Troubleshooting Shaper Tearout

      Solutions for a tearout problem include slower feed speeds, climb cutting, and larger-diameter tooling. April 5, 2007

I have a Bridgewood AP-44 2 speed, 4 tire, 1hp power feed on my Delta 3 hp spindle shaper. Most of my cutters are 3/4" spindle, most are Freeborn. When running cutters with small detail edges, like sticking cutters, I get a lot of tearout on the smaller edges. I am running my machine at 7K rpm, but I have tried 10K also. I believe the two speeds of the power feed are both too fast. I do not recall exactly how many FPM they are. If I feed manually at a slower rate I have no problems at all. I can power feed climb cuts with no problem, but will not climb all setups for safety reasons. Any suggestions on how to slow down the feed rate? Do they make a rheostat or similar device that will allow me to alter the pre-set feed rates?

Forum Responses
(Architectural Woodworking Forum)
From contributor G:
Not sure on the Bridgewood models, but on ours we simply change the drive gears on the backside of the feeder for different speeds.

From contributor D:
Climb cutting is the best strategy when it can be done safely. I have never seen much gain by slowing the feed down; eventually you just burn the cut, and still have tearout. I would make a sacrificial fence of a good dense hardwood and crank it (carefully) into the revolving cutter so as to support the stock right where it wants to tear out.

From contributor A:
The major factors are RPM, FPM, and depth of cut. The Delta won't like running many cutters at 10k like you mentioned. The feed speed will definitely contribute. Taking a 1/8" cut usually produces better results than 1/16" or less. This is more evident with high tearout woods like vertical grain cedar. When taking a heavier cut like 1/8", the tendency to splinter and chip is reduced because the splinter would be huge if it happened. On those feeders I use the low speed for expensive raised panels, low-mid for sticking, high-mid for mouldings, and I rarely use the high speed. You should be able to switch the gears inside the feeder.

From the original questioner:
Thanks for all your guidance, points well taken. I got in touch with tech support at Bridgewood, and was advised that the power feed is shipped with the gears in the higher speed position, and like you have recommended, was told to flip the gears. I will be doing this later in the day. I will let you know how I make out. The old current speed is ridiculously fast. As a matter of fact, I think I saw a set of headers and mag wheels on it.

From contributor P:
The problems you speak of generally occur more frequently with small diameter cutters such as what you are using. The reason for this is the tangent angle that the cutting edge has when it exits the wood is much greater than that for a large cutter. Small cutters tear out because they want to hook the wood upon exiting for a full depth cut.

I am sure you do not want to rush out and buy new cutter sets. But in the future, look to buy 1 1/4 bore cutters even if you have to bush them up. I do not like to use anything under 5.0 in diameter and seem to have the best result with 6.5 diameter sets. Chip removal is much better too. Also, I run LRH mostly these days.

From contributor A:
Do you think the higher rim speed of the larger cutters contributes to less tearout?

From the original questioner:
Flipped the gears this afternoon and ran some test cuts. 100% better. No more tearout and the bead line is nice and smooth. Thanks for your help.

From contributor L:
I agree, larger diameter cutters give better results even with the same chip load. Too small of chip load will also cause problems - burnishing, burning, dulling. You need to set your feed speed to match the required chip loading. Slower with larger cutters at the same feed speed or higher feed rate with the same RPM on the larger cutters (don't exceed the RPM marked on the cutters).

From contributor L:
I should add a safety note: Don't bush up larger heads on your light duty Delta shaper - too risky! If you use a shaper a lot, consider buying a quality European shaper with 1 1/4" spindle, heavy quill assembly and a good fence. You can get smaller spindles for them so you can still use the small cutters, but larger ones give better results.

From contributor R:
I've wondered about this. Before I got my shaper, I frequently did a finish pass on my router table, i.e. a bulk pass to remove most of the material, and then a finish pass. I've heard before, and contributor L is suggesting again, that the appropriate technique with the shaper would be to take the entire amount off with one pass? Like with rail and stile cutters and panel raising cutters?

From contributor F:
It is usually better to machine profiles to full depth in one pass. Of course it's better for production, but also as contributor A mentioned, you can often get more tearout on light passes than with a heavy pass. The reason is that there is more wood backing up the cut on a heavy pass.

From contributor P:
I usually find the bigger 1.25 bore cutters are made better and can also employ better tool geometries, rake, shear, etc. You should be able to take a full cut most of the time without a problem. Sticking cutters with eased edges can help with tearout, providing you do not mind the little radius in the detail. But sometimes no matter what, some species or cuts will give you problems. Quartered white oak and hickory always drive me nuts. I usually make one light climb cut pass, followed by a conventional cut.

From contributor L:
I will climb cut on nasty wood (never on end grain). Your feeder needs to be set tight and some method employed to limit the depth of cut. Wax the table before starting so you get an even feed. Make the finish pass conventional cut. Be sure the "throw path" is clear when climb cutting! A side note: making too thin of a cut or too slow will result in a compressed fiber condition that will come back to haunt you later.

From contributor F:
Speaking of too thin of a cut, I don't understand about climb cutting and then running an additional conventional cut? When I run conventional (against the cutter rotation), I run to full depth in almost all cases. If I get tear out or think I will get tear out, I run climb cut (with the rotation of the cutter) to full depth. Just curious if I am missing some finer point.

From contributor P:
Depending on the profile and how large it is, I use the climb cut as a scribe to assure that a sharp edge or groove remains crisp. This is usually less than half the full cut depth, powerfed a bit faster than the final conventional cut. Since some profiles are just too big or dangerous to cut full depth on the climb. Plus, I get a much better if not perfect finish this way. Great for fuzzy and brittle woods. Of course, I prefer to do a full depth conventional when I can, but I want to eliminate final sanding chipping or the board flying across the shop.

One note: avoid climb cutting with the spindle tilted. If it hooks up, the board cannot back away from the spindle as it flies out. It can bend the spindle and fly out with more velocity than you can ever imagine. By far the worst kickback I have ever seen.

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