Another couple options (i.e. adjusting hammers 
that limit dings to wooden planes).

1] Originally I followed Mike Dunbar's advise and 
got a cobbler's hammer (i.e. with its broad , lightly-rounded face):
For example : 
https://i.pinimg.com/originals/c8/92/8d/c8928d83de989d28e6fbfc423efadb15.jpg

2] Later, when I decide I wanted to try a DIY 
solution, I made myself an all-wood adjusting hammer.

The handle is ash and the head is made from a scrap piece of oak.

Basically it's the size and shape of a largish 
tack hammer, but the head is about 1.5 in-square in cross-section.
Also, one face of the head is flat, while the other end is rounded.

Admittedly this isn't as fancy or as slick as Scott's beauty,
but it's been doing the job for me.
Also, if I decide I want to tweak the design (for example,
so that the whack is heftier/larger) it's relatively easy/quick to do.

N

scott grandstaff wrote: