Achieving Consistent Copes

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Why is it so difficult to cut copes the same every time? October 5, 2004

My shop still makes our own cabinet doors. The biggest problem I have had through the years is getting the coped part of the rail and stiles to look right every time. I use the fillet looking design on the inside of the rail and stiles. I know that when the rail is coped and put together with the stile, the fillet looking design on the inside of the rails and stiles is supposed to look like it was mitered together in the corners. I can't seem to make it look exactly right every time. I am using brand new Powermatic model 27 shapers, Freeborn tantung cutters and a Weaver air tenoning jig. These are brand new shapers and shouldn't be out of whack. I am very particular about the way that the design on the inside of the rails and stiles looks in the corners. I can run samples and maybe get them right, but I can't keep it cutting all of the parts right. Does anybody know of some equipment or accessories that I could get to solve this problem?

Forum Responses
(Cabinetmaking Forum)
From contributor J:
Over the years we have come up with the following solutions.

One: Use a sled to do copes. We use the Ritter. Stack your knives with spacers so the sticking is run on the bed and the copes are run on the sled with no change in height adjustment.

Two: Move the sled bed to be as close to the cutter knives as practical.

Three: Make a backer block that is loose (do not attach it to the sled) for the cope cuts so the flat portion and the portion with the sticking is fully supported. We use a piece of solid maple run through the coping setup so it mates correctly with the sticking. Slip the profile of the sticking into the maple backer and run through the machine, then move the maple and finished cope away from the cutters and return the sled to the original position. This preserves the quality of the backer block.

From contributor M:
I only do a few doors a year and I also use a manual sled. Delta makes a fixture that I use and I use a sacrificial block, so cutter does not shred the edge of my coped edge. It is a pain but no fingers are even close to cutter, and it works well on low production. I think the sled costs about 100 bucks. Well made, I might add - cast iron, etc.

From contributor B:
I used the sled for a while and got a better job without it. I do my rails out of a wider 1x to equal two finished widths of rails plus saw kerf, plus waste to square the finished door. This gives a wider surface of board end-grain to go against the fence. Then I come back to do the sticking on both sides of this piece, cut it apart, and two perfect rails. All stiles and rails are done face down, so if the 1x had a slight difference in thickness, it would show up on the back side. I also use a dial caliper to measure all 1x for consistency after planing and wide-belt sanding to working thickness.

Oh yeah, do you use a powered stock feeder? Holds everything tight to the bed and as I've said, it's all face down.

From contributor C:
We use a Felder F700Z with sliding table, and Byrd insert tooling.

All parts are fed good face down. We feed the profile through the machine with a powerfeed. The counter-profile is clamped against the sliding table's fence with a backer block behind the cut. By the way, we use a pneumatic clamp to secure it.

The joints are extremely tight and consistent. And with the numeric keypad spindle height, setups are very fast and repeatable.

From the original questioner:
I appreciate all the help you have given me. I am using the Weaver air tenoning jig to cut the cope on the rails on one shaper and then I use another shaper (both shapers are Powermatic model 27) to cut the profile on the long part of the rails and stiles. I'm guessing that the Weaver air tenoning jig is similar to the sleds that you are talking about. This jig rides on a small amount of air, so it's easy to slide it across the shaper table.

The coped cut and the long run on the rails and stiles are all run face down. Maybe I'm just real particular about the way the coped joint looks, but I like for the profile on the inside of rails and stiles to look like it was cut on a miter saw. If the cut is a hair too high or a hair too low it messes up the way the corner detail of the cope looks. I can make it look right sometimes, but I can't keep it consistent.

Since a lot of the rails aren't very long on cabinet doors, I have been running random lengths of rail parts through one shaper to make the stick cut and then chopping them up into smaller parts and then making the coped cut. I also use a sacrificial piece of wood next to the rail when making the coped cut. The sacrificial piece has a reverse pattern on it so it interlocks together with the rail to prevent tear out. But, with all this, I still can't get the corner detail of the coped piece to look like it was cut on a miter saw every time. This is just one of those little things that has bugged me through the years.

From contributor E:
I cut the tennon first, 1/8" long. Remove 1/16 from each end with the sled perfectly square to fence, then use powerfeed to do the profile. I use a secondary fence, piece of 1/4" plywood, to hold stock tight to main fence and remove 1/16" from this edge also. This way all blowout is removed from your tennon on rails.

From contributor R:
I will never understand why most people run door stock face down. Everyone says because it throws any difference in thickness to the back side. Some people plane, then even wide belt or drum sand trying to get perfect thickness, before ever starting on the door.

I run mine face up and don't worry about the thickness. A long time ago I bought 13/16 stock and ran it through the joiner and planer trying to have something close to perfect to start out with. That was a long time ago. I now run face up at 13/16'' as I pull it off the lumber rack, setting cutters up with the back side of doors in mind, leaving a large little corner at the edge of profile and front side of rail or stile. This leaves plenty on the front side for the drum sander to never cut into the profile and to make everything look perfect. If your joints are tight they end up perfect, without all the headaches when assembling the doors.

