Problem number one.
How about compatibility, quality of penetration and drying time? Today, with waterborne materials and various new top coatings, these things are very important. One coat slightly damp, a bit rushed or a little too heavy will lead to the inevitable check or crack. The same goes for sealers that do not penetrate properly. They dry on the surface and any expansion or contraction causes you-know-what. This also happens in painting and when using a topcoat over the paint.
The second problem deals with plant conditions. Almost every day I talk to someone who does not know the temperature or humidity in his plant. "It can be quite warm and we do have our damp periods," is a typical response. Some are somewhat aware of plant conditions, but lumber and panel storage -- well, those that have excess humidity can pay for rejects, but not for dehumidification. I just talked to a man who is having door problems. He is using particleboard cor and maple veneer for face and back, and a 40-inch door. The sad thing is that h does not meter for moisture content nor does he know the actual temperature or humidity in his plant.
There are some who do know and just hope for the best. If it's terribly dry, a few water barrels are a help. If it is a bit damp, close the windows, use those overhead fans and keep an eye on the humidistat. If this is so simple, why all the complaints? We just can't finish pieces that are overly dry or damp.
Still, there are other things we do that have been mentioned dozens of times, like removing glue squeezeout on joints before hardening. Those moisture pocket turn to gas after they are covered with finish and "pop" as a result.
All readers who still have these problems, please check if you are following th proper procedures. Be sure you check every board that is shipped to you "dry" and be just as careful if you do your own kiln drying. Much of the lumber today is green from the saw; watch out for any board that is slightly off. That board could be what we call "wild" and may have wet spots in another area and not the one you have metered. Get certificates from the mills that ship dried stock. Be sure it is as close as 6.5 percent moisture content for hardwoods as possible - not under 6 and over 7 for sure.
One more thing regarding finish. Several readers state that their finishing foremen are paid well and should know materials and procedures. We have many good foremen, but many have not used the latest techniques or materials and may run into new circumstances that create problems. None of them are so informed that a visit once a month with a top technical man would not be a profitable da for both the foreman and the company.
During sample time in furniture plants, that technician really pays. He introduces the latest in finishes, helps with the actual finish and follows up to the cutting to make sure everything is right on the money. Dry materials under the finish and correct materials and procedure in finish and we will lose the Number One headache. Plus, the rate of rejection will fall, cost will fall and hopefully, the only checking will be that which goes to the bank.
We have a chance to take over a plywood operation in a nearby town, about 40 minutes away. In your opinion, would it be best to move the equipment or just truck the production to our main plant? I await your reply because I differ wit management and I think that what you will say will be "IT." Our thanks. Mr. E.
The cost of moving is the least of it. Moving a hot press could get the platens out of line, etc., and what about the workers? The foreman? Would they move and at your expense? I would leave well enough alone and get over there a couple times a week. I hope this is the answer that you wanted.
Some time ago, you advised about having a good sandpaper outfit, one that would survey our plant, recommend changes, etc., and then would have a technician set us up to get better results. As a production manager, I was skeptical, but I must admit that not only did it work, but we have improved greatly at a lower cost. I must admit when I am wrong and I can tell others that it may take time to pick the right outfit, but boy does it pay! Mr. T.
I wish I could convince a few guys that need it, although many have joined the clan!
In gluing up two pieces of red oak, each 7/8 inch thick and 48 inches long and if they are exactly 7 percent moisture content, why should they warp? What do you make of this? Many thanks. Mr. L.
One piece could easily have stress from drying far greater than the other or dr faster if actually 7 percent moisture content. Please meter the pieces in questions every foot or so for the 48 inches. You may be surprised. Dressing down from 4/4 could give the piece more stress also.
What in the world is porco? I have never heard of it. Thanks. Mr. C.
Sorry, this is a term some mill has for local wood. This is not a proper name.
I sent you a diagram of chair construction. Please note that the rails are tenoned into the posts and front legs and the blocks also. This eliminates doweling. Can you advise on this and add to this for us? With our thanks. Mr. M
Frankly, I am in favor of doweling (double, spiral type) but I do like the tenoned blocking far better than screws. I would add a single screw through the center of the back blocks into the posts about 3/4 inch. This is a big help and very seldom done.
We have some panels that have a darkening in some areas. Can you tell from the sliver we sent? Thanks for telling us what this is and how to cure it. We thank you. Mr. Y.
This appears to be glue penetration. The spread was too heavy in places and the glue color was just enough to cause the dark look.
