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D1-4 Spindle & Chuck Measurement and Setup

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by Ray C, Jan 2, 2013.

  1. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Hi Folks,

    By popular demand, I'll post some information about D1-4 spindle and chuck dimensions which I hope to include various techniques to measure things. We'll need to do all kinds of measuring, use granite plates etc. This will take a few days to get through but by the end, it will show a technique I've been using to true-up chucks so they mount perfectly and repeatably. This is only loosely structured as I'm really low on time these days. -Have 2 paying jobs in the shop and the 9-5 day job is getting in the way too... Hang in there. I promise this will pertain to Metrology using a live example.

    Note: I'm not a professional machinist -just a lifelong shop rat that loves this stuff. If along the line, I use incorrect terminology or improvements/suggestions are in order, shout it out.

    Regards

    Ray


    Part 1:

    When I recently mounted my old collet chuck on a new D1-4 back, I discovered the back was pretty crude. It would not mount repeatably and closing the locking lugs was next to impossible. Please see the first picture that shows the problem in exaggerated form. There should be no light coming between backplate and spindle face. BTW: I'm demonstrating on a back that's already been properly fitted so, this will show a "sunny-day" scenario of what's going on.

    Also, take a look at the PDF. If you have Adobe Reader, you can click the image and rotate it with the mouse. Please note, the faces of the back and spindle nose must contact at the same time the tapered part of the spindle nose contacts the inner race taper of the back. This is a tough geometry to get right -but if you do, your chucks will mount perfectly -every time.

    Part 2 coming in the next thread...

    The Problem.JPG View attachment 95507
     

    Attached Files:

    Last edited: Jan 3, 2013
  2. jgedde

    jgedde United States Active User Active Member

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    Re: D1-5 Spindle & Chuck Measurement and Setup

    Looking forward to it! Not to hijack your OP, but by interest is piqued.

    I've made some D1 type attachments for my lathe (a collet closer head and a dog driving plate)... Here's a 3d model of the collet head and a photo of the assy:
    Clipboard01.jpg
    IMG_1523.jpg
    I have a drawing for the camlock pin that I made for anyone's reference. They're much easier to make than one might expect... The threads aren't shown in the dwg...
    Cam lock pin drawing.jpg

    John

    Cam lock pin drawing.jpg Clipboard01.jpg IMG_1523.jpg
     
  3. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Re: D1-5 Spindle & Chuck Measurement and Setup

    John,

    Very cool... And I like the way you inserted the PDF as a JPG. I'll do that from now on. Should have thought of that earlier.



    Ray
     
  4. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Re: D1-5 Spindle & Chuck Measurement and Setup

    Part 2

    Word of caution: When you're doing this, make sure your gears are in a neutral/disengaged state and all the safety locks are activated. Nothing here is done under power but you don't want your lathe turning on accidentally while your fingers, hand, head etc are deep inside the cutting area.

    As mentioned I'm intermixing a real problem with Metrology. In this case, the problem is easy to see. -The back is crude and doesn't fit. In real life, the space between the faces was about 2-3 thou meaning, the nose taper was bumping into the back taper first and the overall assembly could not sit flush.

    In general when diagnosing a chuck problem, all relevant geometry should be analyzed. First thing I wanted to do is check for gross errors in the spindle. Use a well trusted square, place it on the ways and verify the spindle face is perpendicular to the ways. Rotate the spindle and check in several spots. Square should meet-up flush with the spindle. If something is way off, it needs to be corrected.
    Check Spindle 1.jpg

    Use a good parallel flat bar and make sure the spindle face is even. No (or extremely little) light should shine through. When I got my lathe, I immediately noticed raised areas around the holes that receive the studs. This was an artifact from the drilling process no-doubt. I used hand tools and very carefully removed the burrs and bumps.
    Check Spindle 2.jpg

    While you're at it, you might as well check to see if your crossfeed is square. Check the DI as you hold the parallel in place and run the x-feed back & forth. If there's a problem, it could either be head-misalignment or crossfeed misalignment. Fortunately, this lathe is dead-on!
    Check Spindle n xFeed.jpg


