It Using Pins to Locate Tram on a Mill—-how does this work out in practice? - Page 2
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  1. #21
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    Quote Originally Posted by Hbjj View Post
    One pin per joint would be limited to the accuracy of the fit of the machines joint...
    Two would be better three pins per joint would be best

    I think one pin per joint to get you close is a reasonable idea

    But if I was constantly going back and forth say from 0 to 45° I would really look at a fixture that had the proper angles built in
    Agree on the fixture if two specific angles were in play repeatedly. In my case, it’s pretty much rotating the head to “about 30” to drag an end mill through a oval recess to make a clean surface out of an as-cast surface. So, only tram is important and one pin would do.

    Denis

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    Quote Originally Posted by Rob F. View Post
    If you are always going back and forth from the same angle and perfect tram then why not have a pin to quickly set the angle, the same as you want a pin to quickly set the tram.
    IF you decide this is a good idea to save you some set up time it would seem easier to drill the hole with the machine at tram and then, set the head at your common angle, drill through the outer hole, using it to guide the drill. Then taper ream the holes. Just seems easier to locate the inner hole through a drilled hole as a guide than through a loose taper outer hole if you want to add it later. Reaming the second holes inner half should be easy to keep the reamer centered in the taper bore of the outer half, so as not to change the angle of the first hole.

    I would make bolt on stops with fine adjusting screw if it was mine though. I've seen enough tools with alignment pin holes that are no longer aligned as tool wears....
    Gotta admit that I have cut only a few taper pin holes for very specific fixtures and the like. But, I thought the idea was to clamp the adjoining parts together, drill the hole and without changing anything, ream to tapered shape. If another taper pin was needed at a new alignment of parts, separate dedicated holes reamed using the same procedure should be made for good accuracy. I’d worry about reusing a previously reamed hole.

    Denis

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    Quote Originally Posted by dgfoster View Post
    I’m having trouble visualizing the touch strip. What was that like?

    Denis
    The saddle was mounted on the cross rail as with most vertical boring machines. On the bottom of the saddle casting there was a little lip sticking out facing the operator, maybe 1/2" wide by 1.5" long. The housing that carried the ram and five sided turret was mounted on a swivelling housing which swivelled on the saddle. On the bottom of the swivelling housing there was also a little lip about 1/2" wide by 1.5" long sticking out. When the ram housing was rotated into the correct position the two little strips came in line with each other. You could feel the slightest little deviation with your finger tip.

    Once the two strips were in line the operator ( if he could be bothered that is ) would climb up onto the table and insert the dowel to properly locate the head in place. Then you finally tightened up the six bolts that fixed the ram housing to the saddle.

    Regards Tyrone.

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    I don't think it's a good idea on a Bridgeport. The machine itself is so unstable that you'd really like to tram it in each time, the pinned holes are not likely to repeat well. I've seen stuff pinned on heavier machines but the Bridgie is so flexible you're likely to end up pinned .002" off when you come back, then where are you ? screwed ...

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    Quote Originally Posted by dgfoster View Post
    Gotta admit that I have cut only a few taper pin holes for very specific fixtures and the like. But, I thought the idea was to clamp the adjoining parts together, drill the hole and without changing anything, ream to tapered shape. If another taper pin was needed at a new alignment of parts, separate dedicated holes reamed using the same procedure should be made for good accuracy. I’d worry about reusing a previously reamed hole.

    Denis
    Separate holes would be better, but I wasn't sure if there was space enough to do that and still have good access to instal and remove the pin. Straight pins are what I have seen this done with. Sharing the outer hole for two locations is probably not the best idea with taper pins.

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    Quote Originally Posted by Tyrone Shoelaces View Post
    The saddle was mounted on the cross rail as with most vertical boring machines. On the bottom of the saddle casting there was a little lip sticking out facing the operator, maybe 1/2" wide by 1.5" long. The housing that carried the ram and five sided turret was mounted on a swivelling housing which swivelled on the saddle. On the bottom of the swivelling housing there was also a little lip about 1/2" wide by 1.5" long sticking out. When the ram was rotated into the correct position the two little strips came in line with each other. You could feel the slightest little deviation with your finger tip.

