Just thought I'd pass this along. I've seen a lot of spring loaded engravers and I've been wanting to make one myself someday. Well today I had a "duh" moment and thought of my micro tapping guide!! I pulled it out, loaded it up in a collet, and away we went! The plunger is tight and has a beautiful slip fit (for now lol!) and has a very strong spring as well. I did not turn the spindle on for this.
I set it up to take .002" and used 2 passes and it really works VERY well. Here's the link to the actual product:

Description:
Micro Tap Guide Type: Micro Tap Guide Tap Size Range: #10 - 1 Length: 3
Type:
Micro Tap Guide

Tap Size Range:
#10 - 1

Length (Inch):
3
Shank Diameter
(Inch):
1/2

Big Book Page #:361 (http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=361&PMITEM=95267472&PMCTLG=00)

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=2360523&PMT4NO=0


Sorry about the pics, but I figured you could get the idea.

Educate me, what size bits will fit in there?

There are no "replaceable" bits as it were, as these are not intended for engraving. Have a look at the catalog page for the description. The points could be sharpened as needed though.

He's basically just using a spring loaded tapping guide as a form of non-rotating scratch engraver. Actually a very nice bit of repurposing there, it seems like a good idea in a pinch or for occasional use. Unfortunately, it would only work as a non-rotating engraver, it doesn't have any ability to interchange bits, and it wouldn't be as clean or consistent of engraving, last as long as a tool, or do harder materials. It would however, take a common and inexpensive tool and serve many peoples intermittent engraving needs in soft materials if you didn't have the need for a true engraving setup.

Thanks for explaining it much clearer than me, stepper. It actually is a very clean scratch and has that "diamond" scratch effect to it as well. The points on these are hardened so it should be interesting to see how long it lasts for me. I like this application for the half hard brass as it's the most success I've had with this particular material. I usually use single flute carbide bits but in this brass I get some nasty burrs that just look horrible at times.