Table Construction

[yankeepapa]

Dana-

Oops. I don't see your email address. You can contact me here or offline: dcm(at)c-sw(dot)com.

TIA

-David

[dana_swift]

David- you have mail. Check your spam folder if you dont see anything.

D

[dana_swift]

David- I keep getting DNS unresolved bounce messages from dcm c-sw com (at and dot not shown). So I put some pictures here..

What I did is drill two holes in a peice of UHMW, the hole geometry centers a dial indicator over a bolt. Hopefully the picture helps show this.


31575.jpg


Then I can "loosly" bolt the dial indicator over any hole in the BT-32 table grid. I chuck up a peice of 1/2" round smooth stock about 3" long into the half inch chuck of the router. Then move the router to above the hole the DI is located in using M2 commands.


31576.jpg

Between these photos you can see the dial indicator pivots over the vertical bolt. When the router is directly above the bolt the dial indicator will not change as you rotate the UHMW.


31577.jpg

(Note in these photos I am actually setup to make parts using the vacuum fixture you see.. if I were really doing the table squareing I would have nothing on the table at all, no vacuum fixture or spoilboard. I just took these pics to give an idea of how I do my squaring.)

Once above the hole I slowly lower the router using the K keyboard interactive mode. Use caution, you must pull the dial indicator probe out of the way during this process! Then change the position of the router using M2 until the dial indicator can swing completely around the router moving no more than 0.001 inches.

Note the position of the X and Y values on the SB3 readout.

Do this again at a position along the gantry motion (BT default is to lable this as Y (I consider this as X in my setup)). Now you can measure in thousandths exactly how square the gantry is with respect to the table.

Then I loosen the bolts holding the right side of the gantry to the extrusion. Using a furniture clamp I put a small amount of pressure on the gantry to move it. See the photos.


31578.jpg


31579.jpg

Knowing the thread pitch on the furniture clamp lets me know about how far to turn the screw to get the amount of movement the dial indicator is calling for.

It is an iterative process, the first time it takes forever, but you will check this every month or two to be sure it is where it belongs. When the average temperature of my shop changes by about 10 degrees F I recheck it. It is usually different from where I set it by 0.001 or 0.002.

So measuring two points on the table using the simple dial indicator fixture allows very accurate squaring. However CHECK YOUR TYPING using the MX, MY or M2 commands.. you can drive the router into the dial indicator and destroy it! So far I haven't done that.

You could use the "center in hole" routine provided by shopbot, but that requires a fixture like the superzero, and I don't have one of those, I did have a dial indicator and some UHMW.. so this is what I did.

Once the table is 0.001 square you can get some real precision from the SB. If the table is not square it doesn't matter what you do, you will not get precision!

D

[yankeepapa]

Dana-

Thank you for the photos and information. My email address is valid, but some systems on the 'net balk at the hyphen (i.e. "-") in my address. (The hyphen is a valid character, but I guess some software developers along the way forgot that.)

Anyway, thank you for the information.

-David "thinking about a new email address" Matthews