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Author Topic: Deforming Plywood  (Read 7222 times)

Offline Duane

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Deforming Plywood
« on: October 27, 2015, 09:28:39 pm »
Back when I was in shop class, I was told about "exterior grade plywood" for use in outdoor applications.  I even found an old piece of plywood laying around which had the words, "exterior grade".  Now, when trying to find plywood for making top and bottom boards, when I ask, I can't find someone who knows what I'm talking about.  Some say exterior glue is used, but not many. 

I ended up getting exterior glue plywood at a place and it's called "34CDP CDX".  When they loaded up the piece, I saw it was quite warped and I questioned them on it, but they said all they had was that way.  They said most people use it for sheeting.  I figured cutting it up in small pieces may not matter much.  I made some tops for using with top entrances and glued shims along the sides.  It fit fairly well.  Then we had moist conditions, not really rain, but lots of fog.  The plywood bowed up slightly.  Now we've had a light mist all day and, well, I wouldn't need the shims as it's bowed so much the bees could crawl through the gaps.  Even one I put metal over the top bows up some.

Anyone else have this problem?  I had thought the different plywood layers were at different directions preventing such a thing from happening.  I haven't inspected it that closely to see if it wasn't made correctly.  It doesn't sound like this is going to work through the winter.

Offline little john

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Re: Deforming Plywood
« Reply #1 on: October 28, 2015, 06:39:29 pm »
I've pretty-much given-up on using plywood for bee boxes - precisely because of this tendency to warp. Occasionally I manage to source some really old reclaimed 'exterior grade' plywood which is fine - it's the modern stuff which has this problem.

So - I now make bottoms from pallet wood, and 'soft' crown boards (inner covers) from heavy-duty plastic (ex-polytunnel). It's still possible to use inverted jar feeders with such a set-up - just cut a suitable hole in the plastic, reinforce it with polytunnel repair tape and place the jar on top with a bee-space shim between them. Works like a charm.

I think my plywood-buying days might well be over ...

LJ
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Offline Duane

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Re: Deforming Plywood
« Reply #2 on: October 28, 2015, 09:16:17 pm »
I really didn't want to hear that.  I always thought of plywood as strong and rigid but this stuff flexes.  What if I made nuc boxes from it.  Do you think screwing it together would keep it in shape?

So to make tops or bottoms, the process is to glue the pallet pieces together?  I was hoping using plywood would be more efficient in building.   

I didn't follow with the plastic.  Sounds like you affix the plastic instead of thin plywood to a frame, reinforce it with tape, but I was lost about the bee-space between ...what?  The jar and plastic?

Offline little john

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Re: Deforming Plywood
« Reply #3 on: October 29, 2015, 07:38:23 am »
First of all, let me say that plywood has many beekeeping advocates - I'm just not one of them.

Quote
  What if I made nuc boxes from it.

It can certainly be used to make nuc boxes - here are a couple of shots of one divided nuc design in which I used 10mm plywood. It has a fixed base which has helped to keep the walls straight. I made 8 of them, and they're still in use.





Quote
Do you think screwing it together would keep it in shape?

Yes - that's the method I used in this experimental Long Hive (long since modified - but again, still in use) in which I glued 2 bowed pieces together so that one bow cancelled out the other, making 20mm plywood in the process - you can see how many woodscrews I used !



Quote
So to make tops or bottoms, the process is to glue the pallet pieces together? 

Well - it depends ...

This is how I make large, wide planks (these were for a Long Hive) using pallet wood - 'cause we don't have the luxury of your Oregon forests over here ...

Simply run the planks across a router table to clean-up the edges, glue the edges together on a flat surface with weights on top to hold the planks flat - then pull them together tightly with clamps.



But - for a floor, that's overkill. Here is how I make bases - the planks are simply nailed to 2 thick battens running at 90 degrees to the planks, which also then act as 'feet'. Gaps don't matter, as it's only the floor.



