Jimmy154 said:
Tell me measurements and I will believe you.
These are samples I found:
MDF is 1000-1500 Janka and birch is about 1260, what else can I say? Janka is how many lbs. it takes to embed a .44" half-sphere into the wood.
I wish some one would believe me
I agree with you, good 18mm MDF easily outperforms finnish birch (Betula pubescens or betula pendula)in hardness. But slow-grown Rowan(Sorbus aucuparia) is a different beast
I am more or less the oppisite of an expert, so my mistake, could you tell me what is the reasons than?
Send me your adress and I send you two samples:
1) MDF as it is available in many of the shops here in the Netherlands.
2) The Fins Baltic birch I use (and from my knowledge still isn't the best available tho it comes close).
Mvg Johan
Yes and no
Luan is a mahogany want to be. It is devilishly difficult to stain evenly and requires all the tricks of the trade. It can be made into a good quality plywood. Many thinner plywoods that are sold in North america have a luan base. It is not as strong as birch but a close second. I have used it in 1/4" ( 6 mm ) 1/2" ( 12 mm ) and 3/4" ( 18mm ) and it was heavy and very solid. I liked it. If it was available in 1mm ply sheets it would be very comparable.
Mark
Luan is a mahogany want to be. It is devilishly difficult to stain evenly and requires all the tricks of the trade. It can be made into a good quality plywood. Many thinner plywoods that are sold in North america have a luan base. It is not as strong as birch but a close second. I have used it in 1/4" ( 6 mm ) 1/2" ( 12 mm ) and 3/4" ( 18mm ) and it was heavy and very solid. I liked it. If it was available in 1mm ply sheets it would be very comparable.
Mark
Wow this really took off! I appreciate all the tips, but just to clarify;
1. I already have BBply panels cut and ready to go, so no need to convince me to use MDF instead
2. I generally use clamps & glue, havent found the need or benefit of screwing as well, though maybe that will be different with BB. I only use screws to mount drivers and such.
3. Interesting discussion on 'hardness' of MDF vs. BB. I would like to point out that I've seen several types of MDF, some coarser, some finer, some lighter, some darker, etc. I'm sure BB is the same. Also, lots of people are using the term 'hardness'... is this the same as stiffness?
1. I already have BBply panels cut and ready to go, so no need to convince me to use MDF instead
2. I generally use clamps & glue, havent found the need or benefit of screwing as well, though maybe that will be different with BB. I only use screws to mount drivers and such.
3. Interesting discussion on 'hardness' of MDF vs. BB. I would like to point out that I've seen several types of MDF, some coarser, some finer, some lighter, some darker, etc. I'm sure BB is the same. Also, lots of people are using the term 'hardness'... is this the same as stiffness?
All pedantry aside,
the original question was:
a few thoughts
1) For either type of material, you want to use the highest quality tooling possible, and freshly sharpened. Either will burn if tooling is dull, or stalled during cuts. You'll get the smoothest edges with fast cutter speed (i.e. knife cuts per minute) and slow feed rate. Baltic birch definitely requires slower and consistant feed rates to avoid splintering and burning.
2) Precision joinery and modern adhesives can preclude the need for mechanical fasteners (screws or even brads) in the assembly of speaker cabinets, but then you need to wait for the glue to fully cure. Many commercial speaker boxes are assembled using folded v-groove joints and hot melt or RF cured glues.
It's been my personal experience that 13ply baltic birch strips less readily than MDF, but both should be pilot drilled to the shank diameter of screws; use "Lo-Root" screws.
If you're looking to stain the raw face veener on birch ply - good luck! Actually a natural lacquer, shellac or varnish can look quite acceptable and only require a smooth sanding to about 220G; but darker stains or oil finishes will almost certainly require seal coat.
3) Dust and shavings from MDF is not only just a nuisance, but a significan health hazard. (so is dropping a 90lb sheet of MDF on your foot)
4) All plywood, particle board and MDF sheet goods are man made products, thus subject to a wide range of specifications, qualifications and misinterpretations.
