Here are my thoughts on making a plane adjust hammer.
   I am experimenting.

Wooden planes are a problem. They always were.
Sometimes you have to hit them pretty hard to get them to loosen up...
and now its dangerous.
  Like you want to leave hammer marks in a plane from 1779??? hah

I have found med hard rubber........... Not the hardest, but not squishy 
either,
can deliver a wallop, and you would never know it from looking.
The worst you are ever going to do is burnish it a teensy bit.

   Wedges you still have to be super careful of course.
You can't afford to give a wooden plane wedge a dirty 
look................ lol.
Anything will hurt a wedge.
But something soft enough not to wreck it easily, would be nice.

Even the blades are sensitive. Don't want to be forming a big ol 
mushroom on the blade from hammering with steel.
Better to waste the mallet than the blades, I think.
Sacrificial brass seems good.   It'll deform and mushroom easy, but oh 
lah de dah.
Better the mallet suffers

So here I am so far.
Rubber and brass. It weighs in at about 14oz.
  Its 8" long

BTW its all Ron Harper's fault. He got me going on an old idea I had 
long ago.

I am still not sure this is the totally right thing,
but it'll do until the right thing comes along hahahahaha

Next one will be better

http://users.snowcrest.net/kitty/sgrandstaff/images/hometools/malletplane.JPG

yours scott

  --
*******************************
    Scott Grandstaff
    Box 409 Happy Camp, Ca  96039
    scottg@s...
    http://www.snowcrest.net/kitty/sgrandstaff/
    http://www.snowcrest.net/kitty/hpages/index.html

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: