Drag Engraver

[Regnar]

After a few attemps to find a affordable drag engraver the cheapest I could find ready to buy was 345.00. So I gave up on that ideal a while ago. Next I was reading an article in Digital Machinist although good I dont have a lathe and dont think I would use one often enough to buy it (Although it might become an edition to the shop) and I would need someone to teach me how to use it.

In the end I just bought a cheap carbide tip from Here

Next was 3.00 of .75 6061 alu from local supplier.

Chucked it up into a 3/4 collet and this is where we are so far. Im having alittle trouble making a nice tight fit but I think I have it down now. I wasnt thinking in terms of dividing half of what I want to cut off. So I ended up with loose fits. No biggy I could make 6 of these with the amout of stock I purchased.

Now that I know alittle more than nothing about turning I figured I would do a writeup on it if you guys are interested. Might even put a few videos up. So let me know and I will get to work. I am looking to be done with this by next weekend if all the supplies come in on time like springs and engraving bits. Now for the pictures.

[fretsman]

Very cool, I look forward to seeing this finished. About the aluminum though, isn't that a bit soft and won't it "gall" with movement?

I was in the same boat you are and posted this thread a little while ago about a very cheap way to go using a micro tapping guide with a hardened tip and it's still working perfectly:

http://cnczone.com/forums/showthread.php?t=57555

[Regnar]

I was thinking the same thing that it would be too soft. But the author of the article made his out of brass! If this works out nice I will probably try it out on cold rolled. Your thread infact got the wheels turning again. I just wanted something that I could replace the bits and maybe make it able to spin.

[Bob Shaw]

Hi,

I made one for a friend and then made a couple to sell.

There's video of my using it on this site someplace!

Or look here... http://www.dragengraving.com/

[Arquibaldo]

Dear Bob Shaw:

I enjoyed your video at http://www.dragengraving.com/ and am interested in one of
your "drag engraver"'s. However, I have a few doubts and questions, if you please:

- I understand the drag engraver is simply pressed into the work by a spring - if
this is so, how can the depth of cut be controlled? It seems that it would vary
considerably for different materials, depending on their hardness.

- What is the rpm you're using, and do you have to change it for different materials?

- Do you need a fancy spindle to drive the drag engraver? In your video, it seems that
you're using a standard wood router - is it true?

- Also, your CNC machine caught my attention - It seems very nice. Is it homemade?
Is there a description somewhere? Could you post a few pictures?

Thanks a lot for your attention

Nelson

[Bob Shaw]

Hi Nelson,

To answer your questions...

- the depth of cut is controlled by a) the spring preload b) the amount of Z you impose on the machine. Clearly, as you surmised, different materials require different conditions. Preloads for glass are clearly much higher than those for plastics.

- There is no RPM. The engraver in static, hence the term "drag" engraving.

- Yes, in the video is a normal wood router. In point of fact, no spindle at all is required. Only a mounting place for the engraving tool.

- Sadly the machine is not homemade, it is a SHOPBOT. However, I believe there are plans on the net to buld your own machine which is almost identical. It is a simple but elegant design.

MechMate CNC Router - Build your own with our detailed plans

My friend and I are currently building a slightly more ambitious Plasma table. We have recently completed the Y axis.

[DMF_TomB]

the spring is needed for drag engraving.
.
if your part is even 0.005" different in the Z axis you can easily snap off the carbide if you have no spring especially with harder materials like steel.
.
i made one using the replacement point for a dremel vibrating engraver which is about $3, they have a diamond one but that is even more sensitive and breaks off even more easier.

[Bob Shaw]

Yes, a spring is essential. My engraver has a travel of about 15mm so you can engrave curved objects like belts buckles & pens unless you track that surface using the CAM program as the height decreases the point pressure increases and the line thickens.

Obviously this is only an issue where the curvature varies a lot and the material is soft.

[Arquibaldo]

Dear Bob Shaw

Thanks a lot for your kind reply - Now it makes sense... I had to idea
the tool doesn't rotate, specially after seeing it mounted on a router...

Nelson