Surface Prep

[Ken Howell]

Hi Everyone,

I'm getting ready to do my first real build on a chest of drawers. I realize I can't take my wood directly from the thickness planer to finish so my question is should I fit the pieces together then prep or prep the wood before assembly? Another question I have is how much should I leave on the wood to compensate for prep? in other words if my final dimension is 3/4" thick how thick should I plane it to on my thickness planer.

Thank you,

Ken

[Jim Becker]

Other than test fitting, it's almost always easier to do most of your sanding on individual components before you do actual assembly. And if you've fitted carefully and also use your glue carefully, you'll have a lot less work to do later.

[Prashun Patel]

I would my parts to final thickness normally. Sanding and or hand planing won't take appreciable thickness off.

The general advice is to sand and finish before assembly as much as possible. I say, sand and finish those parts that are hard to do after assembly - like the insides of cases. For everything else, I normally only sand the aggressive grits before assembly; things like a panel or a table top, where it can be more ergonomic or dust friendly to do it before assembly.

Typically during assembly, I will scratch or dent my piece despite best efforts. So, I don't final sand the show faces of anything that will be subsequently glued and or clamped.

[Ron Citerone]

What they said. Anything with an inside corner gets sanded before assembly at the least.

[Ken Howell]

Thank you you all for replying! That helps me a lot!

Ken

[Bill Carey]

Ken - I always pre-finish everything. When it comes to finishing I'm a bull in a china shop - I always get runs, splotches, missed areas, etc. when I try to finish an assembled piece. Probably because I hate finishing... I tape off the tenons and fill the mortises with backer rod, and hang 'em up to dry.

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[Ken Howell]

Thank you Bill!

[Michael W. Clark]

I plane to final thickness and usually start with 120 grit. When you dry assemble before glue, also look to see what is going to be hard to sand after assembly. I do very little sanding, if any, before joinery.

[Ken Howell]

Thank you Michael!

I watched a few Doucette and Wolfe videos last night and it looks like he was planing before and after assembly. My plan is not to do any sanding, all hand plane smoothing, unless I absolutely have to.

[Andrew Seemann]

Unless you are specifically going after a hand planed look (e.g. intentionally leaving plane marks), there is no disgrace in using sandpaper. Note that this is coming from someone that owns at least a dozen bench planes and whose favorite tool is a cabinet scraper

Even when I hand plane, I typically sand afterwards. It removes any marks and helps the finish absorb evenly, which can be particularly important on stained pieces.

if possible sand after cutting the joinery, but prior to assembly. This isn't always possible, but if you can do it, it makes for more accurate joinery and less grit dulling your cutting edges.

Also, don't be afraid to start with lower grits on a random orbit sander, especially if it is taking a long time to pull out the mill marks. It can be faster (and do a better job) to start with 80 and then go to 100 or 120 than to try to remove them all with 120 or 150.

[Ken Howell]

Thank you for the advice Andrew!

[Tom Bender]

I start cleaning up the surfaces as soon as the material hits the shop. This makes measuring and marking easier and more accurate. It shows the grain. It reduces splinters. It shows any material defects. And it makes finishing easier.

[Jim Dwight]

My answer is a little different. I agree that you plane to the thickness you want and ignore material removed during sanding. But when I sand depends on what part of which part it is. I will be making a chest of drawers soon. It will be a woodsmith design I've built several times before (part of their cherry bedroom set). I will probably enlarge it significantly, however. Anyway, the end panels are like flat panel doors. I will sand the panels and inside edges of the rails and stiles and even put on a coat or two of finish on these surfaces before assembly. I don't want an unfinished edge of the panel to show. Then glueup, then rough (to 100 grit, usually start with 80, sometimes 100) sanding of outside and inside but not outer edges. The inside gets sanded to 150 - as high as I go inside. The outer edges get trued up but they are glued to other pieces so I do not sand them. Drawers get sanded inside but not outside before assembly. I use half blind dovetails and need to sand the outside to get everything perfectly flat after assembly.

The general rule I go by is to sand inside, because it's so much tougher after assembly, but not outside before assembly. A lot of times I need to take a little off joints after assembly so I don't want a fully sanded surface. Any joints do not get sanded where the glue goes because the edge tends to get rounded. Inside of doors is an exception and I use a flat sanding block and sand by hand to not mess them up. The two important points to balance is not to mess up a flat surface with sanding if it has to stay flat versus sanding inside is MUCH harder. It's also much easier to finish things laying flat.

I sand the outside to 220 after it's together. I really like my Bosch DEVS 1250 because it cuts my sanding time significantly.