6) It's the high number of cross laminations and quality of adhesives and pressing/curing that gives "baltic" or "euro" type birch the higher degree of stiffness vs MDF, PB, or even lower grades of plywood.
5) At a recent speaker builders get together, we attempted to answer the MDF vs Baltic Birch question by comparison of two dissimilar twins. (i.e. CSS FR125/WR125 bipole MLTL) Guess what, there was no absolute consensus - everyone "heard" or described something different.
My own taste is definitely for the baltic birch
the original question was:
morbo said:
a few thoughts
1) For either type of material, you want to use the highest quality tooling possible, and freshly sharpened. Either will burn if tooling is dull, or stalled during cuts. You'll get the smoothest edges with fast cutter speed (i.e. knife cuts per minute) and slow feed rate. Baltic birch definitely requires slower and consistant feed rates to avoid splintering and burning.
2) Precision joinery and modern adhesives can preclude the need for mechanical fasteners (screws or even brads) in the assembly of speaker cabinets, but then you need to wait for the glue to fully cure. Many commercial speaker boxes are assembled using folded v-groove joints and hot melt or RF cured glues.
It's been my personal experience that 13ply baltic birch strips less readily than MDF, but both should be pilot drilled to the shank diameter of screws; use "Lo-Root" screws.
If you're looking to stain the raw face veener on birch ply - good luck! Actually a natural lacquer, shellac or varnish can look quite acceptable and only require a smooth sanding to about 220G; but darker stains or oil finishes will almost certainly require seal coat.
3) Dust and shavings from MDF is not only just a nuisance, but a significan health hazard. (so is dropping a 90lb sheet of MDF on your foot)
4) All plywood, particle board and MDF sheet goods are man made products, thus subject to a wide range of specifications, qualifications and misinterpretations.
6) It's the high number of cross laminations and quality of adhesives and pressing/curing that gives "baltic" or "euro" type birch the higher degree of stiffness vs MDF, PB, or even lower grades of plywood.
5) At a recent speaker builders get together, we attempted to answer the MDF vs Baltic Birch question by comparison of two dissimilar twins. (i.e. CSS FR125/WR125 bipole MLTL) Guess what, there was no absolute consensus - everyone "heard" or described something different.
My own taste is definitely for the baltic birch
more bs from chrisb
well done
If you're patient enough to wait for the glue to cure, that's great. I actually like to use T-nuts and machine screws for mounting drivers (M4 for smaller drivers, and M6 or 8 for larger) - provided you've got enough mounting margin. Unfortunately many driver flanges are way too narrow.
hardness -
a)"the cohesion of the particles on the surface of a mineral as determined by its capacity to scratch another surface or be itself scratched "
b) "resistance of metal to indentation under a static load or to scratching"
stiff(ness):
1a) "not easily bent"
syn. Rigid : applies to something so stiff that it cannot be bent without breaking"
Try breaking a 3/4" x 4" strip of MDF over your knee, then try the same with BB. No, actually please don't
That's the difference between "hard" and "stiff"
morbo said:
well done
If you're patient enough to wait for the glue to cure, that's great. I actually like to use T-nuts and machine screws for mounting drivers (M4 for smaller drivers, and M6 or 8 for larger) - provided you've got enough mounting margin. Unfortunately many driver flanges are way too narrow.
