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Misaligned centres

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Forum topic by JoshNZ posted 08-27-2015 01:36 AM 947 views 0 times favorited 13 replies Add to Favorites Watch
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JoshNZ

53 posts in 535 days


08-27-2015 01:36 AM

What can you do about this? My tail stock live centre is about 1-2mm to the left of centre (when looking at the head stock from the tail stock). I’ve tried applying pressure as I clamp it down but it sits in the same position each time pretty snugly.


13 replies so far

View Oldtool's profile

Oldtool

2374 posts in 1656 days


#1 posted 08-27-2015 02:41 AM

Well, here’s my two cents worth:
First, don’t know what lathe you have, so can’t reference any manufacturer’s information, which I typically Google when I need repair or fix instructions.

However, I have a cheap Harbor Freight lathe, the cheapest they sell, the 7” X 40” model. This lathe has a tail stock that has a lot of sideways movement, and “a lot” is an understatement. I thought about it, while eyeballing a center location lockdown, but it occurred to me that it’s not mandatory these be exactly on the same center line.
What will happen is that your turning will be round, but just not on the same center line as the bed. You probably won’t notice this slight misalignment, and you’ll probably compensate for it in the adjustment of the tool rest when turning.
I’m in the middle of making a Shaker style headboard, with turned bed posts, and they came out just fine. If you want, I can PM you a few photos of these 3” X 3” posts l’ve just finished turning. I’ll be posting this project when finished, & have the photos already.
In brief, if your lathe is not under warranty & the manufacturer’s responsibility to correct it, and you are leary of using it, don’t be. The center turnings will be to your satisfaction.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

View LeeMills's profile

LeeMills

271 posts in 767 days


#2 posted 08-27-2015 03:08 AM

You can get a double 2MT taper from Nova but I agree with Oldtool.
For most spindle turning (unless one end is held rigid by a chuck of some sort) you are turning between centers.
If you take a yardstick and hold it between two fingers it doesn’t matter where you move your fingers the yardstick is still a straight line.
The other place where true alignment may make a difference is drilling, such as a peppermill.
On my lathe there are 4 screws under the tailstock than can be loosened to adjust alignment.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View REO's profile

REO

889 posts in 1539 days


#3 posted 08-27-2015 03:59 AM

WOW! I didn’t expect these answers! I have been through this discussion before on several occasions and the vast majority believes that they have to be exactly aligned. Nice to find practical application ,understanding and explanation concerning this. Between centers it has no effect, when the part is worked in a fixed mount such as a faceplate or chuck and the tail stock is used for support or rigid drilling would be the occasions that it could make a difference. when drilling for raw removal and finishing the hollowing with tools either rigid or fixed the part will come out round and concentric to the headstock bearing axis anyways.

View LeeMills's profile

LeeMills

271 posts in 767 days


#4 posted 08-27-2015 07:13 PM

REO, I do think it is best (but maybe not necessary) for them to be “perfectly” aligned. My headstock rotates and I use it often so it is seldom perfect alignment, I can normally see the 1-2mm difference. If I need it close I put on my reading glasses to align the points. I do have the double end 2MT for “perfect” alignment but only use it when drilling.
Perfect is best, at 2mm at the points it is a lot further off 12-16” away as in drilling.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View JoshNZ's profile

JoshNZ

53 posts in 535 days


#5 posted 08-27-2015 07:25 PM


WOW! I didn t expect these answers! I have been through this discussion before on several occasions and the vast majority believes that they have to be exactly aligned. Nice to find practical application ,understanding and explanation concerning this. Between centers it has no effect, when the part is worked in a fixed mount such as a faceplate or chuck and the tail stock is used for support or rigid drilling would be the occasions that it could make a difference. when drilling for raw removal and finishing the hollowing with tools either rigid or fixed the part will come out round and concentric to the headstock bearing axis anyways.

- REO

This is exactly what I am doing and why the issue has bugged me enough to post here. I was prototyping a few chess pieces which I want fixed at the head stock so I can sand the tops of the pieces perfectly round (or shape them as appropriate). So I mount the stock on the head and run the lathe as slow as it goes and ease the tail stock into it. I notice it penetrates slightly off centre and bores a conical centred hole as a result. It is actually not too bad, as I said it is slightly to the left when looking up the stock so it is supported in the direction tools will exert force.

