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  • oldtiffie
    replied
    A "heads up"

    Originally posted by hitnmiss
    12 pages of "Mines bigger than yours"

    !

    I don't know what's sadder, the fact that you guys wrote 12 pages or that I read them!
    Thanks hitnmiss.

    Good "get back to reality" post.

    Served me right for being a "smart-ar*e" and a "big-noter"/"skite".

    I guess I deserved and needed that.

    So - how to do it with stuff that can be found in many/most HSM shops?

    It took a bit of looking around for tools and materials and then getting back to first principles and re-focusing on the job at hand - checking the taper reasonably accurately.

    Here we go.

    There are too may pics to post in one go - even with multiple successive posts, so I will do it in one post using direct links to the pics and readers can "click" them (or not) to suit themselves.

    The principles here were and are sound but far too expensive for may HSM shops:
    http://i200.photobucket.com/albums/a..._sine-bar1.jpg

    I will use my HF-45 mill and 2 rotary tables - "Rotabs" - (6" and 8"). The 6" has a 7 1/2" lathe face-plate that I modified to suit my lathe and rotabs.

    Both rotabs are calibrated to read to 5 minutes direct and at least 2 by interpolation. The test sheets show a maximum error of 1 arc minute.

    The 8" has a 10" face-plate that is part of the rotab package.
    http://i200.photobucket.com/albums/a...-up/HF45-6.jpg

    My basic idea was to set the MT sleeve and an MT with a chuck "Jarno" taper up to be suspended/fixed between centres in a rotab.

    The centres were made from spare 18mm (3/4") Cold-rolled steel rod that I had. I set them up in the lathe to less than 0.0002" (2 "tenths") Total Indicated Run-out (TIR) with my TDI which is calibrated to 0.01mm (0.0004") and turned the 60 degree tapers. So maximum "run-out" as measured was 0.0001"

    The rotab was set to indicate zero run-out with/along the 20mm centres OD's with the TDI at centre height.

    The work-pieces were to be fitted between the centres to be a light turning fit with no "slack" or "end-float" .
    The rotab reading was to be recorded at that setting (setting 1).

    The rotab was to be rotated until there was zero deflection on the TDI as it was run along the taper by using the mill table "X" lead-screw. This setting was recorded (setting 2).

    The difference/s between the settings was the taper of the work-piece (ie half the included angle) as in the sketches in the first link.

    This worked very well. No clamps were needed. I could have used small bags filled with lead shot over the centres to hold them.

    Checking concentricity and/or run-out was very easy as well.

    In retrospect, I would have done better with the centres made from 2" CR stock - mainly for centre height and weight (for stability).

    http://i200.photobucket.com/albums/a...re_set-up1.jpg

    The next method was a variation on the first. I used 2 vee blocks (matched set) on the rotab table. The vee blocks were aligned by dropping either a straight round bar or a piece of straight extruded brass angle stock into the vee blocks. The alignment was excellent.

    The centres were placed in the vee blocks and the work was suspended easily without clamping. The blocks did not move on the rotab either. If they had, I would have used paper between the blocks and the rotab table.

    This too worked very well.

    http://i200.photobucket.com/albums/a...re_set-up2.jpg

    The next pic is a variation on the previous pic. but is set up on the 6" rotab using the brass angle to both keep the vee blocks in alignment as well as providing a very successful extension of the "V" to rest the centres in/on to support the work piece.

    http://i200.photobucket.com/albums/a...re_set-up4.jpg

    The next pic is another variation making use of the larger (7 1/2") angle plate on the 6" rotab without the brass angle.

    http://i200.photobucket.com/albums/a...re_set-up5.jpg


    The next pic is a variation of the previous pic except that the brass angle is used.

    http://i200.photobucket.com/albums/a...re_set-up6.jpg

    The next pic is of using the centres in the top of the "T" slots in the mill table. It was surprisingly accurate and would work as/for a quick check for concentricity for anything that could be held between centres.

    http://i200.photobucket.com/albums/a...re_set-up7.jpg

    I hope this helps.

    Leave a comment:


  • hitnmiss
    replied
    12 pages of "Mines bigger than yours"

    !

    I don't know what's sadder, the fact that you guys wrote 12 pages or that I read them!

    Leave a comment:


  • oldtiffie
    replied
    See previous post

    Originally posted by J Tiers
    The "bumps, dips, or deviations" is a lot harder than the basic determination as to whether the two ends are consistent with the correct taper.

    ...............................................

    .................................................. ..

