Avoiding router tear-out

Eliminating tear-out when routing the edges of stiles. February 13, 2001

How can I stop chipping on the edge of the stile when routing? I have a CMT router cabinet with a 3 1/4 HP Bosch router and I am using CMT router sets to make the stiles and rails. There is always some chipping on the edge of the board at the slot for the panel. It is especially bad with oak.

Forum Responses
Place some sort of board behind your stile to avoid the splintering as they exit the bit.

Use a sacrificial fence and cut the stile shape through the fence. This will back the material at the point where your chipping occurs.

If you make an initial pass that only cuts into the edge of the stile 1/32", you should get a nice sharp corner to your grooves. When you cut the stile to its full depth, you should not get any chips. It helps to keep your fences as close to the cutter as possible.

Make the stiles and rails conger and cut these first, then chop to size to make the coping cut. Run a sacrificial piece first and then use this as a support when making the coping cut. The CMT catalogue tells how to make these cuts.

It is unclear from the last response whether you are having chipping problems along the edge of the stile or where the cope cut meets the profile on the rail. If it is the latter, there is a very simple solution. Make your cope cuts first, then profile the edge of the rail. The profile cutter will remove any chips created in the coping process. This works much better than trying to back up the profile while coping the end of the rail.

I don't have a problem with chipping--I just prefer to make the coping cut last.

One further point to the first writer--I run my stiles and rails through the sander first, to get them all to the same dimension.

If you are going to cope last, use a back up block behind the good work piece. This sacrificial block holds the wood together during the cut. It is also important to use a sharp cutting tool. If the tool begins to dull, chipping increases.

Depending on your quantity, you may consider a high-speed steel bit with one of the new high temperature coatings on it.

Dave Rankin, forum technical advisor

Score the edges of the groove with a properly sharpened mortise gauge and plunge the cutter through a sacrificial fence.

Climb cut it. This will eliminate the problem. That is, if you have the right equipment. There is a danger if you don't.

A dado cut on a radial arm is climb cut. Done on a table saw, it's a power cut. Which has tearout?

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
There seems to be some confusion to some readers about where the tearout is occurring. It is more likely to occur along the edge of the stile (stick) not the edge of the rail (cope). It is more likely to happen with open grain wood, like oak. My suggestion is to first select wood that has the straightest grain. Irregular grain pattern is prone to tear out, especially when cutting against the grain. Cut the stiles and rails to finished width. Cut the rails to finished length. The stiles can be cut either to finished length, or cut over sized and trimmed later. Use a router that is 3 HP or better, and has variable speed.

I agree with using a sacrificial fence placed close to the cutters. Cut the ends of the rails (cope) first. It is best if you use a coping sled or equivalent. Adjust the speed of your router to the router bits manufactures suggested speed. You may need to adjust the speed, depending on the quality of the cut. Cut the rails (ends) with one pass and cut the stiles with one pass. If tearout still occurs, then you may want to score the edge about 1/32 with a light pass with the same bit. You will make two passes. Moving the fence will allow you to make the first cut (score), then move the fence to make the final pass. This should help.