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Flattening problem using planer sled

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Forum topic by Travis posted 02-22-2020 08:34 PM 1439 views 0 times favorited 63 replies Add to Favorites Watch
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Travis

398 posts in 447 days


02-22-2020 08:34 PM

Hi all,

I wasn’t sure if I should post this here or the jig forum. It’s a follow-up from my previous post here.

I decided to go with the planer sled for a variety of reasons. I used an 8’ piece of 3/4” melamine and tried to support the sled all the way through and out. I tried it out with a 5’ board of 8/4 ash. The board had a little twist and was cupped. I placed it with the bow up (ends down) to try and minimize any rocking effect as it went through the planer. I made sure to shim it with the sled on the flattest surface I had (my kitchen counter top) because I read in other posts that that was perhaps the most important step. It seemed to work fine, but when I came back to test the newly flattened surface on my counter top I noticed it now had an opposite cup.

In other words, it seems to narrow in the middle of the board. Laying the rough side down (as originally placed) and the board rests on its ends. Flip it over and lay the supposedly flat side down and it also rests on its ends. The gap is smaller than the rough side, perhaps about 1/16th of an inch.

I’m just trying to figure out what would cause this. I don’t want to keep running this board through the planer if there is a problem because I’m trying to preserve as much thickness as possible. I thought the ends were secure when I ran it through on the sled, but I can’t think of another explanation for the thinner middle. I’m assuming the rollers pushed the ends down a fraction and then they “spring back up” when free. Are there any other reasons I could be observing this? I suppose my counter top might have a valley, but I don’t have a long enough straight edge to test that with.

Pictures below are the “flat” side down.

-- The plan is wrong; my finished piece is right.


63 replies so far

View bilyo's profile

bilyo

1039 posts in 1783 days


#1 posted 02-23-2020 02:41 AM

When I first tried to use a sled, I did exactly as you did and got similar results. It was only when I made my sled into a torsion box, stiff enough to stay flat, that I was able to get good results. Your melamine board (sled) is quite flexible and there is no way you are going to keep it perfectly flat as to goes through the planer. Another way you can try (I haven’t done it) is to place another piece of melamine through the planer, make sure it is flat and well supported and anchor it in position. Then let your sled slide on it. That way it will stay flat all the way through.

I have had this discussion before here and others have said that they have no problem doing it the way you did. That’s fine. I haven’t been able to succeed that way.

View Aj2's profile

Aj2

2792 posts in 2478 days


#2 posted 02-23-2020 04:02 AM

Now don’t you feel silly spending all that time and some money on a silly fixture.
A planer is not a jointer.

Good Luck

-- Aj

View MrUnix's profile

MrUnix

7841 posts in 2879 days


#3 posted 02-23-2020 04:11 AM

You just didn’t shim/secure it properly… somewhere, it had some give. Not the sled, but the stock you were trying to flatten. Placing it with the bow up (ends down) probably made shimming it properly more difficult as well. You also don’t want to try and take much off on each pass, so go lightly.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Andybb's profile

Andybb

2639 posts in 1284 days


#4 posted 02-23-2020 08:14 AM


When I first tried to use a sled, I did exactly as you did and got similar results. It was only when I made my sled into a torsion box, stiff enough to stay flat, that I was able to get good results.
- bilyo

+1
I posted this in your other thread. This is a torsion box sled and it works great.


Planer sled.

Nothing unique or special about it as many have made ljs these and plans are readily available but I ve been meaning to make one of these for a few years now and finally got around to it. Just thrilled that it worked so well. Boards came out dead flat. It ain t pretty but it works great for flattening warped boards too wide or twisted for my 6 jointer. Spent about $15 on various hardware at The Borg.

