Pen mandril saver

[Penpal]

In these days of so many and various pen kits you can come to grief very easily with directions varying mandrel sizes bush variations. Your valid question and the following answers must have sent you into orbit. Personally where you buy your kits etc is the best place to seek the answers otherwise chaos will follow. First thing mixing metric and imperial sizes will cause you grief. In Dorset seek out a Turning group where you can join and as a member get through these early stages. Have fun I do.

Peter.

 

[21William]

What you are calling 7mm mandrels are just the normal mandrels on sale.

Peter

It's not my description of the product, Penn state say clearly on their website that their Maxi-Mandrel "features a 7mm mandrel shaft that slides through a headstock collet".

https://www.pennstateind.com/store/PKM-FLC.html

No ambiguity there, BUT, elsewhere on their website in the Q & A someone asks if their mandrel saver works with the Maxi-Mandrel to which the answer is yes. The mandrel saver is stated as having a .245" hole in it so I asked how the 7mm shaft of the Maxi-Mandrel fits into it! My question duly appeared on their website only to be deleted some minutes later! The recommended bushes also have .242" holes in them so it seems quite clear that the shaft isn't 7mm as stated on their website but something under .242".

I've read lots of complaints about bits not fitting properly so hoped to avoid it by knowing exactly what I'm buying but clearly some manufacturers have trouble describing what they sell properly. As others on here I'll be making my own bushes etc so it's not a problem now I know.

 

[Lons]

Hi William

I have one from http://www.penkitsuk.com/ which was a cheapie and more recently an Axminster http://www.axminster.co.uk/axminster-evolution-series-compression-pen-mandrel-ax942635 'cos I got a gift voucher as a pressy. I make pens of all sizes with those 2 mandrels.

i'd have to read through the posts as I've probably missed something but I can't see why you're getting hung up on that specific mandrel and saver from PSI.
I'd just buy something more easily obtainable and check that everything fits properly as Brian said. If you're making up your own bushes to suit larger than 7mm tubes it matters not one jot what size the mandrel shaft is as long as a good fit in the collet end and the saver. Just make sure the centre hole of your bushes are accurate, turn part down to a good fit inside the tube and the rest to the dimension of the pen component. a number of kits have one tube smaller than the other (just look through instructions on the websites) so you need bushes for both tubes, or use callipers.

Here's an example though don't know which kit.

 

[Lons]

It's not my description of the product, Penn state say clearly on their website that their Maxi-Mandrel "features a 7mm mandrel shaft that slides through a headstock collet".

https://www.pennstateind.com/store/PKM-FLC.html

No ambiguity there, BUT, elsewhere on their website in the Q & A someone asks if their mandrel saver works with the Maxi-Mandrel to which the answer is yes. The mandrel saver is stated as having a .245" hole in it so I asked how the 7mm shaft of the Maxi-Mandrel fits into it! My question duly appeared on their website only to be deleted some minutes later! The recommended bushes also have .242" holes in them so it seems quite clear that the shaft isn't 7mm as stated on their website but something under .242".

I've read it and it's very badly written but if you dig deeper it's also clear that it's pretty standard and as normal intended for turning from 7mm tubed kits upwards. If you look at the instructions and the link to additional bushes you'll see that.
Even for American English it's confusing if you don't know!

 

[wm460]

Taken from Bear Tooth Woods website.
Berea has A and B Mandrels.

A mandrel is a round steel rod that you slide the wood blank with the brass tube inserted onto. Unlike most other companies who offer only one size mandrel we sell two sizes. The A mandrel (sometimes called a "7mm" mandrel) which is 0.247 +0 -0.002 inches in diameter and and other mandrel which has a larger diameter, the B mandrel. This is 0.291 +0 -0.002 inches in diameter. We use the B mandrel on some kits because the thicker diameter helps prevent whip while turning and allows for a much better result.

 

[Phil Dart]

Is it not time to campaign for a voluntary British standard regarding shaft diameters and bush i/ds ? If The Berea size A dimensions above are correct, there are very few bushes sold in this country that would fit actually fit it without the need to drill them out.

 

[Grump]

Is it not time to campaign for a voluntary British standard regarding shaft diameters and bush i/ds ? If The Berea size A dimensions above are correct, there are very few bushes sold in this country that would fit actually fit it without the need to drill them out.

