Follow up on pen blank preparation

[jimr]

I really appreciate everyones thoughts and help. I do use a barrel trimmer and mount it in the drill press. I was beginning to think that if the barrel was not parallel to the blank sides then you bring the cutter head down on the blank, and that calls for some force depending on the wood, the blank would only be seated on the drill press base by one edge. If the pressure applied by the drill press is enough then the entire blank could be skewed out of square with the trimmer shaft. Now that I think about it and read all the comments I don't believe that would happen. Someone mentioned not tightening the knurl knob to tight. I do tighten it as tight as I can but I am doubtful that would spring the mandrel. Everything is to close to a center. Another point was the mandrel not running true. That is very likely my problem. I have an old lathe and would not be surprised if the morse taper is worn. I take great pains in trying to get the live center exactly centered on the mandrel and not tighten it to tight. I am getting more certain the culprit is the morse taper. I do know that there is some tiny vibration of the bushings when roughing a blank at low speed. My solution is probably to break down and spring for a new lathe.
I sure appreciate all the responses and comments. Discussing a problem is what is needed in many cases to make the whole thing a lot clearer.
Thanks to all

 

[Daniel]

Just ot let you know, I have been turniing pens for two years on a $99 Horbor Freight Special lathe. So you don't necessarily need to break the bank. of course just a few months ago I bought a $360 mini Lathe. adn it is much nicer. Although I have never had problems with the old lathe.

 

[fmunday]

Originally posted by jimr
<br />I do tighten it as tight as I can but I am doubtful that would spring the mandrel. Everything is to close to a center. Another point was the mandrel not running true. That is very likely my problem. I have an old lathe and would not be surprised if the morse taper is worn.

It doesn't take much to force runout in the mandrel shaft. I can't quote Russ Fairfield word for word so I would suggest that you look on his site for his bent shaft tuning procedure. Unless the bearings supporting the drive are badly worn or you've been spinning something in the head stock MT, it seems to me that it would be unlikely that the head stock MT is worn enough to cause much runout. One quick and cheap thing that you could do is put your chuck on and see if it looks like it is running true. That should eliminate worn bearings etc. I've had rounout problems in the past and it has always turned out to be something that I caused. The "professional" mandrel from Woodcraft and other sources is not much better than the cheaper ones. I now use my chuck with spigot jaws and chuck down on a mandrel shaft. Seems to work fine for me. Your mileage may vary. []