Best way to smooth a MASSIVE beam

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Forum topic by danielhoer posted 04-29-2017 05:34 AM 2284 views 0 times favorited 18 replies Add to Favorites Watch
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38 posts in 1119 days

04-29-2017 05:34 AM

Topic tags/keywords: plane sander planer sanding milling question

I just bought a pretty massive rough-sawn beam (Douglas Fir) that I’m using to make a fireplace mantel. The dimensions are 10” wide x 4” tall x 12 feet long. (I had to buy 12 ft. because that is the shortest length they sell but I’m going to cut it to about 7 feet long). I’m basically going to stain it and finish it and that will be the mantel – no additional cuts or modifications. BUT, I would like to make it as smooth as possible, especially because the cut end will be silky smooth from my 12” Miter saw and yeah it’s just the look I’m going for.

I thought I could just use my random orbital sander to smooth it but I am seriously rethinking this now.


First question: would one of those 13” Dewalt benchtop planers be able to handle something like this? It’s so heavy I can’t imagine how I would run it through. In all the planing videos I’ve seen the workpiece automatically goes through the planer like a conveyer belt, but this beam literally weighs nearly 100 lbs. Even if I cut it, it seems too heavy to run through a planer. If I’m wrong, someone please tell me because I am almost tempted to buy a benchtop planer but they are like $500…

After reading the forums about power hand-held planers, I almost ruled them out because they sound impossible to use on a smooth surface (the 3” ones.., unfortunately I can’t buy the makita 12” hand planer!). I don’t have any hand planes and I have no handplanng skills and handplanes are not cheap. I am almost tempted to go buy a Harbor Freight $39 handplaner and see what it can do, but in the likely event that it sucks, I’d like to have my plan B because this thing is taking up my whole 1-car garage!

BELT SANDER: Would a belt sander work? I read reviews of several cheap ones and supposedly they all eat through belts like crazy. So more money spent on belts in the long run… I would like to use a belt sanding frame to keep it level and avoid gouging… has anyone had luck with these? Is an expensive belt sander really noticeably different than a cheapo one? Would I screw it up never having used a belt sander before and not having a sanding frame to hold it level??

I’d love to just stain it as is and mount it but the rough sawn is pretty ugly, crazy machine marks.

ANY feedback of help would be awesome as I am somewhat at a crossroads with my approach here. Cheers!

18 replies so far

View TheFridge's profile


10859 posts in 2094 days

#1 posted 04-29-2017 05:59 AM

A typical planer should be able to handle that if youre gentle and have an outfeed table or help. Planing alternate sides will keep it pretty straight if it’s straight to begin with. Typically you’d want to joint it first somehow. With handplanes or machines before planing.

A belt sander seems like a good idea but they can mess something up in a hurry. I’d try paying a cabinet shop or someone with a thickness sander before I went with the belt sander route.

A harbor freight handplane would be a waste of money in this situation unless you wanted it for smoothing or scrubbing.

Get a machine, borrow a machine, or get some hand planes seems to be your options. I like planes myself.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Rich's profile (online now)


5146 posts in 1197 days

#2 posted 04-29-2017 05:59 AM

Any DeWalt, or other brand of benchtop planers can handle that. You need good infeed and outfeed support though.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View Dave Polaschek's profile

Dave Polaschek

4460 posts in 1190 days

#3 posted 04-29-2017 10:22 AM

I’m in the finishing stages of hand-planing a 20” x 3” x 66” slab of elm to be a new workbench top. I picked it up from the sawmill on February 18th and I’ve been using a LN 5-1/2 jack-plane to do most of the work. So if you’ve got three months… But I wouldn’t want to tackle that with a cheap HF plane. The plus side is that I’m a lot more skilled with a hand-plane than I was back in February.

The other thing to consider with this is that even if the wood is dry, you’ll clean up a surface and discover it moving a little. I’ve re-flattened my slab at least three times as it moved around after I relieved stresses and as it dried out. The wood moisture content was pretty high, but even with dry wood, you’ll get some movement.

