Calibration offset & accuracy

[Amonaug]

Since I've never really did a offset calibration before due to a faluty board sensor (would give an error when trying to measure although I could carve, it has been replaced). I took a scrap piece of aspen that was somewhat square and ran the calibration. Then to check the accuracy of the cut/rip I took white covered MDC scrap, squared/jointed it and had the CC cut it to 14" x 7.5" then ran the measurement and came out to 14.04" x 7.46". Notice it is off by .04 on each side but it's .04 long on the X-axis and .04 short on the Y-axis. Ran the measurement several times to make sure the board wasn't slipping, etc.

Came to the forums to read up on it and realised I should have used a really good squared board for the calibration. So that is what I did and re-ran everything. When that was finished I took the same board I cut before and this time cut it to 13.5" x 7" and it came out to 13.53" x 6.98". An improvement on the Y-axis but still a little long on the X-axis.

Is this as accurate as I can get with the machine? I mean it's less than 1/32" error but still....

[Digitalwoodshop]

Can we say "Belts"..... Belts will give you a little error.... It is not direct drive.... Masking tape on the X gives it something for the brass roller to bit too.

AL

[Amonaug]

That's just it. I ran the measurement routine several times, loading and unloading the board. If it were the belts or anything slipping I should have gotten slightly different readings for each run. I didn't, the reading is exactly the same each time thus nothing appears to be slipping.

[Jeff_Birt]

CW suggests calibrating with the same type of stock that you normally use (or something in the middle color wise) as the board sensor will read different colored stock differently. The initial measurements that you type in for the stock you use for calibration must also be very accurate. A tape measure isn't very accurate.

[Amonaug]

CW suggests calibrating with the same type of stock that you normally use (or something in the middle color wise) as the board sensor will read different colored stock differently. The initial measurements that you type in for the stock you use for calibration must also be very accurate. A tape measure isn't very accurate.

Aspen is fairly light color and the board I used to cut was white. Used a digital caliper to get the thickness for the calibration board (it didn't ask for anything else).

Have you guys gotten exact measurements after using the cut/rip? Or has it been off a couple one hundreths of an inch?

[Jeff_Birt]

Try cutting the outline of a square (say 6") in the center of your board, so that it stays under rollers. Use the 3/8" bit if you have one. You should wind up with a square that is 6 3/16".

[Dan-Woodman]

Jeff
There has always been some confusion as to how big a square would be if cut out of the center like you are saying. If the 3/8" bit was cutting on center of the line wouldn't the final cutout be 6 3/8" .
Just as a matter of discussion, is the default on center or offset to the inside. Seems I read somewhere that you can change the offset by some , but not much.
any help would be appreciated.

later Daniel

[Jeff_Birt]

Well actually we are both wrong :( If you cut on the center-line of a 6" circle with a 3/8" bit you would be taking 3/16" off of each side so your square would be 5 5/8"

You can offset a bit up to 1/2 its diameter starting in version 1.125 or 1.126.

[Dan-Woodman]

Thanks Jeff
I was acually refering to the opening or hole in the board.
I've never tried the new bit offset, thanks for reminding me.
later Daniel