I am shaping parts for a three piece base moulding application that allows curving around each 1.5" radius jumbo bullnose cornerbead. I've devised a sound sliding fixture for the shaper, but can't seem to avoid burning. With such a small radius, I can't physically feed fast enough on the shaper to avoid burning, and nothing seems to help!
A) After processing, I cut the inside radius of 1.5" on the W&H with a convex knife set.
B) Next I cut a 3" radius rough profile with a quarter-round knife set (W&H again).
C) Bevel on T.S. completes the blank, which is held vertically in the sled, started against a starting pin and shaped on the weighted sled with bearing offset accounted for.
D) Part is cutoff on the table saw with a miter sled.
E) Part either burns horribly, or burns beyond very horribly.
On the upside, the parts aren't blown out (or blown up!) and are of perfect dimension/fit. I am using corrugated back knives of about 5" swing and a 4" rub collar. I have tried 3600, 5100 and 8000 rpms. When pushing as fast as I possibly can, the burning is minimized, but still too much to sand out. The species is cherry, and I'm afraid to attempt climb cutting freehand with this application. What is the next step?
(Architectural Woodworking Forum)
From contributor B:
The reduced cutterhead rpm speed, as you have tried, is the right direction to be going. Also, try a larger bearing for a first pass that leaves 1/32" to be removed with the final size bearing on a second pass. This might help.
Note... I made my templates, which comprise the base of the sled, out of Lexan. The rest of the sled is made of Corian, hickory and fiberglass. It has a "hopper" which is filled with lead shot for stability and reduced chatter.
I consider using a lathe (or a competent wood turner and his/her lathe) frequently, but lack all resources to carry this out. I'd love to try it sometime, and would further really love the time for the learning curve.
Accurately cutting machined wood parts from a turned product perplexes me. I'm aware you only get 3 90 degree parts from a turning due to kerf. Accurately cutting those is the challenge. Could anyone elaborate?
As I am challenged with 3" inside radius, 7 1/8th" 52/38 crown outside corners which will come up in about two weeks. I'm planning to rough on the table saw and hand scrape, but would be likely to try turning if I thought I had a snowball's chance at yielding precise results.