We are making door panels of red oak, 1 3/4 inch thick, two pieces glued to tha thickness, the doors being 20 by 44 inches. We must keep them straight. How? Thanks. Mr. G.
First of all, experiment. Make a few and hot and cold press them. The strips from the rip saw must be 3 inches and less, every other strip reversed end for end. We have mentioned this many times in past columns. Every strip must be right on the head for moisture content 6.5 to 7 percent and your plant conditions must be set to keep the units just that way. Again, try a few and check them out. Even if the work is perfect, I would judge that stress is going to show up and there will be some failures. Remember, no variations and careful stacking when you run them IF you are pleased with the experiments.
Note to readers: There is a lot of this sort of work going on. Be sure and follow the rules -- ask questions -- and stay out of trouble.
The questions we have concern moisture and humidity. What do you require for lumber and veneer that goes into furniture and what humidity should finished furniture be in -- home, office or otherwise? Thanks for all the past information. Mr. S.
Lumber and veneer going into furniture that is considered hardwood, should be 6.5 percent moisture, plus or minus 0.5 percent, allowing 4 percent more for softwood. Room temperature for the finished product is best at 60 F to 80 F. Well-made furniture will handle more temperature variations, considering that i is well finished on all surfaces. Sunlight can have fading result if the finish is not supported by a barrier.
Q In making curved panels for all purposes, I have heard that there are cores that actually bend. Have you heard of them and what can you tell us? Many thanks. We appreciate the service and the help. Mr. K.
A As far as I know to this point, the only bending core is one that is reasonably new. So far, it looks great. I have tested it and so far, so good. The information is attached.
Q I sent full details on our panel problems. We always made good, straight panels, not ones that caliper heavier at one end, etc. Do you suppose the cores are uneven or there is different hardness at one end? I am sure you have had this one before. Thanks. Mr. L.
A Get the press platens checked every six months. Have the source do it. I feel sure this is the problem.
Q We sent a small package of blocks that show pitch. Please examine them and tell us what the problem is and how to avoid it. Many thanks -- again. Ms. P.
A Note the end wood. This shows you that there is a strong sap in all the growt lines. That penetrates the surface. This comes from the ground and you have to blame the area. To avoid this, a stain- toner should be applied, not just a one coat clear finish.
Q The small panel that we sent Federal Express tells the story. Finish is comin off of the edges and the small cove cut in the moulding. Please tell us why and what we do now. Appreciate it! Mr. R.
A The softwood was very dry -- at least 5 percent low and had a lot of soft spots. The base seal coat was absorbed in these areas and the topcoat had no penetration. The captured air, as you know, forms a gas, and eventually, with change of temperature, pops the finish. Be sure that softwoods are on the button, be it 10 percent, 11 percent or 12 percent. And, make sure the base coa is good and dry before sealing. Any rough spots or edges should be gluesized before sanding. Any questions?
Q Please note the high spot in the small sample of moulding. What causes the finish to chip? The rest of the surface is perfect. I cannot understand why jus this small shape should do this. Please guide us here. Thanks. Mr. H.
A Look closely. Use a magnifier and you will see that the sanding is sub-par. There is little, if any, penetration of the seal coat and those little air bubbles are pockets that result in tiny explosions. I would glue-size the moulding before sanding and be sure the block that fits the mould pattern is perfect.
Q I am in charge of one of the larger furniture plants and I read your column every month with great interest. As a result, I have had success adhering to th "Metz Rules." I have received permission from my boss to get your opinion on something upon which he and I do not agree. I follow your method of preparing solid oak doors. We do not rip over 3 inches and we reverse every other ripping end for end. We take the rippings to the clamp carrier and glue into panels, removing the glue squeeze before it hardens. My boss says that we are wasting time and material ripping 3 inches and less and he can't see anything wrong wit stripping at 6 inches if the stock is at the correct moisture content. He also says that reversing the strips takes unnecessary time. He is not so insistent o glue removal, but he does not argue it either. He knows that you have super expertise, but claims that these rules are designed to keep those who do not have perfect drying out of trouble. Please help me out. Mr. E.
A I heartily stick to the "Rules." Even if the drying is perfect, stress comes from any taking on of moisture, or giving off during manufacture of finish, change of climatic conditions, placement in the finished product, even changes of humidity and temperature after assembly of the finished product. Glue remova is very important. Trapping of moisture under the glue squeezeout results in moisture turning into a gas that can easily cause checking. Good luck -- I hope you win.
