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Thinking About Acquiring a Mill

Darren

Ultra Member
Premium Member
Don't be afraid of a CNC knee mill. They can usually be operated manually. My Kent had a missing/broken cnc control and a broken x-axis ballscrew when i bought it. I pulled the belts off the servos for less drag. I replaced the ballscrew and run it manually. Its great because it has hard chrome box ways with turcite, auto oiler, ballscrews , a 6000 rpm EVS head (so it came with a vfd system already). It has an R8 taper which i have no problem with. Its silky smooth to operate, and has zero backlash due to the ballscrews. I will eventually return it to cnc control, i think. Anyways, i've seen CNC machines with broken controls sell for less than a clapped out manual machine, despite all the advantages.
 

PeterT

Ultra Member
Premium Member
My ears always perk up when I hear ballscrew leadscrews used on manual machines. Just out of interest, what is the equivalent thread pitch?
 

Six O Two

(Marco)
@Tecnico - Yeah, it was definitely a bit of a gamble. But I figured with what I was saving, I could still afford to fix anything that was too far gone, and it would be a good learning experience. I picked a small auctioneer who seemed to mostly sell equipment found in technical schools. I got lucky. The mill was expertly crated on a pallet and loaded at no extra charge. The auctioneer also had a preferred shipper whose prices were inline with online quotes I got at freightquote.com, so I chose to use the preferred shipper. I paid for liftgate service and had visions of the mill being delivered to me right in front of my garage.

Of course, life has a way of throwing curve balls at ya once in a while. Our town is in the mountains and very hilly and my street and driveway are nowhere near level. When the mill arrived, the driver and I could barely even lift the 2500lb mill off the deck of the box truck with his pallet truck, let alone try and move it out of the back and onto the lifgate. I was pretty crestfallen as the driver gave up and drove the mill off to the dispatch office in the next town over. I thought I'd have to try and rent a forklift or something, and was pretty worried about shipping costs snowballing, but instead I just called the local towing company. A few days later, a tilt-bed wrecker went to the shipping company's offices, the mill was loaded with their forklift onto the wrecker, and the towing company drove it 45 minutes to my place and I helped to winch/slide/roll/pursuade the pallet off the tilt-bed onto my driveway for something ridiculously cheap, like $200 or something.

If I had to do it all over again (when I do it again?), I'll just get shipping quoted to the local shipping depot and then get the towing company to take from there to me, and not bother with liftgate at all.

As for the mill, it was pretty excellent considering its age, although not perfect. The backlash is good, but bed is pretty pockmarked, and it does howl like a banshee at certain speeds (maybe needs new bearings?). I'll get to fixing that one day. But other than that, I've been extremely happy with it. Definately got lucky. I was less lucky when got a lathe shipped from Pennsylvania to Washington state, but that's whole 'nother story.
 

PeterT

Ultra Member
Premium Member
Thanks. And what is the leadscrew OD? And do you lock your set way axis each pass?

No it wasn't the DRO/measurement aspect. It's that some references have claimed the ballscrew retrofit can self feed on itself while cutting because the ballscrew resistance is so low compare to conventional acme thread form. I suspect all mills have locks on both axis but some lathes don't on certain axis. Anyways, in the absence of any direct retrofit experience I had a hunch finer pitch may be less prone to drift than coarse, but sometimes you cant get the desirable nominal feed per rev with available ballscrew selection.
 

Darren

Ultra Member
Premium Member
Thanks. And what is the leadscrew OD? And do you lock your set way axis each pass?

No it wasn't the DRO/measurement aspect. It's that some references have claimed the ballscrew retrofit can self feed on itself while cutting because the ballscrew resistance is so low compare to conventional acme thread form. I suspect all mills have locks on both axis but some lathes don't on certain axis. Anyways, in the absence of any direct retrofit experience I had a hunch finer pitch may be less prone to drift than coarse, but sometimes you cant get the desirable nominal feed per rev with available ballscrew selection.
The original ballscrew was 25mm. The replacement i got was 32mm. I had to bore out the yoke to fit the new ballnut and modify the one end of the new screw. But i got a brand new precision ground screw on ebay for 200 bones, so the effort was worth it.

Backdriving of the screws is not really a problem, most of the time. Heavy deep roughing cuts might move the y axis a few thou but i can flip the lock on if needed, and it never moves on a finish cut. So it really hasn't been a problem. Paying attention to the DRO helps,

Ballscrews on a manual mill are a dream to operate. Sooo smooth, but the zero backlash is the best.
 

Tecnico

(Dave)
Moving along in my thought process of finding a suitable machine I have some more questions.

I've seen several of the machine I started this by looking at, they seem to get many different "brand" badges put on them (Drummond, King, Lilan, Kondia, Darbert, Acra, Modern) but appear to be the same machine or family originating in Taiwan. I`m wondering if they`re all the same under the label and how hard parts are to come by for them (interchange?). Also what wears out on them?

What got me thinking about this is an ad I saw for one of these that had a lower price and said the variable speed control of the head needed work. Would that be a can of worms or a good opportunity? That ties into the question whether the Taiwan sourced equipment is well supported for parts?

