# Turning Using Tailstock Center For Support Is P***ing Me Off



## tomw (Jul 17, 2015)

Dear All,

I am having a frustrating problem.  I can't turn between centers without getting a taper.

Here is the set-up:
1) Sherline lathe 4400, purchased in February 2015. This lathe was sent back to Sherline for adjustment of the tailstock (which was off a bit). Sherline reports the tailstock is now very well aligned.

2) I want to make a shaft that is 2" long, with each end being .19" in diameter for .19". The intervening diameter (between the two .19 diameter ends) should be approx. .09" in dia. This is thin enough and long enough that I need to turn this using a center in the tailstock.

3) I am mounting a 3/8" dia brass rod in a three jaw juck. The rod is center drilled on the outboard end (drilled with the stock snugged up short in the chuck) and extends from the chuck about 2.25 inches. A live center is mounted in the tailstock, and this is snugged up against the outboard end of the stock and locked down. 


4) I then attempt to reduce the stock to .19 diameter over most of this length. I am using HSS, turning at 2500 rpm. I am getting no chatter. My final pass is .005 DOC.

The problem:

When I turn a bit of 3/8" brass rod stock between centers to bring to down to .19, I am getting a taper of .06 over the 2" that I am turning. So, if the end of my shaft in near the chuck is .190, the other end will be .196. The tolerance on the part, for the ends, is .002. So, I'm sort of screwed. Yes, I could swap the thing around and machine both ends close the chuck, but then there is no guarantee that they will be concentric, which will be important for later machining operations. Plus, this seems wrong.

In the below photo I am showing the diameters at points 1.5" apart to correspond to the next test (see below)



To see if the headstock or chuck are misaligned, I took a piece of .75" dia aluminum, approximately 2" long, chucked it in the lathe, turned it down down to around .5". Again, my final pass was .005 DOC.

Over 1.5" I am getting 0.000" of taper.



My request:

Please look over the photos of my set up and tell me what I am doing wrong. 

Thanks,

Tom


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## Doubleeboy (Jul 17, 2015)

adjust your tailstock, its pretty simple.  I imagine there are details in your owners manual.

michael


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## eeler1 (Jul 17, 2015)

Try what Michael said.  If still no good, you may have a little play in your live center.


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## tomw (Jul 17, 2015)

The tailstock on a Sherline is not adjustable. They are fitted at the factory. According to the tech I spoke with, over a 10" test bar the tailstock/headstock offset of MY LATHE was less than .0015. Thus, over 2", it should be far less than .001.


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## chips&more (Jul 17, 2015)

You gave a good report of your problem. If I am remembering correctly, the tailstock is not adjustable? It’s either the tailstock or the live center is out of whack. I would not be looking at the headstock or carriage adjustment. You could turn a center in the headstock and line it up with that live center and visually try and see how close they are in alignment…Good Luck, Dave.


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## T Bredehoft (Jul 17, 2015)

Does the spindle have a Morse taper in it?  (many do) could you put a dead center in the spindle (with the chuck removed) and see how that alligns with the live center?  Use a loupe (10x magnification) to verify alignment, or lack thereof.  If you don't have a Morse taper, try what Chips (above) said, turn a point on a piece of scrap and bring the live center in to not quite touch.


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## rrjohnso2000 (Jul 17, 2015)

Everything very well may have checked out with the lathe while at sherline.

Now it is home. Maybe something shifted in transit, the temperature is different, the lathe is supported on a different base, or they just plain screwed the pooch. Really doesn't matter, the tailstock is likely out of alignment and needs to be adjusted in its current location to correct whatever issue is wrong.

They also sell adjustable live centers. I would guess to make it easier to adjust. I'm not familiar with the tailstock adjustment on this particular lathe. 

You might want to look into using a test bar to aid in the adjustment and for future verification of alignment. 

Good luck getting it going. There are some very experienced here to assist.


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## Bill C. (Jul 17, 2015)

I went to their website, http://www.sherline.com/latheins.htm, tapers are cut but moving the headstock. I am beginning to think your tool is pushing the stock out the .003.  The larger stock is to thick to be pushed.  Double check the clearances on the tool bit that it is not rubbing instead of cutting.  Use a black marker and mark all the cutting edges.   The only other thing would be to take the tailstock off and be sure there are no chips trapped under it.

I wish I could be more helpful.


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## NightWing (Jul 17, 2015)

Try indicating the bar from the chuck to the center before you machine it.

What are your tolerances on the finished part?  A two place decimal dimension isn't usually held to great accuracy.

Machining slender stock like that requires dead on-center cutting.  A hair high or low will give you crazies at the tool tip.