    Now, it's a good idea to measure the angle of the nose taper. First, set the angle of the toolpost to match the angle of the nose taper. I used a small square. Metrology Issue: Getting the DI to meet the taper perpendicularly is important. The ball tip of the DI is parabolic -not round. If the shaft of the DI is not perpendicular to the angle, your measurement could be off a thou or two and in this next measurement, we can't afford that. Please see the next 2 pictures to see what's going on. -And I acknowledge, there are other ways to skin this cat but, this is how I happen to approach this and the steps I personally took. Again, other ideas are more than welcome.

    Setup Toolpost Angle.JPG Setup Toolpost DI.JPG

    OK, moving right along... Now we need a way to measure horizontal travel of the carriage. We're going to measure "Rise over Run" to calculate angle. Put another DI to measure the carriage travel. If you have DRO, more power to you! Here's how I set it up. -Pretty intuitive...

    Setup Carriage DI.JPG

    Ready for our first Metrology measurement now... Position the Toolpost DI at the tall edge of the nose taper and then move your carriage DI to contact the carriage. Zero the faces. Helps to thump the machine a few times to make the DI's settle-out. Next, move the carriage to the right until the toolpost DI reaches the other edge (low side) of the taper. Measure both DI's. You probably want to do this 4-5 times to make sure your setup is rigid and repeatable. Adjust your mag bases and fixtures for rigidity until you get several readings of consistent numbers.

    In my case, the spindle DI gave me 0.025" the carriage moved 0.200". Arctan (0.025/0.200) = 7.125*. Guess what, the D1-4 spec says it's supposed to be 7*, 7", 30s -and that equals 7.125*. So far, the spindle is looking good.

    OK, Sasha is extremely bored with this and has decided to rest her head on a pile of laundry to demonstrate (in only a way a dog can do) that it's time to do something else. Not only that, 5:30AM is coming up soon and I gotta sleep fast.

    More tomorrow....


    Bored Sasha.JPG

    Check Spindle 1.jpg Check Spindle 2.jpg Check Spindle n xFeed.jpg Setup Toolpost Angle.JPG Setup Toolpost DI.JPG Setup Carriage DI.JPG Bored Sasha.JPG
     
    Last edited: Jan 3, 2013
  5. tripletap3

    tripletap3 United States Active User Active Member

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    Re: D1-5 Spindle & Chuck Measurement and Setup

    Ok I am now subscribed. So I can ask lots of questions. Some may be dumb. :nuts: First one. I see you are using your PM1236 which is a D1-4 for demo purposes. Are your taper measurements only for a D1-5 or do they work for both?
     
  6. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Re: D1-5 Spindle & Chuck Measurement and Setup

    Oops. LOL... Another lathe I used was D1-5 and I got the title wrong. Hopefully I can change the title. :thinking:

    EDIT: BTW, the nose angles for D-4 & 5 (and all the D-types) are the same. Diameters are different though but everything here custom-mates all the pieces so, getting the diameters right happens by virtue of the process.


     
  7. Ray C

    Ray C United States Moderator Staff Member Moderator

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    All,

    I'm going to go back and revise history and change all occurrances of D1-5 to D1-4 to go along with the example. Some might be wondering if the reason my chuck didn't fit is because I had the wrong back. -No, that's not the case. A #5 wouldn't even come close to fitting a #4 spindle and all of the factory supplied backs were maladjusted in the same way. Truth be known, just recently, I mounted several #5 chucks for the prototype shop at work and the two numbers are bouncing around in my head...

    I apoligize for the confusion.


    BTW: A quick search of D1 Spindle Dimensions will bring you to a chart like this -which is worth having a look at. http://www.tools-n-gizmos.com/specs/Lathe_Spindle_Mount.html

    Ray
     
  8. GaryK

    GaryK In Memory Rest In Peace

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    Great stuff Ray!

    Here's a jpg of something close to the link you provided.

