Vetus Poly-wood Instructions D'installation page 11

2.4 Choice of tool
High-speed steel is adequate for cutting Poly-wood. Carbide
tipped tools are long-lasting and achieve high productivity. 'K'
type hard metals (K 10) are best due to their low thermal expan-
sion coefficients and high thermoconductivity.
Minimum cutting force is required for machining plastic. Blunt
blades require greater force for cutting and produce a poorer
surface finish. Working life is particularly affected by cutting
speed, feed and width and depth of cut.
The greater the clearance and rake angle, the less cutting force
is involved. To avoid excessive weakening of the cut wedge,
there are limits to the clearance and rake angle that may be
used. The cutting force should run in the direction of cut.
Selecting the rake angle allows the direction of working to affect
the processed material. Spiral-toothed end mills have proved
suitable in practice. Take care during machining to avoid deep
scoring or sharp crossover marks which, given the known notch
effect, can cause early breakage of the material under load.
Final polishing with a polishing wheel can improve surface fin-
ish. Edges left after sawing, drilling or milling can be reworked
with blunt scrapers or special deburring equipment and cham-
fered. The following tables give guidelines for the machining
process. Data for machining plastics is given in VDI Guideline
2003.
2.5 Methods of processing
2.5.1 Sawing
Fast-running band and circular saws are suitable for cutting
thermoplastic materials. The cut surfaces can be smooth when
the teeth are lightly set. Saw blades with teeth more than 15 mm
apart have been shown to produce a better quality cut. Hard
metal saw blades improve performance and have a longer
working life.
α Clearance [degrees]:
10-15 HM / 30-40 SS
γ Rake angle [degrees]:
0-5 HM / 3-8 SS
t Gullet [mm]: 5-10
Set [mm]: 0.8-1.0
Cutting speed [m/min]: 3000
Feed [mm/tooth]: 0.1-0.3
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2.5.2 Planing
Surface and panel planers used in woodwork are also suitable
for Poly-wood. Surface quality largely depends on feed, cutting
speed, clearance and rake angle as well as ths state of the cut-
ters. The machines should have extra strong bearings.
Clearance [degrees]: 15-30
Rake angle [degrees]: 15-20
Cutting speed [m/min]: 3000
Feed [mm/tooth]: 0.1-0.3
2.5.3 Milling
In milling, particular care should be taken to keep the machin-
ing cross-section as large as possible, to reduce heat genera-
tion. Cutting depth and feed also need to be Iarge, and cutting
speeds low. Fast woodworking machines with fairly high feed
rates and rpm have been used as well as universal milling
machines from mechanical engineering.
α Clearance [degrees]: 5-15
γ Rake angle [degrees]: 5-15
Cutting speed [m/min]:
up to 1000
Feed [mm/tooth]: 0.2-0.5
2.5.4 Drilling
Spiral drills can almost always be used. Angle of fluting should
be 20-30˚ and point angle 110-120˚. A considerable level of
heat is generated by drilling, which must be taken away with the
swarf or by further cooling. For deeper drilling it is helpful some-
times to remove the drill from the hole to empty out the swarf. If
high precision is required, it is advisable to pre-drill the item and
put into intermediate storageas appropriate. A reamer should
be used for precise drilling.
α Clearance [degrees]: 10-12
γ Rake angle [degrees]: 15-25
ϕ Point angle [degrees]: 60-90
Cutting speed [m/min]: 30-70
Feed [mm/rpm]: 0.2-1.0
ENGLISH
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