Avoiding Shaper Blow-Out

Various suggestions for achieving clean, sharp profiles without tear-out and blow-out when running moulding on a shaper. July 28, 2007

When I feed the stiles through the shaper by hand, they come out fine. When I set up my power feeder (on the slowest feed rate), I get chatter or blow out on the edges. Do I need to get a slower power feeder? It is set for 10 feet per minute.

Forum Responses
(Cabinetmaking Forum)
From contributor L:
Make adjustments to the feeder and make sure you are running enough pressure to the fence and to the table. The feeder needs to be slightly angled and just one wheel or less in front of the cutters. Make sure the fence is locked down well.

From contributor F:
This is a common problem and is caused by the groover in the cutter set that is hogging out a lot of stock that is unsupported, unlike the cut on a table saw which is supported or backed up with a zero clearance insert throat plate.

Backing up the groove cut on a door stick setup is not possible because of the other two interlocking cutters above and below the groover. This problem had been addressed by the door cutter manufacturers that now sell cutter sets that put a small radius on both edges of the panel groove which effectively removes the tearout/blowout created by the groover.

Unfortunately in my case, I bought my cutter sets before this option was offered. The solution for me is to climb cut my stickings. That is, using a power feed only, I set it up so that the edges of the stiles and rails are run through the shaper in the direction of the cutter rotation instead of the normal against cutter rotation direction of feed. I find this is necessary on brittle woods like cherry and maple but perhaps not on poplar or alder.

From contributor H:

We always climb cut our stiles for this reason. The shaper will try to push the stiles away from the fence when climb cutting, so the solution is to clamp a board 2.5" or whatever your stile width is, away from the fence. Also, make sure your feeder is putting plenty of pressure on the stiles and is slightly angled to the fence. And then make sure no one stands directly in the line of fire.

From contributor B:
What kind of shaper are you using? I use a Bridgewood 4 tire. When I first got it, I was experiencing the same problem. If you open up the side you may be able to flip around the two gears which should slow the feed rate significantly (five minute job). I will still get a little tear out every now and then on hard maple or similar, but the problem was greatly reduced. Just something you may want to check out.

From contributor L:
Another safer way than climb cutting is a stage process. Put a spacer fence in of 1/4" MDF. Run all the stiles, remove the spacer, place a door skin on for spacer, do it again, run final pass. We finally sat down on chairs one time running 3000 stiles of white oak to accommodate this. Zero blow out and a whole lot safer that climb cut.

From contributor D:
Climb cutting is no more dangerous than any other production shop method. One must be trained in the particulars, and have their wits about them before doing so. Proper power feeders, with good posts and clamps, good wheels and tires are essential. One could make the point that the shaper, with a power feeder, all properly set up, is safer than many of the other pieces of equipment in a shop. The equipment also needs to be positioned to anticipate the path of any problems, just as you would with a tablesaw or ripsaw. Marking the floor with yellow tape and keeping an eye on new hires is also basic.

You might also look around this site to see where some folks are running the fence opposite the cutters, while conventionally feeding the parts. This is also a viable way to run parts, and width accuracy is also determined, much like a planer. I don't think you'll find the folks at the big cabinet door manufacturers sitting down while they run parts multiple times.

From contributor K:
The solution to your problem is actually quite simple. You need to machine off an extra 1/16" beyond the depth of the profile of your cope and stick. In other words, don't set your infeed fence flush with the smallest diameter of the cutter set. Set it back an additional 1/16". This will machine off any chipout produced and will allow you to machine in a standard direction.

From contributor F:
While I agree it's a good practice to remove some material from stile and rail edges mainly to insure full depth of cut, this will not eliminate chipout caused by the panel groover or any other cutter in the set for that matter.

From contributor G:
I used to always get blowout also. I started taking 1/16" off as suggested and almost never experience it now. This also works for most edge profiling. Eased edge cutters also help, as do sharp cutters. I almost never have to climb cut. About the only time I do is if the grain changes direction a lot in the work piece. I think I get a better cut and better dust collection if I do not climb cut in fairly straight grain wood. The 1/16" thing really works.

From contributor L:
Seen climb cuts blow through shop at an alarming rate. Contributor K's suggestion has worked for me many times. Climb cutting is not for the faint of heart and everyone knows it.

Nothing wrong with a chair when you are at the shaper station for three hours. Don't large door manufacturers run moulders? The post said "when running by hand, no blow out, when running by feeder, problems." Just giving one of a million solutions to one problem.

From contributor U:
10 ft/min seems slow enough - any slower would be like watching molasses in January. Are you sure it isn't 10 m/min? How fast are your cutters spinning? Any significant vibration from unbalanced spindle or cutter stack?

Add me to the list of people machining off the entire edge to set final width. Eased or straight, insert or brazed stacks - we only cull one or two stiles a week due to tear out from grooving (and most of them can be trimmed down to smaller door sizes).

The only parts we climb cut are raised profile, solid slab drawer faces where the cutter doesn't hit the edge, just the top. It only took one projectile to figure out how to safely and consistently climb cut: good balance and bearings, sharp cutters, enough pressure and toe-in, and a continuous fence running under the cutter for the drawer to ride on. Just make sure the exit is safe while you are learning!