Engraving bits in mini mill?

[patmat2350]

I'm upgrading the drive on my X2 mini mill... the LMS kit says I can get 4500rpm, I hope so.

But I want to do some fine line engraving- mostly things like graduation markings, on steel, aluminum & brass.
What bit works well at the relatively low speed of 4500?

Or should I be dragging a diamond bit?

I see a lot of choices out there, such as offered at https://bitsbits.com ... Vee tips, micro ball ends, etc.

Thx, PM

 

[Wreck™Wreck]

You may engrave at low spindle speeds using equally slow feed rates, this will be time consuming however.
We use a Haas TM1 for engraving, it has a 6000 RPM spindle and it does a fine job slowly, for very small graduation lines dragging a spring loaded marking tool would be the best option I suspect.

 

[JimDawson]

You need a lot more spindle speed for those bits. I have successfully run them as slow as 18,000 RPM, but that's a bit on the slow side. I use a pencil grinder from Harbor Freight at around 30,000 RPM.

Here is how I do it http://www.hobby-machinist.com/threads/50-000-rpm-mill-spindle.23186/

 

[Wreck™Wreck]

You need a lot more spindle speed for those bits. I have successfully run them as slow as 18,000 RPM, but that's a bit on the slow side. I use a pencil grinder from Harbor Freight at around 30,000 RPM.

Here is how I do it http://www.hobby-machinist.com/threads/50-000-rpm-mill-spindle.23186/

Quite right.
There are spring loaded scribing tools that do not rotate and just scratch a line as used in the glass fabrication industry, an air spindle is another option but I suspect that the OP will not want to go there.