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When is Manual Machining Better than CNC?

Nov 28, 2012   //   by Bob Warfield   //   Blog, Manual, Techniques  //  5 Comments

Monarch 10EE LatheLet me start out by going on record as saying I don’t think manual is ever better than CNC except in certain special circumstances that are really not a test of manual vs CNC, but of other factors.  I’ll walk through the three special circumstances in a moment.

I’ll be the first to admit it is a controversial viewpoint.  Machinists will spend hours debating the whole manual versus CNC thing and every related issue.  For example, they will debate whether you can be a decent CNC machinist without having trained extensively on manual machines first.  I’m not going to try to answer that one here, but rather, I want to focus on when or whether manual machining is a better answer than CNC for a specific job.  As a backdrop, there seems to be a large audience that will say there’s no point in CNC if you only need to make one part and it is a simple part.  I disagree, and here is a paraphrasing of the answer I gave on the LinkedIn forum when the same topic came up:

If you know MDI, CNC is just a manual machine with power feeds and DRO’s on all axes. If you argue against the CNC, in many ways you’re also arguing that the DRO or power feed on the manual machine doesn’t help.

In fact, the CNC is better than any manual machine I ever saw because it can do arcs without having to set up a rotary table and it has canned cycles that do all sorts of other things that have to be done manually on a manual machine. If you have conversational CNC on your control or as separate software, it can do even more. For many parts you can just call out the coordinates from the print into the conversational CNC and go. There is no need to go back to the design office and fire up the CAD/CAM. Plus, just think of all the tooling you’ll never need on the CNC–I mentioned the rotab, but taper attachments and all sorts of other things have no purpose with CNC.

You can do all the stuff on the CNC you could on manual, including rework like chasing threads. BTW, the article on chasing threads using CNC was very popular on my CNCCookbook blog.

That’s really the gist of it.  You can do all the things on a CNC you can do on a manual machine (plus a lot you can’t), and they are faster on the CNC.  When they argue you can’t just jump on a CNC and make a quick part, I think too many machinists are thinking about having to do a CAD drawing, then fire up a complicated CAM program, and finally post a g-code program before they can even get started.  But if you know g-code well enough to get by with MDI (Manual Data Input, where you type in an individual g-code and the machine does that one g-code immediately), you really do have a very fancy manual machine with DRO’s and power feeds on all axes as described.  BTW, if you don’t know the g-code well enough to use MDI, you’re missing out on all sorts of convenience.  Check out our g-code tutorial and you’ll be there in no time.

What I find disqualifies the CNC versus the manual machine a lot of the time are issues that fall into three major categories:

1. The CNC machine is busy

Probably the number one reason to use a manual over a CNC is that the CNC machine is too busy making money on some production run, so you go back to the old manual machine to do the simple jobs or second ops.  In this case, the manual machine is free money.  Yes, you might do the job better or faster on the CNC (or maybe not if the other two reasons disqualify it), but you can’t even get started because the CNC is busy.

2.  The Manual machine is cheaper and we can’t afford Toolroom CNC

Manual is cheaper, there’s no doubt about that.  Heck, you’ve probably got an old Le Blonde lathe or Bridgie mill in the back that’s been there forever and was paid for a long time ago. But putting that aside (after all, that’s hardly the fault of CNC or the manual), I don’t see how you can really do the job faster on the old machines if you also have a brand new CNC toolroom lathe (Haas TL series or a Romi, for example) ready to go. I recently made an R8 tightening fixture that required an R8 taper. It was a one off (silly things are hard to find in R8 and essential to get a collet chuck properly torqued), and it took almost no time to punch up the taper on a Romi CNC Toolroom lathe and crank it out. Blued up near perfectly and I was very pleased. I could’ve done same on a manual lathe, but there’s no way the Romi wasn’t faster.

3.  My CNC doesn’t have the right options to compete with my manual machine

This one comes up a lot too.  The easiest way to think about it is to consider the average production slant bed CNC lathe versus a proper toolroom lathe.  Your slant bed is a little gang tool or other production oriented machine. It doesn’t have as big a spindle bore as your manual lathe or maybe there’s no 4-jaw chuck and no tailstock. That’s not a CNC problem, that’s a choice of machine problem. You can buy CNC Toolroom lathes that are set up the same as any manual lathe and they’re a wonder to use.

