Is It Necessary to Sand Mouldings?

Sanding equipment for your moulding operation shouldn't be needed if knives are sharp and well balanced and the machine is well set up. September 5, 2006

Question
We have two five head moulders that do great but would like to go a little further with the quality. Do the fladder sanders on the end of a machine make that much a difference? I saw one on a 5 head Wadkin which was my competitor’s and was curious from that point on. I wasn’t comfortable asking him. The one I saw at the show was a 2 head top -one spinning clockwise one counter-clockwise. It was explained to me that one lifted the fibers opposite of the last top head on the moulder, and the other sander slicked it off. That makes sense, but the one I saw of my competitor’s was a single head. Do the two heads make that much difference? What type of head would you use or are you using? Which way would you spin it if you only had one head? Any particular rpm?

Forum Responses
(Architectural Woodworking Forum)
From contributor A:
The ultimate decision is yours. In my days around moulders and installations I have not seen a noticeable improvement in the quality of the mouldings. My thoughts would be more focused on sharp knives, hold down solutions, and the quality of steel used. You should have about 14-18 knife marks per inch on your products depending on your speed. I am assuming you are running a 6000 rpm and single knife finish @ 25-30 feet per minute. If you’re looking to get rid of the knife marks, the fladder is not your answer. If mouldings are run at the correct speed for knives finishing and the knives are sharp there should be no need for sanding. 14-18 knife marks per inch is acceptable standard in the industry. Just my thoughts - I am sure others will have more on this subject that I hope will help you decide.


From contributor B:
I agree with Russ. The only cause of chatter in moulding is an imbalance. This could be knives, heads, or even drive belts or pulleys. The belts seem to be a big cause. The use of a linked type belt seems to cure a lot of it. Use one belt rather than 2, 3 or 4. No two belts are the same. Multiple belts will fight each other and set up vibration in the head. If you grind your own knives, or even buy them, make sure they all weigh the same. I like them within 1/10th of 1 gram. A little grind on the outside edges is a good safe place to remove material. If you use bedboards, make sure they lay completely flat. A bedboard that isn't flat will cause bounce that results in gouges and tear-out. Only one or two thousands can cause vibration and produce chatter. You also need good dust and chip removal. Wood chips will collect behind the knives and also cause imbalance. You need a good, strong dust collector.

From contributor C:
I have a fladder sander and it isn't worth the money at all. I've had it for about 2 years and it has been used once to see how it works. I couldn't tell any difference on profiled or flat stock. Sharp knives and proper feed rates will do much better.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor D:
Any quality finish requires the wood to be sanded to at least 150 grit. We have a state of the art molder and sand all our woodwork before finishing. There is not a molder out there that can eliminate sanding no matter what is promised. For the runs over 500 feet we use a molding sander with hard shaped heads that spin to remove the knife marks. A fladder type sander is used after this. Sanding is a necessary evil that has to be done period if a finish of any quality is to be achieved. If there was a way around this I would have found it as the time to do this is significant as well as included in our bids. 32 years of trial and error have brought this conclusion.


Comment from contributor E:
Moulding sanders like Fladder and QuickWood sanders are used to break sharp edges, remove fibers from the surface and to make the staining come out more even. If you are trying to remove deep knife marks it’s not the right sander. To do that job you would need a profile sander where the profile wheel is the same shape as the moulding you are trying to sand. I have seen the brush sanders used in many shops as a finishing sander where to parts comes out very smooth and the profile is not changed. In some cases the machines are also used to remove very light knife marks but it’s not the norm.

Comment from contributor F:
We use such sanders to prolong the life of our knives to clean the rough edges on MDF profiles.

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