Sanding small flat surfaces so they stay flat

Hi,

I'm trying to sand fairly small wooden objects that are about 1/2"x1" and sometimes a little larger. I often find that one side is thicker than the other or the corners are no longer perpendicular.

I am trying various techniques, like taking a chunk of 2x4 and wrapping it sandpaper and then vice it to my workbench. Then I rub the object against the paper block. That is getting better results. 

I've read that some people use spray-on adhesive to secure sheets of sandpaper to a granite top and that it is supposed to work well.

There are a few instructables that explicitly talk about sanding and I've read many of them. They advocate a bunch of techniques.

I'm wondering what other folks have had success with.

Thanks,
Andy

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If you have more than one piece and want all to be the same and flat:
Make a box like frame where you can adjust one side with screws to press your blocks together.
The side walls should be slightly lower than your blocks.
Add your blocks, put a little pressure on the srews and tap the blocks down.
Increase the pressure so the blocks stay secured.
Now you can move the entire frame over some sandpaper, preferably glued or clamped onto a flat surface.
When one side is finnished open the srews, turn your blocks and repeat the process.
Do it six times and you should end up with very even and flat blocks.
Using a frame for small parts makes sure you don't wobble the part you are sanding.
It is very hard to keep even pressure without increasing the pressure towards to outside of small parts.

AndyWilson (author)  Downunder35m2 years ago

This is a really interesting approach. I think I can do this one pretty easily too by milling out a custom jig for each part and then aligning a common vice for each one. Great idea! Thanks

http://www.harborfreight.com/power-tools/sanders/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.html

AndyWilson (author)  avocadostains2 years ago

Hi, thanks for commenting. I haven't used a sander like this... yet. The object is very small and the sander seems like it can take a lot of material off very quickly. Is there a way to limit the amount of material it removes?

AndyWilson (author)  AndyWilson2 years ago

I realized that it is probably easier to see what I'm doing then to guess at it. I'm trying to sand smooth the sides of some home-mode wooden lego. The process for making them will leave a the sides a little rough and so they need to be sanded smooth.

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Those look amazing andy. How did you make those? Theres got to be some type of jigging involved.... A wood finish would protect and smooth out the wood, linseed oil, tung oil, danish oil. THe finish of your choice thinned with mineral spirits. For the harbor freight sander you ca buy up to 240 grit in the store for the disk part elsewear it can be gotten up to 1000 grit. A machine sander is going to be faster and more precise than a hand sander. If you buy a disk sand sander you may have to put a second table top on it that is closer to the disc due to the small size of the pieces but such a table could then include any custom wooden stops you wanted to add. When finishing wood floors, to get the smoothest finish possible, the finish may be apllied and the floow wet sanded with a fine grit at the same time, making a slurry that fills small gaps. At the stae your at the liquid finish itself may be enough to fill the small gaps/roughness, but if not you could try finishing with a finish slurry made from finish spirits, and the finest wood dust you can manage to create. Be careful not to breath too much sanding dust or you can get the woodworkers flu. See my dustmask ible if concerned. God bless it I keep makeing typos and then having to retype portions of this message when i try to fix them because I dont know how to change from typeover to insert. Have you seen the lego quatros? Theyre discontinued by theyre basically the double of duplos. I always want to extend the concept. Lego Ochos....Lego diezyseises. (16's)

AndyWilson (author)  avocadostains2 years ago

Thanks, I'm building an ible with detailed instructions on how to make them yourself. Actually, I have 2 archetype lego's done and am working on a third.

I use a CNC router to make the legos and make several bricks at a time.

I have tried a number of finishes, some parts with better with different finishes. Like flat-top plates look amazing with aerosol lacquer. I was thinking either linseed oil or shellac as the finish.

I, um, have a full face respirator because I work with other aersol's, paint thinners and sanding at 180+ grits. Plus it makes me feel a little like darth vadar.

My current sanding process is to use really strong double sided tape, like nitto p-02, and apply a piece of 180 grit to a piece of mdf and then secure it to a fence. It is OK, but I would really like to refine the process. I'm usually just trying to clean up some tearout or something slightly worse.

The wet sanding is interesting. I've read about it but never tried it and this would be a good test. Would you suggest applying linseed oil and then immediately sanding with like a 600 grit? Or something different?

