Anti-Kickback.....or ‘BG’ Test?
The term ‘Anti-Kickback’ has been an industry topic for quite some
time and relates to cutting tools such as router bits, saw blades,
etc. There are several brands of ‘Anti-Kickback’ router bits
presently on the market and all of them, it seems, would offer some
degree of safety to the end-user because they limit the ‘chip-
thickness’ of the material being cut. In other words, the cutting
tool will take less of a ‘bite’, thereby decreasing the likelihood
of a kickback. While this is true, however, it should be pointed out
that there are significant details to be considered when designing,
manufacturing and using industrial cutting tools.
1. What is ‘BG’? ‘BG’ is an acronym for ‘Holz
Berufsgenossenschaft’, the German Woodworking Trade Association.
For the sake of worker safety, this esteemed group has established
basic rules for the design, manufacturing and use of cutting tools
for the wood and plastic industries.
These basic rules concern testing the working safety of woodworking
machine tools. They establish test procedures and indicate all
essential regulations and rules of technology, which need to be taken
into account during testing. Precise geometric design, as well as
the use of high quality materials and replacement parts complying
with DIN standards, will ensure a safe tool with a high degree of
precision in the production and the balance of the tools. The
purpose of the test is to ascertain whether it is ensured that users
or third parties, who are handling the tools properly are, in fact,
protected as far as possible from risk to life or health.
Tools for use in wood and plastic working are classified into two Manual Feed Operations
groups: manual feed operations and mechanical feed operations.
‘Manual feed’ describes the holding and/or guiding by hand of the
workpiece or of a machine element incorporating a tool. Manual feed
includes the use of a hand-operated carriage, on which the workpiece
is placed manually or clamped and the use of a demountable power feed
Tools for manual operation marked ‘BG-TEST’
are designed according
to the following rules:
a) Thickness of chip limit with a maximum cutting edge projection of
1.1mm (.043"), over the total length of the cutting profile;
b) Restricted maximum chip clearance width, including the regrinding
range as a function of the cutting flight circle;
c) Kickback ratio must not exceed 0.25 Vr/Vs <
(where Vs = cutting velocity and Vr = kickback velocity).
Special purpose tools which, for reasons of speed and economy, cannot
be inspected by the German Woodworking Trade Association may be used
manually, if they conform with the above requirements.
Mechanical Feed Operation
‘Mechanical feed’ means a feed mechanism for the workpiece or
tool, which is integrated with the machine and where the workpiece or
machine element with incorporated tool are held and controlled
mechanically during the machining operation.
All the tools may be used for mechanical feed operation. The rules
that characterize manual feed operation tools do not apply to them,
except for the manufacturer’s label and maximum permitted speed.
The basic rules applying to manual feed operations do not apply to
router bits with diameters smaller
2. ‘BG’ Form vs ‘BG’ Test - ‘BG’ Form is a term indicating
cutting tools which have the same general circular shape of ‘BG’
Test tools, but which do not comply with the strict regulations
governing ‘BG’ Test as outlined above. (1.1mm cutting edge
projection, restricted maximum chip clearance width etc.) There is a
significant difference between the two.
Important Note: Unless specified otherwise, all router bits over
16mm (5/8") diameter in this catalog are ‘BG-TEST’. This does not
apply to CNC, Insert and tools with larger than 1/2" shank diameter.