How Flat is Flat? Plus Planer Leaving Lines on Wood

[Steve H Graham]

I've been trying to get my planer to face-joint pieces of walnut for a guitar body. The pieces are between 20 and 24" long, and they're about 7" wide. They will range in thickness between 3/8" and 3/4".

Someone recommended checking out the simplified planer sled at Modern Wood Shop. (http://modernwoodshop.com/2008/06/18/flattening-wide-boards-with-a-planer-sled/) It looked good, so I made my own version. I made a 28" by 12" piece of 3/4" MDF and screwed a 1/4"-thick piece of scrap across the front end.

I fiddled around with a piece of scrap spruce until I get what seemed like a good result, and then I got to work on a 24" by 1.75" by 7" piece of walnut. The sled worked fine, and it was way easier to handle than my 4'-long Keith Rust knockoff, which is made of thick MDF and weighs tons.

Here is the situation I'm in now. I have the walnut shimmed and taped up until it can't rock at all, and the top of the board looks flat when it comes out of the planer, but when I turn it over and put it on my table saw, I still get a tiny amount of rocking. I would guess that the problem amounts to less than 0.010", but it's definitely there.

My question: how flat is flat? I believe I can sand this thing down and clamp it to another piece of walnut, and it will work fine. But should I be satisfied with a board that rocks at all?

Another problem: I'm getting lines down the top of the board, as if it were being dragged under tiny imperfections somewhere. These will sand out very quickly, but I'm wondering if anyone knows what causes them. I'm using a DeWalt DW735.

I'm seriously tempted to blow for a Rikon 10" planer/jointer and put one of my motorcycles outside so I'll have room for it. This jointing problem is really annoying.

[scott spencer]

The lines are caused by nicks in the blade...pretty common, and pretty easy to remove. New/freshly sharpened blades will eliminate it, but its usually just a matter of time before there's another nick or three. You can rerun the piece with the knives set at the same height and staggar the entry a little so the good spots on the knives can remove the ridges.

The rocking is harder to diagnose online....are you making multiple passes until the entire top surface is engaged with the blades?

[David Helm]

You have to decide how flat is flat. The lines are probably caused by nicks in the blades.

[Steve H Graham]

I made multiple shallow passes, and the blades contacted the whole width of the wood.

Thanks for the info on the nicks.

[Kent Chasson]

Based on the 3/8" thickness, I assume these are drop tops to be laminated over other wood? If so then flat within .010" should be fine.

Also, are you sure your table saw is flat? Does the board rock the same way in different orientations on the saw?

Things that typically cause planer marks:

-Feed rollers when taking a very shallow cut.

-Something stuck to the table or rollers.

-Inadequate dust collection and chips not clearing.

[Myk Rian]

Make sure the leveling shims are set tightly.
The sled and stock are rolled under a lot of pressure. Even thick wood will move under that. Also, the shims may be compressing.

[Steve H Graham]

I would hate to think that my table saw is not flat, but I guess anything is possible. It's a Powermatic 66 from about 1997.

As for the guitar parts, the plan is to have a thick slab in the middle and thinner bookmatched slabs on the top and bottom.

[David Christopher]

you need a drum sander

[Steve H Graham]

Will a drum sander face-joint crooked wood?

[glenn bradley]

IMHO, that style of sled will only do a really good job on a piece of wood that is thick enough NOT to respond to the pretty decent pressure applied by the feed rollers. I would say based on your thickness and method that you are getting pretty good results. Just my .02

[Pat Barry]

If you are getting some deflection in the board due to pressure, then it will help to finish with a few very light cuts and/or to rerun the planer sled and board thru the planer without changing the height setting. Each progressive pass will take off less material and less material removed means less pressure applied so less chance for deflection.

[Steve H Graham]

I'm starting to understand why woodworkers used to apprentice for years.

[John Coloccia]

Want to know how flat it is? Run two pieces through your jointer. Put the newly jointed faces up against each other. Do they lay flat against each other? Then you're flat. Is there a gap anywhere? That gap is twice the defect, i.e. if there's a .010" gap between the two board, you have a defect of .005" on each board. That's assuming both boards have the same defect. Anyhow, you get the picture. You can measure against itself and take the table saw right out of the equation.

