#! /bin/zsh
#
# this file:
#   https://dataswamp.org/~incal/conf/.zsh/tools
#
# symbols that seem to indicate:
# - use safety gloves, earmuffs, and goggles
# - for cutting only
# - read the manual
# - don't use a broken disc (?)
# - cut Inox or SS
#
# EN 12413
# a DIN standard: "Safety requirements for bonded
# abrasive products"
#
# 125*2.0/1.0*22.23
# outer_diameter, thickness; inner_diameter, thickness (mm)
#
# MAX 80 m/s
# RPM 12200
# when disc is at 125 mm
# when disc is at 22.23, speed is 14 m/s
# the program below computes this
#
# AS 60 T INOX - BF
# INOX is again Inox and/or SS
# the rest - ?
#
# Fe/S/Cl <= 0.1%
# a chemical property of the material?
# health related?

rpm2ms () {
    local diam=$1 # e.g.,   125 mm
    local rpm=$2  #       12200 RPM
                  #       ---------
                  #          80 m/s

    local diam_in_m=$(( $diam / 1000.0 ))

    local pi=3.1415

    local c=$(( $diam_in_m * $pi ))
    local dist_per_min=$(( $c * $rpm ))
    local dist_per_s=$(( $dist_per_min / 60.0 ))

    printf 'm/s = %.0f\n' $dist_per_s
}