thickness sanding

mikeyb2

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So I've finally finished my jigs and made a thickness sander driven by my lathe, and started to attack my first guitar set. The guitar sets are about 4.5mm thick and need to come down to about 2mm. The sanding drum set up has a 3" diameter drum loaded with 80 grit green paper and works pretty well, providing I use light passes. It takes a long time and lots of passes, so is this normal? Is patience required or a lower grit paper such as 40 or 60? Thanks, Mike.
 
I'm no expert, but with my home built drum sander, fitted with 80 grit paper, it does take many passes to get the job done. Since buying a plane, I now use this to take off most of the wood, then finish with the sander.

Bob
 
Thanks Bob, I've changed to 60 grit which should help a little but it looks like a bit of patience is needed then. Mike
 
Thickness sanders are exactly that. Sanders. Whether they are belt driven or like you home made jobbie. It takes light passes, and lots of them especially if the timber is prone to burning or clogging belts. You'll know when you get one of those species.

I'd follow Bob's recommendation in your instance to go with a plane to start.

You need to be careful about going too coarse with the sandpaper. That grit goes pretty deep and as you sneak up to the final thickness you actually go past it to get to the bottom of those deep scratches.
 
Funny, I used a setup like that until I got tired of the noise and mess, then decided to build my drum sander! The router sled system is also quite slow compared to using a plane. I managed without a plane for a long while, then one day I saw the light and now my plane is the first thing I reach for when shaping wood. It's quick, quiet and no dust!

Bob
 
thanks Allen, I'll experiment with planing and take care with the 60 grit. It was my intention to get down to about 2.5mm and then change to 120 grit until almost there and then use an orbital sander with 220 to finish off.
 
I've been told that the most you should try to remove with a drum sander per pass is half or less the height of the grit. Now how do you tell how tall the grit is? I have no idea.
 
I don't own a drum sander. Can't afford it. Don't want to make one. I always visualized basically feeding in the wood and viola! out comes a perfectly thinned piece of wood. I use a block plane and an orbital sander and it can be extremely TEDIOUS. It kind of warms my heart to know those with drum sanders suffer from the dreaded thinning boredom. Sorry. I've always suffered from drum sander envy (DSE). Now I don't feel so bad. However I would still sell my grandmother to get one. Note: My Grandmother has been dead for 23 years.
 
yeah. legitimate woodworking factories may have super powerful abrasive planers and widebelt sanders. i have a 5 hp drum sander in the shop and that's a big motor, but not big for a sander. as mentioned multiple very light passes are the key. for simplicity sake i use 100 grit for nearly everything, sure 80 would work but how much faster would it be and 100 is both fine and coarse at the same time in that it won't scratch up the surface.
have what you can afford. one of those crazy little planes must be the ticket for yankee surfacing followed by orbital sanding.
 
I'm wondering whether using a hand held power planer might be an option before running it through the sander?

I wouldn't go there ! They are great for hogging off the bottom of doors and other joinery things like that but are very difficult to control for anything delicate like thicknessing plates. Have a look at the Quansheng planes, very good value and well made. Take the time to learn to use it and sharpen it and you will appreciate the effort put in. Check the search functions for hand planes on the OLF and MIMF guitar forums as there is lots on info on there. Also lots of info on YouTube. Once it is set up properly and you know how to use it you will enjoy it. I can take plates down to 1.5 mm with just the plane and just a very light hand sanding and I only started last year. (started using a plane that is, not started thinning the plates!)

Cheers, Bob
 
well i had a go with the power planer( before I'd read your replies!), and could see how right you are. Not easy to control and very uneven. Fortunately I didn't go too far and no damage done, the sander evened it out. Looks like the sander for now and a whole lotta patience, thanks everyone.
 
I've been told that the most you should try to remove with a drum sander per pass is half or less the height of the grit. Now how do you tell how tall the grit is? I have no idea.

I can confidently say that half the height of grit on 80 grit sandpaper is equal to exactly 1 RCH. If you don't know what the RCH system of measurement is, please do not ask.
 
You really can't plane curly koa so if my plates are especially thick, say 3 or 4 mm, I'll start with 40 grit followed by 80 and then 120. I usually finish up with 220 on the ROS. The 40 makes very quick work of it but as has been mentioned previously you need to know when to stop.
 
I've been told that the most you should try to remove with a drum sander per pass is half or less the height of the grit. Now how do you tell how tall the grit is? I have no idea.
Some years ago i did an engineering college course on "Surface Finishing"....from what I remember grinding/sanding produced a deeper CLA (Centre Line Average) than say Milling or Planing ..the magnifyed images "I remember" showed that altho' the grinding looked smoother to the eye the scratching went far deeper than the other methods...So I say! if you want a good sanding finish avoid the heavy grit and finish with Scraping/Planing.
 
I opted to buy a Jet 10-20 and am glad I did. I'm using 120 grit paper and don't go more than 1/8th turn per pass, and usually do two passes before adjusting the height an eighth of a turn. One full turn is 1/16th of an inch (0.0625"), so an eighth of a turn is about (0.0078") 1/124th of an inch. So, I do about 16 passes to get down 1/16th of an inch. I have the speed on the Jet set about 60% of fastest speed. I can avoid problems with this set up. Too deep a cut or too slow a pass causes problems. I have recently picked up my plane and have gained confidence using it. I'll use it to cut thick wood to a thickness that I want to sand.

Those who plane, how do you stop the board from moving when you plane to thickness? Do you use a final thickness stop? Thanks.
 
Those who plane, how do you stop the board from moving when you plane to thickness? Do you use a final thickness stop? Thanks.
In one of the pics in this here blog post you can see my planing board. I found some self adhesive rubber that some guy wanted to use in a roof gutter on a church I was working with. I immediately saw the use for it. So I asked him for a sample, a much bigger one than he wanted to give me really, put it in my bag and said to him, no I want you to make the gutter from bent, hammered and soldered metal sheets as it was originally. He did give me a funny look, then looked at my bag, said something about architects and what profession he thought my mother had. Strange fellow! But I went home and made a planing board. And in the end got an old timey gutter in which a modern material like rubber would have been completely invisible.

Most of the time it holds thinner boards in place by itself, but a very uneven piece is best held with clamps at the edge until it lies flat. Then it can rest against the wooden stops.

See the link here:
http://www.argapa.blogspot.co.il/2014/05/a-saturday-well-spent.html
 
Those who plane, how do you stop the board from moving when you plane to thickness? Do you use a final thickness stop? Thanks.

That is such a good question and one nobody every talks about very much because it is a huge challenge. How to tame the plate when planning? What I have settled on using is not ideal, but it works for me. Clamp your perfectly flat surface (I use a 16x16" piece of 3/4 " melamine) down to the bench and then clamp your piece to that securing it. Obviously the clamps get in the way so you can only plane about 3/4 of the work. What I do is plane the upper bout (for a top or back) counting the passes then quickly flip and reclamp and do the lower bout with the same number of passes. Surprisingly I get a very even thickness. Also when I flip I get to measure and find the high and low spots. One can get pretty quick with the clamps. Not ideal, but like I say, it works. I suppose one could build some sort of 0.05" high frame, but who has the time?... Hmmm....
 
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