Some pretty effective looking flattening bits here; most of which available on amazon etc:
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Router Planing Fixtures
- Thread starter Bruce Johnson
- Start date
Based on what I seeing on this page, it looks like you have to be careful with hardwoods unless you change out the blades...?
Don't get me wrong I appreciate the feedback, I just wouldn't want someone buying one of these bits thats made for MDF or balsa and trying to lay into some rock maple...
I wouldn’t go hogging into a bunch of rock maple either. But I’m under the impression you would get great results using them for what they’ve been designed for... skimming, resurfacing. Wether it’s MDF or Maple, I reckon it wouldn’t make a difference if you let the tool do the work safely. IMHO
It's all good, I was just reading the descriptions and it looks like there were some caveats about using the bits for hard materials....
I’m going to pickup one of the smaller, stout looking ones and compare it to my Whiteside rabbet; which is the same as the CMT posted above. If I see any improvements, I’ll post them up here. 
I’m going to pickup one of the smaller, stout looking ones and compare it to my Whiteside rabbet; which is the same as the CMT posted above. If I see any improvements, I’ll post them up here.
Sounds good! Always good to share results experiences, and I certainly appreciate it!
Just FYI, its not the same for all the bits on that page you linked but for at least some (see bottom):
Can't tell you how glad I am to see that such an informative thread is being updated even 2 years later. No questions as Bruce and others have been kind enough to offer such detailed responses.
I'm working on build one myself. Spending all the time this far making jigs... Making a table saw, mounting 9" bandsaw, making routing jigs, improvising clamps... I thought some of this would be easier(?)... Some things I didn't think about at all. Sometimes you just don't know until you know.
Thanks for all your help.
I'm working on build one myself. Spending all the time this far making jigs... Making a table saw, mounting 9" bandsaw, making routing jigs, improvising clamps... I thought some of this would be easier(?)... Some things I didn't think about at all. Sometimes you just don't know until you know.
Thanks for all your help.
I am sure there are things you can pay for to make 'em easier but personally, I don't want to sink too much $$$ into this until I know I *want* to sink $$$ into it. By then, I will probably appreciate those tools and jigs you can buy to speed up the process.
Yes, I deliberately keep adding new info to threads like this, to keep them going. Bringing them up to the top with a new post means new people will see it for the first time, and hopefully learn some things and get some ideas. And, although I'm leading the way, we want you guys to contribute too. Show us your versions of these fixtures, problems you've run in to, innovations you've added, variations that you've come up with. Add them to the record.
This is all about building up a library of information for everyone's use, that's permanently available, and easy to find in a search.
A quick general note about this type of router bits:
This is called Carbide Insert Tooling. They are heavy duty router bits, in which the carbide cutting edges are separate parts attached with little screws. The carbide "inserts" are easily replaceable when they get dull, and also, many different inserts are available which are specially ground to be optimized for particular materials and applications. This is what you use out in industry when you have powerful CNC machines hogging material all day.
They are expensive and, for our level of light occasional woodworking, unnecessary overkill. Most of us would never wear out the first set of inserts. And the inserts aren't cheap, either, like several bucks each. Standard router bits, which have the inserts permanently brazed in place, are cheaper and work fine for us. And, in most cases, there's no real performance advantage to insert tooling. The big advantage out in industry is that you can change out the inserts quickly when they get dull, without changing the setting of the cutter in the CNC toolholder.
Someone will mention about the spiral cutterheads with carbide inserts that are available for jointers and planers. Those things are great, and well worth the high cost. They cut much better and smoother than standard straight planer knives. But the performance advantage isn't so much because the carbide inserts themselves cut better, but because they form a row of small teeth in a spiral. Much better cutting action.
Likewise, there are some carbide insert router bits, like the ones shown above for CNC surfboard surfacing, which are optimized for particular applications. But no real advantage for us.
Also, whenever we talk about router bits, I like to refer you to this thread from last year. Particularly from my post #8:
Router Pattern Bits
The main points are that, in our light-duty usage of routers, very rarely do we ever actually wear out carbide router bits. Out in industry, those carbide edges last hundreds of hours of continuous heavy usage before they get dull. Our usage is measured in dozens of minutes.
The reason our router bits get "dull" and start cutting badly is that they get a buildup of hard varnish on the carbide chips, right behind the cutting edges. That varnish buildup rubs on the wood, building up heat and keeping the cutting edge from cutting. If you clean that varnish off of a "dull" router bit, you'll usually find that the cutting edge is actually nice and sharp, and it will cut like new. No need to resharpen it.
In that thread, I show how to clean the varnish off router bits using a small scraper and a brass brush. It only takes a minute, and can be done with the bit still in the router.
So many complaints and problems with router bits are caused by varnish buildup. Clean your router bits!
Router Pattern Bits
The main points are that, in our light-duty usage of routers, very rarely do we ever actually wear out carbide router bits. Out in industry, those carbide edges last hundreds of hours of continuous heavy usage before they get dull. Our usage is measured in dozens of minutes.
The reason our router bits get "dull" and start cutting badly is that they get a buildup of hard varnish on the carbide chips, right behind the cutting edges. That varnish buildup rubs on the wood, building up heat and keeping the cutting edge from cutting. If you clean that varnish off of a "dull" router bit, you'll usually find that the cutting edge is actually nice and sharp, and it will cut like new. No need to resharpen it.
In that thread, I show how to clean the varnish off router bits using a small scraper and a brass brush. It only takes a minute, and can be done with the bit still in the router.
So many complaints and problems with router bits are caused by varnish buildup. Clean your router bits!
I just did another cleaning with one of my router bits in prep to surface one side of a body blank. Thanks Bruce!
Due to space constraints I try to make my fixtures multi-purpose when possible.