One of the reasons I got into CNC was I had a good machinist friend who encouraged me to put all of my manual machining activity aside and focus on getting my CNC mill up and running.  His argument was that I would be so much more productive with the CNC that it was the most important productivity thing I could do for my shop.  It didn’t take me long after getting the mill up and running to realize that he was exactly right.  The most compelling argument for me in favor of manual is the cost argument.  That, and I’ve got a bit of nostalgia for amazing old manual machines like the Monarch 10EE I have pictured.  But if budget was no object, I’d set up a shop entirely with CNC machines.  In fact, even if budget was an object, depending on the type of work I needed to do and the volume, CNC would still be my first choice.

Gentle readers, I’d love to hear your stories.  Is there a case where manual beats the heck out of CNC that doesn’t fit one of my 3 categories?  Tell us more about that case so we can understand.  Maybe there’s more to the manual than power feeds and DROs on all axes of a CNC can satisfy.

5 Comments

  • I’m retrofitting a circa 1990 Acra CNC mill with Sanyo-Denki closed loop steppers and drives that have 4000 P/R encoders. I expect its performance to be plenty better than the old Crusader M system with linear scales (which will be used in addition to the rotary encoders) and brush type DC servos that are less powerful than the steppers.

    To start with there’s one part I will be making that is impossible to do on a plain manual mill, even with DROs. A manual operator would have to be an etch-a-sketch master to make this part, and do it time after time.

    I imagine the molds used to make the original die cast part in the 1940′s were likely made with a hydraulic tracer mill but the patterns such mills traced were cut and filed by hand by master pattern makers.

    The CNC cut 7075 aluminum replacements for the die cast originals will be superior in every way to the original, except in nostalgia.

    On the other hand I have a Montgomery Ward 10″ lathe made in 1940 which I use for basic plain turning when I just need to turn something to fit. It’s simple and quick to chuck a piece into the Bison 3 jaw and carefully turn or bore until part A fits part B. With a carriage stop to set for the end there’s no possibility of a programming error crashing into the chuck. It’s just as easy to cut off too much with a CNC lathe as it is a manual one!

  • You missed a few categories. OK, they’re maybe mostly aesthetic, but they’re genuine.
    1. Turning the cranks on a manual machine is a lot of fun. I have seen young men stand in line patiently for a turn at the old machines.
    2. Turning the cranks is good exercise. I have been recovering from a severe lung problem, and the manual machine was a good start on the road back.
    2. The manual machine represents a piece of history. If you’re making a reproduction or a model, there’s a kind of authenticity and a deep understanding of why things are the way they are you can achieve using original methods that you can’t have if you do it with the automatic tool. Ask the Woodwright.

    I have a Tormach, and I use it to get things done. Love it, wouldn’t want to be without it. The Bridgeport and the heavy ten have their places in a crowded garage for other, very different reasons.

  • People think manual machines are so slow because no one knows how to set them up to make them quick. There are so many simple tools to make that can instantly be used on to the machines to make simple jobs quicker. I make no claim that I can produce 10 of the same little complex shafts, or machine 5 little bearing housings quicker than a CNC, I never could, and no one ever will. I also make no claim to ever compete with the radiuses and curves that can be produced nowadays with sweeps and ruled surfaces ( Australian terms for 3D milling lol ) But, I could make simple jigs, shafts, pins, bushes and repair jobs faster than a CNC will on a WELL SET UP manual machine. Most manual machines in most shops are treated like shit. No tooling, nothing set up, machine is trashed, cant turn straight, slides all worn beyond repair. But if you step into my shop, or my old manual one off/prototype/ repair area at my work ( a CNC production shop ) then you’ll see the ways I set them up. A few things I do to my machines:
    -LATHE. Obvious, quick change toolpost with at least 10 holders, all set up rigidly and tightly so they don’t move and ness with your centre height. Set them to centre height, tighten them as tight as possible and engrave ROUGH, FINISH, BORE etc on them and don’t touch centre height. Rough turn, finish turn, chamfer, thread, part off, groove, knurl, and a tool to hold 5/16th HSS bits. Also I make up my own design of boring bar holders. Very similar to a CNC lathe boring/drilling pod. Standard 32mm or 40mm bore and sleeves to slip in and adapt to the size of standard boring bars. ( 8,10,12,16,20,25,32 and 40mm for our metric country ) The larger bored sleeves ( 16mm and up have a slot running down them for the grub screws in the pod like holder to lock to the bar. The smaller ones have their own grub screws intergrated to lock the bar. The way it is orientated insures the bars are all exactly on centre height, and takes about 15 seconds to change out to a different bar. I would like to have 3 of these pod things set ( only have one at the moment.) Chuck spiders for getting faces to run true quickly with seconds ops. Centre drill holders, standard centre, reduced ( slender centre ) pipe centre, two drill chucks all set up right next to the machine. All corresponding to the tailstock taper so you dont have to change sleeves. A good smooth 3 jaw chuck that runs true, a nice smooth 4 jaw ( also have two dial indicators at the machine or atleast with in eyeshot ) a spindle mountable collet chuck, equipment to turn between centres ( you never know ) and a faceplate. Bore polishing sticks ( to wrap emery paper around ), ALL the spanners and allen keys ( aussie term for hex keys ) you need for EVERYTHING on the machine you need to adjust, ALL the torx keys and allen keys for ALL the indexable tools that are standard on the machine. A simple handle to make tailstock drilling easier. Work light properly installed and positioned, good quiet coolant pump and clean coolant. Of course a digital readout ( should be first in this list! )

