Adjustable Mandrels

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sdemars

sdemars

Member
Joined
May 17, 2008
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318
Location
Louisiana, USA.
We received (2) adjustable mandrels from Craft Supply. After examining them both I was a little concerned because the morse taper was not smooth. If you drag you nail across the morse taper from end to end , it feels like it has hundreds of rings. Kind of like a worn out file. Is this normal, everything else I have with a morse taper is smooth as glass. It also has a threaded hole at the rear (small) end, what is this for.

Will this hurt my spindle?

I slid it in to see if it ran true & it was rather hard to remove. Had to take it out with the rod.

Thanks in advance,
Steve
 
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The threaded hole in the small end is for a draw bar. This is unusual in a mandrel chuck, but quite common in drill chucks, collet chucks and buffer arbors. The idea is that you put a bolt through the headstock into that threaded hole to retain the taper.

This past weekend I was over at another shop turning bottle stoppers and being used to my thread mount Beall collet chuck, I did not notice that the other guy's PSI collet chuck was taper mount, and he had no draw bar. I was very surprised when his collet chuck started to eject itself at 3000 RPM!

I expect you would use the draw bar on the pen mandrel if you were doing closed end pens with it.

As to the rough surface, I have one taper with a rough surface and thats the one on my 3 in 1 buffing system. As the torque applied on pen making is rather low, I doubt this is a problem with a pen mandrel, but not having the thing in my hands its hard to say for sure.
 
Mandrel

My collet chuck has a 3/8 thread at the small taper end and since I dedicate one lathe for Modified Slimlines I bought some threaded rod and having lightly reamed the female morse taper hole fitted the mandrel and locked it in place through the head stock, I have done this on my bench drill following the release at full speed on one occasion of the tapered drill chuck. On my largish Mill Drill and whilst making a supposed accurate cut the cutter descended and wrecked the job ,cured that forever with a captive chuck with threaded rod again.

Most frightening to me is the number of folks who use Morse Taper shafts for buffing after all Morse Tapers depend on being held in for accuracy and safety, anything that creates sideways stress can drop out MT,s.

I would return immediately any MT with so called steps or rings as sub standard and unacceptable.

Have success Peter.
 
if the ridges are tiny , I'd ignore it..having to tap it out is normal..the threaded end is for a rod that threads on and then runs thru headstock & out the back..you need to put a washer & wing nut on & cinch it tight..that way it won't work it's way loose
 
holmqer said:
The threaded hole in the small end is for a draw bar. This is unusual in a mandrel chuck, but quite common in drill chucks, collet chucks and buffer arbors. The idea is that you put a bolt through the headstock into that threaded hole to retain the taper.

This past weekend I was over at another shop turning bottle stoppers and being used to my thread mount Beall collet chuck, I did not notice that the other guy's PSI collet chuck was taper mount, and he had no draw bar. I was very surprised when his collet chuck started to eject itself at 3000 RPM!

I expect you would use the draw bar on the pen mandrel if you were doing closed end pens with it.

As to the rough surface, I have one taper with a rough surface and thats the one on my 3 in 1 buffing system. As the torque applied on pen making is rather low, I doubt this is a problem with a pen mandrel, but not having the thing in my hands its hard to say for sure.
Click to expand...


The hole at the end of the MT is to allow the mandrel to extend out when adjusted for short blanks. The pen mandrel cannot present a problem of coming out in normal use. The tailstock holds it in place.
 
From a quality standpoint, a Morse taper should be very smooth, the holding in of the mandrel is by interference fit, the surface if both the socket, and mandrel should be a ground or reamed surface (NO RIDGES REQUIRED) what you have is a poorly machined mandrel, it is entirely possible that this will eventually put undo wear and tear on you headstock spindle. This is just my opinion as a machinist, you might check with Johnnycnc see what he says about it.
 
holmqer said:
The threaded hole in the small end is for a draw bar. This is unusual in a mandrel chuck, but quite common in drill chucks, collet chucks and buffer arbors. The idea is that you put a bolt through the headstock into that threaded hole to retain the taper.

This past weekend I was over at another shop turning bottle stoppers and being used to my thread mount Beall collet chuck, I did not notice that the other guy's PSI collet chuck was taper mount, and he had no draw bar. I was very surprised when his collet chuck started to eject itself at 3000 RPM!

I expect you would use the draw bar on the pen mandrel if you were doing closed end pens with it.

As to the rough surface, I have one taper with a rough surface and thats the one on my 3 in 1 buffing system. As the torque applied on pen making is rather low, I doubt this is a problem with a pen mandrel, but not having the thing in my hands its hard to say for sure.
Click to expand...

It probably was the woodcraft collet chuck, not PSI. PSI's collet chuck threads onto the headstock.
 
I would not be terribly concerned with the rough finish on the taper, if it is just tiny 'rings'. I have used both smooth and rough. Tapered sleeves I use at the shop are not ground finish. Most important thing is that the tapers match. The fact that you had to knock it out is a good sign to me. I would use the draw bolt if it is drilled for it.
 
Thank you . . .

Paul in OKC said:
I would not be terribly concerned with the rough finish on the taper, if it is just tiny 'rings'. I have used both smooth and rough. Tapered sleeves I use at the shop are not ground finish. Most important thing is that the tapers match. The fact that you had to knock it out is a good sign to me. I would use the draw bolt if it is drilled for it.
Click to expand...

Thank you Paul . . .

Steve
 
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