Shaper Cutter Choices, Alignment, and Balancing

In this interesting thread, a question about good cutterhead choices for occasional use in hardwood evolves into a conversation about setting up and balancing the shaper. August 19, 2013

Question :

I'm looking for suggestions on raised panel tooling, but first a little background. I don't do very many raised panels at all, and most of the ones I do are usually MDF. As such I have a small collection of brazed carbide cutters that have worked well enough over the years. In the last year I've had two small jobs with raised panels on hardwoods and found the carbide tooling didn't cut as cleanly as I would like. It's great for MDF but I'm wondering if I'd be better off with HSS for hardwoods like cherry?

I'm looking at the Innovator heads which seem like a good way to go for a pretty reasonable price. The Freud heads look a little light for my liking. I'm sure there are serious production heads, but I don't want to drop $1k plus for something that gets taken out once or twice a year. So is the Innovator the best bet for an inexpensive raised panel head? Or are there other alternatives in the same ballpark I should look at?

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
Yes you are better off using hss for most solid woods. With fresh knives you will get a cut that doesn't need much attention. The innovator is a great tool. I have one and use it for exactly the same purpose as you intend to. Since the knives are relatively inexpensive it makes for a cost effective way of doing small quantities of custom profiles. When you fire up the 6" innovator with knives that project even further it's pretty freaking scary though.

From Contributor S:
I have two innovator heads and love them. As Contributor J said with small inexpensive knives you can have easy custom profiles, and HSS means you can sharpen or even grind them yourself. As for starting one up, your shaper needs to weigh more than the head.

From contributor A:
Another alternative would be to get a carbide insert head like an alloy Stark. Infinity also sells one. They have much harder carbide that stays sharper. You could have two sets - one for MDF and one for wood. The heads are alloy so they spin a little easier.

From contributor R:
The Innovator is a good way to go. One thing to bear in mind is that getting custom ground HSS profile knives will add up in cost over time. If your profiles are non-standard, this would for sure be your best bet. I've sold the Innovator and custom ground knives on a regular basis over the last 20 years and found it to be a great tool!

Contributor A does bring up a good point concerning carbide insert heads. The solid carbide insert head setups are used by companies like Pella, Andersen and Simpson Door for production runs. The difference between brazed and insert type cutters are the carbide grade and ground finish. The inserts utilize a harder C4 carbide that is ground by Stark for instance to a mirror finish to produce cleaner cuts.

From the original questioner:
Thanks Ė it sounds like the Innovator is the way to go! I have no concerns with the size or weight as my shaper can handle that and quite a bit larger. I also have a custom made fence for the raised panel heads which adds a level of safety for me especially when doing narrow panels. I just completed three panels that were under 4" wide! Of course it will need to be altered a bit for the larger head.

As for the insert tooling, I priced out some door tooling a couple years ago and the pricing was more than I wanted to invest. Cabinets only make up probably less than 30% of my production and raised panels maybe 10% of that - at most. So there arenít enough of them to make a large investment worthwhile. Also I think the flexibility for doing custom profiles in HSS is a real bonus.

From Contributor G:
If you are cutting MDF and then solid wood you will have a problem. If you have cutters for MDF and cutters for solid wood then you won't have these issues. Just one MDF panel is enough to take the sharpness out of a carbide cutter so that it will be much less suitable for solid wood.

From the original questioner:
That's the exact problem I just had on this job. I knew I should have had it sharpened, but for one vanity? Let's just say I spent more time sanding burn marks out of cherry than I care to! Anyway the plan is to have the HSS for all my hardwood panels and keep the carbide tooling around for the MDF.

From Contributor G:
Yep, all it takes is about 2' of MDF to kill a cutter for solid. Usually I don't get burning, but I get to sand the endgrain for a while because the sharpness is dulled by the MDF. If you only use one or two profiles for panel cutters it might be less expensive to just bite the bullet and get another carbide cutter, just label them wood and MDF and stick to it without exception. If you need several or plan on offering clients whatever profile they want then the changeable cutter head is the way to go. It is expensive to get setup, but once you have the head the cutters aren't that expensive.