That's fine if you want a solid floor. If you should want to use an Open Mesh Floor, then I make a 3-sided skirt to fit between the OMF and the solid base. A sheet of Correx, suitably cut, can then be slid on top of the solid floor to catch the debris, and thus easily removed and cleaned-off without disturbing the hive. A fourth (detachable) side to the skirt can be placed in position for when first introducing a new colony (to stop them from 'getting lost' underneath the mesh), and for whenever severe winds are forecast.




Quote
I didn't follow with the plastic.

Ok - this was an early test run of using a plastic 'soft top'. I was a little concerned about feeding through the plastic, so made a closeable flap from the lid of a butter carton, and made a simple hinge from tape.



It worked well enough, so I then went ahead and made a more permanent version.



However, I didn't much fancy placing inverted jar feeders directly onto the top bars, in case they should then leak and empty into the hive. So I made-up some beespace 'shims' from plywood offcuts and placed these under the jars. So far, so good - except that when I came to refill the jars, some bees had glued propolis between the shim and feeder lid, so that the shims then had a tendency to slide across the plastic. To prevent this, I then attached some thick plastic offcuts underneath the shims with drawing pins (thumb tacks) and then secured this onto the soft top with tape. Bit of a bodge, but then, this is still 'work in progress'. :)

Perhaps I should also mention that my reason for having 4 feeder jars on each hive (2 per nuc), is that we don't have your large Mason jars over here - so I use the largest jars we have - 1 pint - so that 1/2 gallon of syrup can be given in one go. That's the best I can achieve with what's easily available.

Hope at least some of the above clarifies my earlier post.

Best regards, LJ
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Offline amun-ra

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Re: Deforming Plywood
« Reply #4 on: October 30, 2015, 04:32:44 am »
 polymer construction board

NEMA Board?

A polymer board with all the working & processing properties of timber as well as additional benefits such as being water proof, weather proof, self extinguishing, light in weight, strong, flexible and can be recycled!

Amazingly versatile: the range of possibilities for NEMA Board? is limited only by your imagination.

The standard sheet size is 2440 x 1220mm. Thicknesses range from 1mm to 32mm. Densities of 600kg/m³ (0.60g/cm³) & 450kg/m³ (0.45g/cm³) are available. The raw finish is white however colour variances may occur.

NEMA board is a raw material and as such the physical properties, including the colour, density and dimensions may vary slightly from batch to batch and minor defects may be visible due to manufacturing processes and tolerances.

Variations in the physical and working properties may also occur when the product is exposed to different climatic conditions and direct sunlight. I have hive boxes made of this and they work a treat.
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Offline Duane

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Re: Deforming Plywood
« Reply #5 on: November 01, 2015, 02:01:43 pm »
Little John, I see one of your photos changed from last time I looked at it.  From what I remember in your nuc boxes, it looked like you have a divider board off to one side which could be placed in the middle, or elsewhere.  How tight should that fit?

I'm not sure I want to screw and glue two pieces of 3/4 plywood together.  Kind of defeats my purpose for making things easier.

That's some neat thoughts on not worrying about the floors having gaps.  I guess screened bottom boards have "gaps"! 

Thanks for showing the photos.  I think I understand about the plastic now.

Offline Duane

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Re: Deforming Plywood
« Reply #6 on: November 01, 2015, 02:05:08 pm »
I recall some flooring called, AdvanceTech.  Looking it up, it's warranted for 500 days of exposure.  I saw one photo of a door on a trailer which had been out for 10 years and they said it was still 3/4 an inch thick.  A little weathered, but regular wood would be weathered, too.  I'll have to try and find the NEEMA board.  I think there's possibilities out there, just have to find something not real expensive and easy to work with.

Offline little john

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Re: Deforming Plywood
« Reply #7 on: November 01, 2015, 03:12:57 pm »
... it looked like you have a divider board off to one side which could be placed in the middle, or elsewhere.  How tight should that fit?
I made each one to fit within 1mm or less - so that each box has it's own custom-made divider. With hindsight, that was not a very smart idea ...
If I'm dividing boxes now, I cut grooves into the walls at pre-determined positions - so that the dividers can then be a much sloppier fit, and yet still remain bee-tight.  That's a much quicker way of achieving the same result.

