# My tail(stock) of woe



## swilliams (Jan 10, 2011)

I bought my lathe over twenty years ago when I was rather young and full of hope or promise or something  I got it off an old machine tool reconditioner of great skill who'd reconditioned it to make a couple of bucks. He did a very nice job, but there's the odd thing or two that could be improved. Chief among these is the tailstock alignment. He must of been of the school who has something against shimming up the tailstock and instead scraped the bottom of the headstock to get the heights to match. My headstock is at least 1/16" lower than original spec. All the same the tailstock isn't quite lined up properly height wise. Personally I don't see what's wrong with packing up the tailstock, but then I'm not a machine tool reconditioner.

Having had occasion to drill some small holes recently I've been forced to face up to this misalignment. Yesterday I broke a 1mm drill due to this and decided enough is enough, it's time to fix it. Ontop of this I bought a more modern, lever cam locking tailstock off ebay a while back. After an initial burst of enthusiasm I went cold about fitting this to the lathe, but given the situation I've decided to bite the bullet. So the first thing is to check out what the situation actually is.

Here's my original tailstock height missmatch







and here's my old and new tailstock together






My lathe's a 1952 Hercus and the newer tailstock is off a 1964 model. See http://www.lathes.co.uk/hercus/index.html

The barrel in the new tailstock is a little tighter than my old one but both of them are acceptable.


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## swilliams (Jan 10, 2011)

So I put a bit of steel in the chuck and turned it to the precise diameter of the parallel section on my live centre's spindle (0.502"). Then I ran a dial indicator, mounted on the cross slide, over the two diameters to measure the difference in height. So my original tailstock is 7 thou lower than it should be.

Here's a photo of how my newer tailstock shapes up height wise






and here's the bottoms of my two tailstocks






Looks like the guy who sold me the newer one has hit the bottom with a linisher or something to hide the wear. My original tailstock still has scraping marks visible on all bearing surfaces, so the 7 thou is definately not due to wear since the reco. Upon pulling the base off my original tailstock I discovered that the bloke who had reconditioned it had licked the top of the base on a surface grinder






Anyway I made the decision to use the base of my existing tailstock on the new tailstock. After fitting it all up I established the following. The new tailstock is now 10 thou lower than it should be. The tailstock barrel is about one tenth of a thou out of parrellel per inch in the horizontal direction and about half a thou per inch, pointing up, in the vertical direction.

So the next thing I need to do is get my hands on some 10 thou shim stock. I might do a wee bit of scraping on the base. I'm not skilled with scraping but with a bit of effort and desperation I'm pretty sure I can improve the vertical alignment. 

The alignment's not too bad but I've got something in mind. I've got plans of making a sensitive drilling attachment for small drills. This will have considerable overhang from the tailstock and I want the small drills to still line up with the centre axis of the lathe.

Anyway tomorrow I'll see if I can find a local supplier who has some suitable shim 

Steve


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## Ken I (Jan 10, 2011)

Just a suggestion.

Since the baseplate has been ground - is it parallel ? this could be the source of your up/down drift. Similarly this could be corrected by dressing to counter the error - advise removing say 2mm and adding a spacer shim that can be held in place with screws.
The front to back drift would have to be corrected by machining the front to back keyway and replacing with an oversize key.

You can of course simply use different thickness shim front and rear and adjust your up/down drift by fiddling with the location of the shim - a bit Heath Robinson but it should work.

Assuming you are happy that eveything fits together properly and the various parts don't need any scraping - then since you have errors in two planes - It might be an idea to linebore the tailstock and sleeve it.

Make a suitable boring bar mounted in the chuck (as short and fat as possible) - lightly clamp the tailstock and "feed" it by pushing with your spare tailstock.

I don't know your praticular lathe so there may be some reason this isn't practical but if it is possible it will eliminate all possible errors in one go.

I'm sure the guys are going to make plenty of other suggestions.

Ken


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## Loose nut (Jan 10, 2011)

I had the same problem on my old 9 x 20" (about .012" low) so I put a shim between the tailstock base and the upper part. It worked fine, just sitting there without glue, it has never moved. 

Your only other choice is to make a new lower base and that would be a lot of work. Try the shim stock.


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## Ken I (Jan 10, 2011)

Got to agree shims are going to be much easier - but its not going to correct your front to back drift - is it the tailstock or the headstock ? (might be a dumb question)

Just a thought - whilst on the subject of lathe alignment.

