CNC conversion w/ acme screws

[magma-joe]

Hi to all! I have been gathering info on a 3 axis conversion for my Bridgeport clone conversion. It is a near new Acra 9x42 AC inverter drive mill. I see some conversion kits as well as new CNC mills offered with ball screws OR acme screws. Many people push buying an old Bridgeport Boss and then upgrading the cnc controls. Perhaps because they came w/ ball screws? I am disappointed with the series 1 Boss table travel being only 12" by 18". I have access to a Boss now that has already been upgraded that I could buy for less than a conversion for my Acra but I keep thinking about the table travel issue. If I used my existing near new lead screws currently in my machine I could save alot on the conversion but wonder how much this would affect the machine vs ball screws? Anybody else do a CNC conversion and Used the leadscrews? The 3 axis conversion price w/ ball screws is just a few thousand less than the cost of some NEW comparable 2 axis cnc mills w/ ball screws.
http://www.penntoolco.com/catalog/pr...ategoryID=5432
Not sure what is the best avenue to go, thanks for any feed back any of you might have.

[gus]

If you are happy with +- .05 tolerances, then go ahead. Otherwise it is a really bad idea

Think on how much of your work really exceeds 18 inches. Ponder how many VMC's have 20 inch x travel...

[wcarrothers1]

I must have a huge boss machine then as I have 12x25ish at least travel on my table.. (boss 10 v2r3 machine)

And even though is't pushing 20 years old I'd say it would be a great base for a conversion for some one not wanting to also have to toss a new set of ball screws at the project. How ever I can also say that my boss 10 controller works well enough and is easy enough to use that I will not probably convert to a mach3/gecko setup till something dies so bad on the boss that I can't figure out how to fix. Seeing it's already 20+ years old it probably has another 20 years life in it the way I will use it..hehe

Mach would be nice as on my other 2 machines I have a 3 wheel pendant for jogging and manual stuff that is a little harder to pull off with the bridgeport/boss setup. But all in all not hard enough to use not to keep it. Becides with it having it's own controller I can run my mach machines at the same time rather then shairing my 1 mach /gecko power supply (which is already being shaired between 2 machines.

Oh ... and by the way I would not consider doing a CNC conversion on the acme screws. Even getting the cheep screws (5/8 size) from Mcmaster carr (which I used on my round pole conversion) would probably give better results then acme screws would. assuming they were properly supported as the screws should be bigger then that size but that size is pretty cheep.

b.

[Al_The_Man]

I've always thought that 'CNC conversion with Acme screws' is a bit of an Oxymoron.
Al.