Lever cap spring

[GLFaria]

Sorry if this is a dumb question, but it has made me curious ever since I found out some planes have one and some don't...

What is the lever cap spring really meant for?
I can see only two possibilities, and none of them seems that important, speaking of the work required of a hand plane:

1 - securing the lever in either the "up" or the "down" position (user convenience only?...)
2 - protecting the cap-iron from wear from the lever operation (?... the cap iron steel should be hard enough...)

Would anyone comment tell me the real truth about this matter?

 

[CHJ]

To stop the rotating cam action friction from moving the blade assembly as the cam moves over centre? Although that would be only critical if you did not have a depth adjustment, still good practise though as cam can still be lubricated and the clamping force of the spring leaf/blade assembly friction contact remains unlubricated.

 

[JohnPW]

All three seems good reasons to me.

 

[GLFaria]

To stop the rotating cam action friction from moving the blade assembly as the cam moves over centre? Although that would be only critical if you did not have a depth adjustment, still good practise though as cam can still be lubricated and the clamping force of the spring leaf/blade assembly friction contact remains unlubricated.

Thanks. I'm with CHJ. It was a dumb question, I should have thought of that reason!

 

[CHJ]

No question is dumb, and my logic may be wrong, but it is good engineering practice to have a fixed locking plate to stop cam action movement on any such closure device.

 

[GLFaria]

No question is dumb, and my logic may be wrong, but it is good engineering practice to have a fixed locking plate to stop cam action movement on any such closure device.

Precisely! And I should have thought of that because I have worked for a time in tool and jig design - even if, for an excuse, that was over thirty years ago... Dumb!

 

[Jacob]

No question is dumb, and my logic may be wrong, but it is good engineering practice to have a fixed locking plate to stop cam action movement on any such closure device.

Precisely! And I should have thought of that because I have worked for a time in tool and jig design - even if, for an excuse, that was over thirty years ago... Dumb!

It gets all the friction which is why it's made of hard spring steel. The Stanley/Bailey design is incredibly well thought out and developed in every detail.