    Once the two strips were in line the operator ( if he could be bothered that is ) would climb up onto the table and insert the dowel to properly locate the head in place. Then you finally tightened up the six bolts that fixed the ram housing to the saddle.

    Regards Tyrone.
    Very cool! It is a nice use of the amazing sensitivity to a step off that is the human finger “indicator.” It would have been a treat to have had some time with the designer of those tools. I like the way he thinks.
    You’ve recounted two little-known and very useful design features he incorporated in his tools.

    I wonder if touch strips are used on other machines by other makers. That’s an idea to keep in mind.

    Denis

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    Quote Originally Posted by dgfoster View Post
    Very cool! It is a nice use of the amazing sensitivity to a step off that is the human finger “indicator.” It would have been a treat to have had some time with the designer of those tools. I like the way he thinks.
    You’ve recounted two little-known and very useful design features he incorporated in his tools.

    I wonder if touch strips are used on other machines by other makers. That’s an idea to keep in mind.

    Denis
    I've also seen touch strips on planing machine swivelling clapper boxes were you need a means of quickly lining up the swivel to the saddle.

    On the vertical boring machines as the years went by the alignments of the saddle/ram housing might deviate slightly. It was the easiest thing in the world to just ream the taper dowel hole slightly deeper and re-finish the touch strips with a file and emery cloth. After you'd made sure your ram was back in line of course.

    Regards Tyrone.

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    Quote Originally Posted by Tyrone Shoelaces View Post
    I've also seen touch strips on planing machine swivelling clapper boxes were you need a means of quickly lining up the swivel to the saddle.

    On the vertical boring machines as the years went by the alignments of the saddle/ram housing might deviate slightly. It was the easiest thing in the world to just ream the taper dowel hole slightly deeper and re-finish the touch strips with a file and emery cloth. After you'd made sure your ram was back in line of course.

    Regards Tyrone.
    Thanks again, Tyrone. You and several others have provided very thoughtful points of view that have made this thread, at least in my opinion, interesting and informative.

    Denis

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    Denis,
    I think that Emanuel Goldstein has a very good point. Definitely, I would avoid using a taper pin for the nodding of the head: just by moving the ram back and forth, you would end up with the head out of tram front-back due to the change of weight on the dovetails of the ram.

    Perhaps, installing touch strips to get very close would be the best solution on a Bridgeport, especially considering that the worm screws help considerably in making fine tramming adjustment.

    Abene milling machines (improved concept of the Van Norman swiveling head) use a straight pin to locate the vertical position of the head, which can nod from horizontal (set with an adjustable stop, if I recall correctly) to 15° or 30° past vertical. As far as I know, the vertical position set by the straight pin is fairly accurate. Much beefier machine than a Bridgeport, but the nod is fine-tuned by gently tapping with a dead blow hammer while the 4 bolts of the head are loose. No mechanical provision for fine adjustments.

    Paolo

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    Quote Originally Posted by Paolo_MD View Post
    Denis,
    I think that Emanuel Goldstein has a very good point. Definitely, I would avoid using a taper pin for the nodding of the head: just by moving the ram back and forth, you would end up with the head out of tram front-back due to the change of weight on the dovetails of the ram.

    Perhaps, installing touch strips to get very close would be the best solution on a Bridgeport, especially considering that the worm screws help considerably in making fine tramming adjustment.

    Abene milling machines (improved concept of the Van Norman swiveling head) use a straight pin to locate the vertical position of the head, which can nod from horizontal (set with an adjustable stop, if I recall correctly) to 15° or 30° past vertical. As far as I know, the vertical position set by the straight pin is fairly accurate. Much beefier machine than a Bridgeport, but the nod is fine-tuned by gently tapping with a dead blow hammer while the 4 bolts of the head are loose. No mechanical provision for fine adjustments.

