Running Dowels on a Moulder
A discussion of moulder set-up for dowel machining, and on improving the tolerances of the finished product. December 6, 2009
Question
We just received 1500 LF of softwood dowels run by our regular molding shop. The were speced at 1.375". We could use pieces a little over or even under. The dowels came in at 1.337 x 1.232" They are out of round by up to .090"! I need to drill them multiple times on 8 quadrants (sides), so the diameter and the roundness is important. The molder rep said dowels are never perfect. I think we need to shop around. Any thoughts would be appreciated.
Forum Responses
(Solid Wood Machining Forum)
From contributor M:
Full rounds on a conventional moulder are a pain and quite difficult to get perfect, if not impossible. I would agree 90 thou is reaching the limits. There are shops out there with machines designed just for the purpose of making full rounds, however the finish tends to be a little rougher.
From contributor R:
1 3/8" dowels can be produced on a conventional moulder if the template and knife design is correct. Most people think they can run full round with two sets of knives, and they can get close. But if the design is made so it takes 4 sets of knives, then you get a much better finished product and the product does not have a chance to float as much, plus the knives can be resharpened easier. Designs that are of the 2 sets of knives have 90 degrees at the blend area and that is a big no-no in our industry, because you can't resharpen them correctly and your bedplates, fences, pressure shoes and chip breakers are further away from the point of machining, thus leading to snipe, wood movement and the kinds of problem you explain. Have them try it with 4 sets of knives and you will see the difference.
From contributor O:
"The molder rep said dowels are never perfect."
I'm sure the molder rep would have accepted that excuse from the technician who installed his machine when it was new... Not!
From contributor L:
We run dowels on the moulder. On the larger sizes our dowels may be up to .010 out of round, the smaller ones being only .005. Dowels are a bit of a specialty, but certainly possible on a moulder with the right tooling, etc.
From contributor J:
Make sure you use a profile hold down shoe while doing this, especially if they are in multiples.