- Andybb

- Andybb

-- Andy - Seattle USA

View ChefHDAN's profile

ChefHDAN

1558 posts in 3530 days


#5 posted 02-23-2020 12:28 PM

Travis, you’re clearly diving into this hobby, I’ve seen your many posts, and applaud your vigor. What is you time worth and where do you see yourself going in this endeavor? How do you feel about that? .... What is your time worth? I found these;

Craftsman Jointer

Delta Jointer

Jet Jointer

Time is a valuable commodity, if you figure what your hourly rate is, the amount of time dealing with sleds etc. between construction adjustment and use. I really believe that you’ll be very pleased owning a jointer, the best work starts with square stock and some stock you can only get for a reasonable price in the rough. If I were in your position I’d be standing in front of the Craftsman Jointer with 2 $100 bills and 2 $50’s, Offer $200 and see if he’ll take $250. That is of course unless the Delta is less, but I’ll bet the seller wants +$400.

Not trying to bust your chops, but I see you’re “Into It” and you’ll be so happy after you run your first board over it, and I’m pretty confident it will not go to waste in your shop as you’re diving in and building your skills… eventually you’re going to NEED a jointer, I say do it now!

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

View controlfreak's profile

controlfreak

568 posts in 282 days


#6 posted 02-23-2020 12:59 PM

I don’t think the problem is with th MDF flexing as it should be a uniform thickness with full bottom support. I think the slight movement in the adjustable support under the board combined with the board movement itself combine to create what you show in your pictures. When I look at the downward pressure that the planner rollers exert I don’t see how there will be no deflection in the board being flattened as it rides on the sled without saturating it with contact points. The same is true over a jointer without the subtle adjustments in pressure by the operator. Even with those adjustments it will require multiple passes. I know this may not help you Travis but I am not being critical here, more like thinking out loud.

View Rich's profile

Rich

5367 posts in 1270 days


#7 posted 02-23-2020 03:02 PM

An eight foot long piece of melamine that won’t flex? Someone will have to tell me where I can buy that!

I’m with billyo.

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

View Travis's profile

Travis

398 posts in 447 days


#8 posted 02-23-2020 03:39 PM



When I first tried to use a sled, I did exactly as you did and got similar results. It was only when I made my sled into a torsion box, stiff enough to stay flat, that I was able to get good results. Your melamine board (sled) is quite flexible and there is no way you are going to keep it perfectly flat as to goes through the planer. Another way you can try (I haven t done it) is to place another piece of melamine through the planer, make sure it is flat and well supported and anchor it in position. Then let your sled slide on it. That way it will stay flat all the way through.

I have had this discussion before here and others have said that they have no problem doing it the way you did. That s fine. I haven t been able to succeed that way.

- bilyo

I looked at similar discussions. I decided to try the simplest solution first. Hopefully I can get this to work, otherwise I’ll look into a torsion box design.

-- The plan is wrong; my finished piece is right.

View Travis's profile

Travis

398 posts in 447 days


#9 posted 02-23-2020 03:40 PM



Now don’t you feel silly spending all that time and some money on a silly fixture.
A planer is not a jointer.

Good Luck

- Aj2

Um, thanks?

-- The plan is wrong; my finished piece is right.

View Lazyman's profile

Lazyman

4837 posts in 2068 days


#10 posted 02-23-2020 03:41 PM

I don’t think that you said how wide the board is. If you have room, you might try putting an already straight board on either side of the board you are flattening as you run it through the planer. This may help reduce any flex. Take extremely light passes. Did you use hot glue to lock the shims and the board down? Not sure how well the hot glue will stick to the melamine but it can’t hurt.

You may also be able to use a straightened board to see if your countertop is actually flat. Turn it at different angles and test it across the ends of the countertop to verify that the theoretically straight board is actually straight. If you make 2 straight boards, you can use them against each other to verify that they are both straight.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Travis's profile

Travis

398 posts in 447 days


#11 posted 02-23-2020 03:42 PM



You just didn t shim/secure it properly… somewhere, it had some give. Not the sled, but the stock you were trying to flatten. Placing it with the bow up (ends down) probably made shimming it properly more difficult as well. You also don t want to try and take much off on each pass, so go lightly.

