From 61253b1f37f991eb740332acc11ff0b9653540e7 Mon Sep 17 00:00:00 2001 From: Adrian Mariano Date: Sun, 29 May 2022 08:57:28 -0400 Subject: [PATCH] screws doc tweak --- screws.scad | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/screws.scad b/screws.scad index 32e0fb5..2d841e4 100644 --- a/screws.scad +++ b/screws.scad @@ -4,7 +4,7 @@ // Included is a function for calculating the standard dimensions of screws including the // tolerance values that are required to make screws mate properly when they are formed // precisely, so if you can fabricate objects accurately then your screws will mate -// with standard hardware without the need to introduce extra gaps for clearance. Those +// with standard hardware without the need to introduce extra gaps for clearance. // Includes: // include // include @@ -94,10 +94,15 @@ include // in cases where no default exists you can specify it. // Subsection: Tolerance // Without tolerance requirements, screws would not fit together. The screw standards specify a -// nominal size, but the tolerance determines the actual size based on that nominal size. Screws -// modeled by this method will have dimensions consistent with the standards they are based on, so that -// they would interface properly if fabricated by an accurate method. Different tolerance designations -// are used for nuts and screws, and also for UTS and ISO. +// nominal size, but the tolerance determines a range of allowed sizes based on that nominal size. +// So for example, an M10 screw with the default tolerance has an outside (major) diameter between 9.74 mm and 9.97 mm. +// The librasry will use the center point in the allowed range and create a screw with a diameter of 9.86 mm. +// A M10 nut at the default tolerance has a major diameter (which is the inside diameter) between 10 mm and 10.4 mm. +// Shrinking the major diameter of a screw makes the screw loose. Shrinking the major diameter of a nut, on the other hand, +// makes the hole smaller and hence makes the nut tighter. For this reason, we need a difference tolerance +// for a screw than for a nut. Screw tolerances Screws modeled by this method will have dimensions consistent with the +// standards they are based on, so that they would interface properly if fabricated by an accurate method. The ISO and UTS +// systems use different tolerance designations. // . // For UTS screw threads the tolerance is one of "1A", "2A" or "3A", in // order of increasing tightness. The default tolerance is "2A", which