Announcement

Collapse
No announcement yet.

Question about dividing plates

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • JCHannum
    replied
    ClintonH is considering building his own dividing head, and is not restricted to any particular size at this point of the game. Designing it to accomodate the larger plates would not present any particular problem and the added hole counts John's plates provide would be a worthwhile consideration.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Dividing plates

    I'd second the comments from 'uncle Pete' about George Thomas's approach.
    My 'one hole' plate was from his deliberations. So was 'my' parting off comments.

    Presently, I am sort of into George's old 'brother' from NZ and making a new improved top slide for my ancient Myford. That is the Jack Radford book which sort of compliments and complements GHT's writings. GHT visited Jack and brought home to the UK, a lot of his writings on dividing and graduating.

    The nicest thing about GHT is that he doesn't flannel, but tells you blow by blow what to do.

    Cheers

    Norm

    Leave a comment:


  • lazlo
    replied
    Originally posted by JCHannum
    If you are considering purchasing plates, I would suggest these. They are made by John Stevenson and sold by his wife. They have the standard holes plus 25, 63 & 127 which adds the most commonly needed divisions not covered by the standard plates.
    Those are the standard Myford dividing head plates, which are 5.7" in diameter: they're too big for the Ellis and Carrol dividing heads, which use 5" plates.

    The ubiquitous Chinese dividing head plates, like the BusyBee plates the OP linked, are 5", and will fit most home-shop sized dividing heads and rotary tables.

    Leave a comment:


  • lazlo
    replied
    Originally posted by doctor demo
    I wonder with all the cut-price DRO's/digital calipers that are able to be produced nowadays why someone hasn't applied the technology to produce a rotary table with a digital display for a modest price? Is there a limitation to the technology that prevents it?
    Thanks Peter, I guess there is no point in going to the patent office....now that You put My idea on the net .
    I actually posted pictures of that exact setup here a couple of years back: rotary encoders output common quadrature signals, so I dropped an MT3 center/drawbar doodad I made into my Yuasa rotab, which is threaded 1/2-13. I shaft-clamped a Heidenhain optical rotary encoder on the drawbar, and hooked up the output to a cheap ($40) Red Lion quadrature display. Instant rotab DRO.

    You can see the top of the MT3 drawbar adapter here:



    ..and this is the Red Lion CUB5 quadrature display/totalizer I use:

    Leave a comment:


  • uncle pete
    replied
    ClintonH, You can if you want build your own plates, A book called "The Shop Wisdom Of Philip Duclos" sold by our host's here (Village Press) has a very good artical on building your own 40-1 dividing head and gives a few different ways to drill the plates.

    A much better book IMO is written by George H. Thomas titled "Workshop Techniques" ISBN 1 85761 106 3 gives a very clever way to drill the plates on the dividing head itself, Altho this is for a 60-1 head. the principle would still be the same. If you buy this book I would also buy George's other book "The Model Engineers Workshop Manual" ISBN 1 85761 000 8, I probably have over 200 books on machining and if I had to choose the two best books, His two books are what I would pick.

    But if you value your time the plates John Stevenson sells are the best deal going.

    Pete

    Leave a comment:


  • JCHannum
    replied
    If you are considering purchasing plates, I would suggest these. They are made by John Stevenson and sold by his wife. They have the standard holes plus 25, 63 & 127 which adds the most commonly needed divisions not covered by the standard plates. He leaves a margin to permit additional divisions at a later date should that prove necessary.

    http://www.metoolsonline.com/product...products_id=55

    Leave a comment:


  • ClintonH
    replied
    No problem on going off topic, it's all learning and that's what I need right now.
    So would it be better to try and build my own or are these cheap enough that I should just pick them up and build additional plates latter as I need them? Anyone good with CAD and has some spare time..?

    Clinton

    Leave a comment:


  • Peter.
    replied
    Yeah sorry for dragging your thread off-topic ClintonH. It WOULD be pretty cool to produce a rotary table with a digital readout though. Shame that electronics is one of my weakest points, I reckon that a simple controller and a mouse encoder could produce pretty good results, perhaps by gearing the encoder wheel for extra resolution.

    Leave a comment:


  • nheng
    replied
    Clinton, Sorry for wandering off a bit here ... but it could be a way of generating precise angle spacing, perhaps on a par with a good x/y DRO.

    Peter, There has been lengthy discussion of using PC mice in the past for encoding. I don't recall if it wandered into optical mice but there's an option possibly worth playing with. An interesting basic study of opto mouse movement is here: http://www.contrib.andrew.cmu.edu/~t...ision_Project/

    Leave a comment:


  • nheng
    replied
    Take a Shooting Start (Canadian) DRO and wrap the scale around the table. It is gear based, as far as I recall.

    added after Peter's last - the hi-res encoders I referred to were those used in precise servo based systems for position feedback. High end ones are in the 20,000 count per revolution, maybe more.
    Last edited by nheng; 03-07-2009, 02:28 PM.

    Leave a comment:


  • Peter.
    replied
    Hmm what about a system that uses an encoder wheel driven off a circular rack similar to how the dial calipers work? That ought to be quite accurate, compact and cheap to produce.

    EDIT: whoops - just re-read nheng's post about cost of them
    Last edited by Peter.; 03-07-2009, 02:25 PM.

    Leave a comment:


  • John Stevenson
    replied
    BW Electronics in the Uk does such a system

    http://www.bwelectronics.co.uk/appnotes/rotary.html#top

    It uses a fine stainless wire to pull an encoder round for rotary work ot pulls it out in a straigh line for linear work.

    I bought a couple in the early days as they were quite cost effective but unfortunately prices have gone up whilst glass scale units have come down. I notice now he's quoting 0.003" accuarcy when in the early days he used to quote 0.001" ?

    .

    Leave a comment:


  • nheng
    replied
    Hi-res rotary encoders are still quite pricey. You could however, do what some have done in the past, convert rotary motion to linear motion.

    You could wrap a steel cable or flat steel strap around the table like an old radio tuning dial, and attach it to a digital caliper. You might need to introduce a some tension in-line with this.

    The problems start when you start cranking the table. An 8" table would need a 24" scale for almost full rotation. A 24" digital caliper can be had for around $100 or less.

    Doing it with a PC would be easier since you can introduce the angle factor:

    (arc segment) = (radius) X angle (in radians) or,

    angle (radians) = (caliper readout) / (table radius) or,

    angle (degrees) = (caliper readout) * 180 / (table radius) * PI

    So, a caliper reading of 1" on an (exactly) 8" table platter would represent an angle of 14.324 degrees

    Den
    Last edited by nheng; 03-07-2009, 02:16 PM.

    Leave a comment:


  • doctor demo
    replied
    Originally posted by Peter.
    I wonder with all the cut-price DRO's/digital calipers that are able to be produced nowadays why someone hasn't applied the technology to produce a rotary table with a digital display for a modest price? Is there a limitation to the technology that prevents it?
    Thanks Peter, I guess there is no point in going to the patent office....now that You put My idea on the net .

    Steve

    Leave a comment:


  • Peter.
    replied
    I wonder with all the cut-price DRO's/digital calipers that are able to be produced nowadays why someone hasn't applied the technology to produce a rotary table with a digital display for a modest price? Is there a limitation to the technology that prevents it?

    Leave a comment:

Working...
X