I once whacked a chuck key into the bed of a Colchester (the only time I have ever done it) - it put the headstock slightly out of line with the bed. (it taper turned about 0.001" over 2")

I pulled the tapered dowels used to secure the two and they were "bent" - slightly sheared.

Replacing them did not completely correct the problem - so I pulled the pins, realigned the headstock, gave the tapered holes a light ream and replaced the pins.

FYI

Ken


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## swilliams (Jan 11, 2011)

Thanks Ken and Loose Nut

I'm gonna shim and scrape it. I've found a place close by that has the necessary shim in stock. The alignments not too bad, I'll be able to manage fixing that. I'll use a very fine Swiss file to finish off the scraping, make up for my inevitable sparse number of contact points per square inch.

Ken, shifting the headstock on your Colchester must have bee a decent stack? What did the chuck key look like? 

Steve


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## steamer (Jan 11, 2011)

There is one other trick you could do

You could make a new tailstock quill, but bore the taper off center of the barrel thereby putting the center where you want it. Of course the screw thread needs to be on center. I have seen this done, and it works...but you will be getting aquainted with your 4 jaw chuck.

Scraping the headstock to match the tailstock was considered the "correct" way to realign a lathe by any scraper. They don't like shims... ;D

But there is a lot of lathes out there running with shimmed tailstocks!

Dave


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## Ken I (Jan 11, 2011)

The square end of the chuck key snapped off - key bent to b.....y.

I was an apprentice at the time - had to sort the lathe out and make a new key as pennance.

Have'nt done it since - lesson learned.

In an earlier post I mentioned that someone mixed up the tailstocks of 6 identical lathes - muggins here got the job of sorting it out - they were all slightly different in height which led me to conclude that they had been line bored in-situ. Years later I replaced the turret on a capstan - the replacement came with undersize bores and instuctions for in-situ boring to size.

Line boring and sleeving or replacing the quill as Steamer suggested might be less work than scraping.

Definitely give the shims a go first.

Ken


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## compspecial (Jan 11, 2011)

Hi guys, I had no idea a lathe could wear so much in normal use, especially the tailstock it doesn't usually get nearly as much sliding movement as the carriage surely?
 when you think of the thickness of a 012 feeler strip, its a lot of wear. I wonder if its partly some sort of abrasive action, like from honing compounds etc. well I learn a few new things every day. 
                 Stew


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## swilliams (Jan 11, 2011)

Thanks for the interest guys, definitely some good food for thought in here for anyone else who needs to tackle this problem.

Dave - that method could be mighty useful for a lathe with a one piece tailstock or such.

Ken - I know Hercus used to do the final fitting of their tailstocks by scraping, on the other hand if you bought one of their turret tailstock attachments it came with undersize holes just as you describe. No doubt different manufacturers used different methods. 

Stew - yep abrasive, many lathes get used and abused. Polishing with emery paper and never cleaning the ways etc.

Anyway I got my hands on some shim stock and found some original specs. The tailstock barrel was originally meant to be parallel to the lathe axis within 2 tenths of a thou per inch, in both the horizontal and vertical direction. Mine is 1 tenth in the horizontal and 5 tenths in the vertical. I'm going to attack it this evening after work. I'll let you know how it works out.

Steve


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## steamer (Jan 12, 2011)

Let us know how you make out.....curious.

Dave


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## swilliams (Jan 13, 2011)

Dave, I shimmed it up and did some scraping. The shim is one piece and trapped in position by the features in the tailstock base such that it won't interfere with anything, including setting the tailstock over for taper turning. The centre is now 2 thou high rather than 7 thou low. The alignment is improved but I still have more to go. Shifting the alignment of the tailstock by scraping is a slow buisness. At least for me.

Importantly. I tried drilling a 1mm hole and it worked great. This is a major improvement. I'm going to build a sensetive drilling attachment, similar to what Myford sells, and see how it works. This attachment will have much more overhang from the tailstock. If I have to do more scraping for this attachment to be able to drill small holes, so be it, other wise I'll just leave as is. Also I now have a lever locking tailstock which I like alot more.

With regard to turning with tailstock support, any misalignment has never been much of an issue. Easy to work around that one.

BTW I leveled my lathe up and measured all sorts of other alignments. The headstock alignment follows the bed to much better than a thou for more than a foot and seems bang on for at least the first 8 inches. Things seem pretty good, so I'm reasonably happy (for the moment). 

Cheers
Steve


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## steamer (Jan 13, 2011)

Glad to hear it! Scraping is slow business...thankfully....Regardless of wheather your going in the right or wrong direction....keep at it!

Dave


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