    Paolo
    Good point, Paolo, about the ram position affecting tram. No doubt that is true. Just for the sake of discussion, in an attempt to defend use of a pin on the BP for the nod function, I would say that the great majority of the time I position the ram more or less midway in and out. If one realized that the pin were valid only for such a mid position, the pin might be useful to quickly get very close to accurate tram at that ram location. Just because of the configuration of the "joint" that nods the head vs the one that rotates the head, installing a pin on the nod would be a lot easier than the tilt. No sense doing it just because it is easy, however, if it not also useful.

    Overall, my guess is that installing pins would be helpful for getting tram good and close enough for 98% of the work I do. Very likely, for very fussy work, fine tuning might still be needed. But just getting very very close quickly because of pins would be handy even if the last little tweak were still needed.

    I do like the idea of the touch strip or lugs on the rotation axis. They could be pretty easily installed there and seem like they would be quite functional.

    One other thought that has occasionally gone through my head is a vernier scale on the rotation axis might be useful. But, I am not sure exactly how that could be practically accomplished. Ideas???

    Denis

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    I can’t swing or rotate the ram on either my my series 2 machines without needing to retram it. My suggestion is practice tramming it quickly. Assuming the table isn’t covered in crap it really should only take a couple of minutes.

    ETA I don’t use the screw adjusters. I just back the bolts off a bit and a few smacks with a dead blow and it’s where it needs to be. Put some dykem on the joint and make a faint line with a scribe. A jewelers loupe will get you in the ballpark then use the precision adjuster...

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    Quote Originally Posted by Nmbmxer View Post
    I can’t swing or rotate the ram on either my my series 2 machines without needing to retram it. My suggestion is practice tramming it quickly. Assuming the table isn’t covered in crap it really should only take a couple of minutes.

    ETA I don’t use the screw adjusters. I just back the bolts off a bit and a few smacks with a dead blow and it’s where it needs to be. Put some dykem on the joint and make a faint line with a scribe. A jewelers loupe will get you in the ballpark then use the precision adjuster...
    Scribed line is not a bad idea. Might try that and compare to the feeler lugs that Tyrone described. I think the lugs by feel will be more sensitive than a visualized line. But the line certainly is quick and easy.

    I should test changing my ram position and its effect on tram. I have never tested that.

    Denis

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    Quote Originally Posted by dgfoster View Post
    Scribed line is not a bad idea. Might try that and compare to the feeler lugs that Tyrone described. I think the lugs by feel will be more sensitive than a visualized line. But the line certainly is quick and easy.

    I should test changing my ram position and its effect on tram. I have never tested that.

    Denis
    I had a similar but more complicated problem on a big " Asquith " portable radial arm drill. I wanted to be able to set the drill up as a conventional radial drill, drilling downwards at 90 degrees. Look up " Apex Auctions " on the internet to see what I mean, there are photographs of a couple of them. The one I worked on had a No 4 Morse spindle. It had a "Bridgeport" style double swivel drilling head but the "ram" could also be canted up and down about 30 degrees as well has being spun around 360 degrees on the column. I created my own " Vernier " style scales out of aluminium and fastened those onto the machine in the most relevant places. They got me " very near " ( see what I did there ? ) pretty rapidly and they were every bit as accurate as I needed them to be.

    Regards Tyrone.

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    Default Flight of fancy?

    OK, I just woke up with a couple ideas running around in my head neither of which may necessarily be practical, but they are interesting to think about and one is pretty easy to execute. So little is lost even if it proves a complete was of time. And both have obvious (maybe) limitations.

    Right now I have sitting in a box a loose 20 arc-second vial that I "intend" to mount in an 18" SE/Level/Prism casting that I poured in my foundry. (Yes, I hear the objections you are thinking of, but hear me out.) I could quite easily make an adjustable and robust mount for it that could be mounted on the head to read its vertical rotation. My machine base, though not formally tested, is likely pretty stable as it is mounted on 4 steel columns that are bedded on the concrete floor of the unheated basement crawl/storage space below my shop. Being a basement with only limited ventilation I know the temperature there is relatively stable year around so that it is unlikely to vary much during any given day. The second source of error should I use only a vial on the tilting portion of the head is that due to heating of the workspace and sunlight exposure of the machine, the primary casting of the machine is likely bending around all day long. That is the likely major source of deviation of the machine column itself. Sooo, if I place a second vial on the machine column somewhere that it can be read and compared with the first, it just might be possible to cancel out flexion of the machine column due to differential (that word will come up again here soon) heating shifting of the base etc. Just watching the vials during a work session would be quite interesting to see just how much movement is going on might be quite interesting.