[Steve H Graham]

The problem is that the wood moves around after I run it through the planer! Maybe your idea requires clamping the boards to compensate for post-jointing flexing.

[Brian Tymchak]

Make sure the leveling shims are set tightly.
The sled and stock are rolled under a lot of pressure. Even thick wood will move under that. Also, the shims may be compressing.

+1. particularly about the shims compressing. and you can toss double sided tape in there as well (voice of experience..). Use some dense hardwood or mdf shims instead of soft pine or cedar.

Also, I can't state this as fact, but based on my personal experience, I believe that on thin stock, even with light passes, if you have not shimmed a cupped board (cup side down) in the center of the cup, the rollers can push the crown down slightly producing a slight rounded top when the center of the board springs back after planing, even when making full contact across the board... Like you, I found this after laying a couple freshly planed 3/4" boards on my table saw and they spun quite easily on the "bubble". Quick check with a straight-edge proved the point. Much better experience the next time with center shims. The trick though is to figure out how thick those center shims need to be. I now use the straight edge across the board in all directions to help me guage that.

[Steve H Graham]

It's starting to sound like making a sled work is nearly impossible.

[John Coloccia]

The problem is that the wood moves around after I run it through the planer! Maybe your idea requires clamping the boards to compensate for post-jointing flexing.

I'm sorry, Steve. I wasn't giving an idea on how to make the sled work. It was more of an easy way to measure how far out you are because you have some doubts about how flat your table saw is. You can get some pretty good straightedges cheap nowadays. I have several in my shop. It's invaluable for this kind of work.

[Kent Chasson]

Sounds like you did get it to work. For what you are doing, within .010" is just fine. It may even flatten out more as you thin all pieces to final thickness.

By the way, I also think the second sled approach is way better than the first. But with either one, I wouldn't stand behind it! It's probably fine but, particularly with thinner stock, you increase your chances of something blowing up if it's not fully supported.

[Steve H Graham]

I really don't want to get a jointer, but this is aggravating. I keep telling myself that if I can't make my existing tools work, I will probably have problems with new ones.

[Erik France]

I really don't want to get a jointer, but this is aggravating. I keep telling myself that if I can't make my existing tools work, I will probably have problems with new ones.You might have an easier time with a new tool that is designed for doing what you want to do. A planer sled is a work around, but it can be made to get the job done.

Have you considered hand tools? like a No7 or No8 jointer? I'll grab my planes, especially for one or two shorter boards before I will use my jointer. My jointer isn't exactly the best one in the world though, an old Chinese knockoff of a Rockwell design.

IMHO, a 0.010 tolerance is incredibly tight for wood. That's 3/256ths, three quarters the size of 1/64. Most gnat's backsides would probably be bigger than 0.010. ;)

[Steve H Graham]

I posted in the Neander forum, and I got some recommendations. I ended up buying a reconditioned Stanley No. 6 from another Creeker. We'll see if I can learn to use it!

I think it would be great to be able to face-joint small boards with planes, because it would allow me to make guitars over 13" wide without gluing pieces together.

[Chip Lindley]

...the top of the board looks flat when it comes out of the planer, but when I turn it over and put it on my table saw, I still get a tiny amount of rocking. I would guess that the problem amounts to less than 0.010", but it's definitely there.

My question: how flat is flat? I believe I can sand this thing down and clamp it to another piece of walnut, and it will work fine. But should I be satisfied with a board that rocks at all?


First Steve, if you are within .010" over 7", I believe your planer sled is doing all it can do! Don't forget that the wood has something to do with this. Each board is different as to grain and will move in it's own way. Guitar makers primarily use quarter-sawn wood with almost perpendicular grain for tops for a reason; least amount of warping or cupping. I am sure that there is a high rejection rate of wood for guitar tops. Only the most perfect pieces are chosen.

I would think .030" (.010"x3) deviance over the entire width of a top could easily be drawn into flat by clamps in the final guitar glue-up. After all, there is extensive wood bracing under the top of an acoustic guitar. .030" is NOT much! Have you read up on accepted practices of acoustic guitar construction? Are you sure you are not tripping up on a non-issue??


