ShopBot PRSalpha - Calculating Feed Rates and Rpms with Chip Load

SBG 00185 Copyright 2015 23
Quick-Start Guide for PRSalpha and PRSstandard tools
Number of utes: The number of utes on a bit is essenal to calculang proper feed and speed
rates. For most applicaons, a bit with 1, 2, or 3 utes can be used, but feed rates and RPMs must be
adjusted to maintain proper chip load (see below).
End shape: Straight and up-spiral bits come in a variety of end shapes. Square ends are most common,
and are a good choice for creang pockets and grooves, cung proles, simple leering, and drilling
operaons. Ball (or rounded) ends are best for 3D carving. VCarve bits are oen used to create com-
plex leers for sign making. They can also be used to chamfer edges and create countersinks for screw
holes.
Calculang Feed Rates and RPMs with Chip Load:
Chip load refers to the actual thickness of the chip cut by each revoluon of the cuer. It is the meas-
urement that all feed rates and speed calculaons are based on.
A spinning bit generates fricon and heat as it moves through the material. Part of this heat is pulled
away by the ying chips. A larger chip load pulls away more heat, but also puts more stress on the
cuer. Each material has its own ideal chip load range that balances heat dissipaon with cuer stress.
A basic chart (in .pdf format) for common materials can be found in the SB3 soware by clicking on “[T]
ools”, “Chip [L]oad Calculator”, and “Chip Load Help”. Use this chart along with the Chip Load Calcula-
tor to determine a good starng speed for each toolpath.
Do not rely on the tool database default sengs when calculang feeds and speeds for a toolpath.
Those values are only placeholders and are not intended for any parcular material.