working with baltic birch plywood

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I'm about to start using baltic birch plywood for the first time, and as someone who has only used MDF before, was just wondering if there is anything significantly differnet about working with/machining ply? Anything I need to do differently when routing circle cutouts, do screw pilot holes get stripped really easily like MDF, do I need to change the speed settings on my router/jigsaw, does BB ply sand differently than MDF? Any tips would be appreciated, as I don't have a lot of scrap to play with.
 
Here are a few things to keep in mind.

Birch plywood is much harder and denser than MDF. That usually means slower cutting. It also means screws do NOT strip as easily.

Birch plywood is of course made of layers. The outer layers are quite thin and it is possible to sand right through it before realizing it. If you intend to paint it or veneer it that might not be too much of a problem but if you want to finish the birch be very careful.

If you have a variable speed router you will probably find that slowing it down a bit and cutting more slowly causes fewer burn marks. If you can use a fine toothed blade in your table saw. Also tearout isn't a huge problem with birch ply but if you can put a piece of scrap under it while cutting on the table saw.

If finishing the birch itself you may find you like the look of having the edges rounded over.
 
Sherman said:
Birch plywood is much harder and denser than MDF. That usually means slower cutting. It also means screws do NOT strip as easily.

Birch plywood is about .7 g/cm^3, MDF is .7 g/cm^3 and higher. Of course some birch plywood might be denser than some MDF, but this is mostly not the case.

Yellow Birch hardness is 1260 Janka (lbs/in^2). MDF is about 1000-1200. Really depends on the type. Also with plywood. In general I would say MDF is denser than Birch plywood. And they are about the same hardness with Birch plywood slightly being harder, but hardness specs are hard to come by and often considered trivial.

This forum is often not the place for accurate information about wood products. I have not heard many say inaccurate things about wood products. People have even taken sides against me and sided with what they called an "expert" cause he worked at a plywood factory or something.
 
Tips from the dark side

Pre drill your screws to the root diamter or there abouts. It makes it easier to drive them in.

BB is much more stiff than MDF so that is a plus when building boxes. As for cutting figure out the best feed rate by listening to your machine and watching the end product of the cut. You know what both of them should look like. And you know what an un laboured router sounds like.

Other than that there is not much to know about. The outer layer of the birch ply is about 1mm so don'r worry about sanding through to easily. Finishing can be tough as birch does not stain evenly. But with a coat of shellac it will take an even stain.

MArk
 
Finishing can be tough as birch does not stain evenly. But with a coat of shellac it will take an even stain.

Could you (elaborate?) a bit?
I'm planning to bauild a pair of fullrange speakers and at the same time redo my old cabinets so it could be a good thing to start collecting facts.

Shellac, isn't that some kind of coating used with metals or something? In any case, shellac first, then stain?

OT
planning to use a ply called Lauan, some kind of red colored wood.
 
Shellac=

It is a finishing product that is taken from the secretions of the lac bug. It usually comes as flakes and is thinned in alcohol. It is like a laquer. Only not as durable. It sticks to anything and it makes a good first coat on raw wood that is difficult to stain evenly. When coated and stained within about twenty minutes it will absorb the stain and allow an even coat colour.

Mark
 
Re: Tips from the dark side

mwmkravchenko said:
BB is much more stiff than MDF so that is a plus when building boxes. As for cutting figure out the best feed rate by listening to your machine and watching the end product of the cut. You know what both of them should look like. And you know what an un laboured router sounds like.

M.o.e of MDF is about 3950 N/mm^2

M.o.e of Birch 3700, 5000 N/mm^2 for a piece I found 18 mm in thickness and 13 plys. 3700 is perpendicular to facegrain, 5000 is parellel to facegrain (the less plys the greater the difference will be, I would imagine). So Birch has more so less the same stiffness as MDF; it is different depending on the orientation of the grain and the type of Birch plywood and MDF used (manufacturing process and what they're made of).

The MDF spec sheet I looked at is made of pine it's called Medite and plywood is wisa Birch plywood. The plywood is .63 g/cm^2. The MDF is probably less stiff and had less density than average piece of MDF I'm guessing.

I think baltic birch plywood would be more stiff than MDF generally. Much more I don't know though. You should check yourself, if you interested.
 
So, you apply shellac and later (approx 20min as you said) you stain the half-dry shellac, not the accual wood??
Then later when it has dried you start the accual polishing, or am i wrong?