Q Years ago, you wrote about a woman that became a chief inspector. We are abou to institute an inspection system similar to the one you outlined. I have a ver capable woman in mind. Do I give her the chance? Mr. T.
A After careful explanation of all details, your complete backing and constant encouragement -- YES!
Q Recently, we were put on a Foreman Incentive Plan. I am a mill room foreman and I understand you are the "founder" of the system. May I say that it works like a charm. I am more than satisfied, even if the extra time is needed to organize things. One thing I question is the time we must spend teaching and going to meetings. I don't mind a couple of hours a week, but so far we are running into several hours and management says that the bonus should be sufficient. What is your feeling? I read your column religiously and it is great. Mr. F.
A At first, and until the training cuts down, there are things that need discussion. The weaker the program was before the system, the more time it take at the start to get things running smoothly. I am sure management is well aware of this. To be sure, I will write and advise them. I am glad you are doing well Be set for each day, encourage your workers and go for quality as well as production. Good luck!
Q We are dimension manufacturers and we also make a line of bookcases that we sell through one connection. Our equipment is fair, nothing real new. We are going to work on increasing our volume and we need advice on adding new equipment. We know what to get first, but when? Do we set for the increase that we are promised or do we wait and worry along with that we have? Many thanks. Mr. K.
A I would get set, all but ordering the CNC unit we talked about. When you are sure about the increase, start slowly with the one machine and go from there. Keep in touch. We'll talk.
Q What ever happened to the safety program with annual awards that the furnitur association had years ago? It was great. Mr. C.
A I really don't know -- let's find out!
Q We finished a run of case goods in what we call "antique white." It is a very attractive, soft off-white finish, done in a special paint that we apply in one thin coat, do a bit of antique work and apply a flat topcoat of a lacquer made to work with the undercoat. We had several complaints of darkening, a sort of yellow to brownish color. You have a sample of this. Is one of the materials defective or did we do something incorrectly. Awaiting your kind reply. Mr. S.
A Whomever provided the topcoat should have used barrier to keep the pieces fre of UV discoloration. In your area, most of the homes are bright and sunny. I do believe the finishing material supplier should have alerted you to this possibility and frankly, I think the barrier should have been used knowing that the finish was a light, paint based job.
Q Well, you got me to use a moisture meter on my trips through the plant. I don't do it every time, but a lot anyway. As careful as we are, I found several boards a bit over or under the prescribed moisture content, even some "wild" boards, as you call them. Can't thank you enough. We are on it now from every angle to be sure and thanks again. Mr. D.
A If one wild board in every bunk is found, the moisture metering surely pays. If the boss finds it, all the better. If you don't think it makes a big difference, you are wrong.
Q You have the specs on our case construction. We can't raise the cost of materials and we want the cases to look as good as possible. This is asking a lot, but if anyone can do it, you can. We can't thank you enough for pulling us out of the finish disaster. Mr. H.
A Now that you have a decent finish, by all means get your designer to go over the hardware. What you are using may even cost more than a few numbers I have suggested. I would stop using staples on the back panels and go to brass finished drive screws. Watch your fit on drawers. Use dummy fronts at the case clamp. This will cut down on sanding for fit and give you a far better job.
Q We are thinking about increasing sales of bedroom furniture by making small chests with desk compartments, armoires with rollable TV storage, extra small lounge chairs with matching woods, waste baskets to match, etc. Please comment and many thanks. Mr. E.
A Have you checked this out with your designer and your pet accounts? Some of this may be OK, but I would check it all out. I think the coming thing is to make groups with ideas and innovation, but mainly, designed for the long haul, with pieces able to be added and removed as needed.
Q Thanks for all the help with my students. The use of the "rules" is really terrific. Mr. K.
A You are doing a great teaching job. Keep it up.
Q sent several blocks of wood trusting you can identify them. We get boards in shipments that are odd to say the least. I have told management, but this still continues. These are from a shipment of soft maple. Many thanks. Mr. S.
A I gather from your sample that some small mill is short on your orders and fills in with similar woods. If no one complains, they continue. I would complain to your purchasing people. The blocks are poplar except for the dark one which is far off from maple -- it is red oak.
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|Title Annotation:||Consult Jerry Metz; avoiding finishing problems|
|Publication:||Wood & Wood Products|
|Date:||Sep 1, 1994|
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