LJ



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Offline OldMech

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Re: Deforming Plywood
« Reply #8 on: November 01, 2015, 04:33:21 pm »
Marine grade plywood is expensive! Can still get it here to use in bathoom walls etc..   I used 5/8 advantech on my roof, its wax impregnated and has a 50 year warranty...  but its also very expensive....
   I use 1/2 plywood for about everything. I dont have to buy 1/4 inch luan for the inner cover, 3/8 for the floor etc, etc... I use 1/2 for it all, saves time and having multiple stacks... I always had 1/4 inch when I needed 3/8 or 1/2...
   I have about half of my tele covers with no metal on them, but painted well that are going into their fourth winter. 3/4 boards around the sides and glued/stapled. and painted. Paint is top, sides, bottom of the 3/4 side boards and inside the 3/4 side boards, but no paint inside the tele cover. You can make ten tele covers from one 4x8 sheet, so at around 22 dollars a sheet it costs $2.20 for the plywood, another couple bucks for the 3/4 side boards, and a couple bucks for the paint. At less than $8.00 each, and lasting 5ish years I just replace them when they start to get bad. If I can repaint them before they get soft I do.
   Not sure why yours are warping unless they have no paint?
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Offline BeeMaster2

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Re: Deforming Plywood
« Reply #9 on: November 02, 2015, 12:52:09 pm »
Keep in mind that Marine grade plywood is pressure treated. You do not want it in your hives where the bees will bee trying to clean it 24 hours a day.
Jim
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Offline amun-ra

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Re: Deforming Plywood
« Reply #10 on: November 02, 2015, 11:06:01 pm »
Jim I have some hive boxes that are CCA treated I just paint the inside and have never lost a bee as they don't eat the wood
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Offline OldMech

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Re: Deforming Plywood
« Reply #11 on: November 03, 2015, 12:57:39 am »
they will chew it, and the paint. Not so much when it is new, but as it gets a bit of age on it and starts to flake/peel/chip they will want to chew it up and remove it so they can seal it their own way.
   I built a frame out of pressure treated wood just to see for myself what would happen...  I dont know if it actuall killed any bees, I didnt see evidence of that, but once they built comb in it, they did not USE the outside ring of wax where it attached to the frame..  that was enough to tell me I needed to get rid of it.
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Offline Duane

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Re: Deforming Plywood
« Reply #12 on: June 06, 2016, 11:14:32 am »

This is how I make large, wide planks (these were for a Long Hive) using pallet wood - 'cause we don't have the luxury of your Oregon forests over here ...

Simply run the planks across a router table to clean-up the edges, glue the edges together on a flat surface with weights on top to hold the planks flat - then pull them together tightly with clamps.
Being not all that good with woodworking, I'm not following about the router table.  When cutting a full thickness off, wouldn't when you get halfway down the fence, the board tilt and change the cutting?  And for sure when that last inch comes to the router bit, wouldn't there be a gouge?  I was trying that yesterday and it cut into the piece at the end.  And it wasn't as smooth as the table saw had left it.


Another question, if not related:  I spent some time ripping some nice pine boards, I used three pieces, and recalling something from shop class, with one top I made, I alternated the tree rings so the center one was pointing the opposite of the outside ones.  I made sure the table surface was flat, the clamps were flat, glued it and made sure the edges were even with each other.  The next day, I unclamped it and held the straight edge up and was well pleased at how flat it was.  Then I got ready to put the metal on and saw it was warped some, about an eighth inch off.  I added the shims for the top entrances and installed it on the bee box and now I see one corner is about a quarter inch twisted up.  Even with a few bricks on it.  Since these are top entrances, putting cleats on the front edges won't work so well.  Now I'm thinking that's why they put cleats on them for entrances otherwise, to keep them flat.

I don't know what else to do.  The thin 1/2" old disintegrating plywood I had used on the first ones seem to be better than the 3/4 new plywood or even glued pine boards.  What do other people use with top entrances?

