Hi all !
I got a questin about bone and tail/end scale when in envelope mode.
Is there a way to reset to default value all bones envelopes and tail/end sizes so that mesh parenting to armature does not weight paint all mesh at each bone ?
thanks for your answers 
Note that the usual ALT+S key does nothing 
Do you have bone selected and in Edit mode? Is selected bone orange in color with transparent gray-white envelope around it? Then, trunk scaling is done with hot key [Ctrl][Alt][S]. Head / tail scaling is done with [S]. The functions work fine for me.
If hot key is not working, try menu selecting Armature > Transform > Scale Envelope/Bbone for the trunk. And, menu select Armature > Transform > Scale for the head or trunk.
hi ridix.
sure all thos key work as usual but. i was wondering wether there’s a method to RESET those scale changes.
Say you got like 150 bones. do you have to rescale them all by hand one by one ? I hope not
What i mean with ‘reset’ is going back to the calculated value done for envelope when you create the armature.
In Edit mode, hit [A] to select all bones. Use [Ctrl][Alt][S] to scale all envelopes at once.
It don’t work !!!
CTRL+ALT+S is for scaling.
what i want is RESET envelope scale, not scale it. i thought i mentioned it in both my previous posts
Hey; I was struggling with that particular problem too, 10 years later though. 
The UI is a bit confusing regarding this feature which employs [ Ctrl+Alt+S ] keyboard shortcut on Bones.
But it’s actually a Bendy Bone feature.
Select the Bone(s), go in the Properties Editor » Bone Properties Tab » Bendy Bones Panel » Display Size X and Z, and then the default values seem to be 0.10000 for both.
So if you have a Multi-Selection of Bones, just [ Hold Alt ] while using [ LMB-Click ] on one of the values’ Slider Button, and type [ “0.1” ] and press [ Enter ]; with still the same Bone Multi-Selection, do the same for the other Slider Button, as it is needed to Clear the BBone Scale for both X and Z Axes.
Best regards.