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Thread: Calipers, Digital Dial?

  1. #76
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    A metal lathe has a tool holder. It is very controlled.

    A wood lathe has a tool rest, as in it will keep the tool from flying to the floor, but the operator does the rest.

    My mind still isn't quite settled on how in heck a caliper is going to help on making a taper. Most likely something is eluding me.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  2. #77
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    Quote Originally Posted by Jim Koepke View Post
    My mind still isn't quite settled on how in heck a caliper is going to help on making a taper. Most likely something is eluding me.

    jtk
    For me, the caliper is only used to set the major diameter of the taper. I use a trick that Jack Guzman on WC taught me.. I drill a proper sized hole in a scrap block and then ream it out with a taper reamer. Then cut that socket in half and use it to turn the matching tenon to the matching taper.

  3. #78
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    I use a trick that Jack Guzman on WC taught me.. I drill a proper sized hole in a scrap block and then ream it out with a taper reamer. Then cut that socket in half and use it to turn the matching tenon to the matching taper.
    My first response to the OP included making a go - no go gauge. That was a few days ago.

    Maybe some folks just do not like doing things the easy way.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  4. #79
    Quote Originally Posted by Jim Koepke View Post

    My mind still isn't quite settled on how in heck a caliper is going to help on making a taper. Most likely something is eluding me.
    If you know that the diameter of your reamer tapers, say, .1" for every inch of length, then you just make two marks on your tenon, 2 inches apart, and and measure with the calipers. When the two measurements differ by .2", you are there. I like to make the marks while the lathe is still spinning, so when I measure, if I keep both blades of the calipers centered on the pencil lines, I will get an accurate measurement.

    At least, that is how I do it. I don't know how it was traditionally done; I don't imagine the bodgers in the forest had Starretts. I guess if you know your tool rest is truly parallel to the long axis of the work, you could use a bevel gauge or something similar.

    Edit: I just saw Bruce Haugen's response--that is a good trick, Bruce, I may try that. Thanks!
    "For me, chairs and chairmaking are a means to an end. My real goal is to spend my days in a quiet, dustless shop doing hand work on an object that is beautiful, useful and fun to make." --Peter Galbert

  5. #80
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    Apparently there is a considerable variety of opinion regarding "the easy way" to make tenons for chairs as the methods used in the three classes I have taken have all been substantially different. I have been considering buying a Galbert Caliper, which would be my choice as the easiest way I know of to check round tenon dimensions. The Galbert device is designed to provide real time feed back as an object is being turned along the entire length of the work. Being new at turning I am not comfortable (yet) with the idea of holding a Galbert Caliper against a spinning work piece. If I plan to stop the lathe to check progress the Galbert devices advantage over a digital or dial caliper seems negligible. Since I do not own a digital or dial caliper I decided to order one for several reasons. Once I garner more experience turning and making round tenons I may revisit the Galbert Caliper idea.

    There is no single dimension on a tapered chair tenon. The method I was taught for turning tapered tenons involves making two cuts on the opposite ends of the tenon area with a parting tool and then removing the waste area between the two grooves. The chair plans I have provide a chart of the smaller and larger dimensions required to make the parting tool cuts for various leg angles and tapers. The groove made by a parting tool is too small to fit a wrench into without additional work and there are two grooves. The Galbert device is made to fit into a parting tool groove. I also think most dial or digital calipers will fit in a parting tool groove with little or no additional work. Checking with the guys on the Turning Forum this seems to be the standard practice for turners making tenons, particularly tapered tenons.

    Winton, regular mechanical calipers tend to move with all the back and forth between multiple tenons on a large number of spindles, especially if the user holds one against a spinning work piece or attempts to measure an irregular surface. I think mechanical calipers are designed more to fit to a fixed workpiece size than move between various measurements. I found the one I had and the ones at Country Workshop tedious to set at multiple given distances on a ruler. Without any scale to let me know I had the correct setting, I found myself rechecking to make sure I had the correct setting.
    Last edited by Mike Holbrook; 04-01-2015 at 12:54 AM.

  6. #81
    I have one like that. Small, quick and light. I like it a lot. It gets a lot of use in my shop. It has metric and imperial scales on it with no vernier scales. It's great for sorting drill bits and the like.

    If I need more accuracy I go for a larger, stainless hardened vernier caliper. It's what I learned on and use the most for work where tolerances approach .001


    Quote Originally Posted by Winton Applegate View Post
    Don't want 1/128ths . . . don't need 1/64ths . . . 1/32nds rarely used ?

    Have you seen . . . are you aware of . . . this ?
    Increments of 1/16th.
    There are a few different ones.
    Personally I need more of a friction thumb brake or locking screw to prevent the setting from changing . . . I have never really made friends with this little caliper but it may be all you need from what I am reading here.
    Shallow jaws though.

  7. #82
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    There is no single dimension on a tapered chair tenon
    Again I am speaking from outside the fence but . . . and "dimension" may not be the term but there is one number/angle you can go by and that is the angle of the taper.
    So . . . set up the lathe how ever you have to to turn an angle equal to the taper of the hole.
    On the metal lathe that is a brainlessly easy thing to do. There is a protractor right on the "compound" and then when the feed is turned the bit has to travel at that angle in relation to the axis of the turning part.

    As far as how to use the adjustable turning calipers I spoke of, the slots made with the cut off tool while holding the caliper to the work until it passes over the work was what I had in mind.