Offline Dallasbeek

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Re: Deforming Plywood
« Reply #13 on: June 06, 2016, 03:31:08 pm »
Something I haven't seen mentioned with regard to plywood is siding called T-111.  It has a rough finish and has grooves cut in the outer face of the siding.  You have to go to a real lumber yard to get the real T-111.  Home Depot has something they sell as T-111, but it's thinner and the grooves are more shallow and spaced differently.  Since it's made for siding on houses, it seems to me this would be "exterior grade" material.  I don't know if that helps you, Duane, but just tossing it out.  I've made a couple of nucs using it and they seem okay, but of course they aren't out in the weather full time for years.
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Offline little john

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Re: Deforming Plywood
« Reply #14 on: June 06, 2016, 06:20:49 pm »

This is how I make large, wide planks (these were for a Long Hive) using pallet wood - 'cause we don't have the luxury of your Oregon forests over here ...

Simply run the planks across a router table to clean-up the edges, glue the edges together on a flat surface with weights on top to hold the planks flat - then pull them together tightly with clamps.
Being not all that good with woodworking, I'm not following about the router table.  When cutting a full thickness off, wouldn't when you get halfway down the fence, the board tilt and change the cutting?  And for sure when that last inch comes to the router bit, wouldn't there be a gouge?  I was trying that yesterday and it cut into the piece at the end.  And it wasn't as smooth as the table saw had left it.

You raise a very good point.

I made my own router table from a sheet of thick plywood, with the router mounted centrally underneath.  With hindsight I should have mounted it centrally with respect to the width (which is 2ft), but offset with regard to the length, so that I could trim wide objects (boxes >18") - but I didn't think ahead - live and learn ...

Ok, so the table is 2ft wide, and when trimming the edges of long boards prior to gluing, I use a bricklayer's 3ft spirit level/true-edge thingy as a fence, held in place with a couple of small G-cramps.

Now the planks I typically trim are around 3ft long, which means that 18" of the plank is in contact with the fence before the wood meets the router bit, and 18" still remains in contact with the fence as it leaves the router bit.  I find that this is sufficient contact for the standard of work I do - which ain't exactly precision.

Now the above may sound alright, but when routering a 3ft plank one edge of which is slightly bowed, you would need a fence which is at least 6ft long in order for the contact points at either end of the plank to remain in contact with the fence during the whole run across the router table.
With only a 3ft 'fence', a plank which is thus bowed on one side will not produce a straight edge on the other side after passing across the router table - but it will be better than before .

So - as soon as (say) 70% of the edge opposite to the concave bow is cleaned up, the edges are reversed (swapped over), and the procedure repeated.  As the cuts on each side are alternated, the plank becomes progressively straighter.  It may take 3 or 4 such alternate-edge passes to achieve acceptably straight edges, for the loss of just a few millimetres of wood.  Any residual bow of (say) 1mm over a 3ft length will easily be accomodated during the gluing-up process.

But - you're quite right to flag this up - perhaps I should have mentioned this before.

LJ

I've just realised there is a much better way.  Simply tack a dead-straight batten onto your plank, such that it is this batten which will run along the fence, rather than the bowed edge underneath it.  Once one edge of the plank is dead straight, you're home and dry ...
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Offline little john

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Re: Deforming Plywood
« Reply #15 on: June 06, 2016, 06:48:49 pm »
I spent some time ripping some nice pine boards, I used three pieces, and recalling something from shop class, with one top I made, I alternated the tree rings so the center one was pointing the opposite of the outside ones.  I made sure the table surface was flat, the clamps were flat, glued it and made sure the edges were even with each other.  The next day, I unclamped it and held the straight edge up and was well pleased at how flat it was.  Then I got ready to put the metal on and saw it was warped some, about an eighth inch off.  I added the shims for the top entrances and installed it on the bee box and now I see one corner is about a quarter inch twisted up.  Even with a few bricks on it.  Since these are top entrances, putting cleats on the front edges won't work so well.  Now I'm thinking that's why they put cleats on them for entrances otherwise, to keep them flat.

I know this one only too well ....

