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  1. #101
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    Quote Originally Posted by texasgunsmith View Post
    Just doing a preliminary check with test bar runout was like .005".
    So, you have TWO test bars, one for each machine taper?

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    Quote Originally Posted by SLK001 View Post
    So, you have TWO test bars, one for each machine taper?
    I also have 3mt, 4mt, and just recently got the 5mt. Smaller stuff like 3mt and 4mti bought cheap ones off ebay. The 5mt i used Brian Miller again. Price in the ballpark of the South Bend test bar. I wanted a higher quality test bar for that as its a pretty serious project for me, and I'd like to get it dialed in tight.

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    My curiosity could get the better of me one day. For the MT3 ones off of ebay did you get one from India? Quality?

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    Quote Originally Posted by Kevin T View Post
    My curiosity could get the better of me one day. For the MT3 ones off of ebay did you get one from India? Quality?
    Yea, the India ones. Value wise, they are hard to beat. Especially as a seldom used item. They've been straight so far, and were not banged up in shipping. Taper dimensions seem correct.

    For the Special South Bend 3MT, there's no choice, you have to buy American. The 5MT I could have taken a shot on the India stuff, but I didn't want to mess around. And I like Brian's work, so it made choosing easy. Its always a balancing act on budget vs need, on this I felt it was the right call, with the nature of what I'm doing.

    Though I have not tried, I would think on headstock, if you have collet adapter you could run a fairly good test as well with a precision ground bar in a collet.

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    Quote Originally Posted by texasgunsmith View Post
    Yea, the India ones. Value wise, they are hard to beat. Especially as a seldom used item. They've been straight so far, and were not banged up in shipping. Taper dimensions seem correct.

    For the Special South Bend 3MT, there's no choice, you have to buy American. The 5MT I could have taken a shot on the India stuff, but I didn't want to mess around. And I like Brian's work, so it made choosing easy. Its always a balancing act on budget vs need, on this I felt it was the right call, with the nature of what I'm doing.

    Though I have not tried, I would think on headstock, if you have collet adapter you could run a fairly good test as well with a precision ground bar in a collet.

    Can you post a link to those India test bars?? I can’t find much on eBay.

    TIA
    BB

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    Quote Originally Posted by BigB View Post
    Can you post a link to those India test bars?? I can’t find much on eBay.

    TIA
    BB
    Posting off my phone is trickier, i usually post from pc.

    Searching morse taper items can be odd in search depending on how seller listed. Try a variety. Mt3, 3mt, No 3 mt etc

    Here's one, but i always check seller activity and such, might shop around:
    3MT Lathe Alignment Test Bar MT3 Alloy Steel Over All Length 335mm 13-3/16 Inch | eBay

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    Quote Originally Posted by BigB View Post
    Can you post a link to those India test bars?? I can’t find much on eBay.

    TIA
    BB
    Just search for MT3 lathe test bars all the choices are from India

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    Quote Originally Posted by texasgunsmith View Post
    ..."For the Special South Bend 3MT, there's no choice, you have to buy American. "...
    So the Tailstock MT3 is not standard MT3 in a 16"?

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    Quote Originally Posted by Kevin T View Post
    So the Tailstock MT3 is not standard MT3 in a 16"?
    The tailstock is a normal MT3 taper. The India test bars are fine for it.

    The headstock is not. The headstock is like a shortened, snub nose mt5. I presume they used "3MT" in its description, Special South Bend 3 Morse Taper, because the taper per foot was the same at .602/ft. But the diameter on large end is in between mt5 and mt4, at 1.629".

    They should have just called it "South Bend taper No 3". Its dimensions are nothing like actual morse taper specs.

    If you look at the chart for regular morse tapers. Look at taper per foot, and large end diameter.

    429.jpg

    That chart is from a real handy link to see specs on many common machine tapers, morse, jarno, B & S etc:
    Dimensions of Standard Tapers - LittleMachineShop.com

    I was looking for where I saw the spec on Special South Bend Taper, this guy had a nice description from 2006, post #5:
    16" SB spindle taper

    I presume the headstock was proprietary because they could get away with it, from a business perspective. Selling in house, special made adapters. Instead of mt5 to 5c collet adapter.