From contributor R:
I was going to say if the existing carbide heads were sharp they would do just fine. MDF will quickly dull even carbide, particularly the nasty stuff not formulated for machining, although I agree HSS is a much better choice for solid wood. Schmidt and Freeborn carry a brazed on material called Tantung which is supposed to be a compromise between carbide for longevity and hss for sharpness. I own a couple of these and they work quite well if you want a solid body cutter, not very expensive either.

I was fortunate early in my career to have been introduced to grinding bevel edge HHS to pattern on a bench grinder to use in clamp collars. I still find this to be the most versatile and inexpensive way to go with arguably unmatched edge and results. A raised panel pattern is probably the easiest to grind even by a beginner. It is still a skill worth pursuing for the small shop.

From contributor L:
Back in the good ol' days I also ground knives for my shaper collars. Just be careful about balance and the amount of knife protruding relative to its thickness.

From Contributor S:
It is nice to hear that others are aware of the joys and flexibility of squint and spark grinding. I learned it out of necessity in the mid 70's and still do it as needed today. I probably do it too easily, and will admit to even doing custom cope and stick pattern sets. Those Innovator heads can be called cope heads if you like. A decent pair of wheels and a grinder or two, with a 1/4" wheel on hand, is all that is needed, and you can match panel raises faster than you can order tooling. As old school as one can be, but you have the ability to pull off about anything.

From the original questioner:
I do like the idea of grinding more of my own tooling. I have done a little grinding to re-shape some existing profiles I have for a Euro block head. It went easier than I expected and my biggest fear of not having the two knives perfect to each other didn't seem to be a problem. Having said that I still have a long way to go in educating myself on that topic! I'm not at a point where I'd feel comfortable grinding my own bevel edge steel. Maybe the lock edge stuff someday? The bevel edge knives may be something I just have to leave for you guys.

From Contributor S:
Don't get too concerned about the profiles not matching exactly. Not only is it impossible to do by hand, but even the multi thousand dollar knife grinders that can grind four knives to withiní a few microns still have only one knife making the finish cut - the one that makes the surface you see. Same as you see in your planer or jointer with conventional cutterheads. It is more important to have the knives balanced.

From contributor L:
I also learned to grind lock edge back in the 70's. Two sets of collars, one with a ball bearing. Assorted width knife stock, an 8" quality bench grinder, and some practice. I had several very soft grinding wheels and a diamond dressing tool to shape them. After you have made a few dozen knives, you can usually find one that is close enough to balance that you only need to grind a single new one. If not just grind a balance knife that is not intended to provide the cut. Some blue machinist dye for layout and a scribe. To see what back bevel you need take your compass and set it to the radius of the head and draw a circle on a piece of wood. Copy the angle of the slots to the circle and extend them. Estimate the length of protrusion you will need.

Due to the knives being mounted at an angle to the center of the spindle the pattern gets compressed a bit. You can approximate that by cutting the sample piece of molding at about a 30 degree angle (memory isn't the best on the exact angle) and using that to trace in the blue layout dye. You can also see the change in length needed by drawing a line from the center of the spindle to the intersection of the face of the knife steel line.

Grind the knife and touch up the edge carefully with a slip. Be careful not to cause the back angle to change enough to cause healing. I used a Foredom (Dremel now) tool to work tight inside corners on the knife steel to allow sharper outside corners on the moldings.

You need a heavy shaper (PM 26 or Delta won't do) to run these as you will almost never get really good balance. That and it wastes a lot of time trying to get it exact. With the lock edge steel you can loosen the spindle nut and turn the screws that engage the steel to make some adjustments. Having a heavy tilt shaper is a great advantage and can lessen the protrusion of the knives when you are running a raised panel profile. Use your power feed and you can make really clean molding cuts. To layout and grind a new knife will take you about 15 minutes, once in practice. Charge well for this skill, there won't be much competition.

