Engraving tool

[Evan]

I have been practicing my engraving skills the last few days and have managed to make the same mistakes only once each time, so far. The machine works great which is more than can be said for the operator.

This machine has a bit more grunt than the average engraver such as the ancient first generation New Hermes CNC engraver I used to repair for a local Jeweler. One way this can be used to advantage is to do "scratch engraving" in which the tool is simply dragged along the metal. Done right this displaces the metal neatly instead of cutting it and doesn't use the spindle motor at all, it is turned off. Your average dedicated engraver machine such as the old New Hermes isn't up to that as it requires several pounds of downforce on the tool.

It also requires very even pressure on the tool to produce a good result. One way to achieve this is to use a spring loaded tool. This also eliminates completely problems caused by slight warps in the metal being engraved and greatly simplifies clamping.

Yesterday I made a spring loaded engraving tool and did some testing with it. It is really nice and a lot less fussy to set up. It does a great job on aluminum, brass and silver. The tip is high quality carbide salvaged from a broken 1/16" solid carbide end mill that I had lying around.



The tool fits in a 5/8ths R-8 collet. It has an integral 1/8th inch collet chuck for the tips. Travel is about 1/4" with midrange exerting about three to five pounds of force. The tip of the tool has about a .010" radius.



The results speak for themselves.



That's my daughter. She is the best photographer I know. She just bought her third Canon XTI as a backup-backup camera. You can see her work at crazywolf.com

[John Stevenson]

I have been practicing my engraving skills the last few days and have managed to make the same mistakes only once each time, so far.

The results speak for themselves.

That is impressive, what did you do the text in ?

.

[Evan]

The font is Caslon Openface BT. It's pretty close to a traditional engraving font.

[Your Old Dog]

That's pretty slick. Is it more of a burnishing affect or is it actually cut in? If there's a flat side to the bit it isn't showing to me. I can see this CNC mill opening up all kinds of worlds to you.

[Evan]

No flat side. The tip is a smoothly rounded profile. I haven't tried to measure how deep the grooves are but they are deep enough you can't buff them out with a buffing wheel. The tool doesn't cut at all. It also produces a very smooth and shiny surface as if flows the metal out of the way. If you do the math a few pounds on the tool turns into thousands of psi on the tip.

After I built the tool I decided to look one up on the net. I was surprised to find nearly the exact same thing from a company. Then I saw the prices, . $300 to $500 for nothing different from what I made in a few hours yesterday. I think I got a good deal.

[John Stevenson]

Evan,
No not the text, what program did you do the text in to get the code ?

Yes those spring loaded tools are expensive.
I note they also list patent numbers for the tool and the add on tip.
However they got those I'll never know as they have been available in the UK for years.
The tip is standard fitting on Gravograph machines.

I made one a while ago out of one of these.



They are an ER11 collet chuck with a 16mm ground OD and a JT1 taper in the end.
Although they are hardened it's possible to cut a slot in the side for a peg to fit and allow it to slide in a holder. My holder is a blank R8.

These can hold collets from virtually zero to just over 1/4"

They are very cost effective and you can even use them as sub tooling similar to the Tormach quick change so you can keep the tool offsets. They cost about £15 each here.

I use mine for small hole drilling and engraving but unlike Evan I have never tried drag engraving.

.

[Evan]

Ah. I used CamBam to do it. It's rather awkward as it is not a completed product yet but it also does many things the way I like. It does have some problems that I haven't pinned down yet. For some reason it won't render certain characters in some fonts even though the font works fine in other programs. Also, CamBam doesn't do the best job of picking a tool path.

Something else that I am about to try is engraving a bitmap. That is usually done by varying the cutting depth in accordance with the light to dark values of the pixels. With this tool it should be possible to vary the pressure using the exact same code but the result will be a varying line width, the same as happens in certain half tone processes.

[lazlo]

Nice job Evan!

Something else that I am about to try is engraving a bitmap. That is usually done by varying the cutting depth in accordance with the light to dark values of the pixels.

Was that how John engraved the picture of the Sieg owner (varying the cutting depth according to the greyscale value)?

[John Stevenson]

Something else that I am about to try is engraving a bitmap. That is usually done by varying the cutting depth in accordance with the light to dark values of the pixels. With this tool it should be possible to vary the pressure using the exact same code but the result will be a varying line width, the same as happens in certain half tone processes.

Evan, two things, first is Andy is about to launch a pro version of Cambam that may clear up a few items.

Second is if you want to do a bit map have a look at PhotoVcarve.

http://www.vectric.com/WebSite/Vectr.../pvc_index.htm

The download whilst being a demo does allow you to save and cut the examples supplied.
Failing that if you try your own file it will process it but not code it - demo limitation, but if you send me the file or pic I'll run it thru a full version and send you the code back.

[BobWarfield]

Evan, that's cool!

This is the kind of thing that made me suggest to the fellow wanting to build scientific instruments that he needed an engraver.

A favor please: could you shoot a piccy that shows the components of your drag engraver laid out when it is disassembled?

Cheers!

BW

[Evan]

Sure, no problem Bob.

John,

Cambam does a heightmap which will translate gray scale to Z so I shall try that first to see how it works.

[John Stevenson]

Yes it does but it works the old way of working in pixels.
Photo vee carve works by doing diagonal lines at differing depths and speeds the process up.
What used to take 4 or 5 hours can now take 45 minutes.

Even if you don't try it it's well worth a read of this page.

http://www.vectric.com/WebSite/Vectr...ithophanes.htm

Some fantastic work.

.

[Evan]

The most important thing is that the plunger be a very close fit in the barrel. It won't do to have the tip wobbling around as the machine changes direction. The fit must be in the tenths range.

A far as other dimensions, nothing is critical. The tool can easily be made to operate under power by simply drilling through the barrel and plunger, opening the holes in the barrel to allow motion and putting in a roll pin to key the plunger to the barrel. I made the barrel to fit a 5/8ths collet as that is the one I use least often. It could just as easily be made to fit 1/2 or 3/4" collets. The tool bit can be retained with a setscrew instead of a collet for non powered drag engraving but if it will be powered then concentricity is very important and a collet will be better.

[Mcgyver]

This is the kind of thing that made me suggest to the fellow wanting to build scientific instruments that he needed an engraver.

expected more from you guys engraving is fine for what it is but if you are trying to capture the beauty of the antique instruments, it doesn't cut the mustard. some sort of cnc Guilloche machine is need, something that instead uses a non-rotating but indexable cutter, some like a graver that can be indexed and tilted. 5 axis. God knows what software to use, but give Evan a rainy afternoon and he'll come up with something. or learn to do it by hand? wonder how hard that is? YOD?

[Evan]

I have no intention of trying to replicate an antique instrument in all respects. What I want to do is build a decent working sextant using modern methods and materials. I won't use brass, too heavy. It will be aluminum and anodized. It will also be nicely engraved, both functional and decorative. Sometimes what seems decorative is also functional, especially when it provides a more secure grip when handling the instrument.

Even now anyone venturing to sea out of sight of land should carry a sextant and the ephemerids and know how to use them. It requires no batteries and isn't destroyed if immersed in salt water. Solar storms don't knock it out of commission. It can even be used to navigate without a timepiece, the ephemeris or even a compass. A common technique usually used before the advent of accurate clocks is to sail a rhumb line of constant latitude. Constant latitude is maintained by taking noon sights. Even a stick can be used but a sextant is much more accurate. Then all you do is aim for a point on the landfall coast that is either well north or south of your destination. That way when you make landfall you know which way to turn.