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## tomw (Jul 17, 2015)

Dear All,

Thank you for your advice. I will try all of the above stuff and report back.

I have made sure the taper and chuck are clean, and I did a visual check with a dead center in the tailstock and headstock. However, I did not indicate it.

Thanks,

Tom


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## T Bredehoft (Jul 17, 2015)

Only trust a co-axial indicator to do this, any other is subject to gravity.


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## Bill C. (Jul 17, 2015)

T Bredehoft said:


> Only trust a co-axial indicator to do this, any other is subject to gravity.




Never heard of this type of indicator before, found a good YouTube video on using it, 



.  

Thank you.  I always learn something new on here.


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## mikey (Jul 17, 2015)

I have a suggestion. The Sherline live center may be off, and I know without a doubt that the tip of the live center can be misaligned with the morse taper. Use a test bar with accurately drilled centers and put one end in a dead center at the headstock end and use the live center at the other end. Use a dial indicator and index the live center (rotate the live center in the socket) to minimize deflection. There will be a position where the live center will show minimal run out. Mark the live center and ram so you can always put the center back in the same position every time you need to use the center.


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## tomh (Jul 17, 2015)

You need to put the dead center in the tail stock turn a piece  and check it  until you do this you will only be guessing at best.  I have seen live centers that were the cause of much frustration.
also do you have the square alignment  bar   under  the head stock.?
Tomh


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## pineyfolks (Jul 17, 2015)

Since you're tailstock does not adjust an adjustable tailstock center may be an option


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## kvt (Jul 17, 2015)

I also have a fairly new 4400,  without the DRO though.   I also had problems,  The live center was not center.   Clean the tapers, insert the dead centers, and check.  Now use the dog to hold a piece and turn it between both centers.  Then check to see what run out you get.   If everything is good, then place your three jaw on the spindle and try another test cut.   Check to see how it did.   If good then replace the dead center in the tail stock with the live center and try another cut.   See what you get.   It does not take much to cause this problem.  
Another problem could be what are you using to drill the center,   If using the drill chuck that can cause you to drill center a bit off also.  

Be sure to put oil on the dead centers.  and recheck often.  .   

Also I have had it where I though it was good on the center but as it spins, it smoothed the item out, and became loose.  thus when trying to turn, it was deflecting away from my tool, causing this problem.  

Note:   I have a second set of fresh pointed centers that I use just to check the alignment as I also due some tapers on purpose, Thus Have to put the head stock back and check it.
I have though about ordering an extra tail stock, or finding one on ebay and making a fully adjustable tail stock to fit mine.   T

I hope this helps you out.


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## RJSakowski (Jul 17, 2015)

If you are turning a taper between centersbecause of deflection due to tool pressure (lack of support or wrong tool geometry), you would get a barrel shaped turning.  If you get a straight taper, it is an off-center tailstock.

Bob


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## Kernbigo (Jul 17, 2015)

adjustable tailstock center


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## f350ca (Jul 17, 2015)

Tom, from your photo it appears your turning from roughly the middle of the shaft to the headstock and seeing the taper. Set up a piece of stock as you have done but take a light cut, say .005 from the tailstock all the way to the headstock. Check the diameters at the ends. If they are the same the tailstock is in alignment, and your taper is due to the shaft flexing.  If the dia at the tailstock is different than at the headstock then you have an alignment problem.

Greg


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## john.oliver35 (Jul 18, 2015)

I have an old 4400 that has a badly worn tailstock ram.  When turning shafts I have put a rod between dead centers, turning with a lathe dog.  Then shim the tailstock at the ways with brass shims until a test cut shows that the diameter at the headstock and tailstock are the same.  Tedious, but it works.  Takes about 1 extra beer per part


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## Kernbigo (Jul 18, 2015)

The last cut should be only .001 on something the springy


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## cvairwerks (Jul 19, 2015)

You may have to improvise and use a sanding stick for the last few thousandths. Checking a couple of the online speeds and feeds calculators calls for a 6K+ rpm for a piece .190" in diameter. I would bet that you are running way slower than that and taking too much cut.


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## tomw (Jul 20, 2015)

Dear All,

I did a turn between centers using 3/8" diameter brass stock, 2.5" in length. I used a  dead center in the tailstock and a lathe dog and center in the headstock. All surfaces and tapers were clean, I used a newly sharpened HSS toolbit with an approx. 1/32" nose radius. I used a loupe to set the tool height to exactly center as compared with the center in the headstock.  I took an initial .005 cut, then reduced that to .003.

