Proper chip formation when turning with graver

Discussion in 'Watch Repair' started by karlmansson, May 15, 2019.

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  1. karlmansson

    karlmansson Registered User

    Apr 20, 2013
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    Hello!

    I recently had the opportunity to turn quite a lot of blue pivot wire as I made a batch of pin rollers for a bearing. The turning was mostly parting off and rounding up corners though, as the diameter of the rollers was simply burnished to size from their stock size.

    I remember reading a while back, can't remember if it was Daniels or Fried, that stated that the hardness and temper of the steel stock could be determined from whether or not the steel formed a long, stringy chip when turning with a graver. To this day I've never had that happen. Short rolls that break off, sure. Powder and needles, a lot of that. But never that stringy, continous spring of a chip that they seem to imply. When turning the blue steel this time around it didn't behave much differently from when I've turned annealed steel before. I used both a HSS graver and a carbide graver and they produced about the same result. I made sure to keep them both sharp.

    What are your experiences with turning hard steel? Should it be a long, stringy chip to be "cricket". Is my technique lacking or does this have something to do with the materials?

    Regards
    Karl
     
  2. DeweyC

    DeweyC Registered User
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    Feb 5, 2007
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    Karl,

    The harder the steel, the less it is going to come off in curls. Long curls are more likely with slide rest, but they become a hazard.

    How do you present your graver (face up, face to the work, point first or point following, etc). Are you turning the work fast? (I run fairly slow) Some pictures would help.

    BUT, the final test is the finish you leave. If it is smooth and even, you likely are doing fine. Turning under a scope will enable you to see what is happening at the graver. I turn at 20-30X.
     
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  3. Chris Radek

    Chris Radek Registered User
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    If I recall correctly, Daniels made his balances and maybe other parts out of stainless steel. Stainless definitely cuts in long curls, and as Dewey says they are hazardous. Stringy stainless chips are especially bad - they are like razor wire.
     
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  4. Dushan Grujich

    Dushan Grujich Registered User

    Jun 20, 2003
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    G'Day Karl!

    Whether shavings are short or long curls matters not much, it is the quality of finished surface, as already mentioned by Dewey, also the shavings should be shiny and bright not greyish or dull in colour. When turning hardened and tempered steel with a graver, I normally cut with the edge slanted or almost parallel to the axis of turning (in the vertical plane), point of attack is always somewhere in the middle of the cutting edge unless doing undercut which is done using the tip, carefully.

    Above all, it is important to have gravers sharp with no feathered edges, and when I say sharp, I mean razor sharp. There is no need to press graver strongly against the work-piece, just light touch and let graver do the cutting, no forcing is necessary.

    Try to get a booklet, "Proper Use of the Watchmaker's Graver" by Homer A. Barkus, he provides a simple and accurate instructions on turning with a graver.

    Cheers, Dushan
     
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  5. glenhead

    glenhead Registered User
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    Nov 15, 2009
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    It's all a matter of graver sharpness, graver angle, pressure on the graver, lathe speed, and the speed at which you move the graver across the part. (Simple, right? :) ) I regularly get long curls with a hand graver from steel or brass. When I took the FSW classes from the late Fred Tischler I had the only jeweler's lathe in the class - everyone else had Sherlines - and we all had collections of the longest curls we could generate. Some of them are quite pretty. Yeah, you have to watch what you're doing.

    All the "all a matter" things are pretty much impossible to explain in print, at least in my opinion. If you have a real expert like Fred looming over your shoulder to say "speed the lathe up a tick" or "you have too much angle on the graver" or whatnot - coaching, in other words - it's a LOT easier to learn.

    Diamond point on the graver, sharpened perfectly. With brass you want the cutting edge pretty much parallel to the axis of rotation, but with steel you want the edge's heel a fraction higher than the tip. (Although sometimes having the tip higher than the heel gives superior results.) Hold the cutting edge nearly flat against the surface, with just enough clearance on the heel to ensure it doesn't drag. Adjust your lathe speed and all the pressures and hand speed until you get good results. That's both the glory and the hassle of hand-held gravers - you can adjust on the fly, but you have to adjust on the fly. It took me several hours of experience and several times of Fred saying "you're doing that wrong again" to really get the knack of it.

    Get a lot of steel and a lot of brass and turn it all into chips. Experience is the only way.

    Hope this helps a bit.

    Glen
     
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  6. karlmansson

    karlmansson Registered User

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    Thank you! I do all of the above. I've noticed that for very small work I have a tendency to either go or get pulled below center if turning with the graver face down. I turn with the face up in those situations, although I often have problems with getting a neutral rake angle in those settings because of the T-rest getting in the way of the graver shank. For bulk turning I use one of the rear corners of the graver or the lenght of the edge. For turning corners or parting off I tend to use the tip.

    Surface finish is decent I think. Although, it's interesting to be to look back on some of the turning I did recently where I started out great with a razor sharp graver only to get worse and worse results, where I would chip the edge of both an HSS graver and a carbide one, probably from applying too much pressure. That also resulted in burnishing the work which of course led to increased frustration, higher tool pressure and even poorer results. I think that the tool pressure is my biggest problem right now.

    I started out using a sewing machine motor powered drive but then switched to a hand crank. I don't know if I'm imagining things but I think I got better results with the hand crank. Possibly from slower speeds but also from greater control.
     
  7. karlmansson

    karlmansson Registered User

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    Yeah, coaching in this would be nice. To busy in the ER to seek out an apprenticeship I'm afraid... :) Guess I'll go back to the drawing board and experiment some more! Thanks for your input, much appreciated!
     
  8. karlmansson

    karlmansson Registered User

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    Thank you! I'll post some pictures when I get the chance. I realize that this is probably as hard for me to describe in words as it is to teach in the same format.
     
  9. karlmansson

    karlmansson Registered User

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    Is that so? Not glucudyr? Interesting. I can't remember seeing much mention of stainless in his "Watchmaking" but that doesn't mean much. Stainless is one of my greatest enemies when it comes to machining. Guess I haven't worked with the right grades of it yet.
     
  10. wrobbie

    wrobbie Registered User

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    Same here. Face down on small diameters or thin brass means a very likely ruined workpiece (and possibly graver) for me. Unfortunately the flip-up toolrest on my Geneva-style lathe is always in the way when using the graver face-up. I don't know why it is so annoying. At one point I made a new T rest for it, but that barely helped.

    (I'll attach a picture later, if that's possible)
     
  11. Dushan Grujich

    Dushan Grujich Registered User

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    G'Day!

    The best I can do is show a scan of a page from the booklet.

    Cheers, Dushan

    Graver use.jpg
     
  12. DeweyC

    DeweyC Registered User
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    Karl,

    You are not imagining things. We proved this to ourselves in Neuchatel. Americans in particular turn way too fast. The harder the steel, the slower the speed.

    Karl, it also sounds to me like you might be pressing too hard on the graver; concerned about how quickly it dulls. When I teach I like to have the student put their hands on mine and then will also put my hands on theirs. Think about your results with the wheel. You are only using one hand.

    Know you are a surgeon, the touch with the graver is really very light.

    I turn exclusively with face to the work, use face up very rarely. I find carbide does not chip as easily this way. Also, be aware there are a number of carbide grades. The best is Micrograin which I get from using broken drills and endmills. I even have sets that I bought specifically to use for cutters.
     

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