[mrquacker]

I am looking to do some engraving on aluminum on my 770. Using a solid bit in a collet works, but the parts are not perfectly flat across, and the markings arent a uniform depth. To fix that, I am told one needs to use a spring loaded tool like this: http://www.2linc.com/engraving.htm But that is $375, and I'd rather not spend it if I dont have to.

If I were to grind a spare tap into an engraving bit, or get an engraving bit that fits a tap holder, could I use my tension/compression tapping head as the spring loaded tool holder?

I know that for axial tools like this a side load is a no-no, but would engraving cuts damage the mechanism at all?

Has anyone tried this? Does it work? Will I damage the t/c head if I try it? Are there any alternative spring loaded engraving tools that are cheap? (~$100)

Thanks!

[TXFred]

EDIT: The information in red is incorrect.

No. It won't work. The T/C head starts out in the fully compressed position. As you tap, you keep the feedrate slower than it should be. This causes the head to extend as the threads are cut.


I have a very nice drag engraver made by a fellow forum member. At the time, it made more sense to buy his than to make my own. But you could easily make one to use. Details here.

http://www.cnczone.com/forums/tormac...ml#post1035735

[shred]

Yes, you can do it (assuming your head includes compression, not just tension-- just load it part-way), but when I asked the supplier of my T/C head, they didn't recommend using it above 2000 RPM, which is a problem for good engraving.

You also have to be careful of sitting too long in one spot and re-passing lines and so on-- pretty much the same as the 2L gizmo.

[mrquacker]

I have the one tormach sells. I havent used it for tapping yet, but it seems that you can squish it down the same way the 2L one does.

[TXFred]

Well, it seems that I was quite wrong.

My T/C head does not have the ability to compress, until I load one of the collets. Then the black knurled ring pops out and it is able to compress.

You can tell that I haven't spent much time with this tapping head yet, can't you?

Frederic

[mrquacker]

Heh, yeah. I'm still playing around with mine, and this idea came up. So that plunging action is similar, but will using it to engrave put a side load that will break something? The same way that if you try milling with a drill/chuck you will break the chuck. I would hate to have that happen with the expensive t/c head.

Does anyone have any figures/ideas for the forces created by a simple engraving bit?

[shred]

Heh, yeah. I'm still playing around with mine, and this idea came up. So that plunging action is similar, but will using it to engrave put a side load that will break something? The same way that if you try milling with a drill/chuck you will break the chuck. I would hate to have that happen with the expensive t/c head.

Does anyone have any figures/ideas for the forces created by a simple engraving bit?

Forces are light if you're only engraving a few thou. My T/C isn't the Tormach model, but I'd check with them on max suggested RPM. You want to spin engraving bits as fast as you possibly can. The T/C mechanism might not like that.

[David Bord]

Ive seen guys use a tap guide as a drag engraver.(spindle stationary) They are cheap and may have a hardened tip as well.

[rowbare]

They aren't very complicated. If you have a lathe, you can probably build one in an evening. Go to Google Patents and look up 6,834,434 .

bob

[MFchief]

Just a quick note to anyone thinking of making the drag engraving holder from the link that TXFred provided. It will likely require modification, because the newer TTS 1/2" holder is not drilled 1/2" all the way thru. Mine are the new ATS configuration holder and it's not only beveled at the top, but the upper end of the thru hole is necked down to about 0.4". Not insermountable, but will require some changes to be made.

Terry