Mandrel?

[EarlD]

Today I turned my first two single barrel pens - Le Rois. I've always turned two barrels at the time on the mandrel. Today I shortened the rod in my morse taper mandrel and was amazed at how much better the blank turned. With two barrels on I always have lots of chatter (I do sharpen the gouge) but had almost none today. I was able to turn lots closer to finished size before starting to sand today. I suspect that the mandrel, when used longer, is giving me some flexing. Does this seem like a possibility?

The mandrel is about 4 years old and came from either PSI or Woodcraft. Are there any better mandrels available? I know I could turn one at the time but with pens like the Comfort with a curve in the shape, It's much easier to turn both at the same time.

Suggestions?

Earl

 

[its_virgil]

Earl,

A shorter mandrel is a stiffer mandrel. I turn all pens on a short mandrel one barrel at a time. You've discovered an excellent technique but as long as you condiser turning on a shorter mandrel to be more difficult or time consuming you will not want to change.

I don't think it is more difficult nor does it take more time to turn one barrle at time on a shorter mandrel. You have a choice: shorter mandrel and better pens or go back to the longer mandrel. The longer mandrel flexing may be an indication that your tools are not shape. Dull tools require more pressure to force the cut which will cause the mandrel to flex.

Better mandrels? Personally, I don't think so. I really think most are all about the same. The age of your mandrel should not be a factor. I use mandrels that are older than 4 yrs and have turned hundreds of pens. I do make my own mandrels using drill rod. It is not a difficult thing to do. But a new mandrel will not solve your problem...I don't think. You must figure out what you need to do: shorten your mandrel, sharpen your tools, turn faster, a combination of all three.

I suppose the no mandrel crowd who turn between centers with special bushings will chime in soon. That is an excellent option but since I don't turn pens between centers I'll let them share that info with you.

Do a good turn daily!
Don

Today I turned my first two single barrel pens - Le Rois. I've always turned two barrels at the time on the mandrel. Today I shortened the rod in my morse taper mandrel and was amazed at how much better the blank turned. With two barrels on I always have lots of chatter (I do sharpen the gouge) but had almost none today. I was able to turn lots closer to finished size before starting to sand today. I suspect that the mandrel, when used longer, is giving me some flexing. Does this seem like a possibility?

The mandrel is about 4 years old and came from either PSI or Woodcraft. Are there any better mandrels available? I know I could turn one at the time but with pens like the Comfort with a curve in the shape, It's much easier to turn both at the same time.

Suggestions?

Earl

 

[Smitty37]

Can be an issue

If the mandrel has been used for finishing using some of the standard finishes a lot of pressure has to be applied to get the finish to take right. The pressure can bow the mandrell some over time. I don't know of any one that is outstanding compared to another.

 

[JimB]

Assuming your mandrell isn't bent I would guess either your tools aren't sharp and therefore you are pressing to hard or you should turn at a higher RPM or both issues exist. There is also the possibility that you are not tightening the madrell correctly (to loose or to tight). Bottom line is you should not be getting chatter all the time.

BTW, I turn using a manderell but also between centers. I have gotten chatter in both situations and it has always been becuase I got lazy and didn't sharpen my tools. I turn at around 3000 RPM.

 

[fernhills]

I am a one barrel on the mandrel at a time guy to. I do not sand to profile but sand only to smooth to take a finish. I will put two barrels on the mandrel to apply the final finish, because i can`t count and forget how many coats i put on, if i do them separate. I stop turning just before final profile and loosen and rotate the blank on the mandrel,then re tighten, and then continue on, that helps a lot to keep things aligned. Carl

 

[JD Combs Sr]

A larger diameter mandrel (B-size) also helps reduce chatter. I have drilled out A-size bushings to fit my B-mandrel to prevent chatter. Of course this only works for bushings that are large enough to drill. You are stuck with the A-mandrel when doing any of the 7mm tube pens. I haven't tried it on 8mm pens either, that would probably push the limits of a bushing.

 

[crabcreekind]

My suggestion to help with vibration is a mandrel saver
http://www.pennstateind.com/store/PKMSTS2.html

I have recently bought one, and it works like a charm. I love it, also i got a dead center to finish between centers. It works wonders and no stuck bushings!

 

[thostorey]

I don't know how many pens you have turned on that mandrel Earl, but after 4 years of use it likely does not owe you anything. Penn State sells #2 MT Pen Mandrel Saver Package for about $27. I have one and it allows me to use only as much mandrel shaft as required and saves undue forces on the full length of the mandrel. that equates to less chance of a wow in the mandrel shaft. fwiw

 

[mtcsss]

No chatter at all!!!

Turn between centers and learn to use a skew and you can skip the sanding step all together. That's great for turning blanks made up of various wood species. There is no carry over of micro sawdust from one species to another at all. Apply a CA finish and you will have a perfect pen every time with less finishing time.

 

[randyrls]

I suspect that the mandrel, when used longer, is giving me some flexing. Does this seem like a possibility?

Earl; that is likely.

The mandrel is about 4 years old and came from either PSI or Woodcraft. Are there any better mandrels available? I know I could turn one at the time but with pens like the Comfort with a curve in the shape, It's much easier to turn both at the same time.

With the comfort, I usually turn the center portion until it is round, then remove the center bushing. I can then make the sweep of the taper on the pen perfect. Turn, sand, then separate blanks to finish.

To check for alignment problems, lay the shaft of your gouge across the bushings at head stock, center, and tail stock ends with the lathe running. Any vibration means something is wrong or out of alignment. USE CARE WHEN DOING THIS! Only touch the bushing with the lathe tool shaft!

While the mandrels from Woodcraft and PSI are nominally the same size, the Woodcraft mandrels run a bit bigger than PSI. The size is the same, but the tolerance is likely different. A PSI bushing may be difficult to put on a Woodcraft mandrel. Both places sell "bare" mandrels with no attachments but the threads on the head stock side are different! [/quote]

 

[ed4copies]

Rather than type a long entry, just read Don's again---he describes "our" way.

Works for "us".