New Small Flat Bottom Level/Prism/Parallel Casting Design
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    Default New Small Flat Bottom Level/Prism/Parallel Casting Design

    I have just cast my prototype small flat-bottomed 8.5" long, 2"high,1.62 at the base Prism/Parallel/ Straight edge.
    It is designed to accommodate (with some machining) almost any of the precision tubular machinists vials currently on the market as well as a cross-level. I plan to drop long vial into a pocket with side windows into the top of the casting and will cross drill the top rail for the cross-level vial.

    I will be machining it over the next few days and will order a couple vials to demonstrate their placement.

    The casting currently weighs 4# 14oz and likely will lose a half pound or so when machined. As you can see in one of the pics, it fits nicely into the hand and should have just enough heft to make it stable and solid on the granite or machine way. There is a step-off to facilitate scraping the angled prism surface. That surface is currently 3/4" long, but will likely lose an eighth in machining.

    level-8-.jpg


    level-8-b.jpg


    Those with sharp eyes will notice below a shrink defect where the gate entered the casting. Likely it will machine out as it is only 1/16th deep, but for future castings I will try a different location for the gate/riser combination I used so that this is not an issue. Getting my other castings right required some experimentation as only an educated guess can be made as to how the gate and riser will interact with the casting as it cools and sucks metal from the riser.
    level-8-c.jpg


    level-8.jpg




    Since this is a prototype, nothing is cast in stone--just iron ;-) Patterns can be changed. Suggestions welcome.

    Denis

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    Looks good, you had posted a potential target price in the other thread, that still the ballpark?
    Thx


    Sent from my iPhone using Tapatalk Pro

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    Quote Originally Posted by ripperj View Post
    Looks good, you had posted a potential target price in the other thread, that still the ballpark?
    Thx


    Sent from my iPhone using Tapatalk Pro
    I have settled on offering it on eBay for 55 dollars and selling here to PM members for 50. Shipping in a padded USPS Priority envelope will add a little less than 8 dollars. Scraping students will get them for net 45 bucks plus shipping. I suspect these, besides being a very useful tool in general, may make nice first-scraping projects as they will involve flat scraping, parallel scraping, vertical scraping, and prism face scraping all for a low initial cost and involving relatively small surface areas.

    I will later offer a machined version with pockets for precision machinist’s ten arc second tubular vial and a cross vial. Price TBD.

    I hope to cast a few next week if the weather cooperates.

    Denis

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    I’m definitely in for at minimum a raw casting, I’ll wait until you decide what the machined price is, I may go that route.
    Thanks for the effort on this!!

    It wasn’t until today that it really dawned on me how much work is in the 18 for the vial machining. I had seen the offset spindle rig, but that baby just barely squeaks in there(the level). The special wrench with the size stamped is a really nice touch

    Keith


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    I did some basic machining on the precision level/prism/parallel today. It is also pretty straight forward except for fixturing to make the cut on the 45 deg prism face. I really did not want to drill and tap holes in the ends to fixture it and found that it would fit lengthwise in my Kurt Milling Vise if I removed the jaws in the vise. I used pieces of baltic birch plywood to pad the vise and level and to provide increased grip of the bare jaws on the iron level. By indicating in the face relative to the already cut surfaces I was able to keep the prism convergence parallel to other long features of the level.

    milling-level.jpg


    milling-level1.jpg


    On the saddle vee of my BP Mill
    milling-level2.jpg



    I think a video also shows well how it looks and handles.


    milling-level5.jpg


    milling-level4.jpg


    This machining should cost about 40 dollars, I think. Placement of the pocket for the precision vial and the cross-vial would add some to that price. I want to see what all is involved in that before indication cost. I am putting the needed vials on order from Geier and Bluhm tomorrow and expect to receive them by weeks end.

    I'll add that the iron milled beautifully---very soft and uniform.

    Denis

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    After tossing around several possible ways to drop in the level vial, I think I have decided to go ahead with end-boring the level slightly over-size and inserting the vial from one end. I had considered the more conventional approach of simply pocketing the level from the top surface and dropping it in. The disadvantage there is that it consumes a lot of the top rail which is also intended to be a parallel surface. I could also drop it in from the back surface by cutting a pocket that would leave the top rail intact except for the window needed to view the bubble. The disadvantage there is the back surface is interrupted and would lose some of its potential utility as a reference surface and would leave a relatively thin-in-section segment of the top rail that might be vulnerable to breakage if dropped or otherwise handled in a ham-fisted manner. End-boring is probably the more challenging method of location of the vial. But it is the cleanest and ultimately most functional method as the top rail is only disturbed by the necessary window and the two holes for mounting studs. Whatever method chosen, there is also interuption of the top rail by the window for a cross-vial. But that is minimal.

