DIY pneumatic graver on a budget

[Moe_from_bavaria]

Hello all,
Im starting this thread to motivate people like me (who want to try out pneumatic engraving but fear the, especially in europe, hefty monetary investment).
This graver is mostly made from trashyard materials, but still has its fancy elements like a teflon sleeved piston, 120 degree division air in- and outlets to adjustable stroke lenght via a m12x1 thread as well as airflow regulation.
I just finished this 2nd gen version, but for now it seems to work very nicely(in my opinion, but by now i have spent more time making engraving tools than actually engraving, so im a complete beginner)



i did not draw proper plans for it yet, but ill update this thread once they are completed so that people who want to have a go on their own have a basis for a good headstart.

Have a good one

 

[Mike576]

Looks like this took some skills to make, nice job!

 

[Moe_from_bavaria]

Looks like this took some skills to make, nice job!

cheers, yes the turning of the cylinder with shoulders on the inside was a challange....a good way to circumvent this job is using the body of a springloaded centerpunch

 

[Tdahl]

Wow. That looks really nice. I can't wait to see your drawings. It must have been quite the adventure designing and developing the prototype.

 

[SlamDunK]

That looks great. I'd like to see the drawings for it.
Thumbs up!

 

[Moe_from_bavaria]

I took measurements on the body of the graver and drew them out in cad...i had to convert it to a png to upload it here, so im not sure about the scaling

 

[Travis_UT]

I wish I had your machining skills! Nice work!

 

[DocH]

Nice work!
I suppose it works on push/pull air system ?
Could you explain a bit what the two brown/ black rings are for?
Also the weight of the piston would be interesting to know ( I use brass pistons ranging from 4 to 12g).
Cheers!

 

[Moe_from_bavaria]

Nice work!
I suppose it works on push/pull air system ?
Could you explain a bit what the two brown/ black rings are for?
Also the weight of the piston would be interesting to know ( I use brass pistons ranging from 4 to 12g).
Cheers!

Yes its a fully pneumatic construction
....the upper ring is for air supply, it has an inner grove allowing the air to enter the chamber from all sides (i have 3 holes diveded by 120deg on this one...this division is also true for the exit ports of the piston, im my imagination this makes the movement more stable but I have no way of verifying this
The lower ring is for exhaust restriction...you can adjust it independently from the nut in the frond which solely adjusts stroke lenght

 

[alexf]

Really nice build!

I've made one just like this. It worked, though I wasn't happy with the amount of air It needed to idle and a few other things, so I'm working on another one, with a smaller piston. Would love to ask some questions/compare notes!

How did you make the Teflon lining? I'm experimenting with delrin, but im not so clued up about machining plastics and I'm struggling to get a good finish in in the bore.
Also not sure out of which material to make the "restrictor" component that divides the front and rear chambers, my first version was bronze but i wonder if it should also be teflon/delrin. [*Edit: I just reread your post and saw you make the internal restrictor part of the body of the graver. I've been machining out the front half of my body 0.2mm larger diameter than the rear end, and press fitting a separate restrictor ring into it. Do you lap out the bore in yours to get a good finish? I'm also Curious about your tolerances between bore and piston? I'm working with 0.1mm difference on the diameter. ]

Would love to see a full plan of your design to see how you solved some of these problems!

Alex