Thanks,

D:cool:
 

Darren

Ultra Member
Premium Member
A Taiwan bridgeport clone should be well supported as far as parts goes. HH Roberts etc should have everything you need for the head.
 

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
I saw for one of these that had a lower price and said the variable speed control of the head needed work. Would that be a can of worms or a good opportunity? That ties into the question whether the Taiwan sourced equipment is well supported for parts?

I agree with @dfloen. With a few exceptions, most of the parts on my Hartford Clone of the stepulley Bridgeport are interchangeable with the genuine Bridgeport.

In addition to HH Roberts in Canada, you can also get parts in the USA at H&W Machinery, at Icai-online, at MSC Direct, and even on ebay. Sometimes parts are cheaper at one VS the other.

If you find one, post some photos and members here can usually help you with advice.

I assume that the variable speed head is a Bridgeport Vari-Speed Clone. There are lots of parts for that. I would not be afraid of it, but you never know. From what other members have advised me, I'd be more worried about the table than the head.
 

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
What got me thinking about this is an ad I saw for one of these that had a lower price

One more thing. If you want a Bridgeport Clone at a good price you shoud get yourself as well informed as possible and then be prepared to buy or not at the drop of a dime. Good deals are usually long gone by the time you go back for a second look.
 

Tecnico

(Dave)
When you speak of a Bridgeport clone with Vari-Speed are you referring to a machine like in the photo I showed in post 1 of this thread? Would that be the type that the Bridgeport (and clone) parts would fit?

When you speak of being worried about the table, is that more the ways/sliding surfaces ot the lead screws/nuts?

I get your point about getting well informed for when a candidate pops up.....climbing the learning curve!

D:cool:
 

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
When you speak of a Bridgeport clone with Vari-Speed are you referring to a machine like in the photo I showed in post 1 of this thread? Would that be the type that the Bridgeport (and clone) parts would fit?

I guess that the word "Clone" means different things to different people. And I am by no means an expert at mill construction and parts interchangeability - I'm not sure that anyone is. Even the people who sell parts routinely screw that up.

I looked at your first photo again more closely. It would seem to replicate the function of a Bridgeport VariSpeed Knee Mill, and therefore it is a Clone in that sense of the word. However, in this mill's case, I doubt that very many of the parts are actually interchangeable, and therefore it is not a true Clone in that sense of the word.

Here is a photo of a Genuine Bridgeport VariSpeed, and below that is a copy of your photo (for ease of comparison).

If you look closely, you can see that the housings have significant differences and many of the controls are in different locations. In my opinion, they are clones in the sense that anyone using them would be totally familiar with their operation and could use them seamlessly. But speaking as someone who has taken two of them apart, (but not dozens) I doubt that many of the parts of these two mills are interchangeable.


BP_01.jpg

Drummond Mill.png

When you speak of being worried about the table, is that more the ways/sliding surfaces ot the lead screws/nuts?

Actually, both.

Almost everything in the head and even the head itself can be replaced or swapped out. But the table and knee can not.

All three pairs of ways wear and/or can be abused to the point of not being able to repair them.

The leadscrews and split nuts can be replaced but are expensive.

Another thing that can be worn out is the gibbs. Again, they can be replaced but are expensive.

Even a badly abused table surface can usually be cleaned up and repaired to some extent. In other words, table damage/wear is mostly cosmetic.

In summary, if I were looking for a BP or a Clone, my main concerns would be the condition of the ways, the leade screws and split nuts, and the Gibbs.

There are some expensive parts in the head too, but it's much harder to tell what is really wrong with the head until you get it apart. Everyone who buys a used knee mill takes that risk. It's always nice if you can run the machine before you buy. But even if not, you can usually put the machine in neutral and spin the spindle by hand to see if everything turns smoothly, and you can usually tell if it's totally pooched.

I'd say that bearings and the belts are the main wear items in the head, but they are just work to replace and are not outrageously expensive.

Last, but not least is the motor. You need to be aware of your power needs and compatibility. Motors come in both single and 3 phase as well as many different voltages. There are ways to accommodate almost anything but that process can add up too.
 
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I've been following this thread with great interest because I am at a similar point as @Tecnico when it comes to looking for a mill. Significant difference may be that I live in Ontario where deals are relatively numerous and I have the experience of buying so far 3 old lathes. Still the whole process of buying an old industrial machine as a mere hobbyist seems like a big crap shoot to me. No matter how much one researches the subject it seems the only way to become really expert is to actually get a machine and play with it. The only way to really know the flaws in a particular machine is to bring it home and spend some time with it. The only way to beat out the competition and actually consummate a deal is to dive in blind sight unseen and snap it up before someone else gets it. Perhaps the ideal would be to see the machine with a more experienced friend but even with all the great guys on this forum I don't know any friends near me that are experienced with mills and willing to help with a purchase. Even scarier is the prospect of moving a piece of iron that is heavier than anything I've ever moved before and heavy enough to kill or maim someone if it moves the wrong way.
 

