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Test bar issues at spindle ID taper

Stag53

Plastic
Joined
Dec 4, 2007
Location
Bay Area, CA
Appreciate any thoughts on the following issue:

I'm at the early stages of saddle alignment on a '41 round-dial. During initial futzing around, I placed my Miller test bar in the spindle to do some cursory testing. With my tenths indicator set up against the bar, I noticed that I was getting some strange 'hysteresis' of sorts where when I push the bar one direction, it will 'stick' .001"-.002" about halfway out the bar. When pushed the other direction, it will return to zero. It had me thinking that I've got some issues with the tapers seating inside the ID of the nose. Set up shown below, although at a different position along the length of the bar.

So, I blued up the test bar taper (well, I had red dye on hand, so I guess I red'ed it) and popped it back in. Gave it a gentle thump on the end with the dead blow and popped it back out to see the print. I'm definitely getting good engagement at the rear half, and rather inconsistent engagement at the front, maybe 90degrees (on the bottom side, so influenced by gravity). This jives with what I was seeing with the test bar sticking back and forth. I attached a pic showing the test bar where you can see the contact. I couldn't get a good photo inside the spindle nose, but it tells the same story.

Was hoping to run this by the Monarch group here and see if I'm onto something, or better yet, if I'm doing something stupid ... it's getting close to my bedtime and I should probably walk away from the heavy machine tools. Thanks in advance for any thoughts.
 

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I'd say either the spindle taper is egged out from use, possibly with an incorrect center, or the taper on the test bar isn't accurate (which seems less likely). I would start by measuring both to see which is closer to the correct .600 per foot.

Someone may have spent years slamming a Morse center into the spindle... Morse 4.5 is very close to Jarno dimensions, but with a slightly steeper taper.
 
Thanks for the thoughtful replies all. I did some more investigation yesterday:
1. Measured the test bar taper as well as the Jarno adapters that came with the machine (just to see if they had maybe been a Morse 4.5). Both were confirmed to be Jarno #12 with .050"/inch taper.
2. Blued the ID of the spindle several more times both ways (blue the spindle ID>print to the test bar, blue the test bar>print to the ID). I'm still getting a pretty confident print that indicates good engagement at the rear, and limited engagement at the front. I don't see any spots that look like 'warts' on that section. Dang it.

I'll probably do some more bluing today and see if I can reveal any 'warts'. I was really hoping that's all it is. Maybe my method is off, so I'll experiment a bit.

I read in some other posts that the spindle shaft on the early 10EE's is pretty soft. Is that true? Is the main fix for this sort of condition using a toolpost grinder and getting in there? I saw a Mr. Crispin video on YT that went over grinding the OD, but not the ID.

If I do have an egg'ed out taper, I'm at a loss for how to align the spindle to the newly ground ways. If I can't seat the test bar, I can't get a reliable/accurate spindle centerline. I do remember seeing a tool in the past that someone built that could be adjusted both in rotation and translation to establish the centerline with an indicator. Does anyone know what that tool is or is my memory off? Or other methods? I'm awaiting a copy of Machine Tool Reconditioning, so that may answer a lot of questions too!

Dang, was hoping to jump straight into Moglice'ing the saddle, but this has me wrapped around the axle (errr, spindle haha).

Thanks!

Adam S
 
On mine, the internal taper is soft. Easy to scrape. I'm sorry if it turns out the taper is really worn. Somebody must have been slapping in some centers and collet holders ALOT. But I would think there are workarounds. Maybe just a good 4 jaw and a big piece of precision ground rod might suffice.
 
Once the test bar is seated such that it has zero runout at the end, I would think that should be all you need for alignment. (That's assuming that the bar is ground nice and straight, and that it doesn't come unseated and start to run out as you proceed.) You can ask over at the reconditioning forum to be sure.

Unless you're planning to use a Jarno adapter and Morse taper dead-center to turn between centers, you don't really need to worry about the taper.
 
I aligned the bed on mine using an autocollimator set up on the spindle axis. The advantage being the ability to align the entire bed based on full knowledge of its geometry and twist. I ended up shimming one of the bed support points .001” to get the best result.

However, even if the jarno taper is buggered, you can align the bed by putting a piece of bar stock in a chuck, doing cuts at beginning and end, and see if it is cutting a taper. If not, the headstock is aligned. If it is cutting a taper, an indicator run along the bed (using the same test piece, but checking at 90 degrees and 180 degrees from the tool position) can be used to find out which way the spindle is pointing.
 
Once the test bar is seated such that it has zero runout at the end, I would think that should be all you need for alignment. (That's assuming that the bar is ground nice and straight, and that it doesn't come unseated and start to run out as you proceed.) You can ask over at the reconditioning forum to be sure.

