We've recently purchased a door making machine similar to the Unique 250. It makes all parts of a raised panel door. Is there a particular cutter design that works well when shaping the arched (cathedral) header of a raised panel door? What we are using now tends to give a less-than-perfect cut with frequent tear out and a bit of roughness as the cutter is heading out of the arch. I know the ideal solution is counter rotating cutters and coming in from each end, but this is not an option right now. What about hook and shear angle or number of wings? We currently have a 4" Royce, 3 wing, one piece insert cutter for making this cut and the Royce people tell me I am dulling the tool after 2 or 3 cuts because we are feeding too slow. The machine turns at 9000 rpm (a little fast) and we can only feed at 6 - 10 fpm because we need to follow a template. They tell me I need to feed at 60 fpm. Anyone using a Unique 250 or a Panel Crafter type setup knows this is impossible. Any advice as to a cutter design to give the cleanest, smoothest cut possible?
From contributor L:
Try to figure out your rotational speed and feed speeds so you get about 30 to no more than 60 knife marks/inch. 8'/m*12=96*45=4320/3wings=1400rpm. It seems like even 3,000 rpm would be a great improvement. So 9,000 rpm looks like it is making way too small of a chip to carry away the heat and the tool is doing more rubbing than cutting! Heat dulls tools! Before a cutting tool actually starts to cut, it compresses the wood fibers some. The compressed wood fibers later absorb moisture from the air and they cause the surface to feel crummy (technical term!). The fiber raise can occur after finishing so the sanding often doesn't take it all out. You will get less of this affect by increasing the chip thickness.
If the motor on your machine is inverter rated, that may be an easy but not cheap fix. That way you could easily change the speed for the process. Variable speed pulley? Multi step pulley?
Also check the tool to see if it has side clearance built in the tool itself. This will help the knife disperse the wood chip through that avenue and will keep the heat from building up. Typical 5 degree side clearance would be normal. It makes a world of difference. Anything from 60-90 degrees incline in the tool should have some side clearance.
1. Reduce the number of wings to two. This will create larger chips at the same speeds.
2. Have your cutters made with alloy tips. Alloy materials start out sharper than any carbides. They are a high temperature cutting material that can handle heat far better than carbides.
Changing the hook angles and shear angles will probably not help very much. I do have to agree with the previous postings, though - you need to slow the RPMs a bit.
Contributor R, they tell me that 8000 rpm is still much too fast for a slow feed rate. They say it will quickly dull your cutters. I'd be curious to see how you make out.
Like contributor T, another person tells me that cutter design is likely not the solution. They say the proper rpm's for 8 fpm would be 1500. I can't grasp that one. Have any of you cut anything on a shaper at 1500 rpm? I plan on getting an inverter installed and playing around with the rpm's to see what happens. While we are on the subject, I discovered something else. When I make a straight stick cut on this machine at 8 fpm and 7000 rpm's, I tend to get knife marks (scalloping) along the length of the cut. Would dull cutters cause this?
I do know a local door shop that builds 500-750 doors a week and he told me he switched to diamond cutters and was not sure how long they were going to last. When he told me that he had been running them for over 2 years, he said they where cutting just like the day he put them on. He told me cost was 1K plus per cutter. I would think that someone would custom build diamond inserts for insert heads at a fraction of that cost.