Snap-on FHF100 Wrist Pin Diameter

[Wamsutta]

Fast Forward to 4:23 Don't even bother watching the rest of the video. The FHF100 wrist pin is on the left and FHFD80 wrist pin on the right. WHY would they beef up the fork of the FHF100, but then decrease the diameter of the wrist pin? Makes no sense whatsoever.

 

[3baygarage]

Idk. Thinking maybe quality flex head tools traditionally suffer from a loose head rather than a broken pin.

 

[KnurledNut]

Likely a planned point of failure.
Cheaper and faster to replace that flex pivot bolt than a bent handle, sheared anvil, or trashed ratchet mechanism. Also serves as a tattletale that a certain torque load (abuse) was user applied, which in this case required a 24” cheater bar and a guy giving it his all.

User safety might have been factored in with this design too. Torque-to-yield control instead of a catastrophic event.
The pivot bolt bent instead of sheared. I dont think this was coincidence. Kudos to the Snap-on engineer that crunched the numbers on this one.

Knowing Snap-on, i’m going with over-engineered instead of under-sight.

 

[65k10]

In that guy's other video where he takes the FHF100 apart he measures the head thickness of it and an FHF80. The FHF100 head is about 2.4mm thinner. I'm curious how much of a role that played into the use of a smaller diameter pivot pin to make sure there was enough material left to not compromise the strength of the pivot point on the ratchet head and the forks.

Still, the fact that it did bend like that bothers me a little. Is it a design deficiency of some sort that will be an issue in the longer flex heads? For that matter, Matco's 3/8 locking flex heads use a smaller diameter pin than the dual 80 flex heads and we do not seem to hear about those having issues (unless it does happen and nobody talks about it online). I'm hoping we see some more feedback soon on these ratchets to get an idea if there is a weakness in the flex joint design or if the pin failure in this video has something to do with how the test was done.

 

[Steve_P]

The F100's thinner head most likely dictated changing to a smaller diameter screw. The 3/8 F100 head thickness is now about the same as the Matco 88, so I'd guess the screw diameter is also the same, or close. I haven't seen anyone complaining about excessive Matco 88 failures here, but any of these super long handled ratchets are going to fail if you exceed their limits, and you don't need to weigh 250 lbs to break a 12"+ long 1/4" drive ratchet, 18"+ long 3/8 drive, etc.

Snap On definitely takes failure mode into account and designs for the low cost portion of an assembly to fail before the high cost portion- when possible; then they can just replace the low cost portion of it on warranty. Replaceable screwdriver blades are a great example of how they manage warranty costs.