Dimensions, dimensions

Gene Davis · Post by **Gene Davis** » Wed, Oct 24 2007, 4:25PM

If I want to set my panel stock thickness as decimal inches, must I do all my cab models using decimal inches as well?

I wish to specify my nominal 3/4 mel as having a thickness of 0.765\", and then have the blind tenon cutting all figured from that.

What I fear, is that my entire library of cabs, having been done using fractional inches, might be fouling my blind tenon fit-ups. This, even though I specified 0.765 inches as my panel stock.

Forrest Chapman · Post by **Forrest Chapman** » Wed, Oct 24 2007, 5:26PM

Gene,

Set your material to decimal if you like. This should not have any affect on your cabinets that are built with fractions because the decimal can convert the fraction to the exact number. Where as an odd decimal will be rounded to the nearest 32nd.

Forrest

Gene Davis · Post by **Gene Davis** » Wed, Oct 24 2007, 7:02PM

I think I've got a problem, and I am suspecting what it is. But let me rephrase the q, anyhow.

The q is, does this eCabs system think in thousandths of inches, or not?

Phrased another way, will it work to 1/1000 precision only when the global setting is decimal inches?

I am hoping that is not the case, and that the DIMENSION DISPLAY setting is merely that, being WHAT THE UNITS ARE FOR DISPLAY.

In other words, if I input my panel stock thickness as 0.765 inches, and that my tenons are to be 50 percent of thickness, with my mortise clearance set at 1/100\" (default, equal to 0.010), then my mortise widths should be cutting at a setting of (0.5*0.765) + 0.010, or 0.3925\".

This, REGARDLESS of whether or not I had set my dimension display to show in decimal inches.

Right?

And, if I have set my edgetape stock thickness using an input of 0.018\", then an overall width of a one-edge taped part specified at 12.000 means a cut width (before banding) of 12.000 - 0.018, or 11.988 inches.

Right?

Or does this program not think this way?

BTW, to be successful in doing blind mortise work in mel, what SHOULD my mortise width clearances be? Twice the default of 10 thou? Two and a half times? What works for you?

Rob Frenette · Post by **Rob Frenette** » Thu, Oct 25 2007, 12:50AM

Hey Gene
Hopefully i can can answer some questions.

1) Ecabinets does work in thousands of and inch.
2) It will work to the thousand when inch /fraction is used for display but only for fit and depth clearances. Everything else seems to round up or down and only as small as 1/32.
3) I'm pretty sure that dim display is more than just display. These numbers need to be accurate in order to get your joinery fitting properly.
But seeing as you can can set the machine tolerances in thousands of an inch while working in inches/ fractions this should not be a problem. My main concern is how the system deals with material thickness. So say for instance you want to set up sheet goods with .765 thickness and the program rounds this down to 3/4 when working in fractions, I'm not sure if you originally set the thickness to .765 and then switched to work in fractions if your original thickness will be retained in the system. We always work in decimal or metric so i don't really know if this works. If you switch the display from fractions to decimal this seems to be the case.
I wonder if this is the case with everything including edgebanding meaning if you originally set up edgebanding with .018 thickness and then switch the display to fractions this gets rounded to 1/32. So if you set up a batch with the display set to fractions do your parts get 1/32 taken off for edgebanding or the original .018 that you set the edgebanding at. It would be nice to know how the system handles this.
4) We use .015 for fit clearance and .030 for depth clearance.

DanEpps · Post by **DanEpps** » Thu, Oct 25 2007, 6:39AM

To add to what Rob says...everything is stored internally as decimal 1/1000ths (computers can't do fractions, just decimals

) but when calculations are done I think the rounding is carried out based on the dimension display setting. If you are using fractions, everything except fit and clearance is rounded to the nearest 1/32\". If you are using decimals, the exact dimensions you enter are maintained.

If you enter a 1/10000\" dimension, there is some funky rounding going on. For example, I created a display panel 10.001\" x 20.0001\". It displays the measurements correctly on the popup but the measuring tool shows the 20.0001\" dimension as 20.0002\".

Of course I don't work in .0001 tolerances so that doesn't bother me.