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Discussion Starter · #1 ·
I have a dozen kitchen cabinet doors that I've stripped, repaired, and am soon to paint. There's a decorative profile on the edge of the rails and stiles that needs sanding and while I have the little rubber Tadpole sanding profiles this has already been an epic journey and I'd like to simplify things so am considering making a custom sanding block.

I recall reading somewhere about a soft but stiff foam (like surfboard foam?) used to make one. I'm not sure I have anything liken that laying around and this is not a commercial undertaking, so I need to use what I have on hand.

Jeff Jewitt has info on making one from Bondo (with I have) and truck bed liner (which I don't have), see attached pic. One question about his method is it requires making a cast of the molding in Bondo and applying wax to the wood as a mold release. Unfortunately, I have no spare sacrificial molding section (nor is this profile on the back of any of the doors). I have a couple doors at floor level which I could use the upper rail to make a cast they will be less visible than the rest of the doors in case of damage. I was thinking I could either, a.) use packing tape pressed to the wood as a release (does Bondo stick to packing tape?), or I could apply a 1-2lb cut of shellac in the area as a barrier coat and then wax the area and after making the mold use solvents to remove the wax and perhaps sand off the shellac before priming. Or use both shellac and packing tape.

Any other suggestions or input on how to go about this or alternate methods? I'm looking for a quick and dirty that will get the job done.

Thanks.
sanding block 1.png
 

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Egg Spurt
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You could possibly grind the edge of a scraper card down to match. I did that with a refinishing job to scrape out the softened paint and the rest of the crud..
 

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Discussion Starter · #3 ·
You could possibly grind the edge of a scraper card down to match. I did that with a refinishing job to scrape out the softened paint and the rest of the crud..
I don't have a grinder and all the paint has been removed ... all of it (monumental amount of work). These just need to be sanded and also correcting any defects and damage from the paint striping work.
 

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Egg Spurt
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Sand carefully with a stick. You can try making a custom block with the bondo method. If you're going to go through the effort it doesn't hurt to know about bondo itself. You'll want the hardest possible mixture you can get which means use the absolute least amount of hardener as possible. It's kind of counter intuitive, but more hardener makes a softer mixture that can crumble in your hand. I did auto body work for years. I've mixed stuff that had to be ground off because I didn't have enough hardener..so hard my sanders wouldn't touch it.. You'll want to make damned sure you have the entire surrounding area waxed well or you may end up grinding it back off the wood itself..I'd tape down wax paper around any and everything that might possibly get bondo on it that you don't want it on and test it on something else that it won't hurt if it doesn't release or then you'll be in a world of hurt..
 

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Egg Spurt
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I'm not sure how you're going to get sandpaper to match the shape you want. You might try the flexible 3m paper with a spray on adhesive. I'd make a long enough piece that you have extra to play around with in case the first try doesn't work out right..
 

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The Nut in the Cellar
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I've used Bondo to make custom shapes for a variety of things. I wrap or cover the shape with plastic wrap and apply the bondo to the shape. When it has cured enough to hold the shape, but still able to be cut easily, I trim the Bondo and then let it fully cure.
 

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Discussion Starter · #7 ·
If I can get a sanding block made to fit the contour the sandpaper isn't an issue, I'll use PSA paper with adhesive back.

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Does Bondo stick to packing tape?
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The other method I recall reading about is to use PSA sandpaper or similar and stick it to the molding profile (could use something like a bone folder - which I have - to press the paper well into the contours). Then take a block of stiff foam (like that blue surfboard foam that can be sculpted) and keeping it carefully oriented, use it like a sanding block on the profile, but in this case since the profile has sandpaper on it its the foam that's being sanded away into a negative profile of the molding. Then the foam block can be used a custom sanding block ... all that's needed is PSA sandpaper stuck to the foam block pressed into all the ridges and curves.
 

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Discussion Starter · #8 ·
I've used Bondo to make custom shapes for a variety of things. I wrap or cover the shape with plastic wrap and apply the bondo to the shape. When it has cured enough to hold the shape, but still able to be cut easily, I trim the Bondo and then let it fully cure.
Does the Bondo stick to the plastic wrap or does it easily release?
 

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The Nut in the Cellar
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Nope, peels right off once the Bondo has cured.
 

