South Bend 10K - (un)doin' the twist!

I have this awful feeling that I have a really twisted 10K lathe.

I'm finally getting started on my 1965 vintage South Bend 10K. First step is measurement and planning. For measurement I set the bed on my woodworking bench and shimmed the headstock end of the until it was level (photo #1). The tailstock end has a leveling mechanism which I left loose so that it was resting on a single point (well, it is really resting on the 1/2" pin which is the fulcrum of the leveling mechanism) (see photo #2). For scraping the prisms the bed will be in a 45 degree carriage on my workbench so that I can scrape level at all times.



I shimmed the bed level, removed the shims, moved, repositioned, and re-leveled the bed several times and was able to get easily repeatable readings from the precision level across the top of the outer ways. I also measured the maximum wear to the ways (front way near the headstock) with a 3' straight edge and feeler gauges as about 0.004"



While the inner ways under the headstock were beautifully smooth and printed a very nice pattern with a 12" straight edge (photo #3), the rest of the inner and outer ways had been flaked by someone with altogether too much enthusiasm, and were quite rough with relatively few points of contact (photo #4). I leveled across the top of the ways at the headstock and then placed the level across the ways at the tailstock end of the bed. Surprise - the top of the front way was 0.004" lower than the top of the back way at the tailstock. At the middle of the bed the front way was 0.0025" lower. Since the bed was resting on three points, and was not bolted down or otherwise stressed, this would seem to indicate about 8 times as much twist as the allowable error (0.0005") indicated in South Bend Form 1351-10K (South Bend 10K accuracy report, available in the files section of the Yahoo SouthBend10K forum).

I lightly stoned the prism surfaces of the outer ways at each end of the bed and checked the level again using a set of SPI V-blocks (photo #5). At the headstock the front way was now 0.001" lower than the back way and at the tailstock was 0.005" lower - the same amount of twist as indicated when leveling across the tops of the ways. If this bed really does have 0.004" twist (in addition to wear), I will have to decide whether to take all the twist out at the tailstock end or to split the difference between both ends. Suggestions are welcome!!! I also realize that taking out the twist will mean truing the rear carriage gib way. What a mess...

Until I disassembled it, this lathe was mounted on cast iron legs with a horizontal countershaft hung behind the headstock on a 1/2" steel plate that was bolted between the bed and the cast iron legs. Even though there was a 3/8" x 1.5" diagonal steel strap from the rear cast iron legs to the bottom of the steel plate, I suspect that the countershaft was inadequately supported and probably caused the twist.

I should probably mention that I'm using a Polish level that is marked "0.0005 in/10 in". Differences were measured by first shimming the bed with the level across the ways at the headstock end and then shimming between the level and the ways at other locations until the bubble was centered. The level reads the same when reversed end for end, and my v-blocks also give the same readings when switched.

Reading Stephen's post was very useful in helping me think about what needs to be done and in what order. At this point my plan is:

1. Create a reference plane using the both ends of the top of the front outside way and the headstock end of the back outside way as three points to define the plane. This will mean taking about 0.004" off the top of the tailstock end of the rear way to get rid of the twist. Since the top of the way is so narrow I will use a file to get it to within a half-thousandth, and then use a combination of scraping and stoning for the rest.

2. Scrape the bottom of the tailstock base flat and parallel to the top. Scrape the "V" parallel to the base and to the tailstock spindle. Although a slight amount of twist (< 0.00025" in six inches from my rough calculations) may be evident in the inner ways under the headstock, it should still be possible to use this area to spot the tailstock base as long as the possible twist is kept in mind. Check to see if the reference plane is parallel to the top of the tailstock base when it is at the far left end of the bed, where the headstock normally sits. If not, I may need to adjust the reference plane by removing a small amount from the top of the front outer way. The objective is to allow me to remove as little metal as possible from the inner ways under the headstock - preferably none from the first two or three inches on the left end of the ways.

3. Scrape the flat inner way parallel to the reference plane (i.e., the top of the outer ways). Remove as little metal as possible. Aim for 20 PPI/50% contact.

4. Scrape the inner way prism using the 3' straightedge, the tailstock base as a template, and the precision level. Again, try to remove as little as possible from the left end of the ways.