    D1-Camlock Dimensions.jpg

    D1-Camlock Dimensions.jpg
     
  9. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Part 3:

    For this example, I'll be citing the dimensions read off this machine, specific to this example. You'll need to make your own measurements -don't use mine verbatim for obvious reasons. As you're doing this, take careful measurements. -Triple check yourself. Also, note that some of these pictures are staged -taken tonight even though I did the work a while back. ...Decided to pull a chuck apart to show you guys this because if done right, the results are very rewarding. Since I put witness marks on the chucks, they'll go back together in a jiffy and it only takes a few minutes to center them.

    The tapered nose on the spindle is build-up on a shoulder that has a recess. See the gap my finger is pointing at in the picture below:

    Recessed Shoulder Taper.JPG

    To measure this we'll take low readings from the face of the spindle then, we'll use a shim that butts-up to the very edge of the wide part of the taper. Admittedly, this is a little dicey but, I couldn't think of any other way to do it. I got lucky and found a piece of scrap that to the best of my eye, came right up to the edge as needed. If anyone can suggest a better way of making this measurement, I'd be glad to hear about it. To make the measurement, you could use a depth gauge or, you could use a DI mounted on the spindle provided the DI has enough throw to gap the distance. Turns-out, the differences indicated a gap space of 0.100". See the setup below:

    Shoulder Depth 1.jpg Shoulder Depth 2.JPG

    We also need the diameter of the wide part of the taper. That's easy enough. It turned out to be 2.475". See below:
    Measure Taper Base Diameter.JPG


    Next, we need to setup for the cutting operation and must adjust the compound to the exact angle of the taper. I used the back end of a carbide holder mounted in the toolpost and adjusted the compound, carriage and x-feed until it matched exactly. Back the compound (not crossfeed) in/out until it's an exact match. Even though we know the angle is 7.125*, you can't trust the markings on the compound as shown. My compound showed about 6.9* as far as my eyeballs can read the fuzzy lines yet, using very precise measurements, we found it to be exactly 7.125*. When you set the correct angle, lock down the compound. See the setup below:

    Ajust Compound Angle.JPG Back-Forth with Compound.JPG Indicated Value.JPG


    OK, almost ready to have some fun.... In the next part (coming tonight) we need to flatten the back then cut the taper. See you in a while...

    Recessed Shoulder Taper.JPG Shoulder Depth 1.jpg Shoulder Depth 2.JPG Measure Taper Base Diameter.JPG Ajust Compound Angle.JPG Back-Forth with Compound.JPG Indicated Value.JPG
     
  10. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    I made a chuck adapter several years ago that had to have the taper nose on it for an A-20 mount. It was 26" in diameter with a 12-1/2" ID hole in it. The register diameter was 16.250" diameter. All I had to measure it with was a veriner caliper. It must have worked, the customer never blinked an eye over it.
     
  11. Ray C

    Ray C United States Moderator Staff Member Moderator

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    All,

    I've deleted the text from this post and split it into 2 parts and re-posted it. Some kind of weird error occurred with the attachments... The written text did not change.


    Ray
     
    Last edited: Jan 4, 2013
  12. Ray C

    Ray C United States Moderator Staff Member Moderator

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    OK, it seems the attachments in the last post went south for some reason. Don't know why; nothing different was done than before. I'll see what can be done and possibly re-post if needed...


    Ray
     
  13. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Since something went wrong with the last post, I'll cut/paste and break it into two posts denoted: Part 4 1, 2. Hopefully that fixes the problem.

    Part 4-1:

    When I first checked the plate, it looked pretty crude overall -spun fast and dirty. Using a parallel, it was easy to see it was everything but flat. You could cut the back on the lathe but, I love using the surface grinder and happen to know that few things are prettier than surface ground cast iron. Turns-out, it was not flat by a good 7-8 thou as that's how much I recall taking off to to get even cuts across it. See the pics on how to check for flattness and the finished work (ain't that purdy?).

    Very Flat Back.JPG Back 1.JPG

    OK, now for the real work. It's tedious and you'll probably need to mount/unmount your chuck several times. The name of the game is to go light and not take off much. We're going to use the dimensions we calculated before as a starting point that we back off from.