The diameter of the part was measured at the closest point to the headstock and at 1.5" from the headstock. Dimensions were measured with my Mitutoyo 1" micrometer (digital, model IP65). The measured surfaces and measuring surfaces were cleaned prior to taking measurements, and the micrometer was zeroed. I used the ratchet mechanism to tighten the ram against the part being measured.

I got a taper of .0065 over 1.5".

I bought the adjustable center from Sherline (part number 1201)


After 6 hours of on again/off again futzing around, I got the taper, measured over 1.5", to .0002. WHOO HOO!!! Eff Yeah! I can now make my part!

My conclusion: the tailstock is very far from being accurately positioned relative to the headstock. Whatever measurements they did at Sherline when I sent the lathe back were not adequate, or it was upset during shipping in the exact way it had been off before sending it to them.

Thank you again for all of your help. I have learned more about lathe centers and center alignment than I ever had known I would need!

Cheers,

Tom


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## Tozguy (Jul 22, 2015)

As already said, it is handy to have an adjustable tailstock center so that you can turn a taper on purpose or turn a dead straight cylinder on purpose. An adjustable boring head that fits in the tailstock quill would be another way of compensating for a non adjustable TS.


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## kwoodhands (Jul 25, 2015)

tomw said:


> Dear All,
> 
> I am having a frustrating problem.  I can't turn between centers without getting a taper.
> 
> ...



Tom, seeing that your TS is not adjustable,make the center adjustable.Either use a boring bar holder and a 60° point instead of the cutter or make an adjustable one. There are plans on the web for this.I use a boring bar holder myself.
I hate realigning the TS after turning tapers that's why I use the boring bar holder.
To align the point,use a round that is center drilled on one end and a 60° point on the other,mine is about 8" long,length not critical.The point sits in the center drilled work piece and the other end that is center drilled goes into the dead or live center in the TS.Now install an indicator on the tool holder. Take readings at the #1 and #3 scrolls. 
Add the two readings and divide by two. This is the correct reading for the #1 and#3 scrolls.Repeat for #2 and #4.
I'm assuming you are using a 4 jaw chuck.Repeat this process until you are satisfied the work is centered.
Any taper should be negligible,probably less than your ability to measure.

mike


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## planeflyer21 (Jul 25, 2015)

Hunt around this guy's channel, as he's doing his lathe work on a Sherline also.  One of the vids I remember him adjusting the headstock to cut tapers.  It may have some useful info:

https://www.youtube.com/channel/UCworsKCR-Sx6R6-BnIjS2MA


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## Wreck™Wreck (Jul 26, 2015)

tomw said:


> The diameter of the part was measured at the closest point to the headstock and at 1.5" from the headstock. Dimensions were measured with my Mitutoyo 1" micrometer (digital, model IP65).



IP 65 is an Ingress Protection Rating issued by the IEC  for electrical and elctronic devices, basically how liquid and dust resistant said device is. You may not have a good deal of experience running a lathe with flood coolant, coolant ingress will cause serious problems with unprotected electronic digital micrometers, calipers and indicators.

IP also covers electrical enclosures, the "ingress" of body parts into the conducting surfaces of terminal connections on motor starters, relays, terminal blocks and timers and so on.


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## 4GSR (Jul 26, 2015)

Your bed has a slight twist in it.  If you have it bolted or screwed down to a piece of wood or bench, loosen the screws at the tail end of the bed and see if the problem goes away.

BTW- the co-axis indicator is not the correct way to check alignment between the headstock and tail stock.  There is one and only one correct and accurate way of checking alignment.


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## tomw (Aug 1, 2015)

Ken,

I am not sure what you mean by Co-axis indicator. I used a micrometer to check for taper, and visual inspection of the centers to look for misalignment.

I will check to see if loosening a hold bolt makes a difference. I was already thinking about bolting the lathe to a machined flat chunk-o-steel.

Thank you all for your help with this problem. The adjustable center solved my turning problems. Using the mill has solved my drilling problems (for now).

Thanks again,

Tom

p.s. Mike, I just read your post carefully. Sherline makes an adjustable center, so you technique isn't needed. However, I can think of several uses for it, so thank you for posting that.


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## kwoodhands (Oct 29, 2015)

tomw said:


> Dear All,
> 
> I am having a frustrating problem.  I can't turn between centers without getting a taper.
> 
> ...



Tom, the quill with your live center may be adjusted too tight.Possible you have slightly bent the shaft.Adjust the quill so the live center just turns,you may have to readjust with use.
mike


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## Bill C. (Oct 29, 2015)

Also when turning small slender diameters try a smaller radius on the nose of your tool bit.  Good luck


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