I’m looking for a little reality check and I figure you guys are the right guys to ask (gals too).

I make a specialty product from silicon bronze that needs to be tapped 1-1/2" NPT. We were sending them out and that got to be pretty expensive $15 each, and really crappy work, so I started doing them on a friends lathe, and it’s a real pain. Had to make a special everything, tap holder, I use a 2 foot, torque arm, and even after reaming the hole with an NPT ream, and using a skip tooth tap, and a lot of cutting fluid, it will stall a 7.5hp lathe. Silicon Bronze is 30% the machinability of steel. It is not friendly to this type of brute force process, that’s why it’s silicon bronze.

So back to another machine shop, now it’s $17.50 each and it’s still a pain in the rear, they do good work. But small passes and a single point is the way to go, but of course it never loads the machine, because it’s single point.

So, I’ve made my fair share of CNC machines back in the day, I’m looking at sacrificing a Grizzly G4002 - 12" x 24" with a cam-lock spindle to the project, just get a new chuck with replaceable jaws and make custom jaws. Don’t need extra length, and really, how much HP do you need to do a bunch of clean up passes with a boring bar and then single point the thread? About 2hp. So what, it takes 10 minutes each, fine. Centroid Acorn, DMM hybrid drives, everything fairly straightforward. The part is only a few inches long, it can be held in the jaws.

The question comes to tool changer…

I figure I need 2 tools minimum, but 4 would be really nice. A little facing, a boring bar, and a single point, plus one extra.

Quick change tool post is NOT an option, me standing there is less of an option.

Here are the options:
Is there an automatic tool post out there, perhaps from China, that can be wired in?

OR..

Convert it to a gang style machine. Get a Grizzly G8750 X Y Table, deck the entire top carriage of the lathe flat, deck the underside of the X Y table, removing the entire Y axis from it, a little bolting magic and now I have 12” of travel! Mount some tools right side up, and the back half tools inverted. This way I never travel that far off center. Basically a gang style setup.

It only has to hold .002” this is an NPT thread, it can probably be .005 and still be fine, I’ve paid for worse.

The machine needs to be less than #1000 said and done, moving in a few years and freighting a Mori isn’t in the budget.

It will run basically one single program its entire life, thread a 1-1/2" NPT into Silicon Bronze.

So I would be interested in a sanity check of my idea, or is there a better way to skin this cat.

We will tap this hole a MINIMUM of 600 times next year. 50 times a month, maybe more.

Interested in hearing ideas.

Thanks
Aaron