    A method of comparison of dimensions to that axis is therefore suggested. Mounting on centers is one way of holding the part for comparison, as it may be turned, and moved axially past a measuring device. (errors of center holes may, I think, be fairly considered to be errors in the part, as they were used as a reference to generate the surface)

    An "exploring probe" is used to examine the location of the surface at each point with reference to the axis. This might be a suitable point attached on the end of an indicator spindle.

    Then the part can be rotated to compare every point on the "hoop" surface with the axial reference (the holding centers). And it may be moved axially to examine successive "hoops" on the surface.

    Errors are accuracy of centering of rotation on the axis, accuracy of axial movement, and the obvious accuracy of the measuring probe system.
    Thanks again JT.

    As is very the case, you have got it right and have explored for and have identified the salient points.

    I have posted pics in my previous post - copied here - which I hope illustrate the very good points you make.

    Leave a comment:


  • oldtiffie
    replied
    Taper measurement

    Originally posted by oldtiffie
    I have yet to see, and would appreciate, a definitive method of accurately measuring/checking the taper and whether it is consistent (ie. no "bumps, "dips" "bends" or deviations) throughout its length.

    Originally posted by JCHannum
    I believe I touched on that when I referred to the use of a sine bar, Jo blocks and height gage. Add a DTI of the desired resolution and and conduct the measurement on a surface plate. Care must, of course, be taken to assure the readings are taken on the high point of the taper.
    Thanks Jim.

    Indeed you did - many thanks.

    I have included a pic with 2 sketches which indicate the basics of the approach.

    It is the "semi-angle" in the second sketch that we are after - is it not?

    The first diagram is very basic and does not show how to retain the axis of the job parallel to the edges/sides of the the sine bar so as to ensure that the job centre is not "skewed".

    The second digram is quite correct in itself as the "hooks" on the bases of the centre holders keep the centre line parallel to the edges of the sine bar and so avoid the "skew". It may not be within the resources of a typical HSM-er or his shop. Many HSM-ers do not have access to or use of a good surface plate or sine bar, slip guages or locating accurate centres. I have them all. I would use the centres from my Tool & Cutter grinder as these have accurately located and fitted keys to locate to the grinder bed. I would use my magnetic sine chuck to hold the centres.

    Provided that the centre holes at both ends of the work under test are OK then that set-up will allow the job to be rotated as well which should sort out all details - including any errors.

    I am not being a smart-ar*e here - and I am not inferring that anyone said I was/am (probably true though!!) but I am just trying to point out how difficult it can be to sort these seemingly apparently "minor/easy" problems out.

    Leave a comment:


  • J Tiers
    replied
    The "bumps, dips, or deviations" is a lot harder than the basic determination as to whether the two ends are consistent with the correct taper.

    The "deviations" part is the worst, since you are trying to prove a physical surface conforms to a theoretical truncated conical surface. Bumps and dips can be found, if not quantified, by comparison to a known mating surface, by bluing-up, etc.

    But that does not, as you pointed out earlier, give a number.

    The surface may be bumpy. The surface may be out of round. The surface may be perfectly circular at every diameter, but those diameters may not have their centers on one axis. There are innumerable possible errors, and only one possible correct surface.

    The general reference appears to be the axis. The desired surface is a series of infinitesimally wide "hoops", each of a different diameter, but each perfectly circular and centered on the axis.

    A method of comparison of dimensions to that axis is therefore suggested. Mounting on centers is one way of holding the part for comparison, as it may be turned, and moved axially past a measuring device. (errors of center holes may, I think, be fairly considered to be errors in the part, as they were used as a reference to generate the surface)

    An "exploring probe" is used to examine the location of the surface at each point with reference to the axis. This might be a suitable point attached on the end of an indicator spindle.

    Then the part can be rotated to compare every point on the "hoop" surface with the axial reference (the holding centers). And it may be moved axially to examine successive "hoops" on the surface.

    Errors are accuracy of centering of rotation on the axis, accuracy of axial movement, and the obvious accuracy of the measuring probe system.

    Leave a comment:


  • JCHannum
    replied
    Originally posted by oldtiffie
    I have yet to see, and would appreciate, a definitive method of accurately measuring/checking the taper and whether it is consistent (ie. no "bumps, "dips" "bends" or deviations) throughout its length.
    I believe I touched on that when I referred to the use of a sine bar, Jo blocks and height gage. Add a DTI of the desired resolution and and conduct the measurement on a surface plate. Care must, of course, be taken to assure the readings are taken on the high point of the taper.