    Second idea that is less easy to implement but is appealing due to its elegance would be to use LVDT's set up like the bubble vials. One could quite easily, using an Arduino or Raspberry Pi microprocessor to sum the output voltages of the two LVDT's to automatically compensate for column shift. This idea is a bit more of a flight of fancy as I have neither access to LVDT's nor the inclination to fabricate them for use. I have on several occasions had the inclination (so to speak) to experiment with LVDT's, but I doubt that it will ever happen as there are enough other things more pressing that I need to keep up with.

    I do think I will take a closer look at just starting out mounting a single 20 arc-sec vial to the x-axis of my head simply to observe how it behaves when I use the machine without messing with the tram. Is it wildly all over the place from hour to hour with the motor stopped at intervals to check it or is it relatively stable? It might be possible to learn what the difference is between the two "trams" I mentioned earlier in the thread might be in actual measured deflection from true level.

    Denis

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    Quote Originally Posted by Tyrone Shoelaces View Post
    I had a similar but more complicated problem on a big " Asquith " portable radial arm drill. I wanted to be able to set the drill up as a conventional radial drill, drilling downwards at 90 degrees. Look up " Apex Auctions " on the internet to see what I mean, there are photographs of a couple of them. The one I worked on had a No 4 Morse spindle. It had a "Bridgeport" style double swivel drilling head but the "ram" could also be canted up and down about 30 degrees as well has being spun around 360 degrees on the column. I created my own " Vernier " style scales out of aluminium and fastened those onto the machine in the most relevant places. They got me " very near " ( see what I did there ? ) pretty rapidly and they were every bit as accurate as I needed them to be.

    Regards Tyrone.
    And how accurate was that?

    And what method did you use to scribe them? I can think of a method or two, but I'd be interested to know what you found practical.

    Finally, I have been thinking a lot about adding a couple of touch lugs to the tilt and nod axes of the BP. I think they would not need to be more than 3/8 to a half inch high and a quarter or so in depth and maybe 5/8 to 3/4 wide. Placed with pins and epoxy they would be very solidly mounted and the faces could be refined to be very smooth and with minuscule gap between them making them quite sensitive as a comparator using touch. (More flight of pure fancy: if they were polished mirror smooth and a pair parallel laser beams were reflected by each set onto scales ten feet away, they would be sensitive indeed. We used reflected beams of collimated light in that way for very sensitive angular measurement in the physics lab at Iowas State 50 years ago---long long before lasers.)

    Denis

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    Quote Originally Posted by dgfoster View Post
    And how accurate was that?

    And what method did you use to scribe them? I can think of a method or two, but I'd be interested to know what you found practical.

    Finally, I have been thinking a lot about adding a couple of touch lugs to the tilt and nod axes of the BP. I think they would not need to be more than 3/8 to a half inch high and a quarter or so in depth and maybe 5/8 to 3/4 wide. Placed with pins and epoxy they would be very solidly mounted and the faces could be refined to be very smooth and with minuscule gap between them making them quite sensitive as a comparator using touch. (More flight of pure fancy: if they were polished mirror smooth and a pair parallel laser beams were reflected by each set onto scales ten feet away, they would be sensitive indeed. We used reflected beams of collimated light in that way for very sensitive angular measurement in the physics lab at Iowas State 50 years ago---long long before lasers.)

    Denis
    The marking was in the form of an arrow head going across both little pieces of aluminium. So one line going straight across and two lines going across at an angle to join up with first line at the far side of one of the little plates. I used a little " Moore & Wright " protractor and a very sharp scriber.

    It was a drill so I didn't beat myself up about measuring it's accuracy but It appeared to be pretty good. I swung trammelled the drilling head off the base and I set the level of the arm with a master level set up the same as the base ways.

    Regards Tyrone.


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