Top Slab Smoothing Question and Help


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I have a question about a project that I was looking for a little help. I am building a craft bench for my wife and making a glued laminated top that is about 30 inches in total width and about 4.5 inches in thickness that was made with 8/4 hard maple.  Since this will be larger than my power planer is there a good way to get the top and bottom both smooth and flat?

Would you use a scrub plane and then jack plane to smooth down?  what do you use to reference flat when you use this method?  Do you just start planing and check with a straight edge?  Any good reference material on how to do this?  

I know you can use a router to smooth out a slab, but since it is not on its legs and the bottom is not flat I was not sure how you referenced the top so you did not flatten at an angle (tilted left to right and front to back).  I think I could get the router sled flat but the slab would not have a flat surface to rest on. 
 

Thanks for any suggestions or reference websites or materials on the topic!

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11 minutes ago, Woodworking_Hobby said:

Would you use a scrub plane and then jack plane to smooth down?  what do you use to reference flat when you use this method?  Do you just start planing and check with a straight edge?  Any good reference material on how to do this?  

Winding sticks are very useful for that and they are easy to make.

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Router sled. Attach beams on both of the long sides of the top and use a string crossing from each corner to get everything flat and true. This flattening method is covered really well in the Roubo flattening method covered by Marc on his bench build but similar methods can probably be found elsewhere.

So the string method uses a strong running from each corner crossing in the middle. When the strings just barley touch in the middle the 2 beams are co planar. There are some minor tricks but it's really fast and easy to flatten this way. I did 2 benches in an hour or so.

Here are some pictures with what it looks like. I used clamps to hold the boards on the side of the slab. The boards were jointed strait on my jointer.

DSC_3801-01.thumb.jpeg.675607ed56c61a0873a0ff89ad44cb04.jpeg

DSC_3800-01.thumb.jpeg.d914c8c8f72afae4ff8d83903e1dcf8e.jpeg

Now my bigger question is why did you make such a stout bench top for a crafting table?

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Hand planes were used to flatten slabs ling before routers were invented, but they do take some effort. You need a solid support to hold the slab still. Use wedges under the high spots to prevent rocking. Winding sticks, a longer straight edge, and a lot of eyeballing will show the high spots on the upper face. Knock those down and recheck. When it gets tough to see the high spots, use a long jounter plane, if you have one.

Once the upper face is satisfactory, flip it over and scribe around the edge, measuring from the flat reference face. Plane down to your scribe line to make the other face parallel. 

Hint* The winding stick & straightedge method works as well with a powered hand plane. The router sled method works great, but seems very tedious to me, unless the slab is small,  the router really big. There are planing bits made for this task, if your router has the HP, I'd use one.

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7 hours ago, Chestnut said:

Router sled. Attach beams on both of the long sides of the top and use a string crossing from each corner to get everything flat and true. This flattening method is covered really well in the Roubo flattening method covered by Marc on his bench build but similar methods can probably be found elsewhere.

So the string method uses a strong running from each corner crossing in the middle. When the strings just barley touch in the middle the 2 beams are co planar. There are some minor tricks but it's really fast and easy to flatten this way. I did 2 benches in an hour or so.

Here are some pictures with what it looks like. I used clamps to hold the boards on the side of the slab. The boards were jointed strait on my jointer.

DSC_3801-01.thumb.jpeg.675607ed56c61a0873a0ff89ad44cb04.jpeg

DSC_3800-01.thumb.jpeg.d914c8c8f72afae4ff8d83903e1dcf8e.jpeg

Now my bigger question is why did you make such a stout bench top for a crafting table?

Ha I wish I knew!!  It was what was requested so I guess I will deliver.  She does a lot of small projects and wanted something pretty stout for her builds. 

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1 hour ago, wtnhighlander said:

The router sled method works great, but seems very tedious to me, unless the slab is small,  the router really big. There are planing bits made for this task, if your router has the HP, I'd use one.

I've done both and found them equally tedious but the router sled faster.

That said the hand plan can get you a good work out.

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17 hours ago, wtnhighlander said:

Hand planes were used to flatten slabs ling before routers were invented, but they do take some effort. You need a solid support to hold the slab still. Use wedges under the high spots to prevent rocking. Winding sticks, a longer straight edge, and a lot of eyeballing will show the high spots on the upper face. Knock those down and recheck. When it gets tough to see the high spots, use a long jounter plane, if you have one.

Once the upper face is satisfactory, flip it over and scribe around the edge, measuring from the flat reference face. Plane down to your scribe line to make the other face parallel. 

Hint* The winding stick & straightedge method works as well with a powered hand plane. The router sled method works great, but seems very tedious to me, unless the slab is small,  the router really big. There are planing bits made for this task, if your router has the HP, I'd use one.

Thanks!  I will give it a try and see how it goes! I must admit I am a little nervous as I have not done that much hand plane  work on my projects and was worried I was going to take off too much or not get flat. I was a little disappointed on how “rough” it turned out but maybe that is typical. I thought I had the boards all milled to the same thickness and used the domino trick for alignment similar to what folks have done on their Roubo builds. From lowest stop to highest spot on the slab is maybe a hair under an 1/8 or a hair over a 1/16…hard to tell. Maybe that is a win but from some other post it made it almost sound like the slab could come out ready to run through a power planer. Maybe that’s just wishful thinking ;-). Thanks again for all of the tips and advice from folks along the way of my projects and learning!  

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@Woodworking_Hobby, were the planks jointed on one face prior to going through the planer? Many new woodworkers do not fully understand the relationship these machines maintain. The jointer is used to create one flat face, while the thickness planer references that flattened face in order to make the opposite face parallel and smooth. Using the planer alone will not remove twists and bows from a board.

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16 minutes ago, wtnhighlander said:

@Woodworking_Hobby, were the planks jointed on one face prior to going through the planer? Many new woodworkers do not fully understand the relationship these machines maintain. The jointer is used to create one flat face, while the thickness planer references that flattened face in order to make the opposite face parallel and smooth. Using the planer alone will not remove twists and bows from a board.

Yes I used the jointer on the surface, then jointer on one edge referenced off that face, and then through the planer. To be honest the boards were pretty heavy and I only have a small grizzly six inch jointer so there is a high probability I did not get them quite right to start off the jointer.  I have had ok success when I have jointed and planed smaller lumber for the kitchen helper and other size projects, but I have never tried something of this size with my machines. I dream about getting a little larger jointer someday but it is down on the list at this point. 

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