It's so demoralising to glue-up a flat composite plank, only for it to warp the minute the humidity changes.  I find painting helps (which is one reason why I paint my boxes inside and out), but it isn't a complete cure.  I find bases and boxes aren't too much of a problem, as weight from above tends to flatten out any warp - it's the stuff at the top which has proved to be a headache.

My solution (mind you, I run bottom entrances) is not to bother with wooden crown boards (inner covers), but to use 'soft' crown boards instead - heavy gauge plastic sheet, canvas, that kind of thing.  I'm finding that this is a much better approach.
For roofs, I prefer the telescopic variety - and even if they warp half an inch or more - who cares if they wobble a little ?  As long as they keep the rain out ...
LJ

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Offline triple7sss

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Re: Deforming Plywood
« Reply #16 on: June 08, 2016, 02:34:30 pm »
As an experiment one time (because I was having the same problem with bowing) I took a leftover piece of 3/8" exterior plywood and cut two pieces the same size but I cut one with the grain going one way and one "against" the grain.  Then I put construction adhesive on one piece, clamped them together with the grain running cross-ways, wiped up all the construction adhesive the the clamping squeezed out, painted the tops and edges and attached a pair of 1x2s to the underside spacing them the width of a hive body just to act as a guide when I was putting them back on the hive. 

When I put it together I clamped the 1x2s onto the sides of a hive body with a piece of corrugated cardboard between the 1x2 and the body just to space them slightly wider and give it a little wiggle room when putting it back on the hive.  Then I screwed my plywood onto the 1x2s from the top.

That has worked well.  It's probably not cost effective and it's sort of time consuming but it did assuage the king-hell frustration of exactly what you describe - the plywood bowing so that your carefully crafted entrance reducers are pointless as the gap everywhere along the top entrance is large enough for bees to pass through.

I had a piece of 1/2" painted plywood I was using as a top cover one time and when it started to bow I couldn't flatten it out even with 3 cinder blocks on top.  Aggravating.

Offline Duane

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Re: Deforming Plywood
« Reply #17 on: June 10, 2016, 02:53:12 pm »
I've just realised there is a much better way.  Simply tack a dead-straight batten onto your plank, such that it is this batten which will run along the fence, rather than the bowed edge underneath it.  Once one edge of the plank is dead straight, you're home and dry ...
That sounds like it'd work!  I still didn't follow the other way you were saying.  Or maybe I didn't ask accurately.  Suppose you had a perfectly straight edge and ran it across your fence.  After the 18 inches went through, wouldn't it tilt against the fence after the bit?  That is, isn't your fence even, so after the bit cuts off a portion, then there's a gap.....
....  Unless your fence is on the other side of your board?  I'm assuming the fence is real close to the bit.  But maybe the fence is far from the bit with the board between the fence and bit?

Offline Duane

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Re: Deforming Plywood
« Reply #18 on: June 10, 2016, 02:58:29 pm »
As an experiment one time (because I was having the same problem with bowing) I took a leftover piece of 3/8" exterior plywood and cut two pieces the same size but I cut one with the grain going one way and one "against" the grain.  Then I put construction adhesive on one piece, clamped them together with the grain running cross-ways, wiped up all the construction adhesive the the clamping squeezed out, painted the tops and edges and attached a pair of 1x2s to the underside spacing them the width of a hive body just to act as a guide when I was putting them back on the hive. 
If I'm understanding correctly, you glue two pieces together crosswise to cancel the bow out?  I was using 3/4" plywood (thinking it was more stable!), but maybe two 1/2" would work better.  Crosswise and maybe flipped surface wise, too.

Offline BeeMaster2

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Re: Deforming Plywood
« Reply #19 on: June 11, 2016, 12:00:11 am »
Plywood is made by cris crossing the layers of wood. The big difference is how many layers were used to make it. The cheaper ones may have as few as 3 layers. The more expensive ones have more layers to make them more stable.
Jim
« Last Edit: June 13, 2016, 08:20:24 pm by sawdstmakr »
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Offline little john

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Re: Deforming Plywood
« Reply #20 on: June 11, 2016, 04:26:02 am »
....  Unless your fence is on the other side of your board?  I'm assuming the fence is real close to the bit.  But maybe the fence is far from the bit with the board between the fence and bit?