    First, you need to mount the back (taper side out to make the cut) very, very precisely. It must be flat and centered. Of course, I used a 4J and had to thump it into position to achieve flattness. It's done in several steps. First, get it very close to center by reading off the inside of the taper, then read off the flattend surface to make it flat. Go back and forth until it's a perfect as you can get it. -Took me a good 5 minutes or more for each attempt and I had to re-do this 3 times to get it nailed. Note that since this is a staged stot, you'll see the TDI reading off the recess cut that was done earlier. The recess cut is actually coming up next.

    Here's how I indicated. See Pics.

    Center as Flat.JPG Center as Round.JPG Thump Into Position.JPG

    .... Continued ...

    Very Flat Back.JPG Back 1.JPG Center as Flat.JPG Center as Round.JPG Thump Into Position.JPG
     
  14. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Part 4-2:

    Now, remember that 0.100" shoulder recess we measured before, we'll cut that in now. Actually, I cut it a few thou less than 0.100 and the radial depth doesn't matter because, the nose taper doesn't contact that part of the back. The little edge that we're making will be the starting point of the back's taper and we'll turn that taper to about the diameter we read directly from the base of the nose spindle. Remember, don't use my numbers. Calculate your own off your equipment.

    To make this cut, I moved the whole carriage to the left just a few thou shy of 0.100. Depth is controlled by pulling in the crossfeed. Go slow, take your time, measure carefully, work smart and keep your mind on your work. Here's the edge cut:

    Shoulder Edge Relief.JPG



    Now cut the taper. Go at it real light and keep making measurements at the very edge to just a few thou less than the diameter of the base of the spindle. In my case, that was 2.475 and I think I stopped cutting at 2.472 or so.

    Here's the cut and a pic of where I read the diameter off of. It helps to slather a little layout fluid when you're ready for a test fit. The goal, it to adjust the diameter of the plate taper such that it's snug on the nose taper yet allows the flat backs to come into contact. Go cautiously and keep your head on your shoulders. You may have to break apart, do a test fit and re-center to take more off. See the pics:

    Cut Taper with Compound.JPG Forcing Cone Taper.JPG Test Fits.JPG Measure From Taper Edge.JPG



    Once you get a perfect fit, install the lugs, mount your back, trim the shoulder flat to accept the the chuck, trim the side and break the edges. I like the side to be just a bit higher than the chuck body. Your call. (Edit: Don't strike witness marks now). Edit: It's a good idea to trim the side to the diameter you prefer now. Coming-up, we'll check the pieces for static balance so, excess material should be removed before balance checking or adjustments. See the pics:

    Trim Side.JPG Trim Shoulder.JPG


    OK, that's it for tonight... We still have much to do. You can mount the chuck now for grins but we still have more work to do like verify flattness, check for static balance and centering... I center different types of chucks differently... We'll get there. -And yes, I actually use those cheap HF carbides on CI because I hate ruining my $4.00 tips. They actually work OK.


    Ray...

    Very Flat Back.JPG Back 1.JPG Shoulder Edge Relief.JPG Cut Taper with Compound.JPG Forcing Cone Taper.JPG Test Fits.JPG Measure From Taper Edge.JPG Trim Side.JPG Trim Shoulder.JPG
     
  15. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Part 4-2 (continued)...

    Also, while trimming the side and flattening the shoulder, the center should be re-bored...

    Rebore Center.JPG


    Please note that in the previous post, two pictures are repeated at the bottom. I have no idea why. They are not shown in the editing panel.

    Ray

    Rebore Center.JPG
     
  16. Ray C

    Ray C United States Moderator Staff Member Moderator

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    OK Guys... The silence is deafening and I'm wondering if this is coming across and well received or if this procedure is being dismissed as lunacy...

    In any event, I'll continue later this evening on how to verify the chuck and do basic static balancing checks and adjustments. The balancing part requires a reasonable balancing apparatus (easy enough to make) and carefully testing on the lathe at different RPMs.