    Whatever method is chosen, the leveling adjustment of the main vial will be provided by trapping small o-rings or wall wall seals between the stud tops and vial the vial end tabs.

    I do plan to plug the end-bored hole with a greased (rust prevention) steel rod that is a loose sliding fit and will be fixed in place with a 4-40 set screw. The plug will have 10-24 tapped center pocket on the outboard end to facilitate extraction and a small flat on the pug will prevent the setscrew from raising an interfering burr on the plug.

    The vial I am choosing is from Geier and Bluhm in Troy NY and is on its way.

    vial.jpg


    I intend to cross drill the unbored end of the level to accept a small cross vial as well.

    I had wanted to include side-viewing windows for the main vial, but doing so would result in weak spans of iron where the cut for the side window and top window are cut.

    Denis
    Attached Thumbnails Attached Thumbnails vial.jpg  

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    Denis,
    I throw in a wild idea: what about mounting the level with a flexure on one side and the adjusting screw on the other?
    As flexure I envision a cylinder with a close fit to the bore (actually, you could put two o-rings, one at each end and you can increase your tolerances), with a piece of leaf spring attached to it.

    Something like this quick and dirty sketch:

    flexmount.jpeg

    Paolo

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    Quote Originally Posted by Paolo_MD View Post
    Denis,
    I throw in a wild idea: what about mounting the level with a flexure on one side and the adjusting screw on the other?
    As flexure I envision a cylinder with a close fit to the bore (actually, you could put two o-rings, one at each end and you can increase your tolerances), with a piece of leaf spring attached to it.

    Something like this quick and dirty sketch:

    flexmount.jpeg

    Paolo
    Paolo,

    Thank you.

    I like the idea. One nice thing about using the flexure is it would eliminate a hole in the top rail---a surface I am trying to keep as clean as possible so that it can be used to maximum advantage as an indicatable surface and as a parallel not to mention also having the level look and function as elegantly as possible. If I were to use the flexure, I would probably bore the level for its entire length rather than using a blind hole as initially planned.

    Challenges that the flexure might introduce would be getting the height of the mounting surface at a fairly close-tolerance height. But that should be doable especially if a trial fit were made, height error measured, and then the flexure was removed and taken to the surface grinder where the height to easily and accurately be adjusted. The plug that supports the flexure could be fixed just like the other plug with a small (likely 4-40) setscrew that originates on the cast convex surface of the finger grip on the prism side of the rail. Since the level would probably bored from each end, the two hole would not meet perfectly in the center area (yes, I could line bore it full length on the mill and get a "perfect" bore) slight alignment errors could be compensated in stud height and flexure height and hole in flexure placement.

    I really appreciate the suggestion. I'd love to hear others. Now is the time before swarf start to hit the floor. I was just out making some minor adjustments to the pattern when I came in and saw your post.

    Denis

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    Put a flexure in the middle, so you can put in two vials, one less sensitive, and one more sensitive.

    If there is room, but in a differential thread so the sensitive level can be adjusted as needed to check work not currently level.

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    Quote Originally Posted by J_R_Thiele View Post
    Put a flexure in the middle, so you can put in two vials, one less sensitive, and one more sensitive.

    If there is room, but in a differential thread so the sensitive level can be adjusted as needed to check work not currently level.
    Thanks for your ideas!

    Two vials—-seems like that could be a very useful setup to first get in the ball park and then dial in the machine surface more precisely with the fine vial. And I think there might just be room to stuff two in.

    The idea of differential screws has come up in off-line discussions kicking around possible design features. I have been looking for an excuse to use them somewhere for sometime as they are so cool. But, in this tool space is at a premium. So, not sure I can use one. If you see a reasonable way to include one, I’m all ears.

    There may be other ways to achieve finer adjustment than direct impingement of a screw on and end of a vial support...

    Also my ideas on finishing out the level/prism/parallel are just one person’s approach. It will be fun and probably instructional to see what various people do with their casting. If their were some folks that said that for one reason or another they needed a longer or beefier casting, nothing is off the table.

    Denis

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    I've been following this and I have a suggestion for a means of adjustment/calibration:

    Drill the hole for the vial a bit deeper and install a slotted plug at the bottom to recieve the 0.156 thick tab of the G&B A3080 tubular mounted vial to center it vertically and prevent it from rotating on its long axis.

