can see the MDF gettin' ready to be cut.  Used a 3/16" pin for the pivot.  I'll let y'all know how it worked tomorrow.

Well, everything went awesome.  This all started because I made the Marty McClary and Todd Stock fretboard radius jig and needed a clamping caul.  The jig worked well by hogging off material then skimming the final pass.

The fretboard was radiused using the McClary jig.  Thanks for your help with that Todd.  Nice fit.