    Ray
     
  17. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Thanks for showing a super job of "tuning up" the spindle nose and back plates for yor lathe. It's a shame that you have to chase problems and fix "junk" that is new, that should have been correct to begin with, from the factory of the far west.
     
  18. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Wheew.... OK, at least you guys can see this. I was wondering because of all the weird problems posting the pictures if the posts weren't even reaching anyone...

    As far as the quality issue... Wow, what to say... The whole world is in a fast-paced mode and people seem to accept quantity over quality. Everyone (US, China, etc) is in a hurry to finish the product with as few hours of labor as possible -and so the burden of fine detail is left onto the consumer. In this case, at least the problems can be corrected. Heck, some things we buy these days can't be fixed so if it doesn't work, you're out $$$. ... If all you have are lemons, make lemonaide. In this case, I'll choose to look at it as an opportunity to learn and do new things. These days, I've had to try to find the sunny side of things -because if I don't, I'll have too much to be sad about :)).

    Ray

    PS: Writing up the last segment for tonight. Will post in an hour or so. -The dog is bored again and we both need a walk.


     
  19. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Part 5:

    Put your chuck together. No matter how you mount it, the rim of the back plate should center pretty well -provided you didn't cut the taper too big. If you did, you haven't damaged the structural integrity but, you'll need to use a DI to center the plate while tapping with a mallot while the D1 lugs are just firm but not tight. Also note that the D1 lugs should not be screwed-in too deep. Often times, the threaded holes are not straight and they stick out crooked. That can influence how the faces mate-up. All the ones I've seen have a line cut in them. That line should be 1 turn above flush with the backplate.

    Once again, safety... disengage gears, apply safeties etc...

    So far we've been working our way from the left to the right (spindle face, back/spindle interface, chuck shoulder...) etc... We continue...

    OK, wipe all swarf off all mating surfaces and reassemble the chuck and mount on lathe. Remove the jaws and put a TDI at the outter edge of the chuck face. Spin the chuck by hand and verify that each segment (in this case 3) is perfect. Over the years, of my 5 chucks, only one was dead on. All others were out a half thou or more -and that don't cut it for me. Now if your chuck face is all banged up, you need to set your expectations of how good a reading you can get... If you're happy with the readings, you can skip a little ahead. See the pic:

    Check on Lathe.JPG

    If you're not happy with the readings, most likely, the issue is with burrs, swarf somewhere, or either the backplate or, the width of the chuck body is cock-eyed around the diameter as shown:

    Body Problem.JPG

    How to check who's the culprit... You really need a granite table for this. A piece of glass or something else that you think is flat -probably is not. I should be using a proper height gauge but I don't have one so I get by with a tenth's TDI and a standard mag fixture. Wipe all your surfaces very clean and first check for small burrs or swarf. Slide the "height gauge" around on both the body and back as shown and find-out who's the culprit. If the body is showing a problem, flip it over and check the rim side. Areas with drill holes are notorious for having a raised ridge. Take corrective actions. In one case, I had a body where the backside needed to go in the surface grinder. Most of the time, it's a burr or hole ridge. See pics:

    Check back on Granite.JPG Check Body on Granite.JPG

    You need to work on correcting the problem but before taking any drastic action, go back and check the basics like the spindle face, bearings etc... Proceed with caution and with your wits about you.

    Once things are corrected we can go on to basic balance checking. Next part, coming up.

    Check on Lathe.JPG Body Problem.JPG Check Body on Granite.JPG Check back on Granite.JPG
     
  20. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Part 6: Balance checking and improving the odds...