I really don't want to get a jointer, but this is aggravating. I keep telling myself that if I can't make my existing tools work, I will probably have problems with new ones.

Astute observation! No guarantees the jointer will be set up perfectly when you receive it. There is a learning curve with a power jointer which will add new drama and questions to your guitar-making quest.


...I ended up buying a reconditioned Stanley No. 6 from another Creeker. We'll see if I can learn to use it!

I think it would be great to be able to face-joint small boards with planes, because it would allow me to make guitars over 13" wide without gluing pieces together.

Aren't most all acoustic guitar tops made of bookmatched slabs?

There is a learning curve to a hand plane also. Honing of the blade is essential to it's success. Simple card scrapers are amazing at removing small amounts of stock that a hand plane gags on! I believe you would find a cabinet scraper very useful in removing minute amounts of stock. But, as always, there is a learning curve in turning the hook of a scraper blade.

Just (lotsa) food for thought...

[Erik France]

I posted in the Neander forum, and I got some recommendations. I ended up buying a reconditioned Stanley No. 6 from another Creeker. We'll see if I can learn to use it!I overlooked that thread, it appears that you got some good advice. One thing I learned with using planes is that proper sharpening can make a world of difference in their performance. I was getting some bad results with my first plane. Once I learned to sharpen the iron properly, and to hone it often, the long curls piled up a lot easier.

Chip's point about scrapers is a good one too. I use a whole lot less sandpaper now since using planes and scrapers.

[Steve H Graham]

This is a solid-body guitar. I wouldn't dream of trying to make an acoustic guitar right now. I felt like a Telecaster was a realistic goal, since you can rout the body out of a flat slab.

[Ken Cohen]

Hi--

FWIW regarding planer sleds, I just built the FWW/Keith Rust planer sled to flatten 7' stock too wide for my 8" jointer. It took a couple of hours to build, but the solid construction and high degree of adjustability paid off.

I ran 3 boards, each with ~1/2" warp and bow. End result was very close to flat, out <1/16 across entire length.

I second the advice to take light passes. I could hear and feel the rollers trying to dislodge a board when I took more than a 32nd. Luckily, the wedges in this design (helped by screws and affixed sandpaper) kept things steady.

Ken

[Clark Harbaugh]

There is a different technique for using your planer to joint the face of wide stock that I have used with very good success. You can cut strips of hardwood that is slightly wider than the thickness of your stock. You then glue the strips on either edge of your stock, creating rails for your planer rollers to run on. As you run your stock through, the pressure of the rollers is on the rails until you plane enough material to have the flat face you are looking for. This way you don't have to fuss with shims, or have to have extra space in your shop to store another sled:). You then only have to rip off the strips of wood with the table saw.

Two things to keep in mind, though. First, the strips of wood you cut have to be flat to start with in order for this to work. I typically use my 6" jointer for this. Second, and similar to what you are already experiencing, depending on the glue you use, the dried glue lines between the strips and the stock can create nicks in some planer blades. Be prepared to hone them or change them after this technique in order to prevent grooves in future projects.

[Steve H Graham]

I may be expecting too much. I have no experience building glued-up slabs, so I don't really know how flat the wood has to be.

[Wes Grass]

"when I turn it over and put it on my table saw, I still get a tiny amount of rocking"

Put the 2 together, and put a small clamp at each end. If light clamping pressure draws them together with no obvious gaps, call it good, apply glue, and clamp.

A 1/16" gap at each end should be no problem at all to pull out. As long as there aren't obvious ripples to the surface, which you would feel running your hand over it, I'm sure the glue joint will be fine.

Actually, a bit of convex seems not such a bad thing. It acts like a curved caul when you clamp, helping to get good contact in the center. And you'll need a lot of clamps. Lots and lots of clamps. Best to precut the outline of the parts so you know where you're clamping. You want the edge well covered to avoid visible glue lines.

[Steve H Graham]

I would have thought a sixteenth would be fatal! Thanks for the info.

