I picked it up on a silent auction at work for less than $600.  It's an early 80's, the head was rebuilt in the mid 90's and neglected every since.  
The X and Y backlash was pretty bad.  I've tightened up the X split-nut so far and lubed everything properly.  The long term plan is to convert to ball screws and go CNC, it'll probably never happen though.

Good buy !

In this area, that's a steal.

Mine does not have power feed or a dro, $1500 at auction.

I'm jealous.....

The power feed needs some work (works when it wants to).  Mine came with a Anilam DRO, but two of the scales were damaged so I sold the whole works.  I'm putting a Chinese ebay one on.

Good buy!

Surely thats an oil stain to the right of the knee dial, not a crack.  Right?

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Yes, it's oil.  A big crack there would be quite bad!

You can CNC your machine with an Arduino, Gshield, and motors for about $300.

Do tell....

Yes...

I have a POS mini-mill that Ive never figured out a use for. I have arduinos, and some gecko drivers and some big ass stepper motors. I was just thinking about turning that thing into a tiny CNC machine the other day.

What are your plans for powering it?

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I powered it with a cheap VFD.  It's not the best setup for reversing and tapping, but works fine for now.

I'm in no hurry to tear it down.  It runs nice and quietly and works great.  I might do it someday though.

I have an Enco mill/drill that I converted to CNC with steppers and a PC running Mach3.  If and when I do the Bridgeport, it will cost a hell of a lot more than $300 since it will involve switching to ball screws.  McMaster used to have an $800 ball screw conversion kit, but those are long gone.  There are occasional deals on ebay.  

The little Enco will be used for making most of the hardware for converting the Bridgeport.

Mine has been running that way for years, no issues here, just a careful brake hand.

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Is there any way to somehow feed the output of a DRO scale to the CNC controller, so that position is read by whatever the scale reads rather than however many turn the computer tells the stepper motor to turn.

Then you could use normal motors (not stepper motor) to move the table since the computer would be basing on actual position as read by the DRO scale.

Seriously - you are much better off keeping it as a manual machine. And as far as an Arduino - yeah they can be used to make a decent DRO but NOT CNC. The cost of proper conversion ball screws alone is more than you would have to pay for a used CNC

If someone starts yabbering about how they could fit 5/8 rolled screws I'm going to virtually bitch slap there ignorant asses.

The market is flooded with CNC knee mills with bad controls ( processors, the servo drives and motors are usually fine) which already have CNC rated lube systems, ballscrews and other essentials.

Shops in the business don't want Open BP type CNC machines anymore. Why?

1] Open machinery causes higher business insurance costs, and OSHA hassles in many states.

2] Requires a higher skilled operator than a basic PHD (Push Here Dummy) machine operator.

3] Reduced capacity tooling vrs CAT or HSK

4] No ATC

5] Limited Spindle HP and RPM ( most CNC machining centers can do 8000rpm and some up to 12,000 before getting into the really high speed options. )

6] Productivity vs skilled operator cost is not nearly as profitable as other options.

BP's sell great on the used markets for people like yourself that want one for there home shop, BP style CNC usually don't sell and often end up at the scrap yard.

In 2009 I could have had 4 Haas VF0's that were dirty as a mud bog - the company moved out of the building and left those cheap ass machines behind - ( they took the Okuma's, Mori Seiki's, Makino's and even the Mazak's)

Owner of the building just wanted them gone so I could have had them for the cost of the rigging and moving. ( I had not closed on my shop property yet, or I would have.

Oh - and for the record - been there done that - I have 2 Hurco CNC knee mills out in my shop. Combined cost about $12,000 but I bought them with huge tooling packages. Dual Kurt vises, Sub plates, about 70 tool holders many new and still in the factory wax. Oh yeah, it also included a CNC rated 10hp rotary phase converter.

You can compensate for backlash when trying to achieve a position, kinda, but not in motion.  IE- the controller can't compensate for the cutter pulling the table around during a climb cut.  You could just conventionally mill everything but that would doesn't produce nearly as nice results.

I agree with the poster above, keep the handles on your Bridgeport.

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I agree that Mach does a great job of backlash compensation.  Like I posted above, I have converted my benchtop mill/drill to CNC with Mach and am quite familiar with it.  

The ball screws are not just for backlash, but also less friction for greater torque and speed.  Better accuracy, but mainly less wear so less adjusting for backlash.

I'll probably never get around to converting the Bridgeport and if I do get serious about it, I will definitely look into a used CNC machine with bad controls.  That really would be the best way to go like ProfGAB101 said.

I followed this page step by step.
This page lists his expenses including the mill.

Bummer. The mini mill conversions do not require ball screws.

I don't know yet. My DROs are a couple of harbor freight calipers bolted to the bed. Supposedly an arduino mod will interface with them. I will post here if I figure it out.See below




Interesting. I use UniversalGCodeSender. I wonder if it has a backlash compensation setting.

.....

How is it working for you? Milled anything yet?

I checked out that DIY machining web site. He has only a basic clue.

"Correct me if I am wrong but I do not know of any industrial CNC controller that uses anything other than a parallel port." - OK I am correcting you, virtually no "Industrial" machines use a parallel port. They can't. There is not enough I/O channels to connect required safety interlocks required by OHSA and U/L even if you ran dual ports.

He is running 2.8 amp steppers on 2.5 amp drivers on a 115lb Seig X2 mini mill from Harbor Freight. I have a Kurt vise that weighs more than that!

The man has failed to do his homework and is posting info that contains blatant errors. He compares certain functions to a HAAS CNC mill and mis-represents how the HAAS works. This is the danger of the internet, any idiot can post anything and others will assume its true and correct.

He claims there is nothing else like this that can stand alone and run a machine without being hooked up to a PC parallel port. - Research - Beagle Bone and Machine kit. BINGO there is just 1 better alternative which can do all the things that GRBL can't that he hopes will be in the next GRBL release.

Well here is a big long story.


Shoot - even this is better than his Arduino box.

What do you think is the best bang for your buck hobby cnc machine? Convert a manual mill?

That is a loaded question and needs more info to answer properly.

What are your goals? - AKA what do you want to do with it and what is your Overall Budget. As in Funds / Shop space consumed / available electrical power.

I am into BIG iron - I admit it. But few people have space to buy a dead or outdated Mori Seiki Machining center and spend the time and effort to make it a renewed viable machine.

For the High end hobby user - wanting a good bench top CNC that can do almost as much as the Pro Industrial machines... I would buy a Precision Mathews PM-25MV Then buy a conversion kit with ball screws and motor mounts. I would use LinuxCNC and Mesa control cards. This mill will work well with steppers, and the new steppers with internal feed back loop won't loose steps like normal stepper drives can. Personally I use full feedback servos on my machines because when I make parts under contract I want to know they are the best I can make them. Don't get me wrong - many Atlas missiles and Apollo rocket chassis parts were manufactured on large stepper based machines. But in todays market place Slow and Steady will always loose the race to FAST and Steady. Thats business, lets get back to hobby systems.

This mill is what the Grizzly G0704 mill should have been. It has a 1HP brushless motor and several other quality upgrades that you as buyer would have to deal with if buying the G0704.

Here is a video by David Clements showing the PM-25 after installing his CNC conversion kit.

If I was just starting out - this is the rig I would buy.

Got more money than time to get started - Then the answer is simple - Tormach PC1100. I still won't trust TTS tooling to hold zero for MY use - but hundreds of satisfied customers like it. ( BTW - All Tormach Machines use Mesa Control cards and Tormach's custom version of LinuxCNC called Path Pilot.)

Thanks for the info. I'll have to check out the PM-25.