I found this link when i googled for "french polishing".
How to apply Shellac

I think it's kinda good and since there's probably going to be more people than me looking for it i thought that i should post it.
 
Morbo, if at all possible get a cheap pneumatic brad nailer, which will make box building a joy [not to mention installing house trim] and the sound they make is so satisfying. Screws are such a pain in comparison. Used with carpenters glue, you'll get boxes that go together easily, you use just enough brads to fixture the parts while the glue sets, they leave tiny holes, and they can only be dissassembled with a sledgehammer.:smash:

If you do use screws, make the pilot holes a bit larger so that you don't delaminate the plies when you drive screws, as the birch is not going to give as much around the screw as you're used to with mdf.
This splitting will be a major problem if it occurs near the ends of panels.
 
3/4 of the way there!

So, you apply shellac and later (approx 20min as you said) you stain the half-dry shellac, not the accual wood??

Hi KMJ!

The instructions as you said are correct. You stain the shellac which is dry to the touch in about 5 to 10 minutes depending on temperature and humidity. Then you stain the box as you would normally to enhance or change it's colour.

As for a top coat to protect the box I would not reccomend shellac as it is not very durable. It makes a great sealer but not a great top coat. Use either a good polyurethane or a good varnish. If you have spray facilities then a laquer is also possible.

Mark
 
Re: 3/4 of the way there!

mwmkravchenko said:


Hi KMJ!

The instructions as you said are correct. You stain the shellac which is dry to the touch in about 5 to 10 minutes depending on temperature and humidity. Then you stain the box as you would normally to enhance or change it's colour.

As for a top coat to protect the box I would not reccomend shellac as it is not very durable. It makes a great sealer but not a great top coat. Use either a good polyurethane or a good varnish. If you have spray facilities then a laquer is also possible.

Mark

Mark Thanks for the tip on using shellac.I use Antique Oil to protect the stain or a water base Polycrylic . By the way your in my neck of the woods.Im in the west-end of Ottawa.Pat.P
 
I looked at some work from an MDF shop who tried some birch plywood work. Their impression that birch plywood seems harder and does not cut as fast. The finished cut looked funny since each layer has different fiber orientation, if the cut is in the same direction as the fiber with less than 90 degrees angle, then the cut is smooth, if the cut is going opposit to the fiber direction, the cut is rough. Wonder what kind of filler one would use to fill the edge?
 
soongsc said:
I looked at some work from an MDF shop who tried some birch plywood work. Their impression that birch plywood seems harder and does not cut as fast. The finished cut looked funny since each layer has different fiber orientation, if the cut is in the same direction as the fiber with less than 90 degrees angle, then the cut is smooth, if the cut is going opposit to the fiber direction, the cut is rough. Wonder what kind of filler one would use to fill the edge?

Or you could maybe try to cut it with the proper tools and use no filler, eh?

Or if you like put tape over the cut and that should work also; if I understand you correctly and cutting perpendicular to the fiber direction refers to the surface layers.

Also, last time, Baltic birch is not necessarily harder than MDF. Baltic birch hardness I found at 1260 Janka and MDF was 1000-1600 for the ones I found.
 
Jimmy154 said:


Or you could maybe try to cut it with the proper tools and use no filler, eh?

Or if you like put tape over the cut and that should work also; if I understand you correctly and cutting perpendicular to the fiber direction refers to the surface layers.

It would be nice to not need a whole lot of filler, and none if possible.

Fiber directions refer to all layers. each layer gets furry depending on how the cutter ir moving. I somehow have the impression that faster spindle speed and slower moving speed would be necessary to get better results?
:confused:
 
Re: Re: Tips from the dark side

Jimmy154 said:
M.o.e of MDF is about 3950 N/mm^2

M.o.e of Birch 3700, 5000 N/mm^2 for a piece I found 18 mm in thickness and 13 plys. 3700 is perpendicular to facegrain, 5000 is parellel to facegrain (the less plys the greater the difference will be, I would imagine). So Birch has more so less the same stiffness as MDF; it is different depending on the orientation of the grain and the type of Birch plywood and MDF used (manufacturing process and what they're made of).

Hi Jimmy154, your findings are very interesting, especially when almost everyone agree on the fact that the MDF MOE is around 350 000 PSI and the Baltic Birch plywood MOE is around 1 800 000 PSI.

So most people say BB is five times stiffer and you're saying it's only 50% stiffer.

If you can do the testing again with a comparable piece of BB versus a comparable piece of MDF of the same thickness/size, I would like to have the results.

Thanks!
 
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