The Specification limit can be
a) max. i.e no part of the measure profile exceed the stated limit.
b) 16%-rule (default) i.e. 16% of the evaluated profile can exceed the stated limit
Reference BS EN ISO 4288:1998
Surface Texture Parameter
includes a Profile letter and a Characteristic letter
Profile Letter...
a) R for Roughness
b) W for Waviness
c) P for Profile (Form)
Characteristic..
a) p = Maximum mean to peak (In sample length)
b) v = Maximum mean to valley(In sample length)
c) z = Maximum peak to valley(In sample length)
d) c = Mean Height of Profile Irregularities(In sample length)
e) t = Maximum hight of profile deepest valley to highest peak(In sample length)
f) a = Average Roughness. The average roughness is the area between the roughness profile and its mean line(over the evaluation length)
g) q = The root-mean-square (rms) average roughness file(over the evaluation length) h) sk =Skewness..Indication of high spikes or deep local valleys (over the evaluation length) h) ku - Kurtosis .. Indication of general spikeness (over the evaluation length)
The Filter parameter
is rarely shown on drawings and indicates the type of filter used. The normal type used now is the Gaussion filter. This is the default and does not have to be indicated. The older 2RC (2-resistor-capacitor) analogue type when used is indicated.
The Evaluation length
Is indicated as a multiple of the sample length only if it is different to the default of 5
Description
No material removal allowed, unilateral upper specification limit, default transmission band.
R-profile, maximum height of roughness 0,5mm, evaluation length of 5 sample lengths (default), "16 % rule" (default).
Description
Machined finish, unilateral upper specification limit, default transmission band.
R-profile, maximum height of roughness 0,3mm, evaluation length of 5 sample lengths (default), "max- rule" applies.
Description
Machined finish, unilateral upper specification limit, transmission band 0,008-0,8mm
R-profile, arithmetic mean deviation 3,1mm, evaluation length of 5 sample lengths (default), "16% rule " (default) applies.
Description
Machined finish, unilateral upper specification limit, transmission band ls = 0.0025mm (Default-BS EN ISO 3274) Sample Length 0,8mm
R-profile, arithmetic mean deviation 3,1mm, evaluation length of 3 sample lengths, "16% rule " (default) applies.
Description
Machined finish, unilateral upper specification limit, transmission band 0,8 -25mm
W-profile,maximum height of waviness 10mm, evaluation length of 3 sample lengths, "16% rule " (default) applies.