    You need a simple balancing apparatus but it doesn't need to be ultra precision but, should be half-decent. Here's one I made and it gets used a lot. Nice feature is that the legs are adjustable for height when dealing with a shaft with different end-diameters. Also has a 3-point base for quick leveling. This one has nice roller bearings at the ends of those studs and it can detect as little as 1 gram on a 40lb chuck. I don't bother to balance to that level though because the jaws at different diameters always throw things off. That too could be corrected but it's never been enough of a problem for me to lose sleep over... Pic shown:

    Balance Beams.JPG


    Now, get a half-decent shaft (doesn't need to be too special) like a good, unbent boring bar and make a plug with a centered hole that fits in your backplate. Check the backplate and mark the heavy end. Put the bar in the chuck by using the jaws (w/o backplate) and find/mark it's heavy side. After doing about a dozen of these things, I've never encountered either a chuck or backplate that balanced right off the bat. See pics:

    Find Back Heavy Side.JPG Find Body Heavy Side.JPG


    Clean all the surfaces again and put the the two pieces together with heavy sides opposite. This increases your odds of ending-up with a balanced unit. Of course, your holes may already be drilled and there's only so much you can do to get the heavy sides opposite. Try it a few different ways if needed and it's your call if you decide to re-drill holes in a different spot. See Pic:

    Mount Opposite Sides.JPG

    Once reassembled, remount the overall assembly on the bar using the jaws and check for overall balance. How'd it turn out?

    We haven't finished centering things but, you can run it on the lathe and play around. Make sure your bolts are tight and jaws either removed or safely installed. Work your speeds up slow to fast even if your chuck is pretty balanced because dynamic balance could still be off. I have corrected those kinds of things based on my own theories. So far it's worked but I don't claim them to be bullet-proof. Also, the type of correction that's made depend if it's a universal, collett or independent chuck as well as how out-of-balance it is. -Not sure if that aspect is related to Metrology but, I will mention and show the kinds of corrections I have made with the understanding that this is a difficult area to deal with and your mileage may vary...

    Going forward, all things related to balancing are your call if you decide to do it or not. I can't guarantee results and I'm only showing you what I personally did to my chucks, by buddie's chucks and the chucks at the prototype shop at work. I don't want to cause anyone grief or upset.

    That's it for today.

    Ray

    PS:
    ... How are things going for everyone?

    Balance Beams.JPG Find Back Heavy Side.JPG Find Body Heavy Side.JPG Mount Opposite Sides.JPG
     
    Last edited: Jan 4, 2013
  21. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Some obligatory statements of common sense and safety...

    If you're taking your chucks apart, make sure you're tightening the bolts adequately when testing them on the lathe and work your speeds up slowly -even (especially) if you have new chucks.

    Don't run your chucks with the jaws wide open. Make sure you have plenty of engagement with their acme screws or scrolls.

    If you're not ready to make precision cuts on your backplates etc, wait until you've practiced enough to proceed. Maybe take some drops and do some trial runs and make a backplate first before chopping-up your originals.

    EDIT: And if you're happy with your chuck the way it is, leave well-enough alone. You know what they say... if it ain't broke, don't fix it -or risk fixing it until it is.

    -And don't mess with your spindle unless you're willing to suffer the consequences.


    etc, etc, etc...

    Sorry to be such a nit about this and I suspect you know where I'm coming from...

    Ray
     
    Last edited: Jan 4, 2013
  22. GaryK

    GaryK In Memory Rest In Peace

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    That's some great stuff Ray!

    Now, if I could only get you down here to do all of my chucks!

    I would really enjoy seeing you do your thing. :))
     
  23. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Thanks for the kind words, Gary...

    You'd have more fun doing your own chucks rather than watching someone else do it. I admit that taking some of those measurements and making the cuts aren't easy. -And getting that disk flat and centered for the taper cut is critical. Very difficult geometries to work with because 2 things need to come together perfectly. Undercut is the way to go -hard to stick metal back on once it's been shaved off. Do this when your comfortable and ready for it. And I must admit, I screwed-up one of my plates doing this. How? Instead of cranking in the compound to make the taper cut, I cranked-in the carriage. -Happens! No biggie, I just made another one. Making them ground-up is easier than modifying one. Finding a piece of stock thick enough is the hard part :angry:.


     
  24. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Guys,

    Sorry for not finishing the post yesterday about centering/balancing the 3 jaw. I was having an "off-day" and aside from that, needed the chuck to finish a job. I took pics of re-centering it and will post later today -probably early evening.

