Metric drawing for inch gear?
Metric drawing for inch gear?
(OP)
I am reverse engineering a double helical pinion. 6 transverse diametral pitch, 1.9375" diameter shaft extensions, .5625" wide keyways, - clearly a part designed in the inch system. My client has asked me to make the drawing metric, to facilitate having the part made overseas. At first I agreed to this, but now I am having second thoughts. Without question, the pitch must be stated in the inch system. So then, having stated the pitch in the inch system, it would seem very awkward to give the pitch and base diameters, for example, in millimeters. As for the rest of the part, it seems like making the drawing metric would be comparable to drawing a 5/8-18 hex head bolt in millimeters; at best it would raise eyebrows, and at worst, it would cause confusion and mistakes.
I would appreciate hearing any comments you may have on this.
I would appreciate hearing any comments you may have on this.





RE: Metric drawing for inch gear?
RE: Metric drawing for inch gear?
RE: Metric drawing for inch gear?
I would show all other gear geometry related dimensions in metric.
There is no problem with showing a metric base diameter, however, the dimension is quite useless, as is showing a PCD, when it comes to manufacturing the part.
It's also not unusual to show a fractional keyway size in a bore dimensioned in metric.
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
http://www.aussieweb.com.au/email.aspx?id=1194181
RE: Metric drawing for inch gear?
In the end, it's just numbers. It is not uncommon to see drawings with dual dimensioning (metric and inch). With the gear data, you just need to do the conversions (carefully). In fact, most of the current AGMA documents provide data in both metric and inch systems.
RE: Metric drawing for inch gear?
Thanks very much for your help. I used mixed units, as you suggested. The drawings are done and the client is very happy with them.
philrock