    Make the plug for the open end. Drill and tap two holes in the plug to accept adjusting screws with long tapers concentric with the screws' pitch diameter. Tap drill through the full length for external access to the adjusting screws with the long end of an Allen wrench. The screws are aligned vertically on the centerline of the plug located 1/4 the screws' root diameter above and below the planes of the vial tab. Differential adjustment of the screws provides vertical motion of the vial via the tapers to bring it into calibration with the level's reference face. The thrust of the screws will seat the vial into the V of the bottom plug.

    Differential adjustment of the screws will cause the vial to slew. A dog or flat point setscrew through the casting wall on either side on both ends of the vial housing will be necessary to center the tabs and provide lateral stablization.

    The tapers machined on the adjustment screws will have to be precisely concentric with their pitch diameters.

    I suggest 8-32 Allen setscrews 1 1/4" long with a 20 degree included angle point truncated to 0.020 dia. The resulting cone originating at the thread root diameter will be about 0.260 long. This will yield +/- 0.020 max adjustment (+/- 1/2 degree, thereabouts.) 1/6 differential turn of the adjustment screws provides about 0.0009" vertical movement of the vial tab or roughly 3 arc minutes in the 3 3/4" length of the G&B A3080 vial. Thus, tweaking the vial in arc second increments will be less tedious than adjusting nuts on a 40 TPI post. In effect, the conical adjustment would be roughly equivalent to a 180 thread per inch post and nut arrangement.

    The screws should have long engagements in the plug to prevent binding and a very low strength locktite should be used to prevent settings from drifting.

    Care must be taken to avoid over-snugging the adjustment screws lest the brass vial tube distort or the glass vial shatter.

    The ends of the tab should be beveled 10 degrees x 3/32" to avoid point contact and consequent metal deformation.
    Last edited by Forrest Addy; 01-31-2020 at 12:48 PM.

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    I have been working on a differential thread adjustment design. Without knowing all the dimensions no final design is possible, but I did want to outline the design. The height of the casting is reported at 2 inches, with a machined height of 1.75 inches. The adjusting mechanism will extend above this- but is removable so the top surface can be scraped parallel to the bottom.

    The differential thread uses an M 8x1.25 left hand thread and an ¼-20 right hand thread. When the adjustment knob is turned clockwise 1 rotation, the ¼-20 thread moves the rod down by .050 inches, while the left hand M8x1.25 mm thread moves its attachment up .04921 inches on the same shaft. The difference of the two distances is an adjustment downward of about .0008” per revolution (.00079).

    There are 4 pieces in the mechanism. All fit within a .500” vertical hole which transects the horizontal hole for the level body.

    A base piece in inserted from the bottom and secured by a setscrew into its body. After the mechanism is fully assembled the base can be scraped true to the base. The base piece has a reduced diameter in the upper portion, leaving room for a spring which will press up against the bottom of the level, pressing it against the adjustment mechanism. The base’s center is drilled and tapped for ¼-20.

    A carrier piece .500 in diameter is drilled/bored and tapped left hand M8x1.25 to close to the end. It is then reversed in the collet, and the end is drilled to .250, and the end turned to match the countersink on the vial frame.

    A central shaft is turned between centers with a lower portion being ¼-20, and the upper being a left hand M8x1.25 turned to be a close fit to the threads of the carrier piece.

    The vial housing needs to have one of the countersunk holes bored out to .250”

    To assemble the mechanism the flexure and vial are inserted first. Next the spring and base piece are inserted and secured after the spring is compressed. The carrier is threaded onto the central shaft to about half of the available thread engagement. The ¼-20 end of the shaft is threaded in from the top through the end of the vial housing until the vial housing is contacted by the carrier. After this has occurred the flexure is secured in place with a setscrew.

    For coarse adjustment the central shaft is turned. The unsecured carrier turns with it, and there is .05" movement per revolution. When fine adjustment is needed, the carrier is held from turning while the central shaft is turned, and the net movement is about .0008" per revolution.

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    Here is what I described drawn out in concept.

    If I were making one I would have knurled knobs on the ends of the carrier and the central shaft.
    Attached Thumbnails Attached Thumbnails differential-thread_20200201_0002.jpg  

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    Quote Originally Posted by J_R_Thiele View Post
    Here is what I described drawn out in concept.

    If I were making one I would have knurled knobs on the ends of the carrier and the central shaft.
    Nicely conceived and illustrated.