    The tail stock would be a harder sell if you tried that. Customers would not purchase a lathe with a special weird taper for centers and drill chucks. That's my guess anyway.
    Last edited by texasgunsmith; 10-29-2020 at 04:00 AM.

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  14. #110
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    Just a little further expansion on the headstock spindle taper.

    The spec sheet 7324, Tooling Dimensions, is here:
    South Bend Lathe Works - Publication Reprints - South Bend Tooling Dimensions Spec. Sheet 7324 | VintageMachinery.org

    The actual pdf link:
    http://vintagemachinery.org/pubs/1617/17500.pdf

    And relevant pics from that:

    432.jpg 431.jpg

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    Having already checked runout, as shown in a previous post, we'll be getting back to the alignment of the headstock.

    In checking the first axis I have dial indicator set up on the compound rest. I'll be running the length of test bar from the 12 oclock position. I'll run a pass up and back, watching that indicator returns to zero.

    Using bull gear pin as my marker, I'll rotate spindle 90 degress after each two way pass. Doing that 4 times, to reach a full 360 degrees. Then average the 4 readings together for my overall reading.

    Guessing most of you know, but on a dial indicator you have a + and - on either side of the indicator. The needle moving toward + would indicate the work, in this case test bar, is getting closer to the indicator, or rising up. While the - would indicate work is getting lower from the indicator position.

    Cant see gauge well, but I'm set up at zero close to spindle:

    433.jpg

    In moving just a couple of inches, I'm beginning to see the test bar rise with a +.001".

    434.jpg

    In this pic, I have reach the end of the test bar for a +.0025".

    435.jpg

    Rotating spindle 4 times, re-running the test my average is a +.0028".

    That means the spindle is slightly pointed up, skyward. The is truly an anomaly on a used bed. On a used bed, with wear under the chuck, I would expect a minus. Because saddle will gradually rise as it moves toward tail stock end. With a saddle rising, it would give the appearance the test bar is going lower.

    A true oddity, because all 4 tests at 90 degree rotations, the test bar always read a plus moving toward tail stock. Anyway, the number is damn near +.003" on an upward tilt.

    Moving the dial indicator to the 9 oclock position, we'll check the other axis. Again rotating 90 degrees a total of 4 times, and averaging the number to account for runout.

    Set up at zero close to spindle.

    436.jpg

    Traveling the length, in this pic we see a +.002"

    437.jpg

    Rotating and averaging, my final number is a +.0015". Which means the headstock is making a slight turn toward front of lathe.

    While I don't expect to hit a true zero, my goal will be to try to get as close to zeroes as I can. I will lift the headstock and shim to try to adjust it out, on both axis.

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    Do you know if the bed and the HS are original?

    Instead of shimming the HS, pull the thing and search for embedded chips in both the HS and ways. Look very closely, because if there is one, it will be difficult to detect.

    Also, do you know if the HS is really pointing up, or is it the ways falling away?

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    Quote Originally Posted by SLK001 View Post

    Also, do you know if the HS is really pointing up, or is it the ways falling away?
    All real good thoughts and questions. Didn't want you to think I'm ignoring it.

    But I'm kind of slow typing and posting on a good day.

    I'm working right now. After work I'm actually meeting up with another forum member, which is about a 4 hour drive each way. Could be real late when I'm back. With a young one still at home, not sure how the holiday will play out tomorrow. . .

    Kind of an involved answer to spit it all out. Hopefully get back to it between late tonight and Sunday.

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    Quote Originally Posted by SLK001 View Post
    Do you know if the bed and the HS are original?
    The attempted quick answers for your 3 questions.

    One, I suspect bed and HS are original. Bed has stamped serial, plus tagged with war time tags, one of the tags specifically match the customer of purchase on serial card. HS is cast iron spindle bearings, maybe by 1947-48 I think they were going to all copper. Not impossible, but if HS were replaced would guess with copper bearings. Lastly, nothing jumped out at me as painted different on underlying coats. Also the overall wear seems to match, not like machine was reconditioned, My guess is light to moderate use when it was young, not heavy war time, or post war heavy use.