Isn't it WONDERFUL when the veil of confusion is lifted ?  Thank you so much for flagging-up those alternative ways of running a router table.

I do indeed run the planks between the fence and router bit (rightly or wrongly).  That way the bit rotation is against the direction of plank travel - such that if I let go of the wood, it can fly back and poke me hard in the goolies - which has happened on a few occasions ...  By running the table this way, there is a constant (and stable) distance between the router fence and router bit over the FULL length of the fence.

But - when cutting a 45 degree mitre on the edge of a plank of uPVC cladding (which I'll be writing about shortly), I set the fence as close to the bit as possible (as you say) and then hold the uPVC 'plank' on top of a 45 degree jig  which is pushed up hard against the fence - and indeed does have a couple of stand-offs to keep the jig itself from hitting the router bit - which forms the same kind of gap as that which you must be referring to.

LJ
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Offline Duane

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Re: Deforming Plywood
« Reply #21 on: June 13, 2016, 08:11:15 pm »
Yes it is!  I was trying to think how you used your level with the bit and then it dawned on me that it's not like I'm used to.  This will be different thinking for me on using the router.  Can't think why it won't work.  Guess all the caution I've heard about the table saw and trying to avoid a pinching the pieces between the blade and fence.  I just tried using the suggestion of trimming your boxes to width after being built so they'll be "perfectly even".  I was being careful with both my fingers and keeping it to the fence.  At the end, it seemed to catch and then I saw the box being pulled back.  Probably all happened in a short time, but I was trying to keep everything flat and against the fence and I saw I was losing it.  I grabbed the box away as it was being flung.  Now I have a big gouge in the edge.  So much for being even.  Since I don't understand what caused it, and had evened up edges before with no problem, I think in the future I will just cut them to width and be more careful in assembly.

So a board between the router bit and fence makes me cautious.  But it should work.  If I did it with my router table and its fence, I'll have to do it from the opposite direction and left handed.  Unless I just add an additional straight edge like you do.

Offline little john

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Re: Deforming Plywood
« Reply #22 on: June 14, 2016, 06:22:24 am »
I just tried using the suggestion of trimming your boxes to width after being built so they'll be "perfectly even".

Just a bit of clarification re: trimming boxes accurately to size.

These are the very last National Brood Boxes I made from pallet wood, which was before Mann-Lake came to town, and was the only viable way from me to acquire cheap boxes. 




Now I buy Mann-Lake boxes flat-pack, and although being 2nd-grade they need some fettling, it's more cost-effective than breaking pallets apart for their wood.

Ok - so having run the planks individually across the table router to clean-up their edges, I then glued-up wide composite planks to form the box sides and ends.  These are run across a table saw to reduce them to size, plus a few millimetres extra for trimming.  Then the boxes themselves are built.  In the following shot, the end plates were obviously left very proud (can't think why, now) but would then have been cut down to remove most of the excess, but leaving enough for the next step.




The boxes are then placed on a dead-flat bed and checked for rock - which I find is a constant issue when working with pallet wood. If it is more than just a couple of millmetres (which would be ignored, as subsequent loading weight would flatten that) then spacers - bits of old credit cards, washers etc - are inserted equally at opposite corners to stop the rock, and then hot-glued in place.




Then the sides of the jig are built up, and a router sledge placed over the top.  This is run back and forth until the edges are uniformly flat, at which point the jig is dismantled, and the box secured with the flat side downwards (no need for spacers now) and the process repeated on the other edge until the desired box height is reached.




Because this router is fixed to the sledge and thus dedicated to this one task - likewise the router fixed under the router table - I've used cheap and cheerful routers (ex bring and buy sales) for these tasks.  But to make such cheap and simple plunge routers more useful, I've fitted them with a means of precise adjustment:




This very simple modification makes all the difference in the world, turning a fairly crude and simple plunge router into a precision tool with controlled variable depth.

LJ
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