    Leave a comment:


  • oldtiffie
    replied
    Taper

    I rather hope that it is safe for people to either put their heads above the trenches or better still to come out and stay out.

    If that is the case, could or would they please address the basic intent and topic of this thread and my following paragraph.

    I have yet to see, and would appreciate, a definitive method of accurately measuring/checking the taper and whether it is consistent (ie. no "bumps, "dips" "bends" or deviations) throughout its length.

    Leave a comment:


  • Pete H
    replied
    Thanks for the heads-up about Victor. I was going to order some stuff from them, now I'll be super-careful that it's right. -Pete

    Leave a comment:


  • JCHannum
    replied
    Having thus far resisted in replying to the latest posts, I succumb to temptation.

    I was gone all day yesterday attending an auction where, among many other things a 17" X 58" Clausing Colchester lathe with flats in the tailstock barrel for some strange reason.

    I must, firstly, apologize to Evan. It was foolish of me and others to question him and refute his expertise by offering paltry, opinionated information from pundits and exhibiting examples of manufacturers' attempts to employ the MT tang to add to the driving force over the one hundred or so years of it's existance. In light of his experience with a 9" South Bend lathe, all other reason fails. I cede the argument to his wisdom and experience. I am abashed and am man enough to admit my foolishness. Please forgive me.

    I do, however, take exception to his statement accusing me of taking his words out of context. I not only directly quoted the statement in question, and explained it's pertinence to the context of the discussion, I cited the entire post, recapped it and responded to each separate topic covered in that post.

    I find it very interesting and valuable at this time and stage of the economy to find that textbooks are of no value as a source of information, merely offering opinion as it seems. With the recent spate of extreme cold weather and the current high energy costs, I find myself comfortably basking in the warm glow of the fire fueled by my reference library. It will carry us through the winter I am sure.

    Leave a comment:


  • lazlo
    replied
    Wow, you really did study engineering Allan -- you used real engineering paper, and even signed the top like every engineering fundamentals student was taught.

    We were also required to put the class title and our social security number underneath the date -- that was in the days before identity theft

    Leave a comment:


  • aostling
    replied
    Originally posted by aostling
    A nice puzzle, which I intend to tackle tomorrow. Will I find a differential equation? Linear? I am intrigued.
    Took me a little longer than it would have done when I was in engineering school, 45 years ago! It's interesting that the frequency of the beam oscillations is independent of its mass, and depends only on the coefficient of friction f, the local acceleration of gravity g, and the half distance between the rollers L.

    I'll let somebody else solve for the amplitude.

    Leave a comment:


  • Evan
    replied
    "it is impossible for a bumblebee to fly".
    You are gonna get me going Jerry.

    What they proved is that a bumblebee cannot GLIDE. Sure enough, they can't. Of course the reporters became confused on the details and the rest is history.

    Leave a comment:


  • J Tiers
    replied
    "Experts" say many things........

    "it is impossible for a bumblebee to fly".

    "Powered flight is impossible"

    "A man will NEVER travel to the moon"

    "Don't bother with way oil, just use Rislone and 20wt, with a bit of bar and chain oil"........

    or my favorite of all time, apparently spoken by an old guy who probably was tired of answering questions.... "don't use any way oil at all, it just collects dirt that will ruin the ways. The lathe should be operated with the ways absolutely bone dry"

    So the advice of an "expert" is fine. But unless it is tested against reality, it may have little validity.

    Some things are better "tested" in "thought experiments", of course, as confirmation of the expert advice, if forthcoming, is likely to damage the test subject........... Probablility theory with regard to certain "one -out-of-six" chances come to mind..........

    I suggest that you all go your ways in peace, muttering like "bag people" if you simply must do it. Or if that is insulting to you, consider that you are muttering like Galileo instead.

    Either way it won't bother us. After all, we won't hear it.

    Please. You are bothering those who can't stand not to read it, but who are then offended when they do.

    Leave a comment:


  • oldtiffie
    replied
    Pack it in/up

    Is there any chance of the protagonists packing it in and calling it quits or "square"?

    Or alternatively, if you really MUST carry on with this, please do it by/on PM.

    Leave a comment:


  • Evan
    replied
    It is very difficult to reinterpret a five word statement.
    Yet you manage. And you are the one that has repeatedly accused me of extracting quotes from your postings without the appropriate context. Sound familiar? Incidentally, Xerox has/had the finest training in the industry. Many of the courses can be counted as credit toward an engineering degree.

    Leave a comment:

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