    There is this and this set of tools I suppose they are not really what is needed for a nice gradual full length taper on the tenon.
    Right ?
    Last edited by Winton Applegate; 04-01-2015 at 1:16 AM.
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  8. #83
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    There is one other thing that came to mind.
    Picture in your mind a whole stack of pop sickle sticks. drill a hole through the stack and put a rod through the hole to keep them indexed and to use as a pivot for them later when you put them to use.
    Then
    cut the stack of sticks off at an angle to the rod same as the angle of the tenon you want to turn.
    Set up the stack on the back side of the lathe so that the axis of the rod is parallel to the axis of the work.
    The work is pre turned round and smooth.
    Put the ends of the sticks so they are on top of the work and rubbing.
    As the required size to the tenon is reached the sticks drop down past the work indicating to stop turning in the area of each stick that drops.
    I have seen Norm use this when turning exact duplicates of posts with common necked dimensions.
    PS: you will probably need to round the ends of the sticks or point them or other wise refine this method but you get the idea.
    Last edited by Winton Applegate; 04-01-2015 at 1:34 AM.
    Sharpening is Facetating.
    Good enough is good enough
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    Better is Better.

  9. #84
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    Winton, In the Schwarz class we used the first Lee Valley tenon cutter you link to above. It worked much like an old style pencil sharpener. When very sharp, much sharper that when they arrive, they work well. I sharpened my brand new LV tenon cutter before the class but ended up sharpening it even more during the class to get it to cut as well as the ones Schwarz sharpened. I suspect it would work better locked in a vise with the work piece turned into it. I have been wondering if the second "set of tools" you mention might work well with a brace, but I have not tried it yet.

  10. #85
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    Quote Originally Posted by george wilson View Post
    I have only ever used DIAL calipers. It is easy to interpolate to a 1/4 thousandth with them. On a dial caliper you are stuck with a 1/2 thou reading..
    What? So, which is it? Dials are good for 1/4 thou, or 1/2 thou?
    I think 1/4 thou is a little hard to get on a dial caliper, unless the dial is 6" diameter.
    Never, under any circumstances, consume a laxative and sleeping pill, on the same night

  11. #86
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    Well, I guess I can jump in. I have the dial gauge, fractions with lines in-between. Not sure what brand I bought it so long ago. However, I hardly ever use the actual measurements, so probably most anything would work for me. I almost always use it to transfer measurements by setting it on one piece, locking it at that setting, and then using it to define the other piece. I guess it is sort of a glorified "story stick" to me.

  12. #87
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    Quote Originally Posted by Myk Rian View Post
    What? So, which is it? Dials are good for 1/4 thou, or 1/2 thou?
    I think 1/4 thou is a little hard to get on a dial caliper, unless the dial is 6" diameter.
    Most likely George typed dial, in the second use, when he meant to type digital.

    In olden days some of us learned to use a slide rule. Part of slide rule usage is knowing how to interpolate/extrapolate digits between the lines. I do this all the time with my "old school" (non-digital) calipers.

    My most used caliper is a 3" Lufkin. It has a 1/32" scale and a 1/64" scale. The 1/64" scale is never used. It is easier for me to just read where the line is on the 1/32" scale. If it is being used to determine a twit drill size needed, the number is then converted to decimal in my head as I take the walk over to where my drill indexes are stored.

    In my last job my supervisor wanted me to write a manual before my retirement. We used precision spacer washers that were always getting mixed together. Here is an "eye calibration" exercise using a caliper included in the manual:

    The Calibrated Eye

    The purpose of this exercise is to train your eye to recognize small sizes for what they are.
    To do this exercise one needs a lot of mixed spacing washers. The sizes found on our TTMs
    are .001, .005, .010, .016, .030 and .040 with occasionally some other odd sizes.
    A dial or digital caliper is also needed. Small containers or pieces of paper to separate the
    washers into different piles are also needed.

    With all the washers mixed in a pile, start measuring with the caliper. Look at the edge of each
    one during the measuring process. Separate the washers into piles of washers that measure the
    same. After a short time, look at the washer before measuring it and see if you know what it
    will measure before it is put in to the caliper. Keep doing this until you get good.

    Congratulations you now have calibrated your eyes. Recalibration may be needed if not used
    on a regular basis.
    In our own shops this could be done with shavings or even drill bits. Empty your drill index into a box and then check each one with your calipers.

    It is amazing what one can see with just a little eye tune up and training.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  13. #88
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    My most used caliper is a 3" Lufkin. It has a 1/32" scale and a 1/64" scale.
    Sounds cool. Any chance of a photo. Or come to think of it is it one of the brass ones we have been talking about ?
    Sharpening is Facetating.
    Good enough is good enough
    But
    Better is Better.

  14. #89
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    Quote Originally Posted by Winton Applegate View Post
    Sounds cool. Any chance of a photo. Or come to think of it is it one of the brass ones we have been talking about ?
    My camera will have to go out to the shop tomorrow.

    The only brass ones in my shop are ones that are seldom used. I do not recall their being mentioned. Maybe someone else has them.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  15. #90
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    For lathe work, I use a Harbor Freight fractional dial caliper.
    http://www.harborfreight.com/6-inch-...per-92437.html
    I don't like digitals due to battery consumption.
    Jim Davenport
    Reporting from the depths of the Magic Garage

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