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Thickness sanding
http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=45616		 Page 1 of 1
Author:  Ruby50 [ Mon Apr 27, 2015 9:57 pm ]
Post subject:  Thickness sanding
I have built 4 guitars so far and have ordered parts in kit form, so I have never thickness sanded a top or back. I have a friend with thickness sander who has offered to run my Red Spruce and White Oak through it.

Is there anything special I should know about sanding such thin pieces? Is some sort of a sled needed to increase the thickness that the sander senses? Any help will be appreciated

Ed
Author:  Bri [ Mon Apr 27, 2015 10:53 pm ]
Post subject:  Re: Thickness sanding
Keep a set of calipers handy, it is easy to remove but putting it back, not so much.
Remember, the more you sand away from your bookmatch faces the less the pattern matches, so try and do the bulk of your thicknessing on the inside faces.
You should not need a sled, not for top and back thickness, though it may depend on the machine.
I can run .030" without a sled.
Author:  Terence Kennedy [ Mon Apr 27, 2015 10:57 pm ]
Post subject:  Re: Thickness sanding
I've gone down to 0.050-.060 on my Performax 18/36 for double sides with no problem. If you are trying to zero in on a thickness you can take multiple passes at the same setting when you get close to fine tune. I usually always take at least two-four passes at each setting reversing the wood.

For the top sand the pieces plenty thick, join, and sand just enough so you know what the face side will be and the joint is flush. Install the rosette and then go back and level the rosette and then thin to final thickness from the back.

Don't forget to make some mark or notch that won't sand off to identify the centerline. A good joint can make it hard to find.
Author:  James Orr [ Mon Apr 27, 2015 11:00 pm ]
Post subject:  Re: Thickness sanding
Cool!

When you start getting close, run it through two or three times before lowering the drum again. It will still take a few thousandths off.
Author:  George L [ Tue Apr 28, 2015 9:13 am ]
Post subject:  Re: Thickness sanding
What they said!
Author:  jfmckenna [ Tue Apr 28, 2015 12:09 pm ]
Post subject:  Re: Thickness sanding
George L wrote:
What they said!

What he said, they said. ;)
Author:  Dave Rickard [ Tue Apr 28, 2015 12:27 pm ]
Post subject:  Re: Thickness sanding
I agree with everything said.
I do use a sled on my sander because the sanding drum is not parallel to the feed belt.
Author:  Rodger Knox [ Tue Apr 28, 2015 2:50 pm ]
Post subject:  Re: Thickness sanding
What they said, and take very light cuts with reasonably high feed rate.
Author:  Ruby50 [ Tue Apr 28, 2015 3:09 pm ]
Post subject:  Re: Thickness sanding
Thanks everyone

Dave - you mentioned a sled to compensate for the parallel problem. Does this mean the sled is not flat?

Also, what grit belt works best?

Love the forum.

Ed Minch
Author:  uvh sam [ Tue Apr 28, 2015 4:31 pm ]
Post subject:  Re: Thickness sanding
What kind of sander?
Author:  Clay S. [ Tue Apr 28, 2015 4:43 pm ]
Post subject:  Re: Thickness sanding
Hi Ed,
If you do use a sled you can thickness sand one face of it on the sander, and as long as you keep it in the same orientation it should be parallel to the drum. If you flip it one side to the other it will double the error. I don't use a sled but tolerate the small amount of error the sander has.
Author:  bluescreek [ Tue Apr 28, 2015 7:00 pm ]
Post subject:  Re: Thickness sanding
If the belt isn't parallel to the drum the sanding action can make the sled parallel
One thing is this is not a finish sander so allow about .005 for bench rash. Also no need to use anything finer than 80 grit. You can build up a lot of heat in a hurry and that will glaze the belt and may burnish the wood.
Author:  Ruby50 [ Wed Apr 29, 2015 7:58 am ]
Post subject:  Re: Thickness sanding
Great information - love the forum. Duh on running the sled through sander first to get its surface parallel. Double stick tape the plate to the sled?

Thanks all

Ed
Author:  kencierp [ Wed Apr 29, 2015 8:49 am ]
Post subject:  Re: Thickness sanding
We don't use them often, but our sleds are covered with abrasive so the object material can be sanded on either side.
Author:  Joe Beaver [ Thu Apr 30, 2015 9:36 pm ]
Post subject:  Re: Thickness sanding
Probably far to late to post this, and also most likely not needed anyway, but... what the heck.

You will want to joint the plates while they are still thick. It is much easier that way. Then start taking it down. Work on getting the show side good. You will have to turn end for end with each pass unless you have a sander wide enough to do the whole piece in one pass.

If the drum is not very close to parallel it should be adjusted first.

Once you get the show side smooth and even then just take it down to the rough thickness from the other side.
Author:  mayor [ Thu Apr 30, 2015 11:27 pm ]
Post subject:  Re: Thickness sanding
using a Jet 16/32, the tops, bottoms and sides were sanded without a sled using 80 grit paper.. On the final passes, I switched to 120 grit and ran the pieces through then flipped them 180 degrees and sent them through again. This will help minimize and unevenness between left and right sides of the drum. The 120 grit will save a good deal of sanding compared to the 80 grit finish.
Now for the rosette pieces, I used a sled (mdf) with a piece of 150 sandpaper glued on to it. When the pieces got down to about 5/128", I epoxied a wood strip on the sled perpendicular to the direction of travel. This is because I ended up making pieces about 4" long which needed to be sanded. Without the strips, there is no way to hold the pieces as the contact the spinning drum, and they would immediately be flung back out. (They are thin and small, so no danger and I did not stand directly behind the sander) I had to sand all the pieces at each 1/16 turn of the wheel, and the backing strip gets sanded down to match the height. I needed to sand the pieces to 3/128" for the design. Any thinner and the wood would curl before hitting the drum, get lifted over the wood strip, and be sanded to a nice 1/128", which is completely useless. 120 grit paper does not last very long, even when taking very light passes. If you use this, have a roll or two on hand because running out in the middle of sanding is not good.
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