Choosing a benchtop mill
Have you ever found yourself wandering a hardware store looking for some piece of hardware that might work for a project? I’ve probably spent hours and hours doing this, just to find the right thing, but getting home and finding out that it won’t work. Then, if you have the energy, you gotta go back to return it or just accept the loss of both time and money.
Having machine shop capabilities at home can solve this problem. You can make your own stuff: how you want it, when you want it, and out a really strong material. Wood is great and cheap, but metals really make a huge difference in what you can do and make.
Buying a mill and lathe has been on my mind for a long time, especially with a CNC setup, but holy cow it’s an investment. But, the way I see it is that it’s a life long investment. If you have a mill and lathe, you can literally build or fix any machine: motors, grinders, bike hubs, casting molds, milling PCB boards, tooling setups, new pistons for your car, fix your laundry machine, upgrade a cheap saw with better parts, etc. The list can go on and on.
For now, I’m only looking at a mill. The lathe will come later.
Here are things I’m looking for in a home mill:
- Benchtop sized – Small and relatively light. I don’t have much space for a full blown machine shop and I don’t want to have to use a forklift to move this thing. If it takes two people to move it, it’s still too heavy. The idea of using a spare closet for a small machine shop is not out of the question, especially because an extra closet is in the temperature controlled niceness of your home.
- Precision – Out of the box precision. I really don’t want to spend several weekends tweaking and fixing a cheap, sub-par mill. Like Apple products, spending a little more on a quality product will give you less headaches and overall a better, happier, more pleasant, and productive experience. More time making, less time fixing. Precision is really important for more complicated parts. For every machining operation you do, the error of the machine compounds into your part. So for a complex part, a good precision mill can be the difference between making a good complex part the first time, rather than the second or third time around.
- Support – Not customer support, but an online forum or large user base and long history. With a lot of people already using the machine, they will all have some tips and tricks to fix any issues or how to do a job faster and better. They will have also worked out any problems with the machine and the manufacturer will have likely solved it. Books and magazines are a big plus.
- Machinist Approved – I work with some great machinists, who eat, breath, and sleep this stuff. There were only a few that they would recommend in the benchtop size range and what I would use it for.
- Sherline 5000/5400 mill- They make great small 35lb, high precision machines and have been doing it for a long time. There is a ton of literature with people using them. The working area is relatively smaller compared to a lot of other mills (5″x9″ to 7″x9″). First mill recommended by my machinist friends. They don’t look very robust (not a problem , see later), but can create very intricate, highly precise parts out of the box. Lots and lots of off-the-shelf parts and good upgrades.
- Taig mill – A middle ground machine. (5.5″ x 9.5″ to 5.5″ x 12″) 65 lb. Heavier and more stout than Sherlines for the same or slightly larger work area. Can machine steel very well. Claims to efficiently “hog” out material due to stiffer setup. Seems to be an answer to what Sherlines are not. In production for nearly as long as Sherline. Fairly large online community. High precision, but not sure that it matches the Sherline out of the box.
- Smithy – Large machines. Make great combo mills and lathes. Expensive, but can make large parts and quickly. If I had more room and a forklift/not plan on moving in the next 10 years, I would get one of these. Highly recommended by machinists.
- Harbor Freight/Seig X2/HiTorque/Grizzly mills – These definite “look” the part. Big, heavy, and stout, but looks can be deceiving. The work area is the same or SMALLER (4″ x 9″ to 5.1″ x 11.8″) and weigh roughly 130lbs! All manufactured off-shore, which makes for a low-cost machine but a crap shoot in quality. Most owners of these machines online seem to post more about upgrading/fixing the mills than actually using them for projects. I can’t deny the cost, but I don’t have a lot of spare time these days. I’d much rather be making stuff than tweaking the mill to a high precision. I think this is worth the extra cost on its own. These are also very, very heavy for their size. They are made with large portions of cast-iron, which is cheap, heavy, brittle, and prone to cracking. I have also seen reports that people receive warped work tables due to improper cooling and aging of the cast iron by the manufacturers. If precision is not in your list of needs, there’s nothing wrong with these machines, just don’t be surprised that some of you parts might come out a little off.
