planishing hammer

[naughtyboy]

got a spare air chisel or 5 and thinking of making planishing hammer.
got ideas on design but not sure on dies.
are they flat or do they need to be radiused?

cheers.

 

[gordon stephenson]

Wyn has made one of those, I'm sure him,Hotrodder or Langy will be along shortly to give us more info!

 

[hotrodder]

Yes and yes... depends what you're doing but the upper is typically flat/extremely low crown with radiused edges, bottom/anvil varies with the work in that for planishing you kinda want the largest contact area possible that 'matches' the shape of the panel if that makes sense. The anvil die is akin to the dolly/stake when planishing by hand i.e. flatish (low crown/large radius) for flatish panels with higher crown/smaller radius for more highly crowned panels

A basic set suppied with some commercially made hammers might include 1, 2 & 4" radius with the bigger radii (for clearance) having smaller contact patches. A wider selection of dies increases possabilities, as usual the sky's the limit in that amount and cost/time of the tooling can quickly exceed the cost/time in the basic machine for example...
https://www.tinmantech.com/html/little_powerhouse_dies.php (ignore the power hammer title, there's various dies all grouped together)
http://www.mittlerbros.com/index.php/mittler-bros/planishing-hammer/planishing-hammer-anvils/lower-anvils-group.html

Various things can be improvised for experiments/cheapness... large diameter coach bolts for example. One drawback with that sort of thing is that they aren't particuarly hard so they get marred relatively quickly and once marred will transfer marks to the work. Several of us knocked one a frame a while ago and for the initial messing around used a valve out of a big block Chevy for the upper die as it it didn't need much work to make it fit the air chisel, a few mins in a lathe cleaned up the face and radiused the edges and it was 'kin hard. For the initial 'test session' a small dia post dolly/stake was used for the anvil as we already had several from flat to highly crowned. Last time i saw it it was gathering dust awaiting 'development' as the valve deal was a bit mickey mouse (it was a get it working in one evening deal)

 

[naughtyboy]

cheers for that.