...It's just super hard to pull the trigger on a machine you can't see.
Or not...
I now own a Bridgeport Mill!
Once I get something in my mind I tend to start really drilling down and looking. I found an auction site with a few Bridgeports, I spoke to the dealer, the rigger and spent some time mulling over the photos and... I placed a bid.
I had my eye on another, cleaner one hoping it would go for around $2500-3000 and it went for $3750. With time ticking down I decided to take a chance on the second one which wasn't as clean. I was very nervous and decided to place a bid that was the most I'd feel comfortable with and then I walked away convinced I wouldn't win it.
And I won it for $3250.
So on Instagram Pat mentioned that he would love to pick up a mill but didn't know where to start and it made me realize that this might be a good opportunity to talk about how to get into machining and maybe buy a mill. Especially since I probably broke most of the rules.
First I'm sure I've mentioned it before but there's a truly awesome book by Frank Marlow that deal with the basics
Machine Shop Essentials It seems to be out of print but you can find used copies on Amazon. He has a second book as well that expands on the first. This is a good book to get used to some of the terms and concepts.
When I started to get into this YouTube didn't exist but now I spend a lot of time watching machining videos - my favorite is
This Old Tony. He takes the time to explain things but makes it fun. Another that is very good is
Tom's Techniques. He's dry but by the book. He also stresses safety a lot which is a big deal.
So, how do you buy a mill? There's plenty of good info out there but I'll try to simplify it a bit. To start you can answer a few questions:
1. How much do you want to spend?
2. How much space do you have?
3. What sort of things do you want to make?
If you want to dip your toe in the water and spend less than a grand there are
small mill/drills you can buy from China. I know next to nothing about them save that they don't/can't do very big things.
But it might help you figure out if you want to go down the deep end.
If you don't have much space a Rockwell like my mill is a good if light mill. Light in mills is something around 1000lbs. Crazy but true. These sort of mid sized mills are hard to find and can command the same price as a Bridgeport. Mine is a rare one that has both horizontal and vertical functions. Prices will vary from $1500 to ones that are pretty rough to $4-5000 for good condition and lots of tooling.
Bridgeports or similar are the end of the line. Mass is what allows a machine to take big cuts of metal and not be deflected and these mills will weigh a ton and up, take up a sizable foot print and cost anywhere from $1000-10,000.
So why the big spread and what are you looking for?
Condition and features. To machine accurately you need that mass but you also need tight tolerances. To machine a surface accurately to within .001" or less you need a machine that fits together with that or finer fits. So most important are the ways. These are the surfaces that hold and move the table: the knee, the saddle and the column. You can't replace these parts and while they can be refinished it's expensive and time consuming. The good news is that they rarely wear out.
More expensive machines like the Bridgeport have scraped ways. Sraping is the old technique of hand shaving the metal to an absolute flatness beyond machining. The pattern created also holds oil. You can see in the photo above that the ways get shinier as you go back because that's the work envelop of the machine - the front doesn't see as much use. This is a good way to tell if the machine has been used in a heavy production environment. Worn ways can still make good parts but you need to be a better machinist.
The next thing people tend to look for is backlash on the handles. Backlash is the loose spinning of the handle when you change the cranking direction. If you're using the numbers on the dials you have to be aware of how much your backlash is and remember to take it up each time you do an operation. Again, you can machine around this but it's another thing to consider. Sometimes backlash can be adjusted and sometimes it's a sign of worn half-nuts or leadscrews. You can replace these parts but it's a real pain to do that.
Now if you're using a DRO backlash isn't really an issue as the DRO (Digital Read Out) simply reads the actual position of the table no matter where the knobs or wheels are turned. At this point DRO's are getting pretty cheap so it's a great thing to have and will make a huge difference in the whole enterprise. They also can calculate all sorts of things like patterns and bolt circles and make finding the edges and centers easy.
After that it's the spindle bearings. As you can imagine these are super precise and super expensive but they can be replaced with a lot of effort. It's not typically something that goes bad.
So it remains to be seen if I got a good deal. I could have tried to be patient and waited for a mill to show up within driving distance but that last mill was the first I'd seen for sale in several years. They're not as common in the PNW as they are in the former manufacturing cites or the east coast. Here's the two I was looking at:
The first thing I did was look at the photos to try to judge the overall condition. The top one was the first one I was interested in. I was prepared to go to $3000 as it seemed pretty clean. It went for $3750 so I had about 30 minutes to decide on the second one and recalibrate my bidding strategy.
I copied the photos and opened them in Photoshop so I could brighten them to see better. Bad photos make things look worse. What I saw was an original condition mill not repainted but not used for a while. Both were pluses to me. The surface rust on the handles and table are really nothing - that sort of thing wipes off easily with some WD40 and scotchbrite. I'm looking for original paint because machinery dealers are famous for taking worn out machines, slapping paint on them and trying to get a premium.
The other things I saw were good scraping on the ways and a table without any damage. No drill marks, no dents or signs of abuse. The caliper on the head is a very old way of reading Z axis. When I spoke to the person from the auction I was told that these mills came from small shops and that means less production time but maybe less care paid.
These two mills are Series 1 machines. Series 1 have a two speed hi/low gearbox and adjustable speeds via a crank handle making them easy to to change spindle speeds. That also makes them more expensive. An earlier mill, the Bridgeport J head, has a similar set up as my Rockwell where the speeds are changed via a stepped pulley arrangement on the top of the head. It's not a big deal but it's not as easy. At this same auction a rough around the edges J-head Bridgeport went for $1150 which is quite the deal. If I was just starting to look for a mill I'd look for a J-head at an auction or on Craigslist. They're falling as Series 1's are climbing.
Another thing to look for or consider is tooling. At an auction you won't get much but at a private sale you might. Expect to spend as much on tooling as the mill - if not more. Once I won the mill I quickly started bidding on some tooling as I knew it would be easy to put on the pallet and not cost any more to ship. I bought a Kurt D60 vise on a swivel base for $190 and 100lbs of various end mills for $100. I will pick out the end mills I want and sell the rest and probably offset the cost of at least 20% of the mill.
Next if you buy a mill at auction is the sellers premium which is typically 15% so another few hundred. After that you're going to need to have it moved and put in a truck so expect to pay the rigger/forklift another $2-300 and finally shipping which can be $300-1000.
You can see the prices start to add up pretty quickly especially if you're buying out of state. Nonetheless I should end up about even after selling my mill at least as far as getting it here.
Next up comes powering the mill. Smaller mills will run on 120-220 single phase power so you won't have much trouble just plugging them in. Big mills are always going to be 3 phase so you're going to need to convert your single phase power into 3 phase. The easiest way to do that is with a VFD or variable frequency drive. These allow you to not only convert the power but program in things like braking, acceleration and reversing. And they will add another $2-400 to the price.
The good news is that once you are on the treadmill and have a mill your collection of tooling can be used with most other machines. And most mills are going to hold their value or even increase in value. I got a great deal on my Rockwell because it had been in storage and was so dirty but after a lot of work it turned out to be a great machine.
So there's plenty of people that know a lot more than me but hopefully it gives you some insight into the process of buying a mill. It will take a few weeks before the mill arrives and it's going to require a complete revamping of the entire shop in order to find the space. I consider this a net positive as I've been wanting to do this for a long time.
We can talk about moving a mill when it comes time for that. It's not something to attempt without a great deal of caution and there's a lot of precautions to consider but it can be done safely if you're smart about it.
Gregor