From Contributor S:
Contributor L - you are right about the balance and large shapers. Back when I was young and new at this, the Tegle and Sonner shaper I usually used was all tied up, and I was in a hurry to raise some panels. I took the nice hand ground lock edge knives and the collars over to one of the little Rockwell shapers in the shop. They had a pretty good protrusion from the head, for about a 2" wide rise. They were far from balanced.

I hit the on button on that little shaper and the head took about 30 seconds to get up to speed - speed being about 8,000 rpm. All the while, the scream got louder and louder and the shaper started dancing on the floor. I remember my impression was that I had made a helicopter of sorts, and it was trying to fly. I had to follow the machine as it was tethered by the electric cord and shut it off. I was not injured, nor was anyone else. Everything stayed intact. I quietly pushed the shaper - all 112 pounds - back to its place and removed the tooling. That did not stop my squint and spark grinding, but I did learn to watch mass and rpm.

From Contributor F:
Some good information Contributor L, however, with all due respect, you are wrong regarding the use of a balance knife. This is one that the old school got wrong. Like you, I was taught that you only needed one knife ground and simply needed another opposing knife the same weight to create a balanced tool, in fact it was common practice with the square heads and slotted knives of an earlier era to simply add additional bolts along with a blank or similar ground knife in the slots opposite the cutting knife to provide a balanced assembly.

The problem is when the cutterheard is spinning, if the projection and alignment is not the same the balance goes out the window. I have seen the nasty aftermath of this practice on a number of occasions. The bottom line is you need to grind two matching knives. The way I achieve this is when I am close to finish grinding two knives. I completely finish one, then lay it bevel up and trace it with a sharp drafting pencil (lead holder) on a piece of paper. I then finish the second using the traced profile as a guide to finish up.

It may be necessary to grind the second knife a hair (literally) back from the tracing but that will be close enough, as Dave mentioned earlier, even if the knives were perfect, short of jointing, only one would finish. However the closer the knives are ground the more equal the chip load, which should decrease tearout, etc. and produce a better finish. The beveled edge collars with integral bearing you reference are undiscovered treasures. I would challenge anyone to name a more versatile tool. It is as safe as the modern corrugated type steel if one understands the tools and machine, I still run some of the non-lock-edge without concern, common sense and a properly guarded setup will do the job with minimal risk.

From Contributor S:
Contributor F cleared up the balance point. Just because one knife creates the finish doesn't mean the other is unimportant. I also think the split collars are essential to the well-equipped shaper. They were all I used for the first ten years in the shop - all I knew. We would occasionally break a long panel raise knife from over feeding (hand-fed), but that was the worst. Pay attention and keep your wits about you and all is well.

I also have a few jigs laying around for tracing knives and I do make an attempt to keep things similar. To round about and to get back to the Innovators, with three knives, my hand ground sets often show that all three are doing some work, as evidenced by wear and resin loads. The next sharpening may alter that, no matter, as long as the cut is what I want.

From the original questioner:
Great stuff guys. You actually answered something I was thinking about last week in regards to the knife balance topic. I had read in the past about guys using knife blanks to balance, and the same thought occurred to me - how can you get good balance if one knife projects more than the other, even if the weight is the same? Well now you've answered it without my having to ask!

I have a tilting shaper which does a pretty decent job the very few times I need the tilt feature. Although it's an industrial machine and probably two-three times heavier than the little Delta's and Powermatics, it's only a 3hp and the table opening is too small to do much with a bigger 1-1/4" head. For most of my work I use an old Martin shaper, so having machine mass is not an issue. I do happen to have an old Schmidt lock edge head with the integral bearing in my stash. No knives for it yet, and still need to develop my skills a bit further before I'd go playing with that one. Good to know they're well regarded though.