Hi all

I'm just trying to figure out whether I should add a fourth axis to my machine or extend the y axis to give me the travel I need so want advice on costs for doing both.

Basically I make my own dive gear from Delrin and really need to the ability to machine large diameter circles, preferably I'd like a capability to do 200mm max but could live with 180mm (this is not large diameter to many on here I understand). Currently my y axis has a max travel of 160mm I think so when you add in tool size then I'm 50mm short of having the capability that I want. Each option has it's own setbacks though:

4th axis
While horizontal I'll lose a lot of the z axis travel to the size of the chuck and rotary table and by time I've finished buying a the equipment I could probably have a more capable mill with less fuss (maybe) by extending the y axis (about £400 for the chuck and rotab I need).

Extending the y axis
- How much extra travel can I get from it without really tearing it apart?
- I was thinking of linear guides/ rails and having a new base machined and bolting it back together. Obviously I understand it has to be square but the question is more about cost and feasibility compared to going rotary.

Cheers
Jools