How to calculate HTD 5mm Belt Lengths?

[Richard Talbot]

Thanks Art,

I suspected there was something like that at play.  One other question - It seems that Gearotic does not support 4D milling of the 5mm HTD?  I can output a spur gear OK, but not the timing pulley.  There is a note there that says only Involute types are supported, but the system names the pulley as an Involute.

All things being equal, I assume the quality of the gear would be better with a 4D machine as there is less deflection in the endmills.  when cutting a gear such as this there is a limit to the length of cut one can make with a 3mm endmill.

Cheers
Richard