Unless you're planning to use a Jarno adapter and Morse taper dead-center to turn between centers, you don't really need to worry about the taper.
Thanks Cal. This is exactly what I've been thinking today. I can get the bar seated pretty well and bump it into center with an indicator. As long as I limit my clumsiness and don't bump into it, all's well. The bar was made by Miller Fab and is dead straight, so not too concerned about that aspect.

Also, good point on use of the taper. I'll rarely be using it.
 
I aligned the bed on mine using an autocollimator set up on the spindle axis. The advantage being the ability to align the entire bed based on full knowledge of its geometry and twist. I ended up shimming one of the bed support points .001” to get the best result.

However, even if the jarno taper is buggered, you can align the bed by putting a piece of bar stock in a chuck, doing cuts at beginning and end, and see if it is cutting a taper. If not, the headstock is aligned. If it is cutting a taper, an indicator run along the bed (using the same test piece, but checking at 90 degrees and 180 degrees from the tool position) can be used to find out which way the spindle is pointing.
Very cool. An autocollimator is not in my toolbox nor budget, but that seems a mighty slick way to approach it. Thanks for the idea on using test cuts too... that could also work. Feels like that's a ways out though as it would imply that I've got the saddle and cross slide all finished up. Sigh, someday.
 
I found on mine, that there was a few little warts on the inside, and threw out the measurement. Some blue and a curved scraper fixed it right up. If any consolation, mine was used very hard, and the taper was fine, just the warts.
Hey Darryl - off this topic, but what the heck: did you Moglice your saddle? I've been searching your threads and haven't been able to find any specifics, but it's been a long day and my brain's a bit frazzled. Did you happen to post anything? I've been glued to rekepler and gernoff's respective documentation and looking for anything else out there before I start pouring epoxy all over my freshly ground ways.
 
Hey Darryl - off this topic, but what the heck: did you Moglice your saddle? I've been searching your threads and haven't been able to find any specifics, but it's been a long day and my brain's a bit frazzled. Did you happen to post anything? I've been glued to rekepler and gernoff's respective documentation and looking for anything else out there before I start pouring epoxy all over my freshly ground ways.
You should also have a look at Harry Bloom's 10EE ("Wreck") rebuild threads:
 
Just a thought on damaged spindle tapers: I've seen a couple that were dinged or damaged not from center and sleeve fretting, but from boring bars running too deep through the chuck and loose material banging around. If the lathe has an arc-of-shame and other tell-tails of less than stellar operators in its past, a banged up spindle taper isn't too much of a stretch.

IMO, the way to do it "right" would be to remove the spindle and have the taper re-ground or hand scraped if it's soft enough, measuring it for concentricity on V-blocks on the granite table first, then back in it's bearings in the headstock.
 
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You can also align the headstock using a big chunk (1.5" or better) of Thompson bar. Chuck it up in a 4-jaw and whap it in on the near and far ends and then walk it looking at the TIR. I think I wrote something up on that? Don't forget the sag, minimal as it is.

Once the headstock is good you can chuck a good flat in the same 4-jaw (I used a 10" sine bar) and check the alignment of the saddle cross slide ways against it. Rotate it to make the ends square to the spindle axis.
 
Thank
You can also align the headstock using a big chunk (1.5" or better) of Thompson bar. Chuck it up in a 4-jaw and whap it in on the near and far ends and then walk it looking at the TIR. I think I wrote something up on that? Don't forget the sag, minimal as it is.

Once the headstock is good you can chuck a good flat in the same 4-jaw (I used a 10" sine bar) and check the alignment of the saddle cross slide ways against it. Rotate it to make the ends square to the spindle axis.
Good call - I'll file that one away as a good technique if I can't get the test bar to behave. Suppose I could even use the test bar itself in a 4-jaw, mounted backwards-ly, if I don't have any ground rod handy. I remember your posts about using a flat in the spindle to check alignment and have seen that method in the Connelly book methinks.

Concluding thoughts:
I've been thinking that I can delay on the spindle aspect and focus my current efforts on the cross slide and saddle. I've got some nice ground ways to datum these against irrespective of the headstock. The headstock can wait and all my other efforts could use the extra 'space' anyhow... but I've definitely gotten some great advice on how to address it when the time comes. Thanks all!
 
Concluding thoughts:
I've been thinking that I can delay on the spindle aspect and focus my current efforts on the cross slide and saddle. I've got some nice ground ways to datum these against irrespective of the headstock. The headstock can wait and all my other efforts could use the extra 'space' anyhow... but I've definitely gotten some great advice on how to address it when the time comes. Thanks all!

