Milling wood

David B

Over the weekend I made a couple of pillow blocks out of a hardwood board. Very basic - they have a pair of flanges to bolt to a wooden base, a horizontal hole to hold an old rollerskate wheel bearing about an inch above the base, with the bearing holder split at the top so a bolt can clamp the wood tighter around the bearing.

I made two of these to support a long threaded shaft so when a stepper motor turns the shaft, some travelling nuts will provide the linear motion for a drawer-slide carriage.

I used a tablesaw to make most of the cuts, and had a hard time getting them cut the same size, with square corners, etc.

With metal, I assume you could use a milling machine to make pretty much all the cuts and holes. But with wood, is there any way to do this that would be better than a tablesaw? Is there such a thing as a milling machine for wood?

Phil Pilgrim (PhiPi)

David B wrote:

Is there such a thing as a milling machine for wood?

'Sure is: Google CNC router. BTW, for hard woods with a tight grain, a metal-cutting CNC mill can also be used, but they typically don't have a fast enough spindle speed to cut most woods cleanly.

-Phil

David B

On the other hand, the parts don't have to be wood.

All I want is it to work, and wood was available in the garage.

Maybe a 3D printer would be a better way to go.

Spiral_72

As you found out, it's very difficult to cut shapes on a table saw. If you use a harder wood like oak, it generally makes for a cleaner cut, birch or poplar would be better than pine....even though I like pine, it's hard to work with. You didn't say what you were building, but keep the shapes as simple as possible and cut them (stacked) at the same time if possible. There may not be a good reason to make a T-shaped pillow block whereas a rectangle with a hole in it would work just as well even though that's no "Pillow block shaped". You can get acceptable results on a table saw, it just takes a lot of care. You might find it helps a lot to use a C-clamp on the far side of your rip fence to prevent it moving..... and measure your cut on the front AND back of the blade. A band saw with a guide / rip fence is very useful as well.

You can machine plenty with a CNC ROUTER which is typically used for wood, foam and plastic. Call around if you'd like. There are plenty of these hiding in cabinet shops, home shops and the like. We found one not 20 miles away from home and another 10 miles from my work,

McMaster-Carr has some very inexpensive plastic pillow block bearings if that will help you any. I'm not sure what your budget is..... If it offers any consulation... I woulda' tried the wood blocks first too

David B

Here's as far as I've gotten. I'm no woodworker; I just wanted a strong bearing support, which these seem like they may perform very well at. I don't know what kind of wood it is but it's really hard.

I had thought about using just a simple rectangle with a hole for the bearing but wanted some control over clamping the bearing so it could be reclamped to be most square fairly easily, and was hoping that this design would let that work.

LoopyByteloose

Trying to do everything with a table saw is a challenge.

Usually for cabinetry, you would use a joiner or planer to get the materials down to standard dimensions and very square. Then the table saw would be used to cut panels and a radial arm saw would be relied on to cut lengths.

Fancy edge details would be done with a shaper. And in some cases, you might need a belt and a disk sanding setup to finish rough ends.

If you want to rely mainly on the table saw, having a planner blade can work in some cases. It has very fine teeth and is intended to produce a smooth finish - but it goes slower and requires more resharpening. When I was doing woodwork, I had a stack of over 20 blades that were constantly being sent out for resharpening. Trying to get everything done with one dull blade is rather absurd and even carbide blades need to be redone.

There is a vast amount of knowledge about different varieties of wood and what they will and can do.

Oak is very good for strength, but also needs to be sufficiently seasoned in order to have stable dimensions. Using green oak wood will result in warps after every cut relieves tension and stresses within the wood. Problems are similar if you get into machine work as aluminum, brass, and steel have individual properties and each has quite a few alloys that can require different handling.

mindrobots

Ouch! Looking at the size of those compared to your mouse makes my fingers tingle getting that close to the blade. Please tell us you were using push tools and other safety devices....and don't do it again. Something that small doesn't want to be the only thing between you and a spinning 10 inch blade. Maybe a band saw next time or a router with a template and a straight bit.