Good idea Phil but i fear it will fall on deaf ears, it would take an atom bomb to wake this lot up init?
I been trying for years and gave up long ago.

This place has become a jokers paradise and none of them are new.

 

[Penpal]

Alarm bells are ringing constantly in every regard to pen turning the proliferation of different kits, platings ,accessories we have to use our judgement what we do about it. Refreshing to learn others share this concern.

Peter.

 

[21William]

The A mandrel (sometimes called a "7mm" mandrel) which is 0.247 +0 -0.002 inches in diameter and and other mandrel which has a larger diameter, the B mandrel. This is 0.291 +0 -0.002 inches in diameter. We use the B mandrel on some kits because the thicker diameter helps prevent whip while turning and allows for a much better result.

Thanks for that. This really gets to the crux of the matter. Having decided that most of the kits I liked had larger tubes it made sense to me to use the largest available mandrel as it would be more robust. The so called 7mm therefore seemed to be a better bet for the reasons given.

It's not surprising I've read so much about stuff not fitting properly as they all seem to use slightly different sizes.

Thanks again for the data about that A and B mandrel, very helpful.

Edit: just had a look at the Bear Tooth Woods website and they say this, wish I had seen it before!

"Why are there two sizes of mandrels?
Berea Hardwoods and Bear Tooth Woods support two different sized mandrel systems. The “A” sized system is mainly used for the pens based on the 7mm tube (with two notable additions, the cigar pen and the sierra pen), while the “B” sized system is used with all other kits.

The “B” sized system has the benefit of being thicker than the “A” system. This added thickness provides a much more stable platform for making pens. This stability reduces the out of round problems that can occur when making pens."

 

[21William]

Video of the centre posted by the OP:

http://youtu.be/OTKBZN86c0M

 

[Penpal]

Made of a 2 morse taper shaft stepped down to hold a bearing and tapered body. There are so many look alikes made today. Essentially the through hole should match your mandrel whatever type you go for.

Peter.

 

[wm460]

I have got both A and B mandrels from BTW will measure them later today for you.

 

[wm460]

The best mandrel saver I got from Peter, made to his Specifications.

 

[wm460]

I just measured my mandrels the A mandrel are all 6.25 mm or 0.289" the B mandrel are all 7.35 mm or 0.289". Have taken a photo will post later when I go inside
Don't buy B mandrel unless are going to make Barea large pens.

Sent from my D6683 using Tapatalk

 

[wm460]

The bottom shaft is an A mandrel.

 

[21William]

Thanks for that, very helpful.

 

[Penpal]

Video of the centre posted by the OP:

http://youtu.be/OTKBZN86c0M

This is a CSUSA Mandrel Saver for your info.
'
Peter

 

[qquake2k]

When they say "7mm pen mandrel", they are referring to a mandrel that will fit the ID of 7mm OD tubes. For pens that take larger tubes (8mm, 10mm, 3/8, etc.), the bushings have steps cut in them to fit the ID of the tubes. The through hole of the bushings will fit onto the "7mm mandrel".

As for the original topic, I have the PSI version of the mandrel saver. I haven't been able to use it. I can't get enough pressure on the bushings to prevent the blank from spinning, especially during roughing. It's not "tailstock creep", as the tailstock on my Jet lathe is rock solid. I'm sure it's my turning technique, I'm probably too aggressive. I know many turners use the various mandrel savers with good results.

https://www.pennstateind.com/store/PKMSTS2.html

 

[21William]

I wonder what type of bearing that is, I think it needs to be an Angular contact type to do the job properly?

 

[Penpal]

I do note with interest you use a real lot of spacers every one is a potential slip factor the other is mandrel savers are better used with a cut off mandrel ie the thread cut off because there is a distinct change in size right there that can promote both a wobble and a misfit. An advantage of a longer nose mandrel saver is you can straight way do away with two spacers on the outboard end. Using the Collett chuck or the slip through feature in both ends of your set up and only turning one half of a pen at a time you could restore the grip for turning. The mandrel saver I use and the one that went to the north of Australia to Tennant Creek made for me here are turned from a tough steel giving long life and precision made.

Peter.