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Old 04-08-2014, 05:59 AM   #1 (permalink)
 
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Default Vibration near the tailstock.

Hello Everyone,
I would like to start by thanking you all for your collective knowledge. I am a new wood turner and I am having a little difficulty. I got a turncrafter commander lathe. Out of the box the head stock and tail stock did not align center to center. After searching here I was able to loosen the headstock screws and tap it into alignment (it had a horizontal misalignment). Now when turning pens I get vibration as I get closer to the tail stock. I am not sure if this is the result of more alignment problems or of a slightly bent mandrel. It starts as harmonics in the middle of the blank and gets louder as I move closer to the tail. Is there a way to test the mandrel or to straighten it?

Any advice is welcome.
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Old 04-08-2014, 07:10 AM   #2 (permalink)
 
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I wish I can help you; I have a different lathe. But don't "fear" this group is awesome and will advise you accordingly.
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Old 04-08-2014, 07:27 AM   #3 (permalink)
 
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Does the tailstock have any side to side slop before you lock it down? I looked at one in the PSI showroom and it had some, which my last lathe also had...if I didn't get the tailstock just right I would get the same chatter.
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Old 04-08-2014, 08:07 AM   #4 (permalink)
 
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Michael -- are you perchance using the tailstock with a point that came with the lathe?? Most of those do not have an angle that matches the dimple on the end of the mandrel and that has caused vibration for many new turners.

The machined dimple is at a 60 degree angle and the tail stock needs to be a close fit.

If you are using a mandrel saver tail stock, is it square in the socket with no debris or crud in the tailstock ram??
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Old 04-08-2014, 09:18 PM   #5 (permalink)
 
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I am getting the chatter with the 60 degree live center as well as the mandrel saver.
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Old 04-08-2014, 09:35 PM   #6 (permalink)
 
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Apart from the aspects already mentioned/suggested, you asked how you know if the mandrel is straight well, there are mainly 2 types of mandrels, the ones with a fixed shaft and the other where the rod is separate and can be adjusted on its length.

For this last one, the test is simple, you remove the rod and put it in a straight surface, rolling it slowly and see it it rolls straight or wobbles as it rolls.

On the fixed shaft ones, take any nuts or washes from the mandrel, put it on the lathe and adjust the RPM to no more that 1,000 rpm, (to fast and it will be difficult to spot), bring the tail stop to it and very gently nudge it so that is not too tight, just enough to maintain the rod recess in the tailstock (having the correct 60 dead center is most important). As you turn the lathe on, you will be able to see the wobble, if the rod is bent.

The rods on either mandrel type can be straighten quite easily if you take you lime and are careful in what you are doing, if it is either too bent opr you prefer to have it replaced, you can do so with the ones that the rod comes out, a new rod is inexpensive however, if the mandrel has a fixed shaft, you have to replace the whole lot, unfortunately...!

Hope this helps in regards to the mandrels issue...!

Good luck,

Cheers
George
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Old 04-08-2014, 09:39 PM   #7 (permalink)
 
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Quote:
Originally Posted by Psychmike22 View Post
I am getting the chatter with the 60 degree live center as well as the mandrel saver.
Well, in that case, I think that the alignment is still incorrect, you can have the 2 points meeting precisely, that doesn't mean they are exactly centred, either the tailstock or the headstock have a slight misalignment at the rear of the bases where the 2 points/centers are installed, it doesn't need much but the results can be significant...!

Cheers
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Old 04-08-2014, 09:55 PM   #8 (permalink)
 
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Something I have done since day nearly thirty years ago is only turn one half a pen at a time this reduces tendencies to vibrate simply from the size of the mandrel and the length being reduced. Works for me.

Kind regards Peter.
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Old 04-08-2014, 10:13 PM   #9 (permalink)
 
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That is what I have been doing. Especially with Acrylester. I lost a few blanks before I realized that they always shatter at the tail end. So now I work on the half closest to the head and then take off the blank and reverse it.
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