Advice on Bridgeport converted to CNC for sale

Charlieman22

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Thanks Gents,
I've thrown in an offer for the machine.
We'll see what happens.
If it goes through - perhaps you guys will help me diagnose and tune (where possible).
That process will give me some basic education on the machine I'm sure.

Travel for the week - then hear back at end of week on my offer.
Will update on return.
Wish me luck...
 

Charlieman22

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*edit: Below is a pic of the type to thing I would like to be able to accomplish - that is likely the most sensitive to spec.
This is a half to a Vespa 2 stroke motor case.
The area where the crank shaft sits needs to be enlarged to fit a specific crankshaft.
The clearance between the crankshaft and these aluminum cases in one area of about 2" of the circumference, should be at least .002 but not more than .004, when complete.

After all, you don't care if it returns to zero faithfully. You care if it cuts where it says it's gonna cut, faithfully.
Have no relative experience to place educated bet on weather it will hold my tolerance for what I want to cut as per wrat's comment above - but this type of work will be the measure for me on pass fail for the toughest end of the spectrum of tolerances when cutting.
 

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Charlieman22

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So, where we left off...
I made an offer - $2500 - for the CNC Bridgeport of this thread.
The gentleman - original owner/ machinist - declined.
He noted that there was nearly $2K of tools included. I'm sure that he has spent at least that.
There is a Bridgeport vice and turn table, collets, mills, etc.
I suspect I might get to $3500 - but that is likely the bottom.

I see three options:
1. Sift through the Craigs List iron scrap for a fully manual clone with no DRO @ $2500 with scrapings still highly visible. They are 1 in 10 but do come up.
2. Get one of the top bench mills from PM. Looks like $6500 all in with power everything and it ties my shoes.
3. Grab this Bridgeport @$3500

I see myself using the machine to:
- Modify aluminum 2 stroke cases as in picture above.
- Machine off excess aluminum after a welding up cases.
- Bore a 3/4" hole in 1/4" steel plate when fabricating something
- Make a nicely shaped component in 1/4" steel, or 1/2" aluminum, with curves.
- Drill a damn hole in something that is clean and neat and centered!

I get how the CNC would be great for making that nice shape - but I am not sure if having the CNC on the machine makes it lousy as a manual mill - for quick jobs where I don't want to create a cad file just to machine off some material.
For that type of job - I had imagined the PM machine would be ideal...

Would be great to hear it's not the case - and that the BP can be used just standing at the machine and moving the table around in a traditional manner/ rather than creating files on a 486 computer in another room just so I can tell it what to do. Can you guys help educate me on this?
 

JimDawson

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I suspect I might get to $3500 - but that is likely the bottom.

Not a steal at that price, but pretty good given it's well tooled.

I see three options:
3. Grab this Bridgeport @$3500

That one ^^^^^^^^^^

I get how the CNC would be great for making that nice shape - but I am not sure if having the CNC on the machine makes it lousy as a manual mill - for quick jobs where I don't want to create a cad file just to machine off some material.
For that type of job - I had imagined the PM machine would be ideal...

Would be great to hear it's not the case - and that the BP can be used just standing at the machine and moving the table around in a traditional manner/ rather than creating files on a 486 computer in another room just so I can tell it what to do. Can you guys help

Manual as well as being CNC, the best of both worlds in my book. If I had only one machine in my shop that is exactly what I would want. I use mine in manual mode all the time for many jobs, sometimes it's just quicker. I think mine gets used as a manual drill press as much as a milling machine.
 

Charlieman22

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Manual as well as being CNC, the best of both worlds in my book. If I had only one machine in my shop that is exactly what I would want. I use mine in manual mode all the time for many jobs, sometimes it's just quicker. I think mine gets used as a manual drill press as much as a milling machine.
Chuckled - drill press... am certain it will be true -but one that drills where I want it - which takes an act of congress with my current set up.
I was concerned that it being an older set up - there might not be any good means to operate it manually, without a struggle.
There is some backlash of meaning in it currently... Perhaps I can beat some of that out of it with some tuning and get it to operate nicely for me in a more point of use fashion (imagining doing it from a remote computer just sounds miserable for odd jobs).

Of course if I could manage to have it manual until that moment when I want 5 of the same curvy components, and then use the CNC capability, that would be ideal. Perhaps I can convince the gentleman to show me how.

