Friday, March 25, 2011

Computer Numeric Re-Considerations (III)

I've been enjoying the lively discussion emerging from the previous two posts in this thread, and continue to chat about the issue with other woodworkers. I might be starting to approach the 'broken record' phase for all I know, but I am still engaged in this topic. In fact, repetition is one of the most appealing reasons I can think of for making use of CNC.

When I was a teenager I worked in my father's business on weekends, which manufactured aluminum sailboat masts. One of my jobs was to work on the metal lathe turning sheaves for the mast heads. Sheaves are another term for pulley, in case you hadn't heard it before. I remember the machining sequence well - face off the end of the stock, drill the center for the bronze bushing, turn the outside down to the diameter required, machine the groove in the sheave for the rope, part off the sheave, press in the bronze bushing and it's pretty much done. The first one you make is an intriguing challenge - by the 4th or 5th one you are starting to get the hang of it, after a dozen you could say you have it down. After 20 or 30 of them you can do it in your sleep pretty much.Soon, you might be starting to dread making another goddamn sheave. I think these sorts of highly repetitive sequences of work, where each part really needs to be identical to the one before, are perfect applications for automation. It's simply not interesting work, and certainly not work with significant opportunity for artistic exploration. Repetition of that sort is a little inhuman actually.

I was thinking more about machinist's work today I visited a local machine shop run by a retired shop teacher, named Tim, who must be around 70 years of age. I have my Oliver jointer fence apart at the moment as I am planning to get the fence re-machined in the near future. There are a few pieces of the fence hinge mechanism that will benefit from some fiddling that only a machinist can provide. I paid a visit to see Tim and ask if he could take a look at the fence hinge parts sometime next week. While chatting with him, I noticed he had a couple of CNC-lathes, both Japanese. He had conventional metal working equipment as well of course, and much of that was Japanese as well. I was thinking to myself, it doesn't seem like machinists have much issue with using CNC equipment. And then thinking of making those sheaves again reminded me of how pleasant it would be to have such parts made on a CNC.

Academics like Sōetsu Yanagi might romanticize the unconscious excellence of the mass produced Korean tea bowl that is the most esteemed piece of among chanoyū cognoscenti. He liked the fact that its beauty was the product, not of deliberate intent on the part of the artisan, but as a by-product of their automata-like perfection of skill. That might be an ideal from an academic view, however such is not always the case for the maker.

A lot of people romanticize woodworking I think, with images of the craftsperson out in their warm and toasty shop, trusty dog snoozing nearby on a cushion, wisps of shavings falling from the board as they construct one perfect surface after another and effortlessly assemble another beautiful creation with pride and satisfaction in a job well done. Well, it might be like that sometimes folks, but a lot of the time its not quite so romantic. A lot of tasks in fact are highly repetitious - in my typical sequence it might be: re-saw the boards, joint the boards, plane the boards, trim the boards to dimension, mark out the joints, sharpen the tools, cut the joints, sharpen the tools, wear some skin off your finger tips and bleed all over everything most inconveniently, make some jigs, test the jigs, adjust the jigs, cut some more joints, profile edges, test assemble, adjust, assemble, adjust, assemble, sharpen tools, finish plane, sharpen tools, finish plane, have some tear out, let out a few curses, try some scraping, start the finishing work, rub oil until you think you are going to lose your mind.

Now, out of the tasks I typically need to undertake on a given project, 95% of them I have had considerable practice with and in some cases no longer find the work all that interesting. For example, running 20 boards through the planer half a dozen times each board, is three hours of time I find, at best, meditative. Now, I really enjoy laying out and cutting joints, really enjoy sharpening and planing, edge profiling, jointing, and so forth. I am no fan of finishing work, and running the shaper I find at times a bit on the scary side.

Importantly, one can not zone out when doing certain of these repetitive tasks as unfortunate outcomes can soon eventuate. As me how I know.

While there is much repetition of a given skill in woodwork, be it sawing a straight line, chiseling out a mortise, planing an edge true or a face flat, it is when faced with the making of numerous identical copies of a given object that the work becomes more, well, machine-like.

It's no surprise that one of the first woodworking specialties to take up the CNC with gusto is the stair-making branch of the trade. Stairs, by nature, are composed of units which repeat, and I'm sure after making 50 bannisters/balusters the intrigue wears off a bit, never mind when making hundreds and hundreds of the same thing as a component stair manufacturer would. While the odd variation in a piece might be delightful in the products of the hand, when you have 5o balusters lined up, the irregular ones stick out and do not look pleasing in most cases. What is called for is absolute uniformity - at least by most clients for such pieces. And it is that sort of work where the repetition of making moves well away from any hope of artistic expression.

As an aside, only peripherally related to the topic at hand today, I read recently that more geometrical stairs are being built today than in the golden age of 19th century stair-building due to the advent of 5-axis CNC machining.

I think a lot of people might associate CNC to some sort of situation where the wood is fed into one end of a giant machine and out the other comes the completed piece. To be sure, there is a good amount of CNC work done along these lines. In such a case, the only interesting job is going to be the designing of the product, and maybe programming the machine, as the other workers in the shop will be doing little other than loading, unloading and packaging. Of course, some might like that sort of work but it isn't typically the sort of environment where those of a more artistic bent would tend to flourish.