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Bondo sticks to everything you don't want it to and nothing you do want it to. Don't play a game of "will this material release" unless you have spare molding. Make it a guarantee and properly wax the area, though honestly for a critical project I'd spring for some actual mold release. Bout $10 for peace of mind
 

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Egg Spurt
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It'll stick to wax paper but usually only where it's been wrinkled or creased.. We used it to make flat panels over rust holes in cheap body work shops..Usually for dirt lots.. buy here pay here car lots.. Slap a heavy layer on the wax paper then slap the bondo on wax paper over the hole and viola! No hole..until the next buyer hits a bump in the road.. lol Wax paper peels right off. Buyer is stuck with the crap car and the overpriced note as well..
 

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mike44
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I've used Bondo to make custom shapes for a variety of things. I wrap or cover the shape with plastic wrap and apply the bondo to the shape. When it has cured enough to hold the shape, but still able to be cut easily, I trim the Bondo and then let it fully cure.
I do a similar approach but use Plaster of Paris instead of bondo. Sometimes adhesive backed paper will work. Usually I coat the mold with hot hide glue. When the glue cools I install the sand paper. I often have to push the paper into crevices and use a heat gun to activate the glue. Ordinary sand paper works well . Paper can be changed by heating the mold with the heat gun and then pulling the paper off. Often new glue application is not needed, just repeat the above method.
I like the idea of Bondo, will not crumble with repeated use like my Plaster of Paris molds.
mike
 

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The other method I recall reading about is to use PSA sandpaper or similar and stick it to the molding profile (could use something like a bone folder - which I have - to press the paper well into the contours). Then take a block of stiff foam (like that blue surfboard foam that can be sculpted) and keeping it carefully oriented, use it like a sanding block on the profile, but in this case since the profile has sandpaper on it its the foam that's being sanded away into a negative profile of the molding. Then the foam block can be used a custom sanding block ... all that's needed is PSA sandpaper stuck to the foam block pressed into all the ridges and curves.
Yes, I’ve used this method & it works quite well. It is a little flexible tho. If it were a complex profile or I needed to sand out defects would go the Bondo route (stiffer) .

Fillets can be sanded using a stick with paper on one side,
 

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Discussion Starter · #14 ·
Thanks for all the replies.
One concern is possible wood contamination due to waxing the wood to prevent the Bondo from sticking. As mentioned I have no sacrificial molding ... so I'll need to make a mold off of one of the actual doors.
Any suggestions how to prepare the wood so as to prevent contamination from the wax (or mold release)?

I also have an aerosol can of mold release on hand by a company called Smooth-On, 'Universal Mold Release'.( It's very old and I notice on their website they mention a limited shelf life, but I wonder if that's for aerosol cans or refers to the liquid form once opened. There's no date on my can):

 

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Paste wax comes off pretty well with alcohol or acetone, should wipe right off anot not interfere with most finishes. Least, it wipes off finished wood without much trouble. If you're working with raw wood, might be a good idea to shoot a coat of lacquer before waxing

Smooth-on mold releases don't really clean off surfaces, wouldn't recommend using that particular brand for this. They're silicone-based and resistant to pretty much every way of cleaning them, which I found out to my detriment.... Work fantastic otherwise though
 

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Discussion Starter · #16 ·
Paste wax comes off pretty well with alcohol or acetone, should wipe right off anot not interfere with most finishes. Least, it wipes off finished wood without much trouble. If you're working with raw wood, might be a good idea to shoot a coat of lacquer before waxing

Smooth-on mold releases don't really clean off surfaces, wouldn't recommend using that particular brand for this. They're silicone-based and resistant to pretty much every way of cleaning them, which I found out to my detriment.... Work fantastic otherwise though
Good to know about Smooth-On ... I was looking for silicone content on their website and MSDS but couldn't fins a clear answer.

I don't have any lacquer ... any other suggestions on a regimen to prepare raw wood to prevent contamination from wax?
 

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Good to know about Smooth-On ... I was looking for silicone content on their website and MSDS but couldn't fins a clear answer.

I don't have any lacquer ... any other suggestions on a regimen to prepare raw wood to prevent contamination from wax?
You can use pretty much any film finish to seal the wood, I just suggested lacquer cause it's quick and easy to apply, plus it's equally easy to remove. Shellac would work equally well, polyurethane would get the job done too. Basically you just want something that keeps the wax from working it's way into the wood itself, that way you can clean the wax off before whatever you plan on doing to refinish the wood
 
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