Thanks for the input.
Will update after my next round of discussions and see where that leaves me.
-CM
 

JimDawson

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Of course if I could manage to have it manual until that moment when I want 5 of the same curvy components, and then use the CNC capability, that would be ideal. Perhaps I can convince the gentleman to show me how.

Not sure about that machine, but on mine just push the E-stop button and you are in full manual w/DRO.
 

wrat

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There is a real chicken/egg situation in this.
Do I need the mill to get some work done? Or will I get work done because i have a mill?
I've never known anyone that stuck to their version of "I'm just gonna do THIS with it..." That goes for almost every major tool from forklift to welder. The inventive craftsman with a task at hand is always doing things he never expected - which opens the door for more tasks. Soon, you'll be saying, "oh, wait... i can do THAT."

Then there's this:

2. Get one of the top bench mills from PM. Looks like $6500 all in with power everything and it ties my shoes.

With a wheelbarrow full of cash, you're still out of luck. Basically everything is on backorder. If you can wait until "late summer" - which I suspect will turn into autumn - then you'll maybe be fine if war doesn't break out in Taiwan.

$3500 for a well-equipped, well-worn, well-tooled machine? It's certainly not the best or worst deal I've ever heard.
 

Charlieman22

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Ok Gents,
Don't quit me yet...

What if there was an alternative option to above:
A belt driven PM bench top machine, 32" table, new/unused, & I could have tomorrow.
And it was "basic" meaning no power anything or DRO.

I could install an X feed and DRO - with a custom bracket or two for DRO
And maybe - if I managed to get fancy - or someone here could guid - could figure out how to install a Z power feed (nothing off the shelf from PM).
No powered quill - which would be a compromise on boring I think and perhaps negate possible CNC play? (no experience to know how critical this is to my desired practices).

All in (machine/stand/x power feed) ~ $3500 + delivery (~400)+ DRO(~700?) = $4600 in my garage (and some labor)
Any change of opinion/ thoughts on Z power feed or CNC solutions I would want to understand better?
(I've got a call in to my Bridgeport lead on the other front. Hope to get back to see and operate this week).
 

wrat

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Now you've introduced a lot of moving parts and more factors in the equation. I'm not keeping fully abreast of the dynamics, here.

If you ultimately want to be churning away on an NC machine, you may as well start bare-bones. Sure, naked PM. Good idea. The conversion kit will have motors, scales, and indirectly - through the computer - a DRO. But you're saying at first not getting a DRO and then later paying $700 for a DRO so I'm not really keeping up, here.

If you ultimately just wanna make some chips, your bench top PM machine is not (generally) gonna be QUITE the machine in heft, rigidity, and wear as that Bridgeport mighta been. But it'll make nice chips and it's a really nice machine - especially if new. New matters. It really does.

Power Down Feed (PDF) is a great feature. Yes, it's a big player in a well-bored hole, but it comes in handy in straight drilling and a little of everything else. Maybe not always as critical in 2 stroke aluminum heads, but in a tough steel or some frustrating piece that's way harder than it oughta be (we've all been there), having a very consistent feed is critical to both properly load the cutter and prevent work-hardening.

Not the be-all and end-all, but PDF sure is nice sometimes. If I was legit looking at cylinder boring as a main activity, I wouldn't even plug the thing in without PDF ready to go.
 

spumco

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Bridgeport all the way.

Stiffer, heavier, significantly more flexible for oddball one-off setups like you described. Since it's already CNC'd, if you hate the control system that part is easy to fix. Tons of spare parts on fleabay.

You're in LA, there are TONS of used machines there. 30 seconds on LA craigslist revealed about 8 Bridgeports (or clones) for sale in your price range. There's a clean Enco clone for $2k in Santa Clarita. They all have PDF, and any 3-phase spindle motor can be run with a 1-to-3 phase VFD.

The only downside to a Bridgeport-like mill is the R8 collet. Changing tools and having to re-set Z height is a pain... but there are work-arounds and options. Using the TTS toolholder system is one (for smaller tools). Royal (and others) make quick-change R8 tool holder systems, but those can get pricey.

But that same downside is also present on any mill with an R8 spindle... including the PM's you're considering.

If you can report back on the Brigeport you're negotiating over... like model and/or control, we might be able to figure out what it'd take to make it really useable in manual mode. Most of the CNC Bridgeports I've seen are all a bit different - at least the 'aftermarket' ones and not the OEM.
 
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