    Quote Originally Posted by SLK001 View Post
    Instead of shimming the HS, pull the thing and search for embedded chips in both the HS and ways. Look very closely, because if there is one, it will be difficult to detect.
    Do to my work or career, I'm pretty OCD about checking for dirt, nicks, dings etc on mating surfaces. Some exactly for alignment issues, others for sealing surfaces. I went over the both mating surfaces prior to setting HS.

    Quote Originally Posted by SLK001 View Post
    Also, do you know if the HS is really pointing up, or is it the ways falling away?
    Short answer, no, I don't know. But for all intents and purposes, it doesn't matter in this case. I'm not scraping the bed, so figuring out the answer is not a high priority. This is one of those 'gray areas' I mentioned in post #97, I'm shooting for the best accuracy in the most used area, or the middle ground between most used area and total bed length.

    I said 'short answer', because for your last question there is a long answer, and the question itself cracks the door open to more questions. Recondition or do what you can ? What's the budget ? Value of machine as is, as well as reconditioned ? personal goals ? on and on.

    One question comes to mind when a cranky old timer replies to a new guy posting his "rebuild": 'Is it just a pretty paint job, or did you doing anything to check or improve accuracy ?'

    While the delivery of the question is often harsh, the fundamental nature of the question is a good one. Its a push to improve, or at least know an answer. How accurate can we run ?

    I've done a bit more than just paint and lube to this lathe . But even in the title of thread I didn't want to say recondition, or even rebuild, as it may imply recondition. And the more knowledgeable would associate that with grinding and/or scraping everything.

    My general skill set is very good in many areas. But it does not include scraping, at least not as of Nov 2020 . That means I would need lots of dollars to recondition. Got quotes on my other 16". In the vicinity of $4k to $6k. On this machine that would put me at about $7k to $9k cash investment. noone pays that for a South Bend Lathe as of today in 2020. Now I may attend a Richard King class next go around, but its currently outside my skill set.

    Running alignments and making adjustments is in my skill set. Also I didn't invent test bars, shims, or any of it. Its a legit alternative in making improvements. The same as shimming a tail stock. Its just from a craftsman perspective, scraping things in has a more distinguished respect as its sort of an art really.

    So I have two choices, leave as it is, or do something about it. The .003" rise from 12 oclock will more directly affect drilling and boring, and centers in TS. The .0015" from 9 oclock will also affect those, but will also produce a taper on longitudinal cuts, at about .00075" over 6".

    By making adjustments, my goal is to get inside of .001" at both axis. I fully expect the end result to be inside of .0005" over 6" on longitudinal cuts.

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    Quote Originally Posted by texasgunsmith View Post
    ...One question comes to mind when a cranky old timer replies to a new guy posting his "rebuild"...
    I haven't been cranky, have I?


    Quote Originally Posted by texasgunsmith View Post
    ...So I have two choices, leave as it is, or do something about it. The .003" rise from 12 oclock will more directly affect drilling and boring, and centers in TS. The .0015" from 9 oclock will also affect those, but will also produce a taper on longitudinal cuts, at about .00075" over 6".

    By making adjustments, my goal is to get inside of .001" at both axis. I fully expect the end result to be inside of .0005" over 6" on longitudinal cuts.
    I have never been a proponent of restoring any of the old SB lathes to "factory specs". Cleaning and refelting is one thing, but a complete "restore" is a whole different animal. They simply aren't worth the effort. What are you planning to do that has NASA specs anyway? I vote "leave it as is..."

    Here's why: When drilling, the drill will find the true center. Also, drilling on a lathe is not a precision operation. Boring will have various diameters as it moves in the hole, but not by much. See attached photo.

    Quote Originally Posted by texasgunsmith View Post
    ...but will also produce a taper on longitudinal cuts, at about .00075" over 6".
    I believe that you are grossly over-estimating the taper on your cuts. See attached photo.