Thanks!

I would imagine the tops are cnc'd and then they blocks cut with a saw of some sort. Is that right. What saw cuts makes the square block cuts? To avoid tearout on something small like that you could use a sacrificial piece of wood clamped to the piece you are cutting so their is no possibility of tear out because instead of being able to tear out at the end the blade just starts cutting into the sacrificial piece. An of course the thinnest, finest tooth blade or bit will be the least prone to large tear out.

Ive not done a lot of sanding. 120 is all the higher ive ever seen the benefit of going to for anything ive done.

If the spray lacquer is not too thick of a finish to effect the assempby of the blocks. I would think thinned polyurethane would work, or any thinned all in one stain/sealer. The linseed is not a sealant like lacquer, it wont give a polish, the blocks will still get dusty, also definately thin the boiled linseed oil to at least 50/50. It will be easy to add another coat later, oil improves wood as it improves leather, it's idiot proof but not permant and you dont want to go too heavy or it will take forever to be not oily.

I would go with thinned boiled linseed oil. Its cheap, its naturalish, as wooden legos are naturalish, and it will lubricate the blocks slightly. What was rough before will be softened by lubrication rather than sanding away the roughness.

Wet sanding wont have the same wood filler effect with linseed as it would with poly or an all in one finish. I think tung oil does harden to a plasticlike, almost poly state. I'm not sure though, Ive only read that.

I really think your doing too much with the sanding, one tends to ocd ones own work, forgetting that the awesomeness of wooden legos trumps the slight roughness. I agree with caitlins Dad that you are probably applying uneven pressure with your fingers, I agree with you that or more square sanding block without twists would help. And I agree with me that a power sander would help to limit the need to push with force the workpieces into the sansdpaper, relying instead on the precise force of the download rotating disk sander, barely pushing the block up against it, and agree with you that some jigs or stops would restrict the unevenness of apllied force resulting in the slant or non flatness.

AndyWilson (author)  avocadostains2 years ago

There's a lot there!

I actually cut them with the CNC machine, not a saw. Lego bricks have very tight tolerances and are measured in the sub-millimeter range, like 0.8mm is a standard unit of measure. The 2x4 brick you see is 11.4 x 31.6 x 15.6 mm. The dimensions have to be precise so that the brick will have a snug fit with regular lego bricks. I get pretty close results, but I can't get it perfect and that's ok. The last 5% to perfection is really not worth the level of effort.

I'm very much in the experimentation phase for finishes. The flat top plates need a different finish because they are almost perfectly smooth. I make 3 blocks per batch and try a different finish on each one until I'm happy with the results.

I'll spend some time at Home depot and try to find some floor paste wax. I also have some bee's wax and I'm wondering how that would work since it is commonly used to seal butcher block counters. I have this stuff that is a combination of bee's wax, carnuba and orange. I'm testing that right now. The finish won't last forever, but I can always refinish them too.

You made a great point about the focus being the lego and not the finish. That is the rub :) , lego is tough to make, really time consuming to design the archetypes and come up with a reusable toolpath for the cnc machine. The finish is fairly important because the lego themselves look a world more beautiful when they are finished.

Here's an interasting instructable about wax sealing.

https://www.instructables.com/id/Cheap-and-Easy-Vin...

oils, waxes, poly, they can all be mixed together into a super potion with spirits I believe. Theyre a spectrum. Of course the waxes need melted but heating any finish helps it soak in better.

Something about legos is theyre multicolor. you could get a nice multicolor affect by putting first more or less amounts of stain on the blacks.

I had no idea they were compatible with regular legos. Thats an impressive precision, considering that the legos themselves rely on the slight bend in the complex inside plastic walls of the lego bricks. Are yours three hole only connectors or mimic the actual lego connectors? That would be wild.

A wax finish you would need to remove all the wax for more to adhere, plus Id think the wax would mess with the precision, a harder wax like carnauba less so. I bet your blocks are smooth enough that you could use car wax. It's carnauba based I'm pretty sure.

All this lego business really has me wanting to make some legos. I dont have a cnc, and no coding knowledge. I'd be in the realm of the Maxi legos. I dont know your setup, but have you tried any blocks in the Duplo range? A larger block wouldn't need to be as precise.

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