Avoiding Tear-Out with Very Small Mouldings

Thin stock chatters going through the moulder or shaper, which can cause major tear-out. Here's advice on ways to overcome the problem. March 4, 2009

I have a Woodmaster 718 and am trying to make a small shelf edge moulding (WM137). I have the blanks planed to 3/8"highX7/8"wide. Every time I try to send one through, I get massive tearout and sometimes it just shreds the boards (oak, maple, cherry). Has anyone had similar problems like this?

I've gone through and made sure the bed is flat but I am using the poly bed. I know I must be getting some type of lifting to get the tearout. I am using a 3/8" shim under the board to be moulded to bring it up so the rollers clear.

I've seen other posts saying the poly bed could be the problem but this is the first I've seen it. If I run a 3/4highX7/8wide board it seems to run fine. Any help would be appreciated.

Forum Responses
(Solid Wood Machining Forum)
From contributor A:
Run a 3/4" blank then rip it to thickness on the tablesaw.

From the original questioner:
I was trying to avoid that but with all the wood I'm wasting, I would have been done with it by now.

From contributor B:

The wood is so thin at 3/8" that it is chattering up and down directly below the cutter head. You can solve the problem if you can find a way to keep it on the table. One option would be an out feed side "tunnel" that prevents the profiled piece from lifting upward.

From the original questioner:
It does have an outfeed roller but I'm guessing you are saying a tunnel that would hold it down just as close to the cutterhead as possible. I might be able to run something across the fence boards with some type of featherboard attached.

From contributor B:
That is exactly the idea. The cutterhead on that machine must be something on the order of a 2 1/2" to 3" diameter swing including the knife projection. That puts the feed rollers several inches away from the low point of the knife swing.

Just picture the thin strip being held by the infeed and outfeed rollers, but not held down anywhere in between. More or less in the center of that space is the massive (compared to the 3/8" thick wood) head/knives setup spinning at around 5000 rpm. Just imagine the forces and air currents pulling on that little strip of wood!

You probably should make a complete MDF or particle board sub-base assembly for this moulding. Use something like 1/4" plywood wood fences that run the full length of the board (which covers your infeed and outfeed tables as well) on both side of the moulding. Then between the cutter head and the feed rollers put small pressure plate like wood blocks to hold the mouldings down.

Make sure all hardware clears the knives by at least a couple inches. No steel – brass, screws or even better, plastic nails. Then use the highest quality safety glasses you have "just in case". In situations like this I'll put on a full face shield over my shop glasses. Plus I'll try to stay out of the direct line of fire of the machine to be double safe.

From contributor F:
I run moldings on planer type molders too. I just want to toss out the suggestion that sometimes I think you can be money ahead to run very small profiles with a router bit in a decent router table with hold-downs and hold-ins. I personally have had trouble getting cove moldings to feed well on a planer molder, just not enough feed surface for the outfeed roller to grip. I won’t waste wood or time by making oversized blanks to be further machined after molding. I just use a good quality router bit instead.

From the original questioner:
I did get the trim made by making the moulding on a 3/4X3/4 and then cutting the waste off using the gang rip blade that came with it and using guides on both sides. It came out nice. Thanks to all for the suggestions.

From contributor S:
We run small mouldings on our Weinig Unimat Gold 6 Head Moulder. My moulder operator does not like running small mouldings but with patience and the proper setup they can be made and come out perfect. Patience is the key.