    MILL- READOUT, you can get away without one on a lathe but forget it on a mill! Get as many toolholders as possible ( don’t waste money though, you don’t need 10 ER40 collet chucks on an R8 light duty Bridgeport ) but don’t cheap out. A few good different sized facemills with good quality inserts, 2 drill chucks, a few collet chucks ( on a bridgy an ER40 and maybe two ER20′s ) with collets at the machine and the wrench with it! A 1″ plain stub arbor with collars for your slitting saws etc, taper adaptors ( one MT2 and an MT3, go bigger on a bigger machine of course ) a fly cutter or two, a nice boring head with good boring bars, I even made an arbor to accept the old HSS shellmills that I have a ton of ( got them for free ) and I use them on aluminium. Even make an arbor to hold your dial indicators ( the interapids or whatever is popular in America, here in Australia, mitutoyo test indicators are very popular!
    Key your dividing head so it is aligned when you put it on the table every time, same as its tailstock. IMO you don’t need to do it to a vice, because a vice can be bolted down and aligned in 3 minutes and you wont be wondering, is my vice really lined up. Have dedicated bolts to hold down your vice, dividing head and tailstock, three jaw chuck, rotary table and any other jigs you may have. Tee nuts are cheap, machinists are not so have heaps on hand. A good clamp kit or two for the table AND rotary table and also the wrenches for them, and the vice spanner, and chuck keys for the dividing head and three jaw. Have a few 123 blocks at the machine ( not popluar here, we just use ground blocks, if your lucky enough for the shop to have them haha ) a honing stone, set of paralells. Also every wrench and allen key you need for the machine and tooling. Have a spot drill at each mill too I guess would be an idea too ( might have to buy a couple now! ) I think on a mill you can get away with one mag base and just a test indicator, but if you do any repair work you’ll probably need a standard dial, while your at it, get a separate base for it!

    SLOTTER: A good selection of bars and HSS bits, like, as many as you can make, buy, find whatever. Make up sleeves for them to adapt them all to a standard size ( I used 32mm ) Then mill up a toolblock that bolts on to the slotter ram which the sleeves bolt in to, much like the pod system on the lathe I mentioned above!. You know have a quick change slotter!
    A clamp kit, big paralells, all the wrenches etc, and two dial indicators for the X and Y movements ( or get a readout, you don’t need one but could be nice to put one on I guess )
    A nice big rotary table ( unless your table is a built in rotary table ) and get a three jaw for it. Have some nice cutting oil in a squirt bottle ( have one on the lathe too for screwcutting, and while we are at it, on for the mill for tapping, why the hell not! )

    I have probable missed heaps, and I hav’nt even gone into surface/cylindrical grinders yet, but I don’t have them yet, but when I do you can be sure ill set them up just as well. This makes me quicker for one offs and it works for me.

    • Zak, I still don’t see anything you’re suggesting that can’t also be done on a CNC. I run a QCTP just as you describe on mine with all the tools on center. So what makes your manual faster?

      Cheers,

      BW

  • […] of it or it was just getting setup back then, I cant find that picture on my computer of course) When is Manual Machining Better than CNC? – CNCCookbook CNC Blog CNCCookbook CNC Blog __________________ 6.0L heads are like onions: If you peel off more than the skin it will […]

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