However, when looking at the work done by Karl Holtey and others, we can see that the CNC is only forming a part of the overall process - the artisan is choosing the most appropriate tool for the job at hand out of the equipment available. Sometimes the 'best' tool is going to be CNC-based for reasons of the precision afforded - Holtey's employment of CNC milling to cut the multiple oblique dovetails for the wooden-soled planes he makes would be a good example. He avers that it wouldn't be possible to make that joint any other way, and I would have to agree. Sometimes the CNC is going to be the best choice when the work to be done is highly repetitive and not terribly creative - like cutting plywood to shapes which will interlock to form some sort of chair, for example. I certainly wouldn't be too excited by a job where I did nothing all day but cut plywood patterns and trim them. Some would find that work fun, but not me.

I think when the work revolves around the CNC and not much else, the craft disappears for all those except the programmer and designer. And that's a loss. I have more to say yet in relation to the blue collar/white collar ramifications of CNC, and will be looking at that topic a bit more in the next post.

Thanks for coming by today. --> on to post IV

8 comments:

  1. I want to thank you for writing these posts. To be honest i've been reading your blog for about 2 years now. seeing the projects you build and the WAY you work, i think the only power tool ive seen you use was a circular saw to x-cut rough lumber.

    but this last build, the dinning table(by the way, beautiful beautiful BEAUTIFUL!), you did use your hand tools but the router jigs and tablesaw jigs...i was a little taken aback.

    but then i got thinking...hey there is NOTHING wrong with jigs or cutting dovetails on the bandsaw or what have you. im sure woodworkers scoffed at table saws when they were first introduced. saying they were dangerous and lacked the sensitivity of a handsaw(im sure no one said that, but im just trying to make a point here heh..), then slowly they realized "hey....i could rip this board in two in a few seconds and still have the energy to do the other 20 cuts i have to make..."

    i've been debating cutting my dovetails on the table saw and then veneering a false front to "make" half blind dovetails. i thought id never ever think of doing that...but whats the point of cutting dovetails by hand...spending a week or more on a set of drawers, when one can just get from point A to point B with the same if not better results? i'm sure i'll still be fitting them by hand with a chisel, but my cuts will be straight, square and true in a few seconds as opposed to worrying about wandering saw cuts...paring square...and end up with a major case of gapitis.

    phew.

    so please, continue this series!

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  2. Nick,

    thanks for the comment and the encouragement. Every woodworker has to decide for themselves what they want to make, what techniques they want to use, and how they will get from A to B.

    As you say, there is nothing wrong with using jigs - as soon as you grab a hand plane, you are using a jig (metal or wood) to fix a blade in a certain position, and, well, there goes the 'slippery slope'.

    Of course, while power tools can expedite various woodworking processes, they can also be used to make a mess of things quite fast too, and there are added hazards associated with them. Hard to cut off a finger with a handsaw, but it can happen with a powered saw in the blink of an eye.

    As far as woodworkers scoffing at table saws in the 'old days', it is interesting to note that at Hancock Shaker Village in upper New York state one sees a sliding (wooden) table saw in the original shop. Seems the Shakers weren't adverse to using powered equipment or new-fangled things in the 1800's.

    ~Chris

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  3. Hi Chris, along these lines some might remember Charles H. Hayward, a woodworker and writer whose books for many years were a major source of information on traditional woodworking techniques and hand tool use. A man who very much wanted hand tool skills not to be lost. Yet he made the following comments in a 1984 Woodworking Crafts Magazine article.

    "Over the years I have praised the skill of the men who had to do every operation by hand (and I still admire their cunning), but some years ago I installed a bench circular saw, telling myself it would help in the preliminary cutting out of timber. It certainly did so, but soon I began to cut my tenons on it, then I used it for grooving and rebating, and from that time on until I had to give up entirely , owing to my becoming nearly blind, I doubt whether I have cut a single tenon by hand!"

    Just some more to think about, from a man whose writing taught me a lot back when traditional wood working information was hard to come by.

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  4. Hi Koot,

    thanks for that. I have Hayward's book "Woodwork Joints", now out of print I do believe, so I am somewhat familiar with his work.

    ~Chris

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  5. Plywood! Darned useful material in some regards, but when it comes to working the dead material, if possible, I'd just as soon be able to fax someone a pattern and have the completed product delivered. CNC it, or use some ancient Hopi Indian prayer to get the results desired, it doesn't much matter.

    Apprentice: "It is a beautiful day outside"
    Woodworker Susabe san: ( Laughing) "Aren't you here to work? What is happening outside is of no consequence".

    Apprentice: "Susabe san, do you struggle with repetition, and do you find doing some tasks more enjoyable than others?"
    Woodworker Susabe san: "No, it is all the same to me".

    Apprentice: "Wakarimashita".

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  6. Wow! Chris Hall and Dennis Young discussing handwork, CNC machining and toe-clips! Its like eavesdropping on Hawthorne and Melville, when they are out rowing in Herman's rowboat. I wish I had something useful to contribute. All I can say is thanks for the discussion.

    Tom

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  7. Dennis,

    yes, plywood is indeed a wonder material with many fine qualities - which also lends itself admirably to CNC cutout. Too bad the quality of the stuff is on the decline.

    Thanks for the quote!

    Tom,

    glad you're enjoying the discussion, and I always welcome your contributions.

    ~Chris

    ReplyDelete

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