Cheers,
Brad

- MrUnix

I think that’s probably the biggest culprit. Why would the orientation make it more difficult to shim? I assumed with both ends down it would be more secure/easier to shim. I’m not arguing, just curious.


-- The plan is wrong; my finished piece is right.

View Travis's profile

Travis

398 posts in 447 days


#12 posted 02-23-2020 03:44 PM


I posted this in your other thread. This is a torsion box sled and it works great.

Planer sled.

- Andybb

I appreciate that walk-through. If I were doing this repeatedly I would invest the time to make a deluxe sled like that. I was looking for an easy one-off type solution.

-- The plan is wrong; my finished piece is right.

View Travis's profile

Travis

398 posts in 447 days


#13 posted 02-23-2020 03:48 PM



Travis, you re clearly diving into this hobby, I ve seen your many posts, and applaud your vigor. What is you time worth and where do you see yourself going in this endeavor? How do you feel about that? .... What is your time worth? I found these; Craftsman Jointer

Delta Jointer

Jet Jointer

Time is a valuable commodity, if you figure what your hourly rate is, the amount of time dealing with sleds etc. between construction adjustment and use. I really believe that you ll be very pleased owning a jointer, the best work starts with square stock and some stock you can only get for a reasonable price in the rough. If I were in your position I d be standing in front of the Craftsman Jointer with 2 $100 bills and 2 $50 s, Offer $200 and see if he ll take $250. That is of course unless the Delta is less, but I ll bet the seller wants +$400.

Not trying to bust your chops, but I see you re “Into It” and you ll be so happy after you run your first board over it, and I m pretty confident it will not go to waste in your shop as you re diving in and building your skills… eventually you re going to NEED a jointer, I say do it now!

- ChefHDAN

Thanks for the links ChefHDAN! I have a benchtop jointer that works great for most of my small needs. I am building a kitchen table ATM, not something I will do frequently. While I love woodworking and making things, my “shop” is also a functioning garage and I can’t justify a full-size jointer. I would love it, and I would be willing to buy a used model like you linked. I just don’t have space for it.

I could probably get pretty decent results with my benchtop model on these 5’ boards, it’s got 5’ of combined in/outfeed. But, I know I will not get good results on the tabletop planks, which is why I am testing this method on the 5’ boards.

-- The plan is wrong; my finished piece is right.

View Travis's profile

Travis

398 posts in 447 days


#14 posted 02-23-2020 03:50 PM



An eight foot long piece of melamine that won t flex? Someone will have to tell me where I can buy that!

I m with billyo.

- Rich

It’s not that the melamine won’t flex. It’s that theoretically it doesn’t have to be that rigid. Since the planer references off the sled and the sled is flat/supported through the planer, and the board is shimmed so it won’t flex and the twists/cups are leveled out, you should still be able to get a flat surface. It’s not the same as just running the plank unsupported through the planer.

-- The plan is wrong; my finished piece is right.

View Travis's profile

Travis

398 posts in 447 days


#15 posted 02-23-2020 03:51 PM



I don t think the problem is with th MDF flexing as it should be a uniform thickness with full bottom support. I think the slight movement in the adjustable support under the board combined with the board movement itself combine to create what you show in your pictures. When I look at the downward pressure that the planner rollers exert I don t see how there will be no deflection in the board being flattened as it rides on the sled without saturating it with contact points. The same is true over a jointer without the subtle adjustments in pressure by the operator. Even with those adjustments it will require multiple passes. I know this may not help you Travis but I am not being critical here, more like thinking out loud.

- controlfreak

Thanks controlfreak. I was probably going easy on the shims. Since it is a 8/4 piece of ash, I assumed it would be more resistant to the rollers. I’ll try again with more shims :)

-- The plan is wrong; my finished piece is right.

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