I just received FWW 194 in the mail. The article "Get Serious About Clamping" attempts to tell us that we are all underclamping our work. While Roman Rabeij chose not to "blind us with the science" he makes the assertion that we really ought to have 1200 lbs/sq inch of clamping force to glue together flatsawn sugar maple. That was not even the optimal number, that's his recommended number. Please please please, just show us the graph with the sweet spot of glue joint failure to clamps required.
My main bench is 3 inches thick and about 6 feet long. Am I going to have to scrap my bench because I did not apply 259,000 lbs of pressure when assembling those laminations? I have a pretty decent clamp collection and I think I could get about 15% of the way there with about every clamp I own (those fancy bessy's are only good for 370 lbs of squish y'know).
*** as an asside, he claims that het gets more clamping pressure (470 lbs.) out of a quick-grip clamp than a parallel jaw (Cabinet Master/Bessy)) clamp. I find that a bit hard to swallow.
My take on the article, on the whole, was that his uncited "science" does not jive with my practical experience. I have never had a glue joint failure that could not be attributed to sloppy joinery :-}. Rabeij's conclusion is akin to saying that we should all drive a $259K Bently because Bently can make a better sedan than Honda.
Sounds like I've been doing it wrong all these years, yet not a single piece has fallen apart do to a bad glue up. I drive a truck--it can haul a lot more wood than a Bently. Find it hard to believe FWW would have such an article.
) reveals that the recommended clamping pressure range is 100-247 psi, with further notes that this depends not only on the density of the wood but also on the viscosity of the adhesive and the quality of the surface, and that too thin a glue line is as bad as too thick, with an optimal thickness of .003-.006 inches.
Now it might be that he's bonding with some ancient almost-dried-out Titebond that gives him a good glue line at the pressures that he's using or it might be that he has access to some newer research or it might be that he's full of crap.
Personally though, given the choice between Forest Products Laboratories and the unsupported opinion of some unknown art professor, I'll take FPL.
The article is pretty lame, I just skimmed it. I agree w/ nailshooter's comment above that FWW articles/editing have slipped drastically recently. They have apparently been unable to replace the first generation writers of the class of Tage Frid, et al. with anybody approach their combination of skill and writing and in large part seem to be reliant on submitted articles from wanna-be-published's for content. They also made conscious editorial change to put in much higher percentage of stuff for newcomers which has probably increased circulation at the cost of lower level of article.
Speaking of lame articles, there was a response to some of the criticism of the bandsaw evaluation article that was also extremely lame (the response as well as the article :) ). A Rikon rep went by and saw the setup after the fact apparently and pointed out they reproduced the rip test w/ drastically faster results.
The rebuttal was that while the FWW article mis-identified the blade used for their tests as a hook-tooth when in fact it was a skip-tooth blade they stood by the relative rankings of their testing with still nary a word to justify the gross discrepancies.
WMH wrote in to affirm the earlier information I found in trying to dig out any possible reasons for the discrepances of there being an alignment problem with the riser kits for the Jet and Powermatic saws which caused the alignment "issues" for which there is tech support to resolve.
Overall, it's getting where except for the eye candy of the user work in Readers' Gallery and an occasional article it's surely losing its value. I've subscribed since about Vol 2, but if it weren't for that longtime inertia doubt would any longer...
I thought the article last month saying that yellow glue was stronger than epoxy or poly in gap filling was pretty stupid. Maybe it has changed to being a humor magazine.
I've mentioned before the obvious lameness of some of the "methods of work" and "tips and tricks" in woodworking magazines in general the past few years. Also noteworthy is the general increase in contentiousness of "letter's to the editor's" in these same magazines since the advent of inclusion of "e-mail".
Macrocosm reflecting the microcosm (the general 'dumbing down')? ... probably not too far off the mark.
Franklin recommends 175-250psi for Titebond III on hardwoods.
I know a local maker of bass guitars that uses a 20-ton steel press for gluing up laminated body blanks. He uses custom-made 1-inch thick steel plates top and bottom because weaker materials kept bending.
Of course you can get very acceptable joints with much less pressure than this, especially if your mating surfaces are well machined and in good condition.
I agree with everything said. I consider myself a beginning woodworker and look to FWW and other sources for expert and trustworthy advice.
The "trustworthy" part is very important. What happens when something is published that I know enough about to know is wrong, is that it then casts suspicion on everything else that is published that I don't know anything about.
Even as a beginner I'm seeing the "dumbing down" and repetition of content. Handcut dovetails have pretty much been covered before haven't they?
And another time that is really pissing me off is this trend of having "additional content" on a website. (At extra cost, of course.) I'm in the country with no available broadband, so subscribing to get video feeds is out of the question. That's why I want a paper copy, but somehow I don't think FWW or FHB is listening to me.
This is what happens when you let journalists pretend to be experts. It also happened to American Woodworker when Reader's Digest took over. Out with all the old experts and in with a bunch of journalists. The difference with FWW is that it's been happening slowly, over a long period of time (since the early 90's). It happened all at once with AW. None of the magazines want real (educated) technical expertise - not even if it is offered for free. I'm sure the journalists are making that call too. You can expect this to continue until one magazine suddenly realizes that they can make money by providing correct, technically accurate, useful info.