5. Scrape the front way "straight down" to the level of greatest wear - about 6 thousandths straight down at the ends (about 4 thousandths off the 45 degree surfaces of the prism at each end). Will follow Stephen's thread for ideas on jigs and ideas on measurement.

6. Scrape the rear outer way parallel to the reference plane to take the twist out. That will take it straight down 4 thousandths at the tailstock end but almost none at the headstock end. However, it will still be about 6 thousandths higher than the front outer way along its entire length. I'm tempted to leave it at that and machine the rear saddle "V" down an additional 6 thousandths before applying trucite. Please comment or advise!!!

7. Scrape the rear carriage gib way of the bed (the underside of the rear outer ways) parallel to the reference plane, taking about 4 thousandths off the headstock end and nothing off the tailstock end.

Any comments or advice are welcome!

Have you bolted it down and actually used it yet?

I only ask because it's easy to go overboard on something that doesn't even need it.

iwananew10K said:

Have you bolted it down and actually used it yet?

I only ask because it's easy to go overboard on something that doesn't even need it.

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While I appreciate your comment, it would be nice if you actually had some useful insights on reconditioning a lathe bed with twist, particularly a SB with so much rough flaking on the ways that the usual suggestions that one should spot the saddle to the ways near the tailstock (to use as a template for scraping the outside ways) would be difficult even without having to contend with 0.004" overall bed twist.

I learned long ago while acquiring skills in woodworking not to assume that old or new tools were "ready to go". In the case of a newly acquired 40 year old lathe, it seemed prudent to dismantle it sufficiently for a thorough cleaning, to replace all felts, remove and examine the spindle (looks pretty good), and to at least roughly measure the wear on the bed, saddle, and tailstock. I was surprised by the amount of twist and decided that it made more sense go ahead and scrape the bed while everything was dismantled.

Doe anyone else see the irony in your user name and the your comments above?

D, dont miss the forest for the trees...sometimes you can be so close to something you may not be seeing what you think you are. This is true of most everything. I dont doubt you think it is twisted probably feel that you have done enough inspecting to prove it. But getting angry at people who are honestly trying to offer advise they feel is warranted is not the way to go around here. If you dont like the advise you can just ignore it.

Your issue is not easy to describe nor for us to see so you will have to forgive us a bit if we ask questions that you feel are unnecessary. Others will not be to quick to offer advise because sometimes you can end up going two steps back if you start off with the right advice for the wrong problem.

And now that you have shown so much negative attitude, no one is likely to offer you anything at all, except a hard time.

Finally, I wish to make this clear, this is an internet forum, those of use who frequent this forum also have other things to do. Helping you solve your problem for free isnt on our to do list. And you may have to wait a few days for a good answer, and you will certainly spend a lot more time answering questions before anyone will suggest a course of action.

Charles

Hmm... I replied but I guess it didn't take.

do not know why you would be offended by the question.

likely there is good reason no one else has replied.

even when new South Bends would sometimes have twist when delivered, how to address it outlined in HTRAL

if your gib was bent would you straighten it or try to scrape it out?

wear is wear and twist is twist

have fun.

Edit- sorry Charles I now see you were on it.

Charles - What a difference a word makes - I meant to say "offered some useful insights", not "had some useful insights." I have no doubt that iwanna10k has plenty of insight and far more experience than I do. But it did seem ironic to me that if you want a new 10K lathe, the only way to get one is to recondition an old one, which is what I would like to do. I want a new 10K too.

I've seen plenty of discussions about leveling SB lathes on the SB forum here and on Yahoo, but have not seen any discussion about the logistics of taking out twist while scraping. I thought it might be of some general interest. I certainly did not mean to imply that I thought I was "entitled" to the help of this forum and apologize if anyone took it like that.

Douglas

UHGG....my username is why people should not sign up on forums at 4 in the morning after a long night out.
For the record I don't want a new 10k.

for humors sake and to get this thread back on track, perhaps this username is more fitting.

I notice you are placing your level on the flats atop the V-ways.

My understanding is those are not precision surfaces and I think the
measurements you are interpreting from those surfaces may be
mis-leading you.

I suggest you put the machine together and see if it turns and bores
true. It does not seem to have much wear. The bed adjustment is
critical on this machine and needs to have the screws solidly opposed
to the tab extending down from the bed. 10K is giving you good advice,

jim rozen said:

I notice you are placing your level on the flats atop the V-ways.

