Hobo nickels: intricate carvings in coins - GIF and photos

[Jon]

1:54 Shaun Hughes video:

Also some vise ideas here: Lindsay Engraving Vises, holders and fixtures

[rendoman]

Hi all!
Someone has some good info about how this type of engraver is made?
Thanks!

[owen moore]

I think that is some reverse alien technology!

[rendoman]

At first sight it seems a piston that acts like an hammer. Looking the spring I would think that it works in depression. I remember this tool has a power unit with air flow control. It would be nice to try one!

[Toolmaker51]

At first sight it seems a piston that acts like an hammer. Looking the spring I would think that it works in depression. I remember this tool has a power unit with air flow control. It would be nice to try one!

I think your appraisal is correct. A miniaturized pneumatic hammer. I think a piston could be induced to reciprocate like a two cycle engine - where one port is covered alternately. Light spring operated poppets might work too, opened by piston impact, returning to a starting position triggering that poppet.

[rendoman]

Just out of curiosity, I tried drawing a couple of sketch.
The left tool should should work with positive pressure, in few words a compression chamber and a piston, like you said a 2 stroke engine. According to this design I think the mass of piston, type of segments and force (plus centering) of the spring should be the key of the tool. At first sight I suppose it would be the simplest way, choosing the right size and pressure should be the hard part. I suppose the limit of this setting is the reloading speed, the spring should be the limit itself.

The right drawing should be better and perform faster, if well tuned. A good comparison should be like a desmodromic valve system of Ducati against a normal spring distribution, it should run faster. I think here the hard job is the timing of the valve double air, send and return.

Looking at the commercial product I found in the net, I think the first one should be the most used. I'm thinking about a way to built a simple driver unit to try

What do you think about?



PS: I found this link with some interesting pictures, I don't know if it's possible to post, or it's against forum rules. If it's not ok, please delete http://bbs.homeshopmachinist.net/thr...eumatic-graver

[Jon]

Yes, of course you can post links to other forums; we know many of them, and they certainly link to us! We've logged 400+ different forums that link to homemadetools.net.

You can also browse tools by site, here: Homemade tools by site . For example, here are 509 homemade tools from homeshopmachinist.net: Homemade Tools from bbs.homeshopmachinist.net.

[Frank S]

The Chicago Pneumatic CP 9361 Industrial Scribe and Engraving Pen works well as an engraver just change out the pointed scribe for a shaped tool
They are pricey though And I mean really pricey. at around $300.00 with the regulator

[Toolmaker51]

Rendo;
after googling the desmodromic actuation there are some positives. Doing it miniature may or may not be a challenge.
So that causes wonder if a motor and valve train could be remote, running the handpiece off a hose? Handpiece could have it's own piston, delivering inertia to the graver. A light spring might induce rearward travel with each reduced pressure wave. Probably not feasible, but I've never considered how to run such a device.

re google this turned up. A new frame of reference to what I call "real engineers".
After World War II, when future Ducati engineer Fabio Taglioni wrote his original engineering-school paper on desmodromic valve drive, there was good reason to seek such a system: Valve springs broke at random as an era of rising rpm opened. In the 1950s, NSU pushed to 12,000 rpm,...
https://www.cycleworld.com/2014/04/2...o-desmodromics

[Jon]

Audrey Hepburn on 1925 nickel with copper inlay. By myguitarismymistress.