I can't see a way to align the saddle to the spindle axis when the spindle isn't there. It's a lot easier to align things with the headstock scraped in, without it all you can do is to level things and maybe scrape the cross slide ways and gib but can't Moglice or scrape in the saddle without the headstock.

Personally I found using the tailstock base as the indicator mount to be a lot easier, less mass and good scraping practice.
 
Yes, I used Moglice on the saddle. I also used a Moglice jigging product to precision set the headstock to the newly ground ways. The ways required quite a bit material taken off and it occurred to me soon after, that removing, checking, scraping, removing the headstock multiple times(make that many ,many times) wasn't going to happen, and that an alternate plan had to be formulated. It seemed that so much material had to be taken off of all the way surfaces, that the matching inverted ways (untouched) on the bottom of the headstock would not fit the newly ground (now smaller) ways. Ouch. A call to Devitt and they recommended this product. I jigged up the headstock, and applied this product and literally epoxied the headstock in place. It hasn't moved that I can tell in 20+ years. The saddle was done like most folks that have done it here, fixtures mounted where the ways wipers go. Tim in D made a set out of steel that bore on the sides and top inverted V. This was alot more positive locating than on the sides of the V. I used test bar that Tim had made long before Miller came out with theirs. I, like Rimcanyon used an autocollimator (Hilger &Watts) per Connelly to really dial it in. I really have to give kudos to the factory to scrape these in to such fine accuracy. But I guess when you start with fresh new parts, accurately pre machined and ways ground, and a lifetime of scraping experience... Scraping flat and scraping to alignment are very different things.
 

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I'd bet Brian Miller could touch up the ID of that spindle taper. Might run the question by him for an idea of cost. At $300-ish for a test bar, I'd guess less than that.
 
I can't see a way to align the saddle to the spindle axis when the spindle isn't there. It's a lot easier to align things with the headstock scraped in, without it all you can do is to level things and maybe scrape the cross slide ways and gib but can't Moglice or scrape in the saddle without the headstock.

Personally I found using the tailstock base as the indicator mount to be a lot easier, less mass and good scraping practice.
My thought was to treat the ways as the primary datum (per Connelly) and align the saddle parallel (albeit slightly acute for concave facing) to said datum via a precision square off the freshly ground inverted V-way... and then later align the spindle to the ways as well. I reckon I can check the alignment between saddle and headstock to verify I didn't futz anything up, but my primary objective is to get the saddle to travel parallel to the ways. I saw others align their saddle this way in other rebuilds. Bad plan?

I'll likely attack the tailstock first - I'm pretty rusty wrt scraping, so like you said, good practice... and a good means for indicator mounting parallel to the saddle ways. Win win.

Can't thank you all enough for sharing your knowledge & experience.

-Adam S
 
Yes, I used Moglice on the saddle. I also used a Moglice jigging product to precision set the headstock to the newly ground ways. The ways required quite a bit material taken off and it occurred to me soon after, that removing, checking, scraping, removing the headstock multiple times(make that many ,many times) wasn't going to happen, and that an alternate plan had to be formulated. It seemed that so much material had to be taken off of all the way surfaces, that the matching inverted ways (untouched) on the bottom of the headstock would not fit the newly ground (now smaller) ways. Ouch. A call to Devitt and they recommended this product. I jigged up the headstock, and applied this product and literally epoxied the headstock in place. It hasn't moved that I can tell in 20+ years. The saddle was done like most folks that have done it here, fixtures mounted where the ways wipers go. Tim in D made a set out of steel that bore on the sides and top inverted V. This was alot more positive locating than on the sides of the V. I used test bar that Tim had made long before Miller came out with theirs. I, like Rimcanyon used an autocollimator (Hilger &Watts) per Connelly to really dial it in. I really have to give kudos to the factory to scrape these in to such fine accuracy. But I guess when you start with fresh new parts, accurately pre machined and ways ground, and a lifetime of scraping experience... Scraping flat and scraping to alignment are very different things.
Thanks for the pics and notes about headstock alignment. The shop that ground my ways didn't have to remove a ton of material (it's been a while, but I think it was like .005"), so hoping I don't need to Moglice it in place. Also seems like a less arduous way to do it vs. scraping. I'll keep that in my back pocket should I discover a boogeyman when the time comes.

"Scraping flat and scraping to alignment are very different things" - yeah, good reminder to stay humble, per usual. Lots of learning impending.

I'm just finishing up my wiper-mounted adjusters and plan to call Devitt this week... probably a cart in front of the horse type thing, but what the heck, it's keeping the momentum going while I'm noodling on best plan of attack.

Thanks!

AS
 








 
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