This article reprinted from Wood & Wood Products, August 1976

 

CONSULT JERRY METZ

1976 Editor's note: In this issue, woodworking consultant Jerry Metz kicks off a new monthly column designed to help readers solve their production and management problems.

 

We are using some softer woods, as well as more oak, and I know we are going to have some problems, especially with contract chairs. Screws just do not hold as they should, and if the least bit of failure appears we will have a product liability suit facing us. -- Mr. L.

Consider the boring first and make your fit just a trifle looser instead of tighter. Tight fits squeeze the glue out, whereas an easy fit allows more glue surface. Second, dip all screws in glue up to the shank. PV glue is especially good here.

 

We are dinette manufacturers and of late have had calls for large table leaves -- some as much as 18 inches wide. Our lack of success at keeping some of them straight and lining up with the table tops has us going crazy.-- Mr. H.

When working with plied material, all components -- core, crossband, face and back -- must be of even moisture content. The best result is obtained by using flakeboard for the core and simple five-ply construction with special attention to equal pull of face and back. If you must use a wood core, the core strips must be reversed before gluing and must not be over 1 1/2 inches wide.

Solids in this width are very difficult. Many use steel bands on the back, but even then, holding the boards perfectly straight in many climates is almost impossible to guarantee. My solution would be to make the boards of plied material, even if the tops must be solid.

 

We use planed 12/4 oak and maple and glue two pieces together under adequate pressure to get the strength and thickness desired. Many of the 1 2/4 pieces spring open slightly after gluing, giving us a hairline that is rejected. We have checked every detail and can find no answer. What do you suggest? -- Mr. G.

Providing your planing is perfect and your moisture content is between 5 1/2 and 6 percent, the remedy is quite simple. Just before glue application and pressing, lightly dampen the surfaces to be glued with plain, room temperature water. Be sure your press temperature and dwell are OK and I do believe your troubles are over.

 

We are making African mahogany five-ply panels on flakeboard and getting bleed-through of the glue on a great many runs. What causes this? -- Mr. H.

Mahogany and other heavily grained open-pore woods are subject to bleed if you use the same amount of extender and water that is normal for closed-pore species. The best solution is the cheapest in the long run. Cut the extender to a minimum or eliminate it completely and use a super thin coat of virtually non-extended glue. This means the adhesive costs go up, but the rejects are nil and the extra cost is offset somewhat by setting the spreader to a minimum thickness that you will determine by experiment.

 

We have been told we are adding expense to our sanding by roughing with 3-0 paper and then polishing with 5-0. We produce panels of walnut, oak, mahogany, cherry and maple and we have experimented with one good sanding using 4-0 without success. Also, we cut through too many edges with the 3-0 roughing. We need help. -- Mr. B.

You are among the many with this problem. Continue with the roughing and polishing on open-pore woods, but let up the pressure a bit as you hit the edges when using the stroke sander. Do not put any slightly bowed panels through a widebelt machine that is not designed to handle such irregularities. Your cherry and maple stock are to be sanded with 4-0 only, but in light, smooth strokes in the stroker and with minimum pressure in the widebelt. This requires an extra pass, but is definitely saving for these two species.

 

We lose too much stock from the top of our lumber piles due to weathering. We have tried a lot of remedies. Should we go to the expense of building an open shed to keep the air drying process out of the sun and rain? -- Mr. K.

I do not like open sheds unless the area has a great deal of air movement. Even then, uneven air drying and some "souring" is apt to take place. Placing old lumber or plywood on top of stacks is costly and not nearly as good as an investment in weatherproof tarps specially prepared for this purpose. They are made with rope grommets to enable you to tie them and are not lapped over the standard size bunks by more than a couple of inches to allow good circulation. Experience tells us that the top layers of the bunks do receive ample air and are consistent with the balances of the load.

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