-- Dave - Santa Fe

View tomsteve's profile


988 posts in 1827 days

#4 posted 04-29-2017 12:15 PM

I did a mantle a while ago and used my delta benchtop to get it to thickness. 4 by 10 red oak 7’ long
what I did for support was 1st start on a flat surface- my deck. I had an 8’ section of 3/4” ply I screwed the planer to in the middle. then measured the height of the infeed and outfeed tables and ripped some 2 by stock down to that thickness. cut blocks 12” long and screwed em to the 3/4” ply- 2 on the infeed side and 2 on the outfeed side.
worked great to support the mantle while planing
something to remember- youre working with roughsawn. a planer will plane both surfaces to a parallel thickness, but wont plane out warps,twists, of end to end curve/cup.

a belt sander would work, but youre going to make a LOT of dust. start with something like 60 grit and work up in grits to 120, then switch to RO sander. keep the sander moving at all times. might want to get a belt cleaning stick,too.BUT it is very time consuming, can end up with a wavy surface AND
you need a planer. :)
you can get a planer for under $500. if youre not going to use it much, you can get something like the porter cable pc305 for about $275. I have its predecessor- the delta tp305,which ive had for 11 years and have done a LOT of planning with it, including the mantle mentioned.

View 000's profile


2859 posts in 1507 days

#5 posted 04-29-2017 02:09 PM

Go to Home Depot and buy an already milled 4×10…
Then use your ROS

View Loren's profile


10477 posts in 4256 days

#6 posted 04-29-2017 04:36 PM

Timber framers sometimes plane beams by keeping
the beam stationary and using the feedworks
of a portable planer to move the planer down
the beam.

In your case at 7’ however you’ll probably be alright
setting up infeed and outfeed support. You’ll be
spending $400 or so on a planer and a few
hours probably setting it up to plane the beam.
The planer will do the work quickly though,
but you can’t plane the edge with it.

I’d suggest hand planing instead, something you
may find useful in fitting the mantel closely to
the wall.

View JBrow's profile


1368 posts in 1528 days

#7 posted 04-29-2017 09:04 PM


A surfacing option not yet mentioned is router surface flattening jig. A pair of rails on either side of the timber with the router mounted on a bridge that spans and rides on the two rails makes up the jig. A straight bit or bowl router bit could be used for flattening. After the router has smoothed the surface, some sanding would be needed to cleanup marks left by the router. The amount of sanding would depend on how well the jig keeps the router bit in the same plane during the routing operation.

Addressing some of your unanswered questions…

I would like to use a belt sanding frame to keep it level and avoid gouging… has anyone had luck with these?

I have used a Dewalt belt sander equipped with a sanding frame many times to flush up large glue-ups. The sanding frame, when properly set, indeed prevents the sanding belt from gouging out deep valleys in the wood. Sanding frames seem to be proprietary and work with a specific belt sander. Also the belt sander and the sanding frame attachment are not cheap.

Is an expensive belt sander really noticeably different than a cheapo one?

My philosophy is to buy the best quality tool that I can afford that meets my requirements. If it is a use once tool, I tend to go cheap, otherwise I pay more to get a higher quality tool. A higher quality will almost always produce better results and be easier to use.

Would I screw it up never having used a belt sander before and not having a sanding frame to hold it level??

Close attention is required when using a belt sander. It removes a lot of material in short order no matter the grit of the belt. Keeping the belt sander moving at all times is key to successful results. I also adding witness marks to the workpiece that allow progress to be monitored. The witness marks are from a pencil and the pencil marks cover the entire workpiece surface. When all the marks are gone, the workpiece is fairly flat. During the roughing phase, I like to skew the belt sander to the workpiece and proceed from one end to the other until the workpiece is mostly flat. I then sand with the grain to remove cross grain scratches left from skewing the belt sander. After the cross grain scratches are gone the random orbital sander is used.

Since this is Douglas Fir, I would think the belt sander belts will gum-up quickly. This could become a major source of frustration, even if the belt cleaning stick suggested by tomsteve is used. If you use the random orbital sander, purchasing some Mirka Abranet sanding disks with a hook and loop pad protector may make sanding go faster, since I believe these mesh style disk are less prone to gumming up.

But in the end, buying a planer or out sourcing the timber to a local woodworking shop may be the best ways to go. If a planer is purchased and you continue woodworking, buying the best planer the budget will allow will leave you with a tool that can be used on many future projects. If you are new to planning, leaving the workpiece about 8” longer than the finished length would allow any planer snipe to be cut off once the mantel piece is smooth.

View danielhoer's profile


38 posts in 1119 days

#8 posted 04-30-2017 03:04 AM

thanks to everyone for the replies!

tomsteve – when you said you cut blocks 12” long and screwed them to the 3/4” ply with 2 on the infeed side and 2 on the outfeed side, were the blocks in long 12” strips aligned parallel to the workpiece? or were they arrange in some other fashion? also, would melamine be a good choice of wood to use for this to minimize friction its slickness? also do you thin I would be able to run a 12 foot long piece of 10” x4” through a bechtop planer using this method??