As for the problem with the cope cut on your rails, I believe it's coming from bow in your rails. Just a slight bow in the rail will throw it off from sled to cutter. All bows up in sled will help. Try pulling out some very straight stock for the rails. I run an old homemade sled and don't own a powerfeeder, and for me face up cutter setup, I think about the back side of the door and let the drum sander worry about the face side. Working alone my man hours per door are about 1/2 of what the door shop's man hours per door are. They have 8 people working an assembly line, but I can buy their doors for $19.00 each, which makes it dumb for me to build my own. So I have matched the door shop's cutters so my doors look just like his doors. I can build them or let him build them or even mix and match mine and his on the same job.

From contributor K:
It sounds as if you are having a problem with vertical registration between the rails and stiles. Running face down will help in alignment, but you still have to hold the stock down on the table. For the sticking, use a power feed or feather boards pushing both in and down. On the cope cut, your air cushioned sled may be floating around more than you think. Try a featherboard mounted on the fence pushing down on the stock at a point where it is supported by the sled and the table (i.e. not over the hole in the table). I find I get the best results by chopping the rails first, coping with a fresh backer every time and then sticking. Obviously more time consuming, and very short rails are a pain to handle, but I can get a clean joint every time that way. A belt type power feeder would help with the short pieces. It wasn't clear from your post if you are using a power feeder, but if not, get one. It improves cut quality a lot, as well as saving on fingers. With a good setup you should be able to get the joint flush on the face side within +/- .003" (thickness of a piece of paper).

From contributor O:
If you are lining up everything right and still have that problem, your cutters may not be ground to match each other. I have lrh cutter set with this problem. At final sanding I score the joint at a 45' with a utility knife. It makes the joint acceptable.

From contributor M:
Contributor K just hit on what has been bothering me also. Since your sled is on an air cushion, I suspect that any variable in pressure or just slight tilting because it is on a cushion will drive you nuts and might be at the root of your problem. If you have a good old push-it-yourself-on-the-table sled, try it and see if the problem goes away or at least changes. If it does, you have found one of the issues.

From the original questioner:
The air cushion on my tenoning jig may be part of the problem. Also, I have had my rail and stile cutters sharpened twice and maybe the last company that sharpened them didn't get them matched up just right. I sent the cutters back to the company that made them (Freeborn) to check them out and maybe resharpen them for me. I will try my manual sled again when I get my cutters back and see if the problem goes away. I just really like the idea of the air jig because it clamps the part pneumatically and it slides across the shaper table easily. Does anybody else use a Weaver air tenoning jig? And if so, do your coped joints on the profile on the inside of the rails and stiles come out looking like they were cut on a miter saw every time? I am using Powermatic 3 and 4 wheel power feeders. I am going to put the belt conversion kits on the feeders that I use to make the stick cuts and the raised panel cuts. I was always taught to make the cope cut first and then make the stick cut. I just have a hard time cutting the stick cut on short rails. They have a tendency to have a wavy stick cut if I use my power feeder and it is kind of dangerous to make the stick cut manually on short rails. Again, I appreciate all of your help. I will try out your suggestions.

From contributor V:
I don't use an air jig. I can't afford it! I'd love to have a Weaver. I have their web site in my "favorites" and visit from time to time to dream.

I am curious. This may start a new thread, however, very much related. You said you were taught to cope first, stick second. Every book/article/etc. says to cut door parts that way. I have never fully understood why. I have always done stick, then cope, and it would feel strange to do it in reverse. You also said you feared short stick cuts. I fear short cope cuts. However, I always stick long pieces and then cut to size for stiles and rails... Then only have to deal with a short piece for two cope cuts.

The only explanation (if any at all) in any book, magazine, etc. that explains the process mentions matching the stick cut to the cope. Makes no sense to me. I do the same thing, just in reverse. I've read other threads here where some guys do it like I do. Just curious... How and why do you guys do it?

From contributor M:
I always do stick first. In fact, I run all my material in long lengths, then cut to size and just make the short cope cuts. Way easier, safer, faster and above all, everything matches, since it was all cut at the same time.

From contributor O:
Rip and stick stile material. It's okay to use long lengths. Rip and cut rails to length. Cope rails. For rails under 6", you have to use a sled for stick cut. This method makes for no blow out. If you just do a shaker door, your method will work fine. If there is an inside detail on door frames, my method works best. Hope I explained this correctly.

From contributor H:
There's nothing wrong with your setup or the method that you machine your parts. As contributor R mentioned, the only inconsistent part of machining doors is the material we use. When you put your stock into the air tenon jig, notice where the stock contacts the blowout strip. It will not always be right on. It could be slightly high or low. Select the best and straightest stock for your rails. This will eliminate your inconsistencies to a manageable level. I've been using Weaver's six shaper system for years, which works great. As for machining face up or down, it makes no difference - just depends whose cutters you're buying and how convincing they are that their way is the best. After all, it's only machining parts.

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

Comment from contributor A:
Check to make sure the rail is not moving on the sliding fence or whatever you use. I contact cemented a strip of 100 grit sandpaper to mine and get no sliding whatsoever.