[Wes Grass]

Upon further thought, at 3/8" thick and 20" long I'd bet a 1/16" gap could be closed by squeezing it in your hands. Not full width maybe, but locally.

[Don Stutsman]

To remove the 'nick lines' without replacing the knives - move one of the knives slightly to the right or left. Retighten and use it.

[Chip Lindley]

This is a solid-body guitar. I wouldn't dream of trying to make an acoustic guitar right now. I felt like a Telecaster was a realistic goal, since you can rout the body out of a flat slab.


I've been trying to get my planer to face-joint pieces of walnut for a guitar body. The pieces are between 20 and 24" long, and they're about 7" wide. They will range in thickness between 3/8" and 3/4".


As the Warden said in Cool Hand Luke..."What we have here is...failure to communicate!"

I am clueless as to what your reference was to 3/8 in. thick slabs of guitar wood! Why didn't you say Solid Body?? My vintage Fender Custom Telecaster's body is almost 1-3/4" thick.

You need a jointer!

[glenn bradley]

It's starting to sound like making a sled work is nearly impossible.

Not at all. I used this version (http://www.finewoodworking.com/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=24118) for about a year and a half while I saved up for a larger jointer, I still use it on wider boards now and again. If the issue is support (shim frequency, compression, etc.) you can add or remove the adjustable blocks as required. I made mine out of hard maple and made a few extra and do use them when milling thinner stock for additional support. Takes a few hours (not counting waiting for glue to dry) to make and has paid that time back a hundred-fold.

There is also a video: http://www.finewoodworking.com/subscription/Workshop/WorkshopArticle.aspx?id=5245

[Myk Rian]

Cabinet scrapers remove planer marks.

[Steve H Graham]

As the Warden said in Cool Hand Luke..."What we have here is...failure to communicate!"

It can be hard to synthesize facts from multiple posts, and some of the details are in separate threads.

I'm gluing several slabs of walnut together, back to front, to make a 1 7/8"-thick Telecaster slab with bookmatching on the front and back. I would not want an acoustic made from 3/8"-thick wood unless I were El Kabong.

[Don Stutsman]

I can't respond to the twist issue except to say that I would check everything for 'flat; then test the wood. you are correct that sanding may resolve the issue as would a plane or scraping. As for the planer lines, a previous writer correctly identified the 'line' problem as nicks in your knives. I do not have that planer, but if you can loosen the knives and get any lateral movement, just move the knives from side to side to realign them so that the nick no longer lines up. That will solve your problem until you get another nick or have youe knives sharpened.

[Anthony Whitesell]

I would say the lines are either due to nicks or dull blades. The blades in my planer are horribly dull, but they are fine for now as I'm just taking the rough cut off some knotty pine and not worth new blades in my case.

As for the planer sled, I would say you have one or more issues:
1) Sled is not flat, either top or bottom
2) Sled is no strong enough to fight against the roller pressure
3) You are relieving stress when you plane the wood, causing it to bow after removed from the sled
4) You are applying too much pressure when attaching the wood to the planer, adding stress, then planing, then releiving the stress, thus the bow appears

[Jim Summers]

I would not want an acoustic made from 3/8"-thick wood unless I were El Kabong.

Wow another Boomerang fan!

[Alan Lightstone]

I would not want an acoustic made from 3/8"-thick wood unless I were El Kabong.

ROTFL. Too funny. Dating yourself a little, though.

[eric eaton]

If you are really in love with your piece of wood then glue 2 pieces of flat wood on each side, plane it as a unit and then just rip them off afterwards. If you make them at least 4" longer on each end then they will eat the snipe so your workpiece ends up dead flat.

I have the 735 and it is an excellent but fussy machine. The knives can be shifted left to right about 1/8" of an inch. I always set a fresh edge to one side so I know which way to shift. And most of the time those lines can be ignored as they scrape/sand right off.

Good luck

P.S. Knots and the Dewalt 735 are bad ... very bad.

[Steve H Graham]

I got it working, but I ended up ordering a small jointer anyway.

Here is the odd thing: the lines on the wood went away. The planer works fine now. I think I got some tape or something stuck to the blades, but it's hard to understand how that could make these scratches.