This is what I cobbled together to utilise the spare engraving spindle (the one I'm holding) which came with, but didn't fit, my Gravograph IM3, and subsequently used for micro-machining with my own home-brew spindle.
For constant depth engraving (good for about 20 degrees off centre either way on a 20mm cylinder and on non-level or irregular surfaces) the brass nose has a spherical socket at it's tip, which accepts a steel sphere with a through hole for the cutter and a flat to follow the work surface.
Adjust the amount of cutter tip protrusion and that's as deep as it will cut.
The Del-Tron R702 is a Micrometer Stage with a spring between the micrometer and the moving slide to allow the cutting pressure to be set for different materials and screwed down solid for Micro-Machining.
The spindle in the mount is one I knocked up from an ER11 Collet chuck on a 10mm shank, a bit of ally bar and some bearings, at the moment I use this for micro-machining but I'm planning an attachment allowing the same function as the brass nose on the engraving spindle.
The size differential between the driving pulley on the mill spindle and the cutting spindles gives 28800rpm cutting speed for 6000rpm mill speed, the belt is from Polyurethane drive belt sold by length, cut to length and welded by me using a cigarette lighter.
I hope this will inspire someone else to fulfil their engraving/micro-machining requirements ;-)
Great setup Nick. So is that the spring that could be seen at the picture? It would be great to see some more pictures from different sides. So you say the brass one/ the sphere/ slides on the material?
I have been thinking "how to" and "what belt to use" to make the reverse for milling metal using the 3kw spindle.
The spring in the upper right is the one under the micrometer and is the key to pressure adjustment for engraving uneven surfaces.
The friend who sold me the mill has seen this arrangement and plans to use something similar to run a spindle at slower speeds with reduction driven by his chinese spindle.
I'll make a video once I get the equipment and post it here to show what can be achieved with a setup like this,
Vinyl cutter tool holders are similar, have adjustment for pressure are easily modified best of all available for just a few pounds on eBay. I watched a guy engraving wine glasses on a 4 axis with a diamond tipped bit apparently engravers have been using them for years. Have not tried it yet my vinyl cutter is in the back of my lock up with the toolholders etc. Just have a look at the Roland toolholder knock offs from china etc they tend to be alloy so will have limitations but for fine work look ideal.
To maintain fixed depth you need to
(i) Follow the surface, (this is what the ball nose on the engraving spindle does),
(ii) Have precise control of cutting depth (this is what the micrometer adjustment collar on the engraving spindle gives) and
(iii) Apply enough pressure to ensure cutting to the full set depth, not skimming over the surface or allowing the cutter to lift (this is what the spring pre-load on the ball slide is for)
Thats what the guy was doing with the Roland tool holder no spindle running just dragging diamond tip and scratch engraving the glasses some really fine detailed work.
Last edited by lucan07; 16-04-2016 at 12:48 PM.
You can use a "burnishing" cutter in a rotating spring loaded holder to get wider lines than diamond drag
Here's one that looks quite good, he's got video on YouTube showing them at work, there's a video in the listing too.
CNC Drag engraving tool for router or plotter. Spring loaded.
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