My understanding is those are not precision surfaces and I think the
measurements you are interpreting from those surfaces may be
mis-leading you.

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Jim,

Thank you for your thoughts on this. I was following Connelly in using the tops of the ways. I did lightly stone them with an Arkansas stone to remove burrs. More importantly, I got exactly the same difference in readings placing the level across two matched "V" blocks resting on the prism surfaces (see photo 5 above which shows the level and "V" blocks at the headstock end of the lathe - as noted, a 0.001" piece of shim stock is between the near "V" block and the level). I'm pretty sure the "V" blocks did not introduce any significant error since they produced the same bubble position when the "V" blocks were switched.

Assuming for the moment that my measurement of 0.004" twist is more or less right, do you know if that is within the adjustment range for a 10K bed?

Thanks, Douglas

Douglas-

(Apparently from your report) your lathe has so little wear, i doubt you would notice improvement in your work even if you do spend a week and make it perfect. I'm redoing a bed for mine because the current bed under it has a ~.040" wear ridge. I still do really nice work on it. You can check the archives. However I have reason to want a longer bed for it, and eventually I have a dubious intent to create a Hard Bend lathe out of it as well. So the foundation should be reasonably good. The thing is, moving any components to the non-original bed will require scrape fitting them. It's not like a lathe with .005" wear in front of the chuck, you would be very hard pressed to find the error in your work. It is that the old pieces won't fit the nused bed anyway, they will all need re-scraped, so lets make that part easier by starting with an accurate bed.

Your s appears to be apart at this point. So if you have the means to inspect it accurately (as Jim notes and some of us have been refraining from mentioning, the tops of ways are not accurate reference surfaces. Sure, SB probably did plane them at the same time as the bed,l but that is no assurance the same care was taken. From what I'm seeing on the bed I'm planing, SB was more expeditious than fastidious with their planer work. Then the scraping department accurized it. (This is appropriate efficient manufacturing for that era) Point being the tops of the ways are a legacy of earlier work on the bed and not intentionally a reference surface. You mention that you believe someone since the factory flaked it. It is possible to know whether they filed the tops of the ways to make them more presentable as well?

PS: I see you've been posting while I was typing. The other big factor is that the way small SB's wear with a "wear ridge". Using the tops which *might* be a legacy of how the lathe geometry was when new, if the lathe actually has enough wear to imply rebuilding; would not be a good reflection of the current way geometry seen by the saddle and TS.

smt

I think the main thing to shoot for is getting the bed in the same place as the factory had it. Ie has the bed taken a twist / has it had twist scraped or worn into it? By measuring for level from the tops of the ways as you have, checking those surfaces to the bottom gibed surfaces that the saddle locks run on, and the non precision milled / planed areas between the vee and flat ways. Try and build a picture of what those readings tell you and go from there. If they all say twist then maybe the bed has taken a set, if not then maybe it was scraped on Friday .

Personally, as suggested by others, I think id bolt down and level it. Cant see .004" on that bed being a problem. Put the saddle on it and check its not rocking all over the place, run it up and down checking with your level for twist / way straightness(actually, be nice to have two levels, one to read twist etc and one for base reading, to be sure youre not moving the whole bench/bed as you move things around). Can indicate the bottom gibed surfaces nicely from the saddle. Also, in my minor experience, wood and precisions levels don't work too well together.

stephen thomas said:

You mention that you believe someone since the factory flaked it.

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Stephen - I think the flaking was done at the factory - there is no evidence of flaking over wear, and the area of maximum wear (front outer way near headstock) has worn completely smooth. My photo #4 shows spoting of the front outer way near at the tailstock end of the lathe. Although there is no evident wear, the contact with the straight edge was very poor. Here are a couple of photos showing the tailstock end of the bed and also the area of maximum wear.

One of the reasons I'm tempted to scrape is the excessive flaking and consequent rough surface of the ways. When I run my fingernail over the wear on the bottom of the tailstock base where it slides on the flat way, I can feel lots of little groves where trapped grit has ground metal away.

Demon73 said:

Try and build a picture of what those readings tell you and go from there.

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Demon73 - Thanks - makes perfect sense.

OP. post #1

While the inner ways under the headstock were beautifully smooth and printed a very nice pattern with a 12" straight edge (photo #3), the rest of the inner and outer ways had been flaked by someone with altogether too much enthusiasm, and were quite rough with relatively few points of contact (photo #4).