Another problem with wood is its tendency to want to split along the grain lines. Aircraft grade or hobby Baltic birch plywood is another good choice. It's dimensionally stable and the plus have crossing grain patterns to add strength and remove the change of fractures with the grain.

Most importantly, don't get your fingers that close to a table saw blade - it takes FOREVER for them to grow back!!

graffix

You might want to re enforce those with a metal plate or large washer or something.I'm just thinking they may crack from stress or expansion contraction.

David B

Oh yeah, I used plenty of pushing and holding devices; my fingers don't get near the blade. A number of years of running a newspaper printing press does a pretty good job of teaching respect for keeping one's fingers away from rotating machinery.

These are to hold a long threaded rod to move a linear carriage, so the stress will be mostly be in the direction of the bearing axis. The stress should be pretty minimal; this is for one axis of an optical scanner for a book reader, so the only load will just just be the photodiode array and some LED lighting. I just wanted to make sure they were rigid enough that positioning can be dependeable to about the size of the pixel or so.

I don't do much woodwork, and only have the table saw, a drill press and a dremel for power tools. I looked at CNC tools for doing a better job of making this sort of thing, but also have been looking more at 3D printing - that really looks promising for general purpose part building.

I watched some working at the San Mateo makerfaire last year, and at the time thought, yah, I guess that's kind of cool, but now that I have a need for parts like these, they're looking like they could be pretty useful.

JasonDorie

You can build a CNC machine that will do "wood milling" relatively easily. I made one with a drill press and miter saw from plans I bought online for $50. The machine itself cost about $1200 total, and had a cutting area of about 23" square. I used it to make the machine I have now, which has a 48" x 60" cutting area and it much more rigid and faster.

These are examples of what you can do with just the wooden machine:
http://www.facebook.com/media/set/?set=a.79583123972.102562.671403972&type=1&l=ca50239e9d

And here's the build log and some stuff I've done with the big one:
http://www.facebook.com/media/set/?set=a.10150268257853973.377792.671403972&type=1&l=9c0575f01a


The accuracy I got from even the small wooden one was astounding. I had some vague ideas of what I'd do with it before I built it, but believe me - the stuff you realize you can do once you have one will keep you busy for a while.

Hmmm... I just noticed you're in Walnut Creek - Want to buy a small wooden CNC machine? The electronics alone were $400 new. I'd sell the whole thing for $600.

David B

Thanks for the offer, Jason, but I think I'm I'm starting to lean more towards a 3D printer; it's just amazing what those things can do.

JasonDorie

Yeah, those are cool, and I want one too. If you're looking to make relatively small plastic parts that don't need to be ultra-accurate they're awesome. And they can do significantly more complex shapes than a 3-axis CNC - hollow parts, undercuts, etc, etc.

I want the trifecta : laser cutter, CNC, and 3D printer. I figure with that I could rule the world. Or at least my project list.

LoopyByteloose

There are advantages to wood. Foremost is it is lighter in weight, but it also is much less stressful on the CNC due to lower lateral loading.

So a CNC milling for wood may be more optimal than one for metals. An added benefit is that you can cut block plastics, such as polypropylene with it. There are tons of items that can be made for robotics with polypropylene. And it some cases, 6061 Aluminum might do well. Since there are a lot of good woodworking routers and carbide bits for these, the power module is a rather simple purchase choice - less so that with working steel and other metals.

http://langergrp.com/high-density-polypropylene-block-p-1292.html <= here is a supplier for Polypro slabs.

I also ran across a mention that RC hobbyist are using laser cutter for birch plywood motor mounts. So in some case, the laser cutter can cut wood as well.

I've got a copy of "CNC Robotics" by Geoff Williams and though the electronics have definitely evolved; it is a helpful reference for the mechanical side of things. You might pick up a used copy or take it out of the public library.