With this one I took two of Bruce’s fixture ideas and mashed it up for routing fretboard radius’s and made it wide enough so I could surface body blank halves (8”).
Due to space constraints I try to make my fixtures multi-purpose when possible.
With this one I took two of Bruce’s fixture ideas and mashed it up for routing fretboard radius’s and made it wide enough so I could surface body blank halves (8”).
Here's an example of a disposable router planing fixture that I made up this afternoon, for a one-time job. The big orange thing is a fiberglass mold made by my buddy Jon Wilson, for his upcoming all-carbon fiber version of his GuitarViol. He's changing the headstock design, and needs to rework the front end of the mold. So, he asked me if I could rout off a flat surface at exactly a 16 degree angle. Why, of course I can! This calls for a router planing fixture!
I took these pictures after the job was done, but you can see the technique. I measured carefully and cut a pair of plywood triangles at the correct angle, with their height about 1/4" higher than the material I had to rout off.
I cut them on the bandsaw, and straightened the long edges on my edge sander. Then I screwed them down to a piece of scrap plywood. The fixture took me maybe 10 minutes to make.
I positioned it under the mold, and clamped it all down. Then got out the big bridge router base, the same one I use for flattening my Scroll Bass body boards back on the first page. I took off the bar with the pins.
The job went fine, although it took about 40 minutes of routing. With fiberglass, you have to go in shallow passes of 1/16". And what a mess! I had it partially swept up when I took the pictures, but it was piles of fine white plastic particles. I definitely wore a full respirator face mask. I probably should have worn a bunny suit. I spent almost as long cleaning up as it took to do the job.
But anyway, another example of how router fixtures solve daily problems.
I took these pictures after the job was done, but you can see the technique. I measured carefully and cut a pair of plywood triangles at the correct angle, with their height about 1/4" higher than the material I had to rout off.
I cut them on the bandsaw, and straightened the long edges on my edge sander. Then I screwed them down to a piece of scrap plywood. The fixture took me maybe 10 minutes to make.
I positioned it under the mold, and clamped it all down. Then got out the big bridge router base, the same one I use for flattening my Scroll Bass body boards back on the first page. I took off the bar with the pins.
The job went fine, although it took about 40 minutes of routing. With fiberglass, you have to go in shallow passes of 1/16". And what a mess! I had it partially swept up when I took the pictures, but it was piles of fine white plastic particles. I definitely wore a full respirator face mask. I probably should have worn a bunny suit. I spent almost as long cleaning up as it took to do the job.
But anyway, another example of how router fixtures solve daily problems.
Sometimes my disposable fixtures become permanent. I build it, use it once, put it on a shelf. Then discover it 20 years later, and try to remember what it was for. I'm not kidding. I was doing some housecleaning in the shop last weekend, pulling out old stacks of fixtures from the '90's. And I found several that I honestly couldn't remember or figure out what they were for. But I apparently made them and used them for something. I'm getting old. And I've built a lot of fixtures in my time.
So I finally got around to trying to clamp the board as suggested but I found that I still have issues...
So I am using pieces of a yard stick between the board and the rails so that the bit can get to the edge of the board w/o biting into the rail. When I try to clamp it tight, those pieces tend to angle and push the board upwards (path of least resistance I guess).
Perhaps they need to be fixed to the rails so that they can't move like that? Maybe I just need a firmer material...
I *think* I've solved my own problem, without having to rejigger my... um... jig... 
So I bought some simple molding from Home Depot at $.67/ft:
I tested this by just sliding in a piece on either side of the board and then clamping side to side (hard to see in pic below, but it's there!) and I could not budge the board for ANYTHING and it stayed flush to the base.
Since I only needed about 4' of the stuff, its a $3 solution.
I actually think the fact that its a very soft wood helps here as well, allowing me to apply a decent amount of pressure as I try to get contact up and down the sides...
I'll be trying this out outside in the next couple of days. Hopefully my planing issues will be addressed because I'm backed up on ideas to test after attempting to make these necks...
So I bought some simple molding from Home Depot at $.67/ft:
I tested this by just sliding in a piece on either side of the board and then clamping side to side (hard to see in pic below, but it's there!) and I could not budge the board for ANYTHING and it stayed flush to the base.
Since I only needed about 4' of the stuff, its a $3 solution.
I actually think the fact that its a very soft wood helps here as well, allowing me to apply a decent amount of pressure as I try to get contact up and down the sides...
I'll be trying this out outside in the next couple of days. Hopefully my planing issues will be addressed because I'm backed up on ideas to test after attempting to make these necks...
The vertical position of your side-to-side clamps can make a difference in the behavior you're describing. If you position them even a little bit below the plane of your work piece, the jig (or the shims you put in it) will want to twist and push the board upwards like you described. Not sure if this is contributing for you or not, but figured I'd throw it out since my planing jig is similar to yours and I had to get used to that early on.
I put little "steps" of 1/2" mdf along the inside face of my jig to build-in the function you're using that molding for, laid out such that I can use a lower step for a thicker workpiece or a higher step for a thinner one and still get the top face of the workpiece about where it needs to be for the depth the router bit can get to.
I put little "steps" of 1/2" mdf along the inside face of my jig to build-in the function you're using that molding for, laid out such that I can use a lower step for a thicker workpiece or a higher step for a thinner one and still get the top face of the workpiece about where it needs to be for the depth the router bit can get to.
I didn't know where I could find strips of MDF only 1/2" thick... Home Depot seems to only have slabs that are 1" or thicker and by the square foot so that's why I grabbed the molding. The shims don't have to be precision cut here so this works pretty well. I mean they are already fairly uniform in dimensions, but they are so soft that any warping really is a non-issue once pressure is applied.