I registered on the Taunton web site so that I could read their forums. BIG mistake. Now I get spam from them every day. I think I've seen 200-300 "Last chance for free shipping" messages (how many "last" chances can one get?). So, I guess the MBAs have taken over the marketing department too.
Same here on the broadband unavailability and ticked off about added-cost web sites. Of course, the Taunton site was always so slow as to be essentially unusable anyway, so it's not like we really lost anything except the potential... :(
As last followup on the gluing clamping force article --
I looked for the corroborating science behind Dr. Rabiej's article on his web site --
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only published articles on glueline strength all have to do with laser-cut materials, not normal shop panel glueups. Under those conditions, I could _perhaps_ believe something differing from previous experience, but it's simply ridiculous to publish an article as was done that so much flies in the face of experience without at least a reference to the science behind the work claimed to support the conclusions.
These are typical research projects found above, none of which could I find actual articles online for...
Optimizing Glueline Strength of Laser-Cut Hardwoods. Funded by the United States Department of Agriculture.
Factors Affecting the Magnitude of Glueline Shear Strength Between Veneering and Particleboard Substrate. Funded by Karona, Inc. in Grand Rapids, MI.
Gluability of Wood on a Laser-Cut Kerf. Proceedings of the Second International Conference on Automated Lumber Processing Systems and Laser Machining of Wood. MSU. June 1994.
Factors Affecting the Load Bearing Capacity of MOD-EEZ Connectors. Forest Products Journal, 43(9):49-57, 1993.
Glueline Shear Strength of Laser-Cut Wood. Forest Products Journal
43(2):45-54, 1993.
The Effect of Clamping Pressure and Orthotropic Wood Structure on the Strength of Glued Bonds, Wood and Fiber Science Vol. 24, No. 3, July 1992.
One assumes that the last might have the basis for much in the article.
Well, the text of the article is protected content, but the abstract is available.
R. J. Rabiej, Associate Professor1, H. D. Behm, Professor and Chairman
Department of Engineering Technology College of Engineering and Applied Sciences, Western Michigan University, Kalamazoo, MI 49008 Abstract
Reference values for compression strength perpendicular to the grain were determined for radial and tangential sections of samples of sugar maple and ponderosa pine. Samples to be glued were matched according to specific gravity and orthotropic structure and bonded along the grain in tangential or radial sections. Magnitude of clamp pressure was controlled throughout a range of pressures commonly applied in industry, up to about 80% of the compression strength of the wood sample. Tests were conducted on the bonded samples to determine glueline shear strength and percent of wood failure at the bonded surfaces. Results were subjected to regression analysis to ascertain relationships. It was determined that clamping pressure had a different effect on both shear strength and percent of wood failure depending on species and orthotropic section. It is possible to maximize joint strength by applying proper clamping pressure. Results similar in direction but differing in magnitude were obtained with both PVAc and U-F adhesives. A generalized measure of clamping pressure was defined as the ratio of applied clamping pressure to the compression strength (CP/CS) of the wood section to be glued. Using this concept, the optimum clamping pressure for sugar maple was found to be 0.3 times compression strength using U-F glue and 0.5 times using PVAc glue. This approach to determining reliable clamping pressure data can lead to improved gluing practice and more precise testing procedures.
\endquote
So, using the data from FPL at , the compression strength for dry sugar maple perpendicular to the grain direction is 1470 psi. Half of that would be 735 psi for his optimum by my reckoning. That's at least in the ballpark of his table values so guess the paper probably does form the basis for the article.
How applicable it is to "ordinary" woodworking and, most interestingly, how "peaked" is the maximum of his regression curve and what other factors were controlled (and not controlled) would be of interest and necessary to know something of in order to judge if there's anything in the article pertinent to typical work of the type done by FWW's readership.
I seriously doubt there's much work been done by the past masters that seems to have survived quite nicely that had anything even remotely approaching those kinds of clamping pressures. And, interestingly enough, later on in the same issue there's an article that extolls the use of the old wooden screw clamp (w/ whose flavor I'm quite consonant, btw).... :)
Well, in this case the author is actually a PhD in Industrial Technology specializing in furniture manufacturing technology it appears. See my earlier response.
It appears there is some actual basis for the claims made, what isn't possible to determine from the article is the applicability of the research to the task at hand...
Fri, Oct 5, 2007, 6:43am snipped-for-privacy@primelink1.net (C=A0&=A0S) doth posteth: While Roman Rabeij chose not to "blind us with the science" he makes the assertion that we really ought to have 1200 lbs/sq inch of clamping force What say you?
Sounds like he can't blind anyone with is "science", so he's trying to baffle with bullshit.
The other day I glued two pieces of wood, making a specialized, quicky, one-time use, planer sled. The top piece kept tipping, so I used a few pound lead weight on it, to hold it in place. Titebond II, as usual, and if I'd wanted to part the joint the next day, I'd have had to saw it apart, or beat it with a hammer. If it hadn't tipped, I'd probably still have used a weight, because, while the joint would have held (for sure stronger than the wood), I've found that sometimes the top piece will creep a bit without. Most of the time I clamp, or heavier weight, but I'd say probably seldom, if ever, anywhere near even
200 pounds pressure.
JOAT "I'm an Igor, thur. We don't athk quethtionth." "Really? Why not?" "I don't know, thur. I didn't athk."
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