# Big Machines... Little Machines



## gadget_lover (Dec 30, 2008)

There have been many, many threads about what kind of equipment to buy. Many questions have been asked again and again. Many people have said that benchtop machinery is too flimsy for precise work. The mantra "Mass = rigidity" has been repeated more than once.

Now, I have a micro mill (less than 2 feet tall, 1/5 hp) and a mid sized mill (a touch over 5 foot tall, 1.5 hp) and a mini lathe (under 3 feet long 1/3 hp). I've often said that the bench sized machines were quite capable, and have recommended them often.

But the question has always haunted me; Are the professional machines that much better? I have used the small machines for several years, but had no point of comparison till I bought my big one.

This weekend I answered the question. I spent $60 for a couple of hours with a Bridgeport vertical knee mill and a 12 x 48 Enco lathe at the local Techshop. If you are not familiar with them, Techshop is a membership machine shop with several locations throughout the US. Web page is www.techshop.ws (yes, .ws, not com). 

I paid my $60 of my Christmas money for a "basic saftey and use" (BSU) session. Now that I'm "certified" I can drop in any day from 9 am to midnight and use their machines for $50 a day or $125 a month. 

The BSU was very basic. We went over the basic controls, the do's and don'ts, and then we each got to play with a machine for a while. I used that time to mill a small block to the same standards as similar ones I'd done at home.


I'd like to share some of my discoveries...

1) The benchtop models and the big boys use exactly the same techniques and follow the same basic rules. This makes sense because they follow the same laws of physics.

2) The biggest difference is simply horsepower. This means the big machines NEED to be stiffer, since they have several horsepower and lots of torque to withstand. The 3 HP motor on the mill provides instant torque that would quickly bend the frame of my 1/5th HP micro mill. The 1/5 HP motor on my micro mill does not stress it's frame at all.

3) The Big machines can be just as inaccurate as the small ones, and for the same reasons. If you do not follow the rules, lock down the axis that is not moving, use sharp tools and pay attention, either will deliver shoddy work.

Now some conclusions;

The stiffness of the machine needs to be directly proportional to the power. The depth of your cuts also have to match. I milled three small parts, one on each machine. All were within the .001 that I wanted them to be. All three had finishes that needed little touchup. My midsized mill left the best finish (smooth as silk) , but I spent the most time adjusting the alignment. The big mill gave the worst finish, but I suspect that it was not trammed (aligned) well. The smallest mill had the fewest points where it could be aligned.

If you adjust your cuts to match the stiffness of the machine, you get equal results with all three. It is FASTER to make parts on the two bigger machines since you can use bigger tools that can cut wider and deeper per pass. If you make more passes you can go just as wide (limited by the table) or deep on the small mill.

A bad idea on a small machine is a bad idea on a big one. The Techshop used R8 collets to hold the endmill, which pulled out as we used it. The cut got dangerously deeper as we traversed the length of the piece we were facing, starting at .015 and dropping down to 1/2 inch before we noticed. 

Some folks talk disparagingly of the plastic (phenolic) gears in the benchtop machines. I can see why the big ones would break instantly if they used plastic. The large, single speed 3 phase motors go from zero RPMs to full speed in the blink of an eye. Plastic in the drive train would shatter in no time. The small machines use lots of plastic, but they also frequently have an electronic speed control that provides soft starts. The power is also 1/10th of the big guys, so the stresses are that much lower.


The bigger machines have more room to fit neat stuff. The ENCO 12x48 lathe had lots of extra capabilities that just would not fit on a 3 foot long benchtop unit. The built in coolant pump and motorized carriage travel (infeed as well as Z axis) would be neat, but take a lot of room. I'd kill for the quick change gearbox for threading. The larger tables of the mills make it easy to mount things like DROs', power feeds, lamps and other goodies.

The bigger tables and taller headroom of the bigger mills make it easier to create setups. You can add multiple setup blocks in different combinations to hold the work just so. But the vices, blocks and angle plates are smaller and cheaper for the smaller machines. I'm looking at a 8 inch rotary table for $300 for my bigger mill. The 4 inch rotary table on my micro mill was under $80.

In conclusion, it was nice to see that when working with mild steel or aluminum, my benchtop units compare favorably. Well, they do once you factor in space, power and scaling your cuts to the capabilities of the machines. There are, of course, materials that require deep or aggressive cuts that might not be viable on a benchtop uinit.

Daniel


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## Torque1st (Dec 30, 2008)

That is a nice analysis. 

The quick change gearbox is a big plus for the larger machines but a selection of change gears is OK for limited work. 

Power feeds that do not use/wear the leadscrew are good points for the larger machines. Leadscrew wear is usually not a big problem unless a machine is used in production. Some leadscrews can be reversed to spread the wear out.

The ability to machine larger parts is a plus for the large machines but most flashlights are not large. 

The smaller machines also often have faster spindle speeds to more easily machine small parts or parts made from aluminum. A real plus for flashlight parts.

The smaller machines run off single phase power. Many larger machines require 3 phase power which can sometimes be produced by a VFD or a RPC which cost $$$. The bigger the machine the more expensive it gets.


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## datiLED (Dec 30, 2008)

Daniel,

Thank you for your informative post. I plan on purchasing a small lathe/mill in the coming year, and had some questions in my mind about the reliability and accuracy of the smaller units. I think that you helped set those doubts aside. :thumbsup:


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## precisionworks (Dec 30, 2008)

> The Techshop used R8 collets to hold the endmill, which pulled out as we used it.