However… I have noticed as I work the piece more, sometimes a clicking sound develops (that sound when a hair of wood is hanging off and catching your tool rest – but there isn’t in this case). I can only imagine as the piece is worked thinner it is the tail stock pulling the piece off its axis each revolution. The clicking is movement in the base or maybe even the glue joint flexing, or the bearing on the centre, I don’t know. The issue really reared its head today when I released the tail stock for the final cut, as it backed off the end of the piece found a new centre, very slightly off. I had less than 1/4” to cut and sand so it was ok I didn’t lose the piece but… If there were some way around this I’d be happier hah…

View Wildwood's profile

Wildwood

1886 posts in 1600 days


#6 posted 08-27-2015 07:28 PM

REO, one reason or cause given for out of round turned pen barrels is misaligned head/tailstock. There are other causes too, but that misalignment on the list.

-- Bill

View MrUnix's profile

MrUnix

4233 posts in 1664 days


#7 posted 08-27-2015 07:30 PM

Gonna have to tell us what lathe you got before anyone can give any advice on how to fix it :)

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View JoshNZ's profile

JoshNZ

53 posts in 535 days


#8 posted 08-27-2015 09:26 PM

It’s a mastercraft I’m not sure of the model number, but it doesn’t matter :D I have got it aligned. The head stock swivels around to the short side of the bed for doing bowls as well (though I never really saw this as an advantage and haven’t used it). I pulled the cowl off the head stock and saw the interlocking pin was slightly bent. Not sure how this happened, might have been a mother of all catches for the prev owner lol. I removed it and bashed it straight, then without replacing the pin I got it aligned dead on the live centre of the tail stock and clamped it down, then replaced the pin.

Really does make all the difference I’m glad I took a break from the project to get this ironed out! Thanks for all the help guys :).

View REO's profile

REO

889 posts in 1539 days


#9 posted 08-28-2015 12:37 AM

Wildwood in the case of your pen mandrel the one end is fixed in the chuck. the other is forced to conform to an off center tail stock the different consistency of the wood forced to flex on each revolution can do some wild things. Also the mandrels are pretty flexible over their length and material out of balance can have the same effect. Again the culprit is fixing at the head stock. what is often overlooked is that this condition can happen when the centers do line up if the head stock is not in alignment with the bed. an extremely possible condition with both fixed and rotatable head lathes. another scenario is the tail stock being out of square with the bed same thing. harder to discern but prevalent conditions none the less. Josh hit the nail on the head as to what is creating the noise, cyclically the material slips in each jaw in and out causing the noise. truly turned between centers there is no way mechanically that a lathe can turn out of round without special adapters like an oval turning rig a square hole jig, or rose engine style turnings etc. not including chatter work or sick bearings. try turning between centers and then to finish the tops just chuck up in the chuck.

View JoshNZ's profile

JoshNZ

53 posts in 535 days


#10 posted 08-28-2015 01:40 AM

I don’t have a chuck lol… It’s a little way down the list at this stage but I will get there.

View Wildwood's profile

Wildwood

1886 posts in 1600 days


#11 posted 08-28-2015 04:52 PM

Nice to know info
https://www.youtube.com/watch?v=_c--nfxh8og

Run out more of a problem
https://www.youtube.com/watch?v=16xBV3PggQI

Don’t hurt to check if have a sliding or rotating head stock.
https://www.youtube.com/watch?v=8FF7A6WtzAo

REO, pretty much agree with what you have to say. Merely saying first thing pen turners told to check is head/tailstock alignment. Next is lathe and component run out. Then straighten that pen turning mandrel, caused by using dull tools and or applying too much pressure while turning.

-- Bill

View TheDane's profile

TheDane

4997 posts in 3128 days


#12 posted 08-30-2015 03:28 PM

I have a swivel head lathe … I bought one of Nova’s Acruline alignment accessories and use it every time I rotate the head back to center.

If your head/tail alignment is out of whack when you are turning pens, the mandrel can flex, which causes excessive vibration and produces unacceptable results.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View Rick M's profile

Rick M

7923 posts in 1845 days


#13 posted 09-03-2015 06:31 AM

Once problem I had when the tailstock wasn’t in alignment was it kept wallowing out the indention for the live center causing the spindle to vibrate and come loose.

-- http://thewoodknack.blogspot.com/

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