@
littlebean
(Not sure if I manage to quote your message, sorry.)
AFAIK There a following versions of the 60-teeth ratchet systems, only male square drives are available:
1/4" body size
3/8" body size
3/4" body size
3/4" HD (Heavy Duty 650 Nm) body sizes
The 3/4" sizes are only available as heads, not usual ratchet with handle.
1/4" body size:
Only 1/4" rotating part:
For 1/4" ratchet 411 (and similar no longer listed ones if applicable, e.g. same head but other handles).
I don't remember for sure but I believe there was a small ractchet head for torque wrenched but it is no longer listed since quite some time.
Only 1/4" male square drive.
3/8" body size:
3/8" rotating part and 1/2" rotating part.
For 3/8" ratchet 422 (and similar no longer listed ones if applicable, e.g. same head but other handles) and ratchet heads 735/5 (3/8") and 735/10 (1/2").
Therefore 3/8" to 1/2" and 1/2" to 3/8" conversions are possible but the maximum torque with 1/2" square drive is lower than for "full-fledged" 1/2" ratchets as the size of the parts is designed for 3/8" square drives.
Using a 1/2" rotating past in a 3/8" ratchet body can be convenient due to the smaller size but it is not a replacement for true 1/2" ratchets where high torques are required.
1/2" body size:
Only 1/2" rotating part.
For 1/2" ratchet 515 (and similar no longer listed ones if applicable, e.g. same head but other handles) and ratchet heads 735/10 and 735/20. The torque limit of the ratchet mechanism is 300 Nm (usually the male square shears off first, I can post a pic later).
3/4" body size, normal (non-HD, i.e. 400 Nm) version:
Only 3/4" rotating part.
For 3/4" ratchet head 735/40. The torque limit of the ratchet is 400 Nm.
3/4" body size, HD (Heavy Duty, i.e. 650 Nm) version:
Only 3/4" rotating part.
For 3/4" ratchet head 735/40HD and 735/65. The torque limit of the ratchet is 650 Nm.
The 3/4" non-HD and HD are different, the HD is larger.
In some cases, knurled discs of two different diameters can be used for the same 60-teeth ratchet.
Very important: The central screw must be tightened very carefully, if too tight, the mechanism locks up. New original screws are provided with some thread-lock pre-applied, each time a screw is removed it must be replaced or thread lock newly applied. Original spare part kits include 3 screws to allow 2 maintenance disassembly.
As threads are metric, also 10.9 Allen (INBUS) countersunk screws can be used, ISO 14581 (formerly DIN 7991), make sure to use 1st quality screws as they can be hard to remove. The original 10.9 TORX often end damaged, I absolutely hate TORX with a passion!
Diameter and length depend on the ratchet size. The original screws are no 100 % standard but regular equivalents can be used.
The two first pics show the difference between 3/4" HD (650 Nm) and the smaller standard version (400 Nm).
The 3rd pic shows an old body, the teeths are usually fine, mostly the rotating part ends wears down, see pic 4. Also the locking segment can wear out or even break aparts. The heart-shaped spring rarely ends damaged.