Tolerances-Cartridge Heaters

Re: Tolerances-Cartridge Heaters/Insertion Heaters-Power, Length & Camber Tolerance:

Cartridge Heater Tolerances
The tables below give the maximum and minimum actual diameter of cartridge heaters available with National Plastic Heater. If you're looking for something specific that isn't in our list, you can call us toll free (877-674-9744) and tell us what you need or you can complete our cartridge heaters order form here and we will quote you within one business day.


Cartridge Heater Nominal Diameter Bore/Drill Size Actual Diameter, Maximum Actual Diameter, Minimum Cartridge Heater NominalDiameter
HoleSize (Metric)
Actual Diameter, Maximum Actual Diameter, Minimum
1/8" (0.125") 0.124" 0.120" 6mm 5.97mm 5.87mm
5/32" (0.15625") 0.155" 0.152" 6.5mm 6.48mm 6.38mm
3/16" (0.1875") 0.186" 0.183" 8mm 7.98mm 7.85mm
1/4" (0.250") 0.249" 0.244" 10mm 9.96mm 9.85mm
5/16" (0.3125") 0.312" 0.308" 12mm 11.96mm 11.86mm
3/8" (0.375") 0.374" 0.369" 12.5mm 12.47mm 12.34mm
1/2" (0.500") 0.499" 0.494" 13mm 12.98mm 12.85mm
5/8" (0.625") 0.624" 0.619" 15mm 14.99mm 14.86mm
3/4" (0.750") 0.749" 0.741" 16mm 15.95mm 15.82mm
15/16" (0.9375") 0.936" 0.928" 17.5mm 17.47mm 17.27mm
1" (1.000") 0.999" 0.991" 20mm 19.96mm 19.76mm
1-1/4" (1.250") 1.249" 1.241"      
1.90" (1.900") 1.910" 1.890"      
2-3/8" (2.375") 2.385" 2.365"      


Cartridge Heater Tolerance of Power, Length, and Camber
Power tolerance, or how close the actual dissipated power at the specified voltage is to the specified power, is typically +5%/-10%. It is possible to have cartridge heaters built with tighter tolerances, but it will drive the price up. For instance, we have one customer who uses cartridge heaters as damping resistors in an RF application. For that guy, we specify the resistance and the resistance tolerance of the cartridge heater rather than its power.
Length tolerance, is a measurement of what the actual length is relative to the specified length. For our stock list cartridge heaters, length tolerance is ±0.005" per six inches of length for units up to 12" long and ±0.020" per foot for units over 12" long. For quick turn Build-To-Order cartridge heaters, length tolerance is ±2%.
Camber tolerance, is a measure of straightness of the cartridge heater. Cartridge heaters may vary from a straight line by as much as 0.010" per foot for lengths up to 12", and by as much as 0.018" per foot for lengths greater than 12".

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