Author Topic: Flattening Twisted Slab  (Read 860 times)

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Offline Birdhunter

  • Posts: 3140
  • Woodworker, Sportsman, Retired
Flattening Twisted Slab
« on: September 09, 2020, 05:41 PM »
I had. 18” by 9” by 1” slab of highly figured wood I needed for a small table. Unfortunately, it was slightly twisted. My jointer is 8” so I couldn’t use it. I could have hand planed it, but was feeling lazy.

I cut two 3/8” plywood strips each 18” by 1 1/2” wide. I put the slab on my table saw top and glued the plywood strips to the sides of the slab making sure the strips were flush with the table saw top. The strips stood proud of the slab’s surface by 1/2” like runners on a sled.

I then ran the slab with the “runners” down through the planer. What emerged was a perfectly flat surface with no twist.

I cut off the runners and ran the slab back through the planer. I now had a flat slab with two parallel surfaces.



Birdhunter

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Offline Svar

  • Posts: 2192
Re: Flattening Twisted Slab
« Reply #1 on: September 09, 2020, 06:00 PM »
Nice.
I did similar on a router table. Run the "sled" back and forth over the bit, which is slightly protruding from the table. Flip and repeat. I also used brad nails to affix the runners.
« Last Edit: September 09, 2020, 06:04 PM by Svar »

Offline ear3

  • Posts: 4123
Re: Flattening Twisted Slab
« Reply #2 on: September 10, 2020, 09:31 AM »
That's a great idea @Birdhunter

I had. 18” by 9” by 1” slab of highly figured wood I needed for a small table. Unfortunately, it was slightly twisted. My jointer is 8” so I couldn’t use it. I could have hand planed it, but was feeling lazy.

I cut two 3/8” plywood strips each 18” by 1 1/2” wide. I put the slab on my table saw top and glued the plywood strips to the sides of the slab making sure the strips were flush with the table saw top. The strips stood proud of the slab’s surface by 1/2” like runners on a sled.

I then ran the slab with the “runners” down through the planer. What emerged was a perfectly flat surface with no twist.

I cut off the runners and ran the slab back through the planer. I now had a flat slab with two parallel surfaces.
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Offline Birdhunter

  • Posts: 3140
  • Woodworker, Sportsman, Retired
Re: Flattening Twisted Slab
« Reply #3 on: September 10, 2020, 10:44 AM »
Thanks. The trick is that because the strips(runners) reference off the table saw surface, they are perfectly parallel while the slab can be twisted between the runners.
Birdhunter

Online ultane

  • Posts: 62
Re: Flattening Twisted Slab
« Reply #4 on: September 10, 2020, 10:50 AM »
I had. 18” by 9” by 1” slab of highly figured wood I needed for a small table. Unfortunately, it was slightly twisted. My jointer is 8” so I couldn’t use it. I could have hand planed it, but was feeling lazy.

I cut two 3/8” plywood strips each 18” by 1 1/2” wide. I put the slab on my table saw top and glued the plywood strips to the sides of the slab making sure the strips were flush with the table saw top. The strips stood proud of the slab’s surface by 1/2” like runners on a sled.

I then ran the slab with the “runners” down through the planer. What emerged was a perfectly flat surface with no twist.

I cut off the runners and ran the slab back through the planer. I now had a flat slab with two parallel surfaces.
Pics would help..
I might be wrong… Just ask my X...

Offline deepcreek

  • Posts: 929
    • TimberFire Studio
Re: Flattening Twisted Slab
« Reply #5 on: September 10, 2020, 10:56 AM »
That's a great method if the sides are fairly uniform.

If the slab has irregular edges and is not too big, I have flattened it by using a comparably sized piece of 3/4" MDF as a sled.

I stuck the slab to it with woodturners double stick tape and them carefully shimmed around the perimeter everywhere the slab was high.

I ran the whole assembly through my Supermax drum sander to flatten one side of the slab.

Then I removed it from the sled, flipped it and ran it through to flatten the other side.
Joe Adams
TimberFire Studio
Houston, Texas

http://www.facebook.com/timberfire

Offline Michael Kellough

  • Posts: 4867
Re: Flattening Twisted Slab
« Reply #6 on: September 10, 2020, 01:53 PM »
Adding to Deepcreek, when the sides won’t accept attachment of guide rails (ala Birdhunter) you can hot glue shims to the mdf (and slab) to support the high places of the slab, then glue a backup block to the mdf to keep the slab from being pushed off the mdf sled.

Offline HarveyWildes

  • Posts: 935
Re: Flattening Twisted Slab
« Reply #7 on: September 10, 2020, 07:04 PM »
Good work.  I've used that technique more than once, but in fairness I do have a 20" planer which makes it practical for fair sized slabs.

Offline Birdhunter

  • Posts: 3140
  • Woodworker, Sportsman, Retired
Re: Flattening Twisted Slab
« Reply #8 on: September 10, 2020, 08:57 PM »
I was lucky in that my “slab” was rectangular with square corners. I’ll remember all the other methods for the future.

It is fascinating how people come at a problem with different approaches. I follow two metal worker YouTube channels where the machinists have to solve problems. Different tools, but the same need for thought.
Birdhunter

Offline CeeJay

  • Posts: 172
Re: Flattening Twisted Slab
« Reply #9 on: September 10, 2020, 09:48 PM »
You could also take the guard off your jointer, run the slab over til you have a flat 8” strip with the extra inch hanging over like a rabbet, then glue a piece of MDF on the flattened 8” surface, use that as a sled through the thicknesser till the other side is flat, turn it over, take off the MDF sled, and plane off the 1” ‘rabbet’. I too have an 8” jointer and use this method for pieces up to 12” wide.


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Offline jcrowe1950

  • Festool Dealer Affiliate
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  • Posts: 108
    • Woodcraft Chattanooga, TN
Re: Flattening Twisted Slab
« Reply #10 on: September 17, 2020, 12:12 AM »
You could also take the guard off your jointer, run the slab over til you have a flat 8” strip with the extra inch hanging over like a rabbet, then glue a piece of MDF on the flattened 8” surface, use that as a sled through the thicknesser till the other side is flat, turn it over, take off the MDF sled, and plane off the 1” ‘rabbet’. I too have an 8” jointer and use this method for pieces up to 12” wide.


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   Alternately, you can use a nice hand plane and a pair of winding sticks to flatten one side....this is also a traditional method of work that is quiet and a good skill to have....saves stock too.....
Festool Specialist at Woodcraft, Chattanooga, TN

Offline CeeJay

  • Posts: 172
Re: Flattening Twisted Slab
« Reply #11 on: September 17, 2020, 12:45 AM »

   Alternately, you can use a nice hand plane and a pair of winding sticks to flatten one side....this is also a traditional method of work that is quiet and a good skill to have....saves stock too.....

True enough.


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