hardness -
a)"the cohesion of the particles on the surface of a mineral as determined by its capacity to scratch another surface or be itself scratched "
b) "resistance of metal to indentation under a static load or to scratching"
stiff(ness):
1a) "not easily bent"
syn. Rigid : applies to something so stiff that it cannot be bent without breaking"
Try breaking a 3/4" x 4" strip of MDF over your knee, then try the same with BB. No, actually please don't
That's the difference between "hard" and "stiff"
Feed Speeds,etc
With respect to hand feeding with a router, it is largley a matter of developing a "feel" for how the router performs-the sound of the motor, and the quality of finish on the cut material. YOu want to maintain a constant "chipload" on the router bit. One key factor is to avoid always stopping in the middle of a cut. At 20,000 rpm, the cutting face of the carbide simply burnishes the edge of the material, creating a LOT of heat, and hence the burning... IF you have some experience, I would suggest "climb cutting" the material on the first pass- moving the router in the same direction as the direction of rotation of the router bit. This can be a SCARY experience at first, as the the router wants to run away on you -and from your control. Try it on a piece of scrap first. The advantage to doing this is that the bit pushes all the waster material behind it as it cuts, keeping the cutting edge clear of waste, and does not "plow" the material as it does when conventional cutting. Climb cutting is frequently done on CNC gear and when using power feeders. It offers much better finish on solid woods, where it is used most often..
Bruce
With respect to hand feeding with a router, it is largley a matter of developing a "feel" for how the router performs-the sound of the motor, and the quality of finish on the cut material. YOu want to maintain a constant "chipload" on the router bit. One key factor is to avoid always stopping in the middle of a cut. At 20,000 rpm, the cutting face of the carbide simply burnishes the edge of the material, creating a LOT of heat, and hence the burning... IF you have some experience, I would suggest "climb cutting" the material on the first pass- moving the router in the same direction as the direction of rotation of the router bit. This can be a SCARY experience at first, as the the router wants to run away on you -and from your control. Try it on a piece of scrap first. The advantage to doing this is that the bit pushes all the waster material behind it as it cuts, keeping the cutting edge clear of waste, and does not "plow" the material as it does when conventional cutting. Climb cutting is frequently done on CNC gear and when using power feeders. It offers much better finish on solid woods, where it is used most often..
Bruce
Bruce
Now don't be givin away all the dark secrets of the craft now
It's not all that bad with a router and a 1/2" bit. You just have to be understanding of the forces involved and the potential reations that the router will come up with. A firm hold on the machine and firmly flexed arms will keep it behaving.
Mark
Now don't be givin away all the dark secrets of the craft now
It's not all that bad with a router and a 1/2" bit. You just have to be understanding of the forces involved and the potential reations that the router will come up with. A firm hold on the machine and firmly flexed arms will keep it behaving.
Mark
mzzj said:But slow-grown Rowan(Sorbus aucuparia) is a different beast
Yes slow growth makes huge difference in hardness, stiffness, density. Also age of tree is very important to growth and quality of the wood and let's not forget genetics. We make the same point I feel. There is a lot to consider with MDF and probably more with plywood. Making statements like baltic birch plywood is stiffer or harder (esspecially harder) than MDF aren't always true. For example: if I went down to local lumber yard and bought a piece of MDF at $20 and piece of birch plywood for $45 I suspect there is very good chance that the birch plywood would not be as stiff perpendicular to the grain as MDF from the one Birch Plywood spec sheet I saw. Also not as hard or dense. I could probalbly preform my own crude hardness tests, maybe in the store even
save some money.Also I should say that rated specs for plywood and MDF are different. Plywood made from low quality timber (maybe has lots of knots or tension/compression wood or other things?) would be underrated I suspect, just like lumber because you cannot predict as acturately how a non-uniform piece of wood will preform. I'm not sure about this though, I'm starting to speculate now and I sound like some of the people here.
Rademakers said:
Well that can be your opinion why you think plywood sheets are oriented 90 degrees to an adjacent sheet. Me, I'm not sure whether uniform stiffness of plywood is mostly an advantage or disadvantage. I can speculate that the plywood not splitting when putting nails or screws threw it would be more of an advantage. But I would not say even this clearly advantageous property of not splitting is the reason they orient the sheets the way they do; maybe one of the reasons. The major reason IMVHO for the orientation and definately for the odd number of sheets is http://www.woodbin.com/ref/wood/shrinkage.htm
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