About Cartridge Heater Diameter

If you measure the actual diameter of a cartridge heater, it won't be the same as its specified diameter (i.e., a 1/2" diameter cartridge heater won't measure 0.500"...ever).  The reason for that is simple; the heater must fit a (carefully) bored hole. 

For most folks using cartridge heaters to heat "blocks" of steel, aluminum, or other materials (as used in molds, sealing bars, hot plates, etc.) the typical design process goes something like this:

1) determine the total power required

2) figure out how to distribute the power

3) determine the optimal length and diameter to achieve even heating

Once the diameter of the cartridge heaters has been determined, the holes for the heaters should be bored to the exact diameter.  That is, if you decided that 1/2" cartridge heaters are what you need, then you should use a 1/2" drill to bore the receptacle for the heaters.  It is of the utmost importance, in order to achieve the longest possible heater life, that the drill or boring tool doesn't wander during the process.  We have seen cases where heaters that should have given several years of service life lasted mere hours in holes of non-constant diameter.

And, as always, if you have an industrial process heating task and you're not quite sure about what the best style of heaters would be or how to size them, you can always give us a call at (866) 685-4443, send us an e-mail, or fill out one of our contact forms.  Remember, we're here to help.

Cartridge Heater Diameter Tolerance and Other Tolerances

The tables below give the maximum and minimum actual diameter of cartridge heaters available at O.E.M. Heaters.  Heater diameters shown in bold with orange background are Build-To-Order sizes that are available for shipment in as little as 2 days; links in the table are to the respective Stock List shopping pages for the heater diameter.  If you're looking for something specific that isn't in our stock list, you can call us and tell us what you need or you can use our Cartridge Heater Configurator and submit and RFQ electronically. 

Cartridge Heater Nominal Diameter  Bore/Drill Size	Actual Diameter, Maximum	Actual Diameter, Minimum		Metric Sizes Cartridge Heater Nominal Diameter  Bore/Drill Size	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 cartrdige 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".

Return to Main Cartridge Heater page