Click to expand...

OP, post #14

Stephen - I think the flaking was done at the factory - there is no evidence of flaking over wear, and the area of maximum wear (front outer way near headstock) has worn completely smooth.

Click to expand...

Douglas, from the pictures I think your estimate in post #1 was the correct analysis. Look at the typical SB flaking patter of cross hatching in the area covered by the headstock, combined with their other common alternating, somewhat spare, large and small crescent pattern on the Inverted V.Now look at the flaking on the wings. It is not a typical SB pattern, though I suppose on any given day, someone in the plant might have done it. It looks OK (visually) but does not "feel" SB. Unless the photos are deceiving.

But the real point here is that it is necessary to get accurate measurements and data if you plan to scrape. That can only be done from the way surfaces themselves.

Suppose the technician blues up and lays a full length straight edge on the face of an inverted V-way & spots (marks) it. If the tech then commences to scrape the markings, there are several opportunities. 1.) the way will be caused to taper in height. 2.) the way will diverge toward or away from alignment with the centerline of the lathe & the other ways in the system. 3.) twist may be added to the to the way configuration. 4.) the spacing between adjacent ways will change 5.) the vertical displacement of the ways compared to the other ways in the system will change.

If you have the means, tools, and will to keep track of that, go for it. It's not trivial. I even think it is fun, and apparently you are on the same wavelength. But that does not mean that it will improve the performance of lathe from its current (represented as pretty good) condition in a meaningful way on your work.

I think the main reason to redo ways is when the saddle can no longer stabilize do to the varying width and wind of the ways system. There becomes only a few short areas where it actually beds well on the ways. But this is probably beyond .005 wear in front of the spindle, and .0025 twist.

You are correct, the underside of your saddle does not look so good.

I think most of us are not hearing a real inspection plan. But we are all on this forum because we are idiots whose mammas did not sufficiently dissuade us from picking up scrapers when we were still malleable.

Good luck with it, and keep reporting. You do nice photos.

smt

I don't want to get into a Peeing contest here and when I first read the post, i wasn't going to inject, but that flaking is not factory. it looks like a used machinery dealer did it to hide some scratches as shown in the inside v way of one of the pictures.

Dennis as Charles points out there are a few of us on here who are not guessing on how to do it... No need for you to re-invent the wheel here when you could just ask us how.

I also don't like sitting the machine bed on a wood table and making tests with plastic or wood shims. When the machine was planned at the factory, it was clamped to the machines cast iron table.

I have seen maybe 1% of a good American made (or assembled) machine come out of a factory off and machined bad. But in a lathe bed that I did not get ground of planned first I would assembe the legs and then rough scrape tail-stock base to the area under the headstock and relieve the middle and use that as a sled to set your level on to compare the parallelism of the TS ways while scraping them.

The best way to scrape the bed would be to have a long straight-edge that is longer then the lathe bed and scrape the flat of Tail Stock ways first as the surface under the headstock is not worn and the end on the Tailstock end is seldom worn a .001" if any. Scrape it straight down. Then scrape the Vee ways of the TS way the same way on both sides using your roughed out TS base and level to compare the flat and V of the TS ways to get the parallel. Then mount a mag base and indicate all the other ways parallel to the finished TS ways.

I highly doubt the bed was twisted bad from the factory and scraping one end of the bed to remove the twist is screwing up the machine. As others have said, please rethink what your doing. I would reassemble the legs and start to indicate the machine and be a detective first before tearing into it and re-inventing the wheel and screwing it up. Also many of the chapters or advice in the Connelly book in my opinion is wrong. Rich

Thank you Stephen and Richard - I think my confusion about the flaking was because it was worn away in places so the wear obviously happened after the flaking. I bought the lathe from the estate of a man who had used it in a home shop for many years and must have purchased it used from the machinery dealer who did the flaking.

I will follow Richard's suggested steps scraping the TS ways using the TS base. Unfortunately I only have a 3ft straight edge and this is a 4 foot lathe bed. However I have seen Richard address this in another thread and feel reasonably confident I can achieve a good result. Also, I will take Richard's advice to play detective first and not to screw things up until I've mapped out the existing geometry very carefully...

Thanks again,
Douglas