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PostPosted: Fri Apr 24, 2020 1:59 pm 
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Walnut
Walnut

Joined: Sun Mar 15, 2020 7:59 am
Posts: 6
First name: Bret
Last Name: Deardorff
City: Topeka
State: KS
Zip/Postal Code: 66614-4854
Country: United States
Focus: Build
Status: Amateur
Hi everyone,

I just successfully routing my first two radius discs out of MDF. I read somewhere that those discs can warp if you don’t put some kind of a finish on them or glue them to another full thickness piece of MDF. Any insight on what is the best way to do this. Should I put some kind of finish on them or glue them to another backer board of MDF. Thanks so much for your help.


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PostPosted: Fri Apr 24, 2020 5:25 pm 
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Koa
Koa

Joined: Mon Jul 11, 2005 5:17 am
Posts: 878
Location: United States
I glued mine to another 3/4” mdf. I didn’t put any finish on them though. They haven’t warped. I have one that I left single without the backer and it is warped.


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PostPosted: Fri Apr 24, 2020 6:49 pm 
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Brazilian Rosewood
Brazilian Rosewood
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Joined: Thu Feb 12, 2009 12:12 pm
Posts: 2951
First name: Bryan
Last Name: Bear
City: St. Louis
State: Mo
Country: USA
Focus: Build
Status: Amateur
I don’t have any answer to the question but this post is in the 2013 new builder’s challenge forum which no one is still looking at. Only people who use the “view new posts” feature will ever see it. . .

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.


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PostPosted: Fri Apr 24, 2020 8:48 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Aug 19, 2005 4:02 am
Posts: 2302
Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
Absolutely apply finish. It will protect it from moisture and glue. I use shellac or Zinnser SealCoat.


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PostPosted: Sat Apr 25, 2020 7:32 am 
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Walnut
Walnut

Joined: Sun Mar 15, 2020 7:59 am
Posts: 6
First name: Bret
Last Name: Deardorff
City: Topeka
State: KS
Zip/Postal Code: 66614-4854
Country: United States
Focus: Build
Status: Amateur
How many coats Barry. That MDF really sucks up the finish!


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PostPosted: Sat Apr 25, 2020 9:12 am 
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Mahogany
Mahogany

Joined: Sun Jun 02, 2013 8:16 am
Posts: 67
First name: Brian
City: U.P.
State: Michigan
Focus: Build
I did the same thing Barry did. I clamped the dish and the backer to the top of my table saw to keep them flat. Glued and screwed and left clamped for a couple days for the moisture from the glue to dissipate.

Many coats of Zinnser Seal Coat, I'm thinking 7 or 8, maybe more. I wanted a smooth surface to be able to peel off PSA adhesive on sand paper.

If I did it again I'd screw and glue two radius dishes together back to back and save some MDF and shop space.


As a side note-
I used Zinnser on my MDF bending molds after testing every kind of finish in my shop with heat of bending blankets. I was surprised to discover that nearly every other finish turned to a sticky goo in the presence of heat and shellac held up the best. I put fewer coats on the mold, but enough to seal the MDF.



These users thanked the author rbuddy for the post: Girlsdadx3 (Sat Apr 25, 2020 9:52 am)
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PostPosted: Sat Apr 25, 2020 12:17 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Aug 19, 2005 4:02 am
Posts: 2302
Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
I applied enough coats until I started to get a build up that I could sand smooth. I don't remember how many coats but it was probably 4 or 5.


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