How close to final thickness do you plane before sanding?


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I thought for sure this question would have come up before but I haven't been able to find the answer in searching these forums. My apologies if I am asking a question that is answered often.

My question is how much material should I leave for sanding? I am using a thickness planer and have left myself about a 16th of an inch more than final thickness. I will be sanding with an ro sander and plan to start at 80 and work up to 220. Is a 16th enough? Too much?

How do others handle this?

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I think it comes down to the stock. In my case, stock that planes really well will get taken pretty much to expected thickness, then whatever comes off in finish prep will come off in finish prep. Stock that chips or tears out will get left thicker, to enable more sanding, scraping, or smoothing, but rarely more than 1/32" over.

Like the others have mentioned, exact thickness rarely matters. In most cases parts that get glued edge to edge simply have to be close, final finishing will make them match.

In the case of stock that depends on thickness for joinery cuts, like table aprons or door frame parts that will have M&T's added, take them as close to final thickness as possible, otherwise you might mess up your fits when sanding or finish planing one side more than the other.

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I plane my pieces down to the final dimension. I generally don't sand individual pieces in an assembly. For example, for a frame and panel, I plane all the members to the final dimensions. I sand the panel seperately, assemble the frame and panel then sand the whole frame member together. My feeling is that I hardly remove any material from sanding in reality relative to the amount removed from planing.

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A corollary to what Rick, Barry & Tim have contributed is this: If thickness lost during sanding (negligible, frankly, but let's just follow it for now) becomes an issue, then you need to rethink your workflow anyway. The only conceivable way that could become an issue is if you're planing one piece to a given thickness and sanding it, then planing another piece to the same thickness, not sanding it and expecting the two to match. If two or more pieces need to match thicknesses, then they should go all through the planer (and all other subsequent operations) at the same time and in the same way. That done, it doesn't matter how much thickness you lose to sandpaper because everything will still be even.

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I truly appreciate all the attention my question has received. You guys rock and I love learning from you. Sounds like I can take a bit more off and be good. The puzzle solving part of my brain wants to get the thickness exact to what my plans calls for, but the creative side (which usually wins) is cool with relative but uniform thickness.

Rob - The method I used to plane really started with using the planer to face joint with the sled and hot glue method. Once that one side was flat I then broke the board loose and ran the other side (sans sled) through until it was flat. From there I kept flipping the board over until I was within a 16th of where I wanted to be. I did it this way with mutiple boards, one at a time. Next time I'll stop once I have two coplaner side on each and then run all the boards at the same time until I get to the desired thickness.

Jim

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Rick LoDico has the best advice. However I try to plane to within a 1/32 before moving on to the sander. Lots of times I get paranoid about trying to get boards to .75000000000. It never happens. All the boars get sanded at the same time and when all is said and done "it is what it is."

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I will plane all similar pieces that have a relationship at the same time so they all come off the planer at the same thickness. For example, face frame for cabinets. Other example would be the four legs of a cabinet, end table or similar -- in that case when I set up for mortises or whatever, the marking can be made from the same measurement setup.

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IMO you need to take your planer feed rollers into account, as some planners have serrated feed rollers that can marr the board.

I have a DeWalt 735 that has rubber rollers, so i don't have to worry about marring issues. So I plane to final dimension, then cut joinery & do profiling, and then sand.

Something else you might want to consider, is taking very light final cuts for your final pass. For example if i have some narly 4/4 stock that needs to be taken down to 3/4 this is how i would do it.

1. joint side A flat, keeping track of how much material "on average i removed"

2. plane the side B parallel to side A making sure to take the same amount off of side B that I did from side A

Note: If i have to take more off of side B to get it flat, then i flip the board and take the extra off side A

3. The faces are now initially parallel, and probably around 7/8" thick, so set it aside to rest and move for a day or two.

4. repeat steps 1 & 2 if needed and set aside to rest again the board is probably 13/16" or so

Note: some times up to 3 or 4 rounds of jointing, planing, & resting can be required depending on the size of the board how much the wood species moves.

5. finish planing - lets assume the board is now 13/16" thick so we need to take 1/32" of each side I would do that in 4 passes 1/64", 1/128", 1/256" 1/256"

The benefit of the really light finishing passes is it's almost always tear out free, so you spend a lot less time sanding. I usually start at like 180 grit because the boards look like they have been hand planed already.

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@SDWoodworker. That is my plan for the boards I have already planed but still have a 16th to go. I've got table top, seats and aprons that fall in to this category.

@Dan s - This is the first time I have used a planer and was wondering if I really needed to start as low as 80 grit since the boards are coming out quite smooth already. Also, I bet doing the very light final passes will greatly reduce the snipe that already exists.

Thanks to everyone who has replied.

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@Dan s - This is the first time I have used a planer and was wondering if I really needed to start as low as 80 grit since the boards are coming out quite smooth already. Also, I bet doing the very light final passes will greatly reduce the snipe that already exists.

It will to some extent, be aware though you will use up your planer blades faster. I'm personally OK with this as planing is a lot cleaner operation in my shop, and a lot more mindless activity.

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I plane down to final thickness, typically 3/4". Many of my jigs, router bits, plans, are made around the stock being at final dimension. I will do some presanding before assembly, mainly so I can get to areas that may not be real accessible after glue up, but then I am sanding again to take out any imperfections. The difference in thickness before rough sanding and after final sanding really is negligible.

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I agree with the others.. final dims are not that important, uniformity is.. before woodworking, I had a machinging background with racecars.. where everything was +/-.005 or less.. I nearly quit woodworking several times before I finally drank the kool-aid and went with uniformity and relative dimensioning. ( I still remember telling my wife that it may not have been a good idea to join the guild after seeing Marc do a presentation on Relative Dimensions). It took a while, but he was right. I now go through a lot less asprin!

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