    Later on, I think a thread on importance, detection and symptoms of out of balance chucks is in-order. I'll post my collective observations but don't have answers for some of my own questions... Anyhow, I don't want this thread about D1-x measurement to get "contaminated" with chuck centering and balancing.

    Also, I will start-up a thread about how to inspect, calibrate and do calculations using the compound angle markings...

    How's that sound?


    Ray
     
  25. tripletap3

    tripletap3 United States Active User Active Member

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    I have been following along and have been taking measurements. Looks like my spindle is dead on and I am not going to touch that. The backing plates on the other hand are machined horrible. Easy fix when I get my stuff from QMT!
    Oh well someday.
     
  26. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Ok guys, I'm going to make this quick and talk about an easy-case balancing and a few thoughts about body/shaft centering. Will start a thread later on specifically for balancing and centering issues.

    Safety Issues: When working on your chucks, make sure the jaws are safe, snug-up the bolts well during tests, work speeds up slowly -And don't leave keys or allen wrenches in the chuck. Remember, if they're not in your hand, they're on the table -but not in the chuck.

    Also, this involves modifying your stuff... Don't do it if you're not comfortable or willing to take the risks.

    Part 7:

    By this time, your backplate fits well and centers about dead-on. You've checked the static balance of the backplate and chuck body and the opposite heavy sides have been put back together. When testing chucks on the machine, I leave the balance rod locked in the jaws of the chuck. Note that jaw position impacts the balance. Obviously, the further they are open, the more it impacts balance. I have weighed-out jaws on balance scales and they're far from uniform. It causes noticeable differences in balance but only with an empty chuck. If you're cutting big diameter stock, chuck balance will be impacted anyhow in ways you cannot predict. I have had situations whereby rotating the workpiece a little made a vibration go away. This is not idel and woudn't fly for high-end production/CNC machines but, we can get-away with it on manual homeshop stuff.

    With the opposite heavy sides put back together, with any luck, the chuck has a more neutral balance than it did before. If you haven't already, tighten the bolts and test it on the lathe working the speeds from slow to fast. If you have little to no vibration at all speeds, quit while you're ahead and take the afternoon off. In the absence of a dynamic balance machine there's not much more you should do. If the chuck is really out of whack, it can shake the machine pretty good. -That's what the emergency stop switches are for!

    If you have vibrations which you know will show-up on the workpiece, a small amount of correction can be made in one of two ways. If there's a gentle settling toward the heavy side, you can either drill divots in the backplate on the heavy side or, if you have a chuck that has internal cavities, you can internally add weight to the light side. I've done both methods with good success. I won't be discussing in this thread how I added internal weight.

    When finding how much the chuck is off, I've found it helpful to tape coins to the light side. This will give you a ballpark idea of how much drilling to do. You need to wrap tape all the way around because of the oily chucks...

    One thing to note: A chuck that is perfectly statically balanced could shake like hell when spun at-speed. -Dynamic imbalance rears it's ugly head -and sometimes at one speed but not at others. The point is this: Don't keep drilling divots until the static balance is perfect. No, instead, drill a little divot that helps the static balance a little then, go back and test at all speeds on the machine. If you have a very heavy chuck -too bad! Do the tests anyhow. Proceed and make adjustments conservatively. If you get to the point that the chuck is statically balanced but still shakes, read the next paragraph.

    It's entirely possible you have a no-good chuck no matter what you do. -It's never happened to me or anyone I know but, from a mathematical and physical point of view, it's entirely possible. Of course, someone with the abilty to do dynamic balancing could identify the problem area(s) [note the plural]. I have a technique to approximate this but, it's not tried & true.

    That's about it for balancing (as far as this thread goes). Here's a picture of divots in one of my back plates. Note that I spread them out a little. A Word of Caution About Divots: -Not that you should not be putting your hand on the chuck when it's spinning at any time -But, if you happen to get your pinky in that divot hole, you're going to have one finger shorter than the other. Drill the divots shallow. BTW: the same injury could occur due to the bolt-hole recesses. -Get it? -Don't put your hand on the chuck. I did it once and ended-up with 7 stitches (fortunately, I know how to suture myself but my wife had to tie the knots).

