Tail stock lossing zero

S

skeetlee

Active member
Fellas
My tail stock isnt staying zeroed with the head stock. Seems every time i check it is .020 out, or even more at times. The only thing i can think of is that my concrete floor is moving due to this crazy Illinois weather we are having this year. Hell it was 60 degrees yesterday and today its 30 and raining. two weeks ago the temp was 10 degrees. I dont have a level set in the shop but i think i better be getting one. Do you think the slab moving could cause this much run out? It would be interesting to put a dial indicator on the floor somehow to see if the floor is actually moving. Not sure how i would accomplish this but i may find a way?? We have the lathe set up so that i can adjust the levelness very simply. I think i better get some levels of my own, instead of borrowing them so i can keep an eye on this. Either that or tear out a section of the floor and pour some serious footings under the lathe. I just might too!! Lee
 
Not sure what type of tailstock you have, but mine has 2 aposing screws that adjust the tailstock...I get these pretty tight then I dial it in. Id make those are tight. Also how are checking it? I use a coaxial indicator to check mine from time to time, you can use a dial test indicator in chuck but kind hard to read as its turning. Also if your chuck has alot of runout on test rod when indicating out from the chuck the readings may be scuded IMHO. I always dial mine in by making12" cut and measuring both ends(you can just make 2 cuts big enough for a micrometer to fit on that are 6 or so inches aprart), dial it untill they measure the same. Also there was a thread on here about using a good hardware store level..Should work until you get a machinist level.
 
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I check my tail stock with a magnetic holder on the face of the spider i made with a dial indicator. i rotate it around the tail stock spindle. I use a mirror to check the back side or 9 o'clock position. Lee
 
Are you holding the indicator with just the Spider chuck? Spiders work great for dialing in work thats through the headstock, using 2 points to indicate and 2 points to dial in (a spider on the back of your headstock and dialable chuck in the front). I dont think just a spider chuck alone would work well for dialing in on a single point. You can test by dialing in a test rod or any thing thats known to be concentric and indicate it at the chuck and away from the chuck( at least 3" IMO). I think a good set-tru or 4 jaw chuck works well for checking/adjusting the tailstock.

Heres a video of how I check my tailstock...you can see that the highest point on my tailstock is on top, they say that the manufacturers set them bit high for gravity and wear
http://www.youtube.com/watch?v=18Dcy1ZvfnM&list=UUPt3tSJKgBD07sb-f9djBRg&index=15&feature=plcp
 
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:you can see that the highest point on my tailstock is on top, they say that the manufacturers set them bit high for gravity and wear:

Not true, Actually the tail stocks are set high because as the bearings in the spindle warm up they expand and come in. The bearings may not come in .005 but they will move at least .002-.003 Now Alan Warner gave this little bit of info to me and i think ill take his word for it. I dont think we will ever use our little job shop lathe enough to wear out a bed way. Mine tail stock is .005 high and that measurement never moves even though my side to side does. Lee
 
Skeetlee,
The tail stock on my Jet did not hold adjustment well. I don't recall it being .020, but enough to cause
serious issues. I refitted the mating surfaces and added a thin spacer bringing it back in for height. I then dowel
pinned it to the base ,locking it for side to side. I have no need to off set the tail stock for cutting tapers.
 
Lee,

You might check your procedure for adjusting the tailstock. If your lathe has a socket head set screw {called a locating screw}to lock it on the very back of the tailstock casting you cannot adjust the tailstock until you loosen that and loosen the bed clamp. You can then adjust the tailstock and retighten the lock screw at the back. That is how my Harrison M300B works.

If you set the tailstock with the bed clamp tight even though you loosened the locating screw the next time you loosen the bed clamp the tailstock will move. I hope this is helpful.

Joe
 
Here are a couple things I have found, perhaps you already have noticed perhaps not. Depending how tight you secure the tailstock will affect the position of the tailstock. The tension of the tailstock quill/ram stop will also affect the position of the tailstock. The postion of the ram can sometimes affect your reading as well. Dial it in perfect with the ram extended about 1" now run the ram out about 2" more and check it again, probably not perfect anymore. I would check the face of your headstock spider, be sure it is square. Are you reading off the ram or a dead center you might have a defect on the center or in the ram that give you an inconsistant center position. I always try to make the tailstock adjustment screws tight, but not so tight that they are "stressed". Just a couple things to look at, hope my explanation makes sense.
 
What kind of stand or cabinet is your lathe bolted to? Many of the cabinets and stands that came with those types of lathes are way too flexible to hold any long term accuracy. I’m not saying that you can’t do accurate work on them it’s just harder and takes longer. You could saw cut and dig out your floor and pour a serious foundation for your lathe or perhaps you would like to build a more robust stand for it or maybe both. The slab in my shop is 8” thick, 6 sack mix with 5/8” rebar on a 14” grid, but my lathes have very robust cabinets and I don’t depend on the concrete to hold them straight so I can get away with this sissy floor. On tenders the lathes are bolted to the ship, the ship rolls and pitches and you are hard pressed to find a level on one. What am I saying here is you don’t need to level your lathe you need to make it cut straight and to do that you need to get the bow and twist out of the bed with the headstock aligned with the bed. When you have those things accomplished you can address other issues.

Play safe and have fun,
Nic.
 
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