Engraving on a lathe?

[Bill Tokyo]

I'm going to make a few instrument dials, including a sundial. These are all items with numbers, and various circles large and small engraved on the face. They range in size from about six inches (roughly 15 cm)in diameter up to roughly 10 inches (about 20 cm) in diameter.

I want to make these in brass, and it seems that the easiest way to engrave circles would be
to chuck the plates up in my lathe, use the right type of cutting bit in the tool holder and then
slowly revolve the head by hand to engrave circles.

Here's the question: can anyone advise me about what shape works best for my
cutting bit? What type of profile should I grind my bit to in order to get
the best and clearest lines?

Has anyone done this? Or can someone perhaps recommend and Internet page or a book that shows
how it is done?

Bill

 

[Unkl Ian]

Wood lathe,or metal cutting lathe ?

 

[richard hall]

sounds simple enough, any tool bit with a sharp point should work,say a 45 degree tool. id first locate your center,get out a set of dividers and lay out your circle so you can see it, then bring your tool up to the scribed line. i doubt you are going to deep, so i guess spinning by hand may be ok. IF however it sticks, you may have to turn on your power on the slowest r.p.m. you have available to you. BACK OUT TOOL HOWEVER BEFORE YOU TURN ON POWER. you dont want a loud noise that you arent ready for...

 

[Bill Tokyo]

Engraving in lathe

It's a small metal working lathe, so it has a tool post.

I don't think I will have to turn the power on. I sometimes do fine work by spinning the tailstock with my hand.

 

[jimzim75]

Hi Bill,
The only reason to use a lathe to do this is if you want a lot of depth to the
cut, or you just happen to have a lathe. You can do the same thing with a
metal template and a carbide scribe, or a good compass.
You can do deeper lines with a pantograph, I use my New Hermes for this.
This will give twice the depth in the cut as using a template.

If I truly need a deep cut of a lot of depth would I use my lathe. I use
a block of wood with plate mounted on with hot glue. Using face plate
to mount the wood on, four screws if I'm
doing a single circle. For multiple circle you can use two screws so you
slide the block. This work if the all the circles are in a row. The large
the circle the lower the rpms. It's better to have a cross slide feed on the
lathe.

Since I done metal turning and raising. I tend to use the free hand style.
I make my cutting tools. This is not for the faint of heart. If your going to
try doing this under power, find out more than I'm telling you here.
I use this style because I'm use to it and it's faster than a cross slide.
It doesn't really mean I sane.

Jim

PS: the geometry for the lathe tool is the same as if you were cutting teeth.
I point with a micro radius at the tip.

 

[Bill Tokyo]

Engraving in a lathe

Hi Jim,

Thanks for the excellent advice. As it so happens, I have a lathe and not a pantograph.
also, being a watchmaker, I'm used to making all my cutting tools by hand, so this seemed to
me to be a natural way to go: cut the circles in the lathe.

Also, being a watchmaker, I'm accustomed to powering my lathe by hand or with a bow,
Something you rarely hear of elsewhere, so I wasn't thinking in terms of depth of cut at all.

My main concern was ease in holding the work piece and the ability to quickly produce the
circles.

Your suggestion of heat gluing to a piece of wood to mount the piece is excellent. But what I think
will save me a tremendous amount of work is what you say about a compass and a carbide scribe
being just as easy a way to produce lines of sufficient depth.