Bow Limb Lamination Grinder — Build One

pad 1 pieceThree-quarter-inch-thick MDF (Medium Density Fiber — no idea what that means, but there you have it) cut from a 4’x8′ slab purchased from Home Depot or Lowes for around $35.

If you started here and didn’t go directly to the design source of this machine (Jim Thorne’s How to Build a Simple Lamination Grinder), you probably want to see what happens when a inept dilettante tries to make and use one of these things. Ha ha! I shall not disappoint!

The first photo shows one half of the base of the grinder. To that I glued an identical twin.pad 2 piece

Titebond III’s doing the glue job. Probably any decent glue would work. Elmers? Why not?

Next the feet.base feet4’x’4′ squares.

Then the motor base slabs.motor half pad

motoro pad

OK, all the above we place firmly under the category: The Easy Part. The skills needed are: 1. Cutting stuff, and; 2. Gluing stuff.

motor sans drum

Next came the motor. That mounts on the base there. I marked the holes on the motor support, expertly drilled some holes, and ran the bolts up from the bottom. (But did not bother bolting them down because I would have to unbolt them later.) Then you can, if you like, place the drum sander unit on the motor’s axle. Axle? Is that the right term? No. Shaft. Shaft. Anyway….

motor with drumThat’s what it looks like. Pretty nice. Made me feel so far so good.

At this point, our leader (Jim Thorne) switches from 3/4″ MDF to 1/2″ for the dust collection unit. I don’t know why. Room abounds for 3/4″. I know. I checked it out. I was sore tempted to not go back to Lowes to buy yet another chunk of MDF.

But I did. Staying true to the Thorne design was important. How else can I fairly judge and critique the master’s product? So I bought a chunk of 1/2″ MDF. I will say this: it looks less clunky than the 3/4″ would have.

motor drum dust panel

The 5×7-something-inch board with the cross drawn on it is the only even close to complicated piece of the dust collector portion of the build. The intersection of those two lines is the dead center of the hole that will accommodate the shaft and grinder coupling. A Forstner bit and a rounded file covered that job nicely.

dust plate holeHere’s the dust plate with hole. The shaft sticks through. The hole is wide enough to accept the drum coupling. Forstner bit and file lounging nearby, exhausted from their labors.

The rest of the dust collection unit consists of another identical side without a hole and a 5″x5″ top. The design also calls for plexiglass windows fore and aft. As of this writing, I don’t have those pieces. It’s not because I think they’re a bad idea.

What you also see in that picture is the result of some steps I completely neglected to photograph. But there’s not much more to see. Two 16″x4″ MDF slabs (again, 3/4″ thick) with a hinged end. That unit allows you to adjust the height between your work pieces and the drum. Very important, and part of the genius of Jim Thorne’s design.

Here’s another look, now with the dust collection unit in place and the hinged ramp bolted down (bottom piece only — bolted to the base). Do NOT glue the ramp or dust collector…grinder exit closeSee that small piece of MDF at the base of the outer dust tower plate (right)? That is not a part of the design. I was using it for some experimental farting around.

At this stage, I might as well air my one complaint about this mechanism. Don’t get me wrong, it’s a minor point. It may be my own fault rather than a weakness in the design, but I need to put it out here in case someone comes along with a brilliant answer. Here’s the problem:

With this sucker all screwed down and the motor bolted to the frame, how you going to change that sanding sleeve?

Only way I see is to disassemble the dust collector. You might even have to unbolt three motor mount bolts and loosen the fourth so you can turn the motor enough to move the plate with the hole around enough to get your hex wrench into the two screws holding the sanding drum coupling to the motor shaft.

Again, this might have been my inept construction. But I’m not seeing any easier way to replace that sanding sleeve. What I’m tempted to do is cut and hinge the dust collection tower. That would solve the problem. And if not, how often would you actually need to change that sleeve anyway?

That depends on how often you use it and probably what sort of wood you’re running through it.

OK. Minor issue. Just wanted to point it out. If you can see how I screwed up the build or am missing something obvious, please explain in a comment.

Here’s the unit with shop vac  specialized dust collection hose attached….grinder exit

In the next installment, I reveal how I ran my first taper — how I got a stick to descend .002″ per inch for 36 inches. Or how I tried, anyway. Never underestimate the power of looming failure. A most potent spice.


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