- DIY Hobby CNC Mill – Not really an option, as it is more of a router than mill. As fun as a project making one myself could be, most of these options are made of wood or plastic, which makes for a not very stiff mill. You end up with a mill that only do certain materials well, but metals are pretty much out of the question. Aluminum is doable, but not recommended. There is too much flex to get any reasonable precision and is really limited to making PCBs, stencils, and delrin plastic. The cost isn’t too different from a machining mill, but one plus is that you can make it just about any size you want.
The Sherline and Taig mills are probably the best bang for the buck and for a benchtop, precision, ‘light-weight’ mill. Both are great machines, but each with their pluses and minuses. Compared to the foreign-made mills, the cost difference is only a couple hundred of dollars, and less if you add in cost of freight shipping a 130lb mill compared to UPS for a 35lb mill. And if you’re a patriot, Sherline and Taig are made in the USA.
The most common complaints I’ve seen for the Sherline mill is that they look small, are only for miniature model makers, has an underpowered motor, or not stiff enough. These are all generally true. This is not a machine made for hogging out tons of material very fast, as you would want for production. But, it will cut and machine any type of standard material, but the harder ones, like stainless, will cut just a little slower. Since the machine is small and will not be making large parts, you’re really not going to waste a ton of time. For large parts, you will want a large machine like a Bridgeport or Smithy.
In my engineering opinion, the Sherline 5000/5400 mills are correctly sized for the work area. The amount and type of material are all in the right places, giving you the proper stiffness all in the right ways. It’s well designed. However, this can be good and bad. This gives you a lightweight, precise milling machine, but it’s already near its limit. You can’t upgrade it’s capabilities too much without sacrificing some stiffness and precision, unless you stiffen up and replace everything like A2Z mill parts do. I don’t like the milling column on the updated Sherline 2000 mill for this reason, which features an 8-way Bridegeport-like z-column. It looks to make for a too compliant z-axis, although Sherline claims otherwise. Forum users of the Sherline 2000 state, you can get almost as good stiffness as the standard Sherline 5000 series only when you pull the headstock as far back as you can. Anywhere else, there can be noticeable flexing. As an engineer, I would have to agree with this in theory and would think that vibration would be an issue.
Taig mills are a little rough around the edges, a design that looks cobbled together, but a great mill too. They can be upgraded without worrying about compliance, since they are overly-stiff/over engineered by design. Roughly the same price, slightly larger working size, and twice as heavy. The online community doesn’t seem as large as the Sherline community, but I could be wrong. There isn’t a catalog of readily available parts, tools, fixtures like Sherline has, which can be good and bad (cost). But, mainly, the Sherline parts are sized for the Sherline machine, meaning you won’t have search around for properly sized vice, rotary table, or any other specialty item for the Taig mill. It’s nice to know that these options are there if I need these speciality tools or fixtures for future projects.
It’s basically a toss up on what’s more important: Larger community of users, a large catalog of readily available parts and tools, light-weight, high precision VS. more robust, can machine faster, better for steel and hard metals machining.
Personally, I’m opting for the Sherline, mainly for the precision, weight, and the wealth of knowledge. I don’t plan on doing a lot of machining with steel, mostly aluminum. But, the reasoning that pushed me over the edge is the fact that a lightweight machine also makes it easier and cheaper to upgrade to a CNC setup. You don’t need larger, heavier, high-power motors to run it, which gets really expensive, really quickly, because you need to buy more powerful power supplies, expensive motor controllers (sometimes), and bigger motors. The plan is to build an Arduino based CNC with some cheap robotics motor controllers, an ATX power supply, manual control with a PS2 controller, and a DRO based on stepper increments. This should all cost less than $200 for the upgrade. The Taig could be done for marginally more, but it would require large motors which would make a large and heavy machine, larger and heavier.
More to come…