R8 collets suck, and that's the best thing that can be said

I've used ER40 collets for years ... each has a size range of only 1mm, so you need 25 for a set that goes from 1/8" up to 1". They grip like death. TG collets are better yet, but have a smaller size range so more are needed for a full set.

High quality R8 collets, like Lyndex, work pretty well. Cheapo Asian collets make nice paperweights


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## Anglepoise (Dec 30, 2008)

Interesting topic.

I think one needs to also carefully and honestly evaluate what you are going to produce with your lathe. Are you a hobbyist with lots of time?
Your needs would be totally different from the user that is supplementing his every day job with making items for sale. The later
will benefit from a larger more powerful machine to make the difference from a profit or loss. Also if one is making flashlight bodies with a finished diameter of 1,1/2” then it would be nice, if not essential, to have a spindle bore of a size that will accommodate. In this example, a ‘large’ machine would be needed.

Also the available space is important. I am forced to keep my lathe in an unheated area and move items to use. Very very frustrating.
In my case, a smaller lathe could be set up in the house and there are many times I seriously consider downsizing. Also for some, hobbies come and go, and maybe its best to start small and go up as the hobby matures.


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## KowShak (Dec 30, 2008)

Have you tried milling a difficult material e.g. titanium on your micro mill?

After that you'll be able to tell us whether a bench mill can perform as well as a full sized machine.


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## will (Dec 30, 2008)

I have an Enco Mini Lathe that I have had for a few years now. It is a great machine when used within it's limitations. I can move it around, put it on a shelf when not in use. I can match work done on larger machines when I am working with any soft material like aluminum, brass, copper etc... Forget about titanium, steel, stainless steel. 

size does matter here. spindle bore is 3/4 inch. the orginal chuck was even smaller than that.


I should also point out that some materials produce a better finish when larger cuts are taken. Cast Iron comes to mind, try cutting off .001, it basically just scuffs the surface. .015 produces a nice finish. Smaller that that it is better to grind it down. 

It is a machine that should not be used in a production environment.


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## gadget_lover (Dec 30, 2008)

KowShak said:


> Have you tried milling a difficult material e.g. titanium on your micro mill?
> 
> After that you'll be able to tell us whether a bench mill can perform as well as a full sized machine.



I've done steel and cast iron on my 7x12 mini lathe. I've cut dovetails on a steel tool holder using the micro lathe.

Using carbide tooling, I've milled small slots in case hardened steel. 

I do not do anything with titanium, so I can not say how difficult it would be to work on.



Daniel


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## gadget_lover (Dec 30, 2008)

LOL

I don't think I said that that a bench top is a substitute for full size hardware. It's not. Comparing a bench top to full size is like comparing a pickup to a dump truck. The pickup truck will move a mountain of dirt, but it will take a lot longer. 

What I did discover is that the work that is done on the small lathe or mill is not any harder to do, nor is the finished product inferior. This assumes, of course, that you stay within the designed limits of the machine. From the micromill description :

"Capacities: drill 25/64'', end mill 25/64'', face mill 3/4'' 
Designed for use with steel, brass, aluminum, plastic and wood"

Like Anglepoise said, a small bench top lathe can be set up just about anywhere and makes a great adjunct to the bigger lathe in the cold workshop.


Daniel


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## wquiles (Dec 30, 2008)

Nice thread Daniel. think this "big" vs. "little" also has to do with available space - if you have the space that you can dedicate to a larger machine, then you have more options. For me it was never about the space. I had the space but did not know if I would like/enjoy working with a lathe, so I decided to start with a 7x to keep things simple and lean. 

After a couple of years with the 7x and this year with the 8x, I just went from the smaller machine to the substantial larger machine (12x36), but I don't have any work-time on the large machine yet - maybe in a couple more weeks I can come back and comment on my own experience, just as you have when comparing working on the big vs. little machines. Maybe I will even miss the "little" 8x - who knows :shrug:

Although both small, at least to me, the 8x machine is a much better machine for the projects that I have been doing and that I wanted to do - stiffer, more heavy duty, capable of bigger/deeper cuts, it felt smoother, etc.. Of course it is not a fair comparison since before I even turned ON my 8x machine I had converted it to DC variable speed and installed a massive 6" chuck (I never did any work on the factory 4" chuck!). In a way, all I did I was to convert the 8x to be as easy to use as the 7x is from the factory, so I guess I still have a soft spot for the 7x :twothumbs

Will


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## gadget_lover (Dec 31, 2008)

Thanks Will.

As I wrote up the original post I thought of the reasons that I upgraded from a 7x10 to a 7x12 lathe, and from a 5x9 mill to an 8x30. I also thought about the serious case of tool envy Will's lathe has engendered.

Bigger does mean faster. Bigger means bigger parts are easier to work on. Bigger means you can pile on more accessories to help you do it right. Bigger means you can work on really tough materials.

BUT .....

You don't need 5 HP to turn down a 1.0 inch tube to a .95 inch tube. You don't need 12 inch swing to carve fins into a maglight head. You don't need a quick-change gearbox to cut threads.


AND .....

The best part. All the tricks and tips learned on the small machines transfer to the big ones. You measure the same way. You secure the work the same way. You feed at the same speeds and in the same way using the same types of cutters.

Strangely, my neighbor ( who is experienced with full sized machines ) has been unable to make the transition to the smaller lathe. He does not have the patience to do the extra passes. He grumbles at having to manually change the gears to change threads. He infeeds too aggressively and swears at the machine for not being able to handle it. I just watch and grin.




Daniel


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