    Anyhow, this chuck now balances very well at most speeds when not loaded with a workpiece. BTW: One of the reasons, I'm switching my machines to 3 phase is so I can tweak-out vibrations with frequency control.

    Balance Divots.JPG

    Part 8 coming up -a quick thought about body vs shaft centering when mounting a chuck to a backplate.

    Balance Divots.JPG
     
  27. Ray C

    Ray C United States Moderator Staff Member Moderator

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    OK, here's the last of it...

    Part 8:

    The back now centers well and now the body needs centering. These are my own practices and I'm not claiming them to be the best or only way. And mind you, this is geared toward homeshop manual lathes and "average" chucks. The situation probably changes with high-end equipment and high-dollar chucks...

    For a 3J chuck, I don't center the body perfectly with the backplate but rather, center the body based off a known shaft in it's jaws. Why? First, all jawed chucks have their issues. Swarf can throw them off and with 3J's the scroll and ring gear may not be perfect. Every one I've used may center well at some diameters but not others... With 4J chucks, I center the body reading with a DI on a smooth part of the body.

    Standard Safety Issues Here: Watch the keys, allen wrenches, power switches etc...

    Once the chuck is on the lathe, mount a good rod and if it's dead on, tighten the bolts and go buy a lottery ticket because it's your very lucky day. After that, loosen it's holding bolts just enough so a tap with a mallet can make an adjustment. Of course use a block of wood etc as a buffer. For 3J, hand spin the chuck and make body adjustments until it's centered while reading a TDI indicating off a test rod. Simple as that. If the shoulder on the backplate is cut very tight, you may have to tweak it to make body adjustments. Don't bang real hard on the body -the spindle bearings don't like that.

    Again, for 4J, DI off the body, make adjustments with the mallet then tighten the bolts. After that, you can center a shaft and admire your work. Of course, it's possible that taking a reading 6" down from the shaft that everything is off again. Since we know everything else (spindle, backplate etc) is flat, the problem is due to jaws not holding square. -That's another issue to talk about later. One thing I will say, if you want a shaft perfect, most chucks won't get you there. You stand a chance with a good collet chuck and can only clinch it by turning between centers (if possible). Life isn't perfect...

    Here's some obligatory pictures. I'm showing a collet chuck because the 4J is on the mill at the moment. -and keep in mind that I broke the allen-wrench rule because nobody was around to take the picture -and I only have 2 arms. BTW: My collet chuck is so dead-on, I can center off the body or off the shaft and get pretty-much the same readings. Differences are due to the collets themselves. When I "body center" a collet chuck, I read off the taper the collet sits in -not the body. This $175 chuck was well made!

    ... That's pretty much it. This was intended to pass on some of my observations and techniques (for better or worse) and maybe to help set expectations for folks that are new to lathes. -And again, I am NOT a professional and all the above is worth what you paid me for it.

    Ray

    3J shaft centering.JPG Body Adjustment.JPG

    3J shaft centering.JPG Body Adjustment.JPG
     
  28. outsider347

    outsider347 United States Active User Active Member

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    Outstanding info here Ray. I even understand most of what you are doing

    Anyway, my lathe is a basic screw on Atlas spindle & I know it has dimensional issues, chuck related.

    Now I think I can better locate the problem areas & have confidence to fix it. Every little bit helps

    Keep up the good work & basic verbiage for us rookies
     
  29. Ray C

    Ray C United States Moderator Staff Member Moderator

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    Glad it's helpful. If you encounter issues as you address your own problem, don't be afraid to post questions.


     
  30. MikeWi

    MikeWi United States Active User Active Member

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    I've greatly enjoyed reading this thread Ray, and as I'm receiving a new lathe at the end of the month, it helps me to check up on things before it gets used. I'll need some practice before being brave enough to do any adjustments, but hopefully it won't be too far off out of the box. :)

    I'm learning an amazing amount on this site. This is better than any book, although I always collect all sorts of books on my hobbies. :)
     

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