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
The only way to beat out the competition and actually consummate a deal is to dive in blind sight unseen and snap it up before someone else gets it. Perhaps the ideal would be to see the machine with a more experienced friend but even with all the great guys on this forum I don't know any friends near me that are experienced with mills and willing to help with a purchase. Even scarier is the prospect of moving a piece of iron that is heavier than anything I've ever moved before and heavy enough to kill or maim someone if it moves the wrong way.

A whole lot of truth in what you say......

But I'll make you an offer - keeping in mind that I'm no expert. Many members here have forgotten more than I know. But I do have a Bridgeport and a Hartford Clone, and a smaller older mill/drill that I have diagnosed, repaired, and used under my belt. I don't live in Hamilton, but I do live halfway between Windsor and London which is Canada's Tool & Die Heartland. If you find one down here that you want to look at, I'll happily go with you, help you load it, and give you some advice on how to unload it at your end.
 
A whole lot of truth in what you say......

But I'll make you an offer - keeping in mind that I'm no expert. Many members here have forgotten more than I know. But I do have a Bridgeport and a Hartford Clone, and a smaller older mill/drill that I have diagnosed, repaired, and used under my belt. I don't live in Hamilton, but I do live halfway between Windsor and London which is Canada's Tool & Die Heartland. If you find one down here that you want to look at, I'll happily go with you, help you load it, and give you some advice on how to unload it at your end.
An awesome offer. Thankyou @Susquatch !
 

Tecnico

(Dave)
That's a nice looking Bridgeport! Looks a lot like this:

AVEMAX.png

I wondered about the use of the word clone, the way I've seen it used (not just shop equipment) seemed to imply parts interchangeability but even without it those two mills are strikingly similar even if not at all interchangeable. Clearly someone had a Bridgeport to take close notes from when making the (insert clone name here). I'm getting the sense though that even for the Taiwan machines parts can be had even if they're pricey, it seems different from the lathe landscape for far east machines.

Canadium, I think Susquatch is 100% right, you've captured whole lot of truth and especially out here far from the center of mass for the manufacturing industry. Funny though the shops we deal with at the office are always heavily booked. I guess they're hanging onto their machines!

I think I have more homework to do while I wait & see what pops up.

D:cool:
 
I've been following this thread with great interest because I am at a similar point as @Tecnico when it comes to looking for a mill. Significant difference may be that I live in Ontario where deals are relatively numerous and I have the experience of buying so far 3 old lathes. Still the whole process of buying an old industrial machine as a mere hobbyist seems like a big crap shoot to me. No matter how much one researches the subject it seems the only way to become really expert is to actually get a machine and play with it. The only way to really know the flaws in a particular machine is to bring it home and spend some time with it. The only way to beat out the competition and actually consummate a deal is to dive in blind sight unseen and snap it up before someone else gets it. Perhaps the ideal would be to see the machine with a more experienced friend but even with all the great guys on this forum I don't know any friends near me that are experienced with mills and willing to help with a purchase. Even scarier is the prospect of moving a piece of iron that is heavier than anything I've ever moved before and heavy enough to kill or maim someone if it moves the wrong way.
Where I am, if I want something it's almost always an 8hr drive round trip to pick it up, so most of my deals have been made sight unseen. So far, I haven't regretted anything I have gone chasing after.... Nothing has been perfect, and all have needed tweeking and a bunch of cleaning, and usually a part or two made. It is part of what makes it yours. ;)
 

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
That's a nice looking Bridgeport! Looks a lot like this:

View attachment 18629

I wondered about the use of the word clone, the way I've seen it used (not just shop equipment) seemed to imply parts interchangeability but even without it those two mills are strikingly similar even if not at all interchangeable. Clearly someone had a Bridgeport to take close notes from when making the (insert clone name here). I'm getting the sense though that even for the Taiwan machines parts can be had even if they're pricey, it seems different from the lathe landscape for far east machines.

Canadium, I think Susquatch is 100% right, you've captured whole lot of truth and especially out here far from the center of mass for the manufacturing industry. Funny though the shops we deal with at the office are always heavily booked. I guess they're hanging onto their machines!

I think I have more homework to do while I wait & see what pops up.

D:cool:

That Avemax in your photo is a great talking point example. It is a pulley head quite similar to the Bridgeport Pulley Head. Most of the parts would probably be interchangeable. However there is one major discrepancy that would worry me. If you look at the top section below the motor, you will see that it is not very tall. Certainly not tall enough to accommodate the pulleys, a timing belt, and a bull gear all stacked one above the other. In other words, this mill does not appear to have a low speed mechanism, or it is a different design. There is also an extra handle on the motor and there is no top/bottom disconnect on the spindle hat in front of the motor. I could be wrong, but it also looks like the brake is on the right rear where the hi/low gear change would normally be instead of at the top front left where it is on the pulley drive model.

Functionally, that would not bother me because you can get the low speed from a VFD instead. But it would bother me to wonder how that drive section works, what is different, and will I be able to get parts for it.
 

Tecnico

(Dave)
I should mention that I'm not on the hunt for that one, it's a photo from the Avemax site, I was using it as a clone perhaps closer to the Bridgeport (other then the drive). I just looked and it's listed as 8 speed step pulley with "Unique design on Hi-Low gear speed commutation".

D:cool:
 
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