Z Smooth Rod Hole Sizing

[apapdev007]

I'm more apt to think that it's a physics/geometry problem if an M8 rod won't fit into an 8mm hole rather than a problem in the machine that is making the part. ; )

My Harbor Freight special Pittsburgh calipers measure my VBX hardened chrome rods to me 7.99mm in diameter. The metric tap and clearance chart says to drill a 8.40mm hole to close fit M8.

Line 18, 19, and 20 of conf_bushing.scad //z smooth rod. See note above. You can adjust it in inc/conf_bushing.scad, but the problem is likely to be in machine. translate([-12, 7, 0]) cube_fillet([24, 13, 4.5], vertical=[3, 3, 0, 0]); translate([0, 18, 0]) cylinder(h=2.5, r=(bushing_z[0] + 5 * single_wall_width));

busing_z[0] comes from configuration.scad. I have mine set to conf_b_lm8uu, which comes from conf_bushing.scad and is preset to [4, 7.7, 45, 0, "lm8luu bearing (double length)"]. There for busing_z[0] = 4 right?

[Lodran]

Frankly, most printers, when asked to make an 8mm hole, will make something a bit smaller than that, and most designers work around the problem by adding a slop factor to holes. The better calibrated their printer is, the smaller the slop factor the designer generally uses.

That said, the experimental version of slic3r contains code to compensate for extrusion packing along the inner edge of a hole, so I expect that we'll be seeing lower slop factors as time goes on.

[apapdev007]

So that 4 needs some padding on it then. I wonder how many places touch that value? Should that value be changed or should that arg just be pointed to another variable like m8_diameter in inc/metric.scad. Well, that's for a bolt with threads though and the one it's pointing at now seems to be for defining the size of the hole inside that bearing. Should there perhaps be another variable in metric.scad like m8_smooth_rod or something so that everything needing a void for an M8 smooth rod could reference it? I say this because if someone actually intended to make something to match the inside of that bearing and it had been changed to 4.2 to make a void for a smooth rod, it's now too big for it's purpose.

[apapdev007]

What an ass am I? First off, those lines come from extras/calibrate.scad, not conf_bushing.scad as I previously stated. Then the line that actually makes the hole is 34:

//z smooth rod translate([0, 18, -1]) cylinder(h=20, r=bushing_z[0] + single_wall_width / 4);

Where it is adding a quarter of a layer width to the radius of the rod. I guess I was seeing that plus as a comma.

I'll just keep my mouth shut. Sorry. Someone close my crappy issue please. I promise to not look at any more code in a hurry on my lunch.

[apapdev007]

Please see my last note.