I've got to admit that I can't see what he's talking about in that picture...they look like spur gears to me. But, just to clarify this:
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Originally Posted by Conor Ryan
It's unlikely that its cut at 14.5*, 30* would more likely than not HAVE to be custom made, and a 20* pressure angle, commonly refered to as a Metric gear, is the only other reasonable alternative.
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The pressure angle of 20° isn't limited to gears governed by Metric standards. Years ago, AGMA instituted Imperial standards dealing with 20° pressure angles, which were originally intended to replace the older 14.5° standards. But for various reasons (some performance-related, some logistics-related), the 14.5° gears never really died. So, to summarize: Metric gears are usually (but not always) 20° pressure angle, while Imperial gears are usually 14.5°
or 20° pressure angle; note, though that the terms "Imperial" or "Metric" refer to the measurement system, and
not to the actual dimensions, and that custom gears in either measurement system can have
any pressure angle that satisfies the involute curve equations (though this is limited by practical considerations).
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Originally Posted by Conor Ryan
From what I've heard from people, though Metric gears are better for some purposes, I'm not sure if they are a step up in effiency though, and they aren't desirable because usually of a higher price, and a lesser availability, but at the size 968 looks to be using them, the price difference would be minimal I believe.
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As noted above, this statement is not correct. In the U.S., Metric stock gears tend to be more expensive than Imperial stock gears, because there is relatively little demand. The reverse is true in Europe.
Also, note that helix angle (i.e. in a helical gear, it's non-zero) and pressure angle are distinct quantities.