Squaring a spindle in YZ (lesson learned)

Yesterday I tried facing and deep cuts for the first time. Needless to say, they didn’t come out perfect. I’ve been cutting a lot of 2D profiles in <0.25" stock plywood, abs, and mdf with no problems. (Not true-- there were tons of problems. But none of the problems were with the SO2 hardware.)

When I started facing I noticed that the spoil-board bit was cutting ridges. It was actually cutting a saw-tooth pattern in the surface. It couldn’t be that the material or wasteboard weren’t level, because the facing should fix that issue. So what was wrong.

I got to thinking and I came up with 3 possible causes: 1) my spindle wasn’t square and needed to be shimmed, 2) a beam wasn’t square to the machine, 3) the makerslide beams were twisted/bent. I didn’t have a chance to go measure anything all day, so I was stuck with thought experiments. Also, if the beams were twisted…there wasn’t much I could do to fix them. Here is what I deduced:

If the spindle wasn’t square, I would have a square face and an angled face.
If the beam wasn’t square (or was twisted), I would have two angled faces.

Once I was holding the cut piece in my hand I could see that it had angled faced on both sides. It was pretty easy to tell that my beam wasn’t square (or was twisted…). Whew! I have no easy was of squaring the spindle, so I was relieved.

Here is what I did to fix the problem:

  1. Got my small carpenter’s square out and figured out which beam wasn’t square. For me, the X-axis was off-square in the YZ plane. My spindle was pointed slightly toward the back of the machine. And the problem was consistent across the length of the beam - no twist!

  2. Make sure the X and Z axis V-wheels were well-seated and tightened. This might vary depending on your problem. I was going to torque on the Z-axis and didn’t want to risk damaging anything that was loose. The X-axis wheels were tightened to maintain the X-beam spacing when I loosened the ends.

  3. Loosened the ends of the X-axis beams.

  4. Using the carpenter’s square, torque the gantry carriage to fix the squareness of the beams. At first, I tried to do this by hand–I couldn’t tighten the screws without letting the pressure off. So I got creative. If you’re a real machinist, please don’t cry:

I turned on the SO2 and jogged the Z-axis down really slowly. If you’re going to do this, make double sure that the screw are loose. You could bend the beams for real.

  1. Check that both ends of the X-axis are square to the Y-axis and tighten the front piece of makerslide (closest to the spindle).

  2. Release pressure on the spindle and check to make sure that the beam stayed square.

  3. Move the carriage to either side (to hold the offset) and tighten the corresponding aft makerslide (away from spindle).

  4. Recheck your work and do a test run!

In the end, I think that the weight of the gantry carriage had pulled the beams out-of-square during assembly before I tightened the ends. I have no idea how accurate my machine is now, but it passes the eyeball-test. Anyone else have any other ideas about what might have happened to how to fix this problem?

I had the same type of issue when I replaced the 24V spindle with the 611, and noticed that there was a .012" step when using my 3/4" wasteboard cutter. Turns out the bit was angled toward the front, although the issue was virtually invisible in all directions with a 1/8" bit. Here’s how I fixed it:

.097" of business card strips stuck in as shims at the top, along with longer screws to hold the vertical slide to the X-carriage. I’m sure there’s a more elegant solution, but for now it works just fine.

Looks good to me. Do you have any issues with the paper compressing? I was a little worried about using it as a shim, but it seems like yours is working just fine.

No problems yet, and it’s been more than a month. It’s card stock, so it’s pretty solid stuff.

I just squared my spindle using a combination of both methods (pushing up with the Z axis with both rails loose & shims – altho I used plastic from some packaging).
To measure how far off square I was, I used the following contraption, made from a dial indicator, some 1/4" rod and some scraps of plywood.

I got the side to side height difference to less than a thousandth (over 5" distance) and the back to front to less than ten. When I milled my work surface flat, I used a 1/2" bit and you can barely feel some texture to the MDF. I think it will be fine with the more usual 1/4" or 1/8" bits.


I like your contraption! Looks like a much better option than a $200 spindle square. I think I’ll have to try that. I was thinking about getting a dial gauge to adjust my movement parameters anyway.

Yup, one of these, and the matching test indicator to measure runout. Well worth the money!

OMG, that is brilliant! I think I would use aluminum, but you have provided an AH HAH! moment with this picture.

Thank you.

I’ll have to make oneof these wooden brackets. I was going to use a depth gauge with a magnetic base but nowhere to stick it to!
I have a Protram for my small mill but it’s too big to fit in the router. Perhaps an adaptor…

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Wow, yeah, that is a nice piece of kit!