    It appears it would be possible to make the top portion of the differential screw recessed from the top of the parallel portion of the tool. If the carrier piece had a keyway and there was a pin in the body of the tool, rotation of the carrier piece would be prevented. Properly sized it could remain less than flush with the parallel surface of the level. The central piece could have a hex socket in it so it could also be less than flush. You would lose the coarse/fine adjustment that the unrestrained setup allows. But it would allow easier use a parallel. Trade-offs...

    Incidentally, the vial arrived today (they shipped quickly and economically Priority) and it does measure very close 0/+.002 the size shown in the drawings provided by Geier and Bluhm. The reamer came today too. So, I am ready to start boring the hole in the test level.

    I will also be drawing up a method using no holes in the top parallel surface other than the window for the vial and using two flexures and a single adjusting pin to provide very fine adjustment of the vial.

    Denis

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    With the central shaft and the threads chosen keying the carrier will significantly limit your adjustment range. If the keyway is 180 degrees out of where it needs to be you could have to move the carrier .025 inches. with the differential thread, this would take over 32 rotations of the central shaft- which would move .633 inches. You will quickly run out of hole for the shaft to thread into.

    A way around this is to have a central shaft fixed by an allen screw to the side, around which goes a tube threaded (in this case) 1/4-20 on the inside and a left hand M8x1.25 on the outside. The "carrier" is threaded on the inside for the left handed M8x1.25 and keyed to prevent rotation. To do the fine adjusting the threaded tube must be rotated. This could be done by having it slotted at the top, and inserting a nonthreaded tube to engage the slots. Coarse adjustment could be provided by slotting the central shaft, and rotating it after loosening the allen screw at the bottom.

    I fear I have contributed to "mission creep" in the project. It would be simpler to have a more sensitive level which could be added when needed. The assembly assembly could be held on to the top by magnets, with the adjusting mechanism extending out over the end and down, to reduce the overall height.

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    Quote Originally Posted by J_R_Thiele View Post
    I have been working on a differential thread adjustment design. Without knowing all the dimensions no final design is possible, but I did want to outline the design. The height of the casting is reported at 2 inches, with a machined height of 1.75 inches. The adjusting mechanism will extend above this- but is removable so the top surface can be scraped parallel to the bottom.

    The differential thread uses an M 8x1.25 left hand thread and an ¼-20 right hand thread. When the adjustment knob is turned clockwise 1 rotation, the ¼-20 thread moves the rod down by .050 inches, while the left hand M8x1.25 mm thread moves its attachment up .04921 inches on the same shaft. The difference of the two distances is an adjustment downward of about .0008” per revolution (.00079).
    ....
    One thing: the differential threads have to be of the same hand to differentiate pitches. If they were on the opposite hand, they would sum in pitch like a turnbuckle. Otherwise, great concept. Compact and sensitive.

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    Forrest.

    Thank you for the correction.

    It is an embarrassing mistake. Not sure how long ago or why I got the idea that the hand of the threads needed to be different, but I had thought that for years...

    Unfortunately it is too late to go back and correct my earlier post.

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    Quote Originally Posted by J_R_Thiele View Post

    I fear I have contributed to "mission creep" in the project. It would be simpler to have a more sensitive level which could be added when needed. The assembly assembly could be held on to the top by magnets, with the adjusting mechanism extending out over the end and down, to reduce the overall height.
    Guilty as charged! Well, not really. I have invited folks to chime in with their ideas as to how to finish out the tool. A casting in itself is just a start on making a multi-tool. I am very appreciative of your, Paolo's, and Forrest's remarks suggesting methods of setting the vial in place and adjusting it. I hope there will be more contributions as this project evolves.

    I have not been totally idle myself. I have made some adjustments to the original pattern beefing it up just a bit. I could see that as the concept of boring the casting full length came to the fore, that the casting itself should be a bit larger in all dimensions except length. So here are a couple pics of the bored test piece and the new pattern.

    comparison-original-new-pattern.jpg


    To help insure good hole straightness and trueness, I first bored a 5/8" hole and then drill with a 5/8 hole. Final 21/32" size was cut with a reamer.




    drilling-8.jpg


    The thinness of the undercut and back portions of the casting inclined me to beef up the casting. The "real casting will be substantially thicker.
    one-end.jpg


    other-end.jpg




    Next op will be cutting the window and cross-vial hole and window.

    Denis

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    vial-casting.jpg


    And the vial DOES fit with 30 thousandths clearance. Sure, that was supposed to be the way things work out, but I always feel a little relief when the actual parts do fit together as advertised.





    Denis

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    Denis, that's a very novel and handy device youre building. Could you point me toward where I can get on the list as a buyer?


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