Jbrow thanks for your reply. i thought briefly about the router jig idea (ive seen videos on them before for planing big slabs) but im honestly not sure if i have the skills to make an accurate level etc. jig. i recently buit a soil sifter which was just a simple box with wheels and a frame with a track, and really struggled like hell and made mistakes at every step of the way. i watch these videos of people assembling things and find out its one thing to understand how something is built but another thing to do it yourself.. (like with a skilsaw, i still cant even cut anything well with one yet).. thanks for the advice about snipe leaving 8”. i think a planer is the only way to go. or taking it to a cabinet shop. could i run the timber through a planer sideways to also plane the side faces, or is a jointer the only option for that… ?

i didnt see any timbers at HD this size except for some pressure treated ones. but maybe my local one is on the smaller end of the HD spectrum.

anyway thanks to everyone for the input !

View bigblockyeti's profile (online now)


6192 posts in 2329 days

#9 posted 04-30-2017 03:36 AM

+1 to Loren’s method. You can plane something as long as the extension cord you can buy will let you. Lighter planers work better using this method as the wood being planed isn’t pushing down on the bed, but rather the pressure rollers are holding the weight of the planer up. The DW735 is one of the heaviest and most expensive bench top planers out there, if you’re going to use it normally it’s tough to beat but given the weight, lighter is better.

-- "Lack of effort will result in failure with amazing predictability" - Me

View Carloz's profile


1147 posts in 1200 days

#10 posted 04-30-2017 12:09 PM

With a thickness planer you will finish this in 10 minutes. With a hand plane ( and you do not need the best, practically any plane is good on pine) you will do it in an hour or so if all you need is to smooth, without dimensioning it.
Where did you buy the wood? Is it kiln dried to proper moisture content ? If you bought it in Home Depot it is just from the forest and such wide wet board will twist and crack with time. If that is the look you are after go for it. Otherwise look for a better wood.
One word about using a hand power planer. Forget it. They are good for removing a lot of material quickly but not for smoothing wide boards.

View jonah's profile


2092 posts in 3907 days

#11 posted 04-30-2017 06:22 PM

Honestly, the best way to smooth it is going to be to pay a local shop to do it. They will have a wide belt sander, a thickness planer, and a jointer capable of getting the thing flat, smooth, and square. It’ll probably cost you, but it never hurts to make friends with local shops (hint: bring beer).

View HorizontalMike's profile


7804 posts in 3522 days

#12 posted 04-30-2017 06:28 PM

YES, you can get away with a lunchbox planer. Just make sure of a few things:

1. You know exactly where your high spot is on each side of the beam, before you start planing.
2. Take as shallow cuts as you can
3. You will have to “help” such a larger piece along (pushing to keep it moving), because there is just too much friction/stiction on the ramps for these small planers to do it on their own. Once you have the first foot or so, you can switch to pulling the board/beam from the outfeed side.

I was actually able to plane my 3in X 12in X 90in workbench halves using a 13in RIGID lunchbox planer with infeed and outfeed ramps:

21st Century Workbench

Quickie Planer Table

-- HorizontalMike -- "Woodpeckers understand..."

View HandLogger's profile


6 posts in 196 days

#13 posted 07-12-2019 07:10 PM

Some of the posters here have alluded to using a DeWalt “lunchbox” planer to plane heavy timbers (i.e., 10×10), so I’d love to read more about that. I realize that the original poster (OP) isn’t going for this, exactly, but I’m definitely intrigued by using a DW735-type planer to plane down large [read: heavy] beams in this way. If anyone would care to share any thoughts on this, I’d be much obliged for the help.

-- A CAT backhoe, some Mafell Power Tools and a whole lot of standing timber...

View avsmusic1's profile


564 posts in 1293 days

#14 posted 07-12-2019 11:36 PM

Honestly, the best way to smooth it is going to be to pay a local shop to do it. They will have a wide belt sander, a thickness planer, and a jointer capable of getting the thing flat, smooth, and square. It ll probably cost you, but it never hurts to make friends with local shops (hint: bring beer).

- jonah

This is my vote. My local shop would probably charge 30min of labor which would be much cheaper than buying a lunchbox planer and their equipment would do a better job

View MrRon's profile


5811 posts in 3851 days

#15 posted 07-13-2019 04:47 PM

I would make sure the wood I use is reasonably flat and dry if you are going to get a local shop to do the work. Nothing worse than messing up the sanders and planers of a shop; a good way to lose friends.

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