    I would put most of my efforts into finding out the cause for the horizontal movement of the test bar, not the vertical. Try tightening the HS bolts more, one at a time, to see it that pulls the horizontal variance closer to what you want.

    Here's a chart on the effects of bed wear on a cut. The chart isn't my work, but I do believe the results shown are valid.


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    Quote Originally Posted by SLK001 View Post
    I haven't been cranky, have I?
    You come off sort of crisp pretty often , and your humor is a subtle affair that many don't catch I think. But I wasn't thinking of you. For the most part the SB section is pretty civil, but we occasionally have long time members pop in and their comments can be a bit rough. But its not isolated to the SB section, similar responses to new guys in other sections is what I had been thinking.

    There's a percentage of the forums that are reminiscent of this :

    322.jpg

    Quote Originally Posted by SLK001 View Post
    What are you planning to do that has NASA specs anyway? I vote "leave it as is..."
    I don't have a problem with that line of thought, or your accompanying ideas there. I just feel if I can tighten it up, then I will. In the grand scheme of tooling, techniques, and other means that we try to improve, I think its very cost effective and worth the result.

    Quote Originally Posted by SLK001 View Post
    Here's a chart on the effects of bed wear on a cut. The chart isn't my work, but I do believe the results shown are valid.
    I agree with this in relation to my reading of about .003" from the 12 oclock position. However that chart is solely based in principle from that 12 oclock reading, or rise and fall of ways. And how much, the up/down will effect reading of 9 oclock.

    My actual reading from the 9 oclock position of .0015" per 12", or .00075" per 6" travel, will be a mirror image of what a lathe tool will do, as we set lathe tools at centerline at 9 oclock.

    Also consider this: that .0015" reading was a + reading. By rights, it should be a minus. The 12 oclock position being high, I would not be at true centerline. So the .0015" should be larger once the 12 oclock reading is at zero. So headstock/spindle is surely turning slightly toward front of lathe.

    I don't want to thread jack myself, swing way off topic, or write a novel . But I feel my fundamentals are pretty good in thinking. I'm not a machinist per title, but have done machine work in relation to diesel engine repair/overhauls, valve and seat grinding, boring, line bores, and alignments. Its not my every day gig, but varies from heavily hands on, to confirming others' numbers.

    I feel like I've worked the periphery of machine work, while kind of backing into it, verse working from the inside out. I'm not all knowing or seeing, but from my perspective its all relative, and many things skirt each other for the same fundamentals or processes.

    A little while back Mcload had a thread that turned out quite large. And from a thinking perspective was excellent in considerations and some back and forth arguments. In it I learned some new things:
    Calibrating 9" Model A With Tailstock Alignment Bar

    From that time I have been slowly collecting information on items I do know. I plan on some point a general thread covering different thoughts and considerations in alignment. Not just lathe or machine shop related, but more varied in principles. Though these principles could be applied to machine shop machines. In part I started an off topic thread to set up this sort of alignment thread. You can get an idea of the direction from posts #33 and #34 here:
    O/T V8 EMD Engine

    From those sort of alignments the goals are to get to single digit .001"s. Where a lathe we are trying for single digit .0001"s. Most principles are the same, though some techniques may vary. Those packages are quite serious and expensive. With serious consequence if out of align. And many use shims. My feeling is, if I can use shims on a 6 figure package, surely I can use shims on a $3k lathe .

    323.jpg 324.jpg

    Expanding more into that is the line bores. Again alignment issues. Also questions and checks for deflection readings. It needs to be tight numbers. Looking down the journals of a line bore:

    325.jpg

    A minor consequence of being slightly out of alignment, or having deflection on the shaft. We can see minor wear differences in the bearings. These are the upper main bearings where little or no wear should be seen, bearings are lined up in order, front to rear of the line bore:

    326.jpg

    Point being that I do think there are different ways of doing things, but general principles and results can be expected. Pushing for better results is not always worth while, but where time and cost effective it can be worth it.
    Last edited by texasgunsmith; 11-01-2020 at 08:58 PM.

