How square is enough?

[zeeway]

So as my machine nears completion (I hope), I am trying to get the all the axis (axes?) square to one another using a carpenter level and a framing square and whatever else I can think of. I have one of those laser thingies for hanging pictures which I rarely use - guess I could use that, too.

So my questions:

1. What do you use to square your machine - and what process do you follow?

2. When do you re-square a machine?

2. How square is square enough? Seems to me when you cut 3/4 inch material, if the spindle is not dead square to the table, your edges will be off-square by a like amount, and parts will not fit together correctly. Or am I overthinking this?

Thanks for your help,

Angie

[carvemylog]

I used a 12" caliper to get the Z axis square to the table and realized pretty quickly that I would probably never get my machine square enough, or the table flat enough. One way around it is to always mount the parts you are cutting to jigs that you surface with your machine. That way if the table isn't perfectly flat/square, the jig will be.

As far as the X and Y axes, I got them as good as I could with a T square and then measured test cuts in MDF and made adjustments to the machine until I could make round circles and right angles on rectangles.

[ger21]

Cut some small squares and check them with a good square. AS for the Z being perpendicular to the table, get the largest bit you can and surface the table. If it's not perpendicular, you'll get ridges. Be sure to travel in both X and Y directions.

Re-square if your parts don't fit.

How good is good enough is up to you.

[stevespo]

Ditto what Gerry and carvemylog said. How square it needs to be definitely depends on the types of projects you're doing. You might tolerate a few thou out of square on a small part, but if you extrapolate that to a big part it might really ruin the job.

Personally, I test cut some small squares that I could measure with a dial caliper and was pretty happy. Then I started cutting bigger and bigger parts and realized that my table was about 1/32" out of square over the 24x32" table. Perhaps only .001" per inch, but no good for my needs.

So, I drilled holes in each corner and measured the diagonals. Tweaked the setup, plugged the holes, and redrilled. Only took a couple of iterations. When they're equal, the XY table is square. You can probably get the Z close with a decent machinists square. First surface the table, then check for square. Like Gerry said - the goal is smooth, no ridges.

I like the 1.5" Grizzly bit for machining my worktable and fixtures. The bigger, dedicated "spoil board" bits are very expensive. This is affordable and a pretty reasonable size, especially for benchtop sized machines. Does require a router with a 1/2" collet, but there may be 1/4" options as well.

http://www.grizzly.com/products/Bott...1-2-Dia-/C1261

Steve

[dxhale]

For Z if you have a solid table you could always put a dial indicator in the spindle and sweep a large circle and tweak it from there. If you dont have a dial indicator or a way to put the indicator in your spindle, I would just do what carvemylog suggested and mill the surface the part is going to sit on. This way the part will sit perpendicular to the spindle with out much effort on your part. For X and Y you could square up a steel block to the table and use a c-clamp to hold it down while sweeping it with a dial indicator.

[ger21]

Originally Posted by dxhale If you dont have a dial indicator or a way to put the indicator in your spindle, I would just do what carvemylog suggested and mill the surface the part is going to sit on. This way the part will sit perpendicular to the spindle with out much effort on your part.

For a larger part, that may not work. You can mill the surface with a badly angled tool, and still get a relatively flat surface. It may have ridges, but if the part spans multiple ridges, the part will sit flat, but the tool will still be at an angle.

[scotta99fan]

I suggest placing a .0001 test indicator (mounted on magnetic base) on the face of the spindle. Next check for parallelism of the table to the X and Y plane by simply traversing on the X-axis then on the Y-axis and note your findings. Next, with the indicator extended out parallel to the table (or as close as possible) and sweep the table for tram.

If your parallelism is not good, it will be difficut to make your machine square without scraping. If your parallelism is good, the tram will tell you how square your machine is.

Scott

[zeeway]

Thanks for all the replies. I am concluding that I should square it up as best I can before machine is under power. Then when it is powered, cut some test pieces, measure, and adjust from there.

My thinking for the Z axis is to mount a piece of drill rod in the router collet, mount a dial indicator and check for runout in the x and y direction as the Z axis is run up and down. I am guessing that should be done in a few different spots on the machine.

I have to laugh when I think how I square my table saw blade. I did use a dial indicator to set the rip fence ( Beis clone), but only one end of the fence is clamped down, so it must move some. Then I usually square the blade to the table by eye with a square. This seems to work okay for the simple cabinets/boxes I build. Luckily, I have avoided building space shuttles in my shop, so far.

This stuff can drive you crazy if you think about it enough.