Rip First, Or Sand First?

      For an oak laminating shop, economy, efficiency and safety are all factors. April 10, 2005

Question
I am in the oak laminating business. I need to know which is the safest method that will yield the most, with the least amount of downtime - sanding oak planks before ripping them, or ripping oak planks before sanding them?

Forum Responses
(Solid Wood Machining Forum)
From contributor A:
Because the ripped strips will have splits, cracks and loose knots in them, and because abrasive belts do not like sharp objects, sanding strips is not good option. You will be changing a lot of belts.



From contributor B:
Have you tried ripping, planing out the saw marks, laminating, planing to 1/16 of finished size and then sanding to finished size? That is how I've always done it, unless you're getting a clean enough edge to glue from your rip blade - then glue up, plane and sand. If you have no planer, just sand to finished size. If you decide to sand and are using an overhead sander try feeding your material with any sharp points facing the opposite direction that you're feeding the sander.


From Dr. Gene Wengert, technical advisor Sawing and Drying Forum:
Because a wider piece, especially oak, will have more cup full width than if it is ripped, even if the ripping is on the edges so that the piece is still quite wide, you will find it is easier to rip and then sand to the required thickness before laminating. It is difficult to sand short pieces, especially if high stock removal is used. With high stock removal, the process would likely be called abrasive planing. Abrasive planing after ripping is the standard for the flooring industry. They have no problem sanding narrow strips.

Regarding the yield issue, ripping first will produce higher yields in most cases, especially if you rotate the pieces 90 degrees before laminating. In this case, the thickness of the strips becomes the width of the panel.



From contributor A:
Everything every one has said here has merit to it, but the discussion has not gone far enough.

The proper way to manufacture wood products is to surface plane the lumber after drying and before any subsequent operations. This makes the detection of defects easier. But there are other reasons as well.

Ripping lumber with wide thickness variation is a leading cause of kickback accidents, whether the rip saw is a straight line or a gang.

If you are using a gang rip saw, you need to be aware that no gang saw manufacturer that I know of will guarantee a glue joint unless the lumber has first been surfaced to a uniform thickness.

Someone made the point that yield will be improved if the lumber is ripped first. If the lumber is ripped in long lengths before it is defected and cut to length, there will be a significant increase in yield. However, if your plant layout and your equipment available requires that the lumber be cut to length before it is ripped, ripping before planing will not give you any significant increase in yield. Today's lumber is so narrow that the cup is not significant enough to warrant going through the pain this process will cause because at this point, you now have many small pieces, both short and narrow, all varying in thickness.

How are you going to surface them? One at a time? It will take forever. Side by side through your sander? A kickback nightmare.

Ripping into long strips before planing is regularly done in strip flooring plants because they run everything through the side matcher and edge gluing is not a requirement. When edge gluing is required, this is not recommended.

When using any type of abrasive planer or sander, feeding strips side by side of varying thickness is an invitation to disaster; death by kickback. A heavy planer is much better for this because of the differences in construction, but even with these machines there are limitations and cautions to be observed if one wants to live a long life.

Surface your lumber first and then process it.

Because you do not mention a knife planer, I am assuming that you do not have one. If you do have a knife planer, it will surface rough lumber at a much lower cost and at a greater production rate.



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