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    Except that those devices were designed to be shimmed. Your headstock was not. That's why I wanted you to be doubly-triply sure that there wasn't something embedded in either the ways or the HS. If the headstock is not pointing exactly down the center line, then something is wrong. It would be a good idea to fully understand what that "wrong" is. I say this, because there is no way to shim the HS to correct for that. Up and down, maybe - side to side, not a chance with a prismic set of ways.

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    Quote Originally Posted by SLK001 View Post
    Except that those devices were designed to be shimmed. Your headstock was not. That's why I wanted you to be doubly-triply sure that there wasn't something embedded in either the ways or the HS. If the headstock is not pointing exactly down the center line, then something is wrong. It would be a good idea to fully understand what that "wrong" is. I say this, because there is no way to shim the HS to correct for that. Up and down, maybe - side to side, not a chance with a prismic set of ways.
    What I can tell you is iron changes over time, and can grow slightly. An example would be the engine block in my previous post, showing the line bore. What many don't know, and is surprising when you see it, is running the line bore to STD(standard) when it was already originally standard !

    An old foreman called it 'magic metal'. I've seen where a bearing spun in one of those journals. The process is to install a new main cap. And run the boring bar to STD. Surprisingly, you will actually cut material from the engine block side, the whole width of journal, again at STD. And this would be on cast iron 15 to 30 years old.

    Now take a cast iron bed and headstock that's pushing 80 years old. No doubt there is some distortion. And I don't mean bed wear or other wear, just minor distortion in the cast iron itself.

    As to whether a headstock can, or should be shimmed. . .Again scraping would be preferred. But people can and do shim headstocks to tighten them up. I've done it myself on my last 16" the 2H Turret. And you want to know the really funny part ? I absolutely believe it was shimmed by the factory, South Bend themselves.

    Consider an engine lathe tail stock. Probably scraped in from factory, with no shims originally. But the design allows the the TS to be separated from its base, and shims added to compensate for wear.

    Now take a look at my turret tail stock:

    329.jpg

    The turret TS has 3 moving sections. Base to bed, center section to base, and the head rotates. All 3 can and do wear. But there is no possible way to shim it. What happens when it drops .005" over time ? Its heavy and more expensive than a regular TS.

    The answer was to shim the headstock from factory, alot. When I tore that lathe down there were shims stacked under it. During the entirety of the build, I thought for sure with wear on TS I was screwed, would need to make something, or replace it.

    During the build up when I finally got to it, I mounted headstock straight to bed, no shims. The headstock was low ! I had in the area of .030" to .035" under chuck side just to reach center of TS.

    Also the headstock is not mounted flat its entire length on bed. Each of the four corners of headstock are mounting feet about 3" long. By adjusting those mounting feet, you can manipulate spindle direction.

    To get a headstock to turn slightly, you need to shim just one side of vee way on chuck side. It will pull HS one way or the other.

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    Quote Originally Posted by texasgunsmith View Post
    What I can tell you is iron changes over time...
    Yes, it does, but usually only in the first couple of years. I've heard stories that in early years, South Bend would actually bury their castings for a couple of years in their back lot. A casting from 1925 could not be used before 1928 or later. Researching why the metal was moving lead to much better techniques of pouring/cooling the metal that virtually eliminated most of the changes.

    I'll be interested in hearing your results of your shimming.

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    Working on adjusting the headstock. To recap, on a check I was +.0028" from 12 oclock position, when running the 12" length of test bar. And .0015" from the 9 oclock position.

    I ended up lifting headstock, re-tightening, and checking probably no less than 15 times during adjustment.

    In the beginning I was totally raising HS.

    440.jpg

    As I got more into it, I would raise only one end to adjust amount of shims.

    441.jpg

    I used shim stock from the same kit that I leveled lathe with. I used scissors to cut out the pieces I wanted:

    442.jpg

    With the pieces cut out, I'd lay them on ways, tighten HS down, and re-check. I scewed shims in this pic so they would be more visible:

    443.jpg


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