rotozip bits have more then 1 inch of side cutting area. But the spindle that Robert used will take 1/4inch bits, and those are available in many sizes including the bets of the betst. 65-026 Onsrud Single Flute 1/4inch SolidCarbide with 1.25inch cut depth. I would never try a cut more then probably 1/2in in depth on these style machines, I doubt they are strong enough to avoid chatter at that DOC.

What do those people use to cut 2" foam? I know some use a hot wire but I think I saw a 2.5" bit with 0.25" shank.

Check out this Calculator for what bits can do:
http://zero-divide.net/index.php?page=fswizard&shell_id=199
Also you can calculate the torque at any point on the bit Torque = Force x Length. The force comes from you stepper motors and the Length comes from your bit length between the collet and the material.

I found a pre-alpha program called the machinists math kit
http://sourceforge.net/projects/machmathkit/?source=navbar

ooooooh pretty. Can't wait for the collet chuck to arrive.

In the PhlatForum there is a guy who is building an electric car from scratch. If I recall correctly, originally he wanted to make the body out of 2" foam section but couldn't get the right bit to do the cutting. I think he ended up doing it in 1" foam.

If you have a link to a 2.5" bit, post the link, please. Everybody will be thanking you. lol

http://www.toolstoday.com/p-5202-st...er-bits-12-shank-2-flute-high-production.aspx

Part way down the page you will find 1/2 inch 2 and 3 inch long bits.

There you go, should be great in foam. Not in one of these machines though. I just don't think you will see 2+ inch DOC in 1/4in shaft bits.

1/4"x2 1/4" (4" OAL) is fairly easy to find https://www.google.com/shopping/product/16267331210206391260?espv=210&es_sm=122&biw=1920&bih=1017&output=search&q=1/4" foam cutting bit&oq=1/4" foam cutting bit&ei=c7veUsu6IOWN2gXC_4G4DA&ved=0CH0QpiswAg

If you want longer, you will probably have to go up in diameter.

Well I stand corrected on the 1/4in shank diameter

DOH! Someone beat me to it. But now I know I definitely want 1/4" ER collet tool holder and not 1/8".

Getcher motor runnin'. Here's the wiring diagram I used to get an Arduino to make the motor spin at various speeds. Oh man I messed it up. The white wire goes to the pin9 and the black goes to GND. sheesh.
Just a word of caution, these motors are extremely dangerous. I have mine bolted to a board and the board is clamped to my desk. I tried to run it without bolts/clamps and it took off like a wheel and almost smashed my monitor. You have been warned...

Almost there.

This is why when we build quad copters the opposite side goes in reverse.

To balance the torque.

Hold the motor in your hand and feel the head torque.

This is why i have my Z axis down the middle of my spindle shaft. In relation to X,Y moving parts.
Others might find this method allows for better torque control, as it is more balanced being on the Z - Axis center.

When you move the Z Axis from the X, Y you are exaggerating the torque effect.

Hold motor turn on, hand close to body. Then move the arm to full length turn it on, harder to control. You see.

I think it is torque acting on a lever, when it should rotate around the spindle center @ x, y location reducing this lever effect to ZERO.

interconnect.me.uk

Yep, with washers on both ends. I left off the lock-collar for now and will make a clamp the same way they make scope mounts... maybe 6 screws holding it onto the v-slot. I'll have to add a right-triangular brace in the future to keep the vslot from flexing.

Is it not true if you reduce shaft length on the tool then you get less flex in the tool doing the work?

This is what i would do, reduce errors by reducing long parts to shorter parts that have less flex.

Yes, but the shafts you can buy are always long. The motor bearings are weak and can't handle a side-load so we use the extra shaft to add bearings and then the bigger bearings are coupled to the z axis. The actual distance between the tool and the mount is maybe 2cm. The top of the motor spins freely and the bearings all the way down are fixed to the machine. But yeah it kinda looks like this big long thing which is connected at the top so it has a huge torque radius... but that's not the case, depending how you mount it.

You are right, of course, the longer the shaft the more it flexes, BUT, it also makes it easier to give the shaft support. If you put a bearing, with its support, just before the chuck (or what ever you use to hold the tool), you are way better off than relying on the bearings of the motor and the motor will thank you by living longer. It's even better if you put another bearing on top of the motor. I tried it on my machine but since my machine is made of MDF I had aligning issues and had to take it out.

Hey dudes,
So I am getting ready to make all this and wanted to run it by you all to make sure it will work. I've got a double-fluted solid carbide bit with 1/4" diameter(6.35mm), some aluminium from the recycling centre (plate=12mm or 1/2" and block=37mm or 1.5"), and my spindle is mounted very cheaply with some bearings, hose clamps, and a steel plate at the top. I plan to use foam to test it and then maybe some wood and then finally this aluminum.

Dude, it will work fine. Just make sure you cut in many, shallow, passes at low ipm and use liquid to cool the cutting bit and material.

How shallow a cut? That, my friend, you'll have to find out by trial and error. I would start with 1/64" at 5ipm and then go to 1/32" at 5ipm. If that works fine increase the ipm rather than the depth.

Great build Sir!

This just up my alley



Iv worked with brushless motors for over a year for "non-RC" applications. This homemade electric longboard is what introduced me to DIY side of life I weight 150lbs and can get 27mph out of this little motor (25.2volts and 200A ESC), don't underestimate these little buggers, they'll nock your teeth out.

dang this aluminium is tough to mill. I had the feedrate way down to 100mm/min and it chattered the machine to the point of slipping steps and flexing the gantry. I believe 5ipm=127mm/min... so maybe I can try again at 20mm/min but now the v-slot wheels on one part have a little play that can't be taken up by the eccentric spacers... Does this mean the wheel is hosed or the hole is off or the screw is bent or what?

If the spindle is bucking in any, the bit will bounce rather than bite. You shouldn't be having to push anywhere near as hard as you are. Maybe it's time to rethink the mount.

Have you successfully done any plunge cuts with the bit? (assuming it is plunge capable)

I cut some pine with ease and it came out clean and smooth. Go too fast and it chatters. I guess the bit was bouncing like you said. I don't have any other way to mount it except like Robert did with the angle bracket and no bearings but I was trying not to burn out the bearings on the motor. Sigh, guess I can remount it...

Consider cutting a V-shaped notch in a couple blocks of wood and wedging them behind it. Cinch it down into the notch and that will give you a good grip with minimal contact so you can still easily dissipate heat.

What about making the mounts out of plexiglass? I think they'll hold together long enough to mill some aluminium replacements...

Any material is probably fine, the main goal is just to get it wedged into something with a wider spread to stabilize it. Notice how Mark has the spindle wedged and tightened into a V-shaped support on the OX build.


Photo credit kram242

It's mainly your lower mount that appears suspect, but it wouldn't hurt to apply the same principle to both. Once it's solid, you still have to deal with the play in the wheels.... Sorry, no suggestions there.