Thread: In search of perfection (or close to it)

The road to perfection is a never ending one, the closer you seem to get, the further you will move the goalposts out.

I know what you mean about the shop-bought mandrels, never found a good one yet.
That is one of the reasons I got myself a metal lathe, so I could make bushes and things for myself.
The best system I have found so far is the between centre bushes.
Though one 8mm mandrel that I made myself, that is held in a collet chuck with a homemade madrel-saver type live centre on the tailstock end, does a pretty good job, but I still finish off with the blank between centres, no bushes.

I wonder if something like this

SH-06.350X0304.80-12L14 Shafting - Ground - Cold Rolled Steel

could be useful.

cold rolled steel should be fairly stable and resistant to bending (I think)

We perhaps need some advive from friends in the metalwork forum.

I use the standard bushes for between center turning and have no problem. The manufactures if the doubled the length of the part that goes into the tube would be good and make them more rigid and stable for between center work I feel. I also have bought a mandrel saver and have been impressed with the way it works. Even when I used the adjustable mandrels I only ever turn one barrel at a time, less chance of any type of flexing. Well that is how I do it anyway. Good luck with your quest.

Originally Posted by Avery

I wonder if something like this

SH-06.350X0304.80-12L14 Shafting - Ground - Cold Rolled Steel

could be useful.

cold rolled steel should be fairly stable and resistant to bending (I think)

We perhaps need some advive from friends in the metalwork forum.

Thanks for that link Avery Keep in mind that .250"- 1/4" is slightly larger than our standard mandrels, consequently slimlines will not fit on them in most cases, and most bushes for other kits will need reaming to .250" to slide on neatly. Siver steel is probably the best bet for rigidity and reasonably available ,If I could afford it (not checked) ground toolsteel would be good as well . I went through all these frustrations a few years ago ,and settled for a small metal lathe for the general pen turning ( the purists all groan at this) I still do shaping and finishing on the woodlathe ,but get the best results I can without the dramas . I always turn between centres so get them concentric every time I suspect that as penturners we demand a higher level of accuracy in our turning than the tool providers allow for ,especially on machines designed for handtools and mostly wood. Cheers ~ John

Most of the mandrels I have used, the "post" screws into the taper. Could you not just make your own "post" from another type of metal. eg stainless. All you would need to do would be to add the threads to either end.

Just a thought

What sort of live centre in the tailstock are you using? I would have guessed over tightening the tailstock, but if you say you are no longer doing that, perhaps it is the mating of surfaces and your live centre is NBG

Greg, I think there has been discussion on this in the past, the turning between centres is probably the best alternative, however, I find that if I turn the whole thing round end for end, I notice some wobble even with the between centres method, which frustrates me. I guess that apart from a Metal lathe, it would have to be a very precise wood lathe if that is a possibility, and if it is a possibilty I think it would be an expensive one.Amos

I'm a novice so I use a mandrel saver.
Pen Mandrel Saver

my tuppence worth.

undies.

The biggest problem I found is the "off the shelf" bushes. The hole is not concentric with the outside of the bush on every one of mine I tested.

My guess on this, is the process of how they are made.
I suspect the bushes are made in a small backyard machineshop somewhere, and they use a cheap metal lathe with a 3 jaw chuck, put the rod in and machine the outside dimensions, then part off at the length needed, these would be thrown in a bucket. Then someone else picks up each one and puts it in a 3 jaw chuck, and drills the hole.
This would account for the eccentric hole, as nearly every 3 jaw chuck has runout.
I could be wrong here, but I think if they were using a CNC lathe to make them, they would at least be nearly accurate, but they are not.

I use a 3 jaw chuck when I make my bushes, but I leave the rod in the chuck without removing it for the whole process, all my bushes are perfectly concentric.

Greg, I'm not sure what you mean by "wobble". If you are talking about out of round results they can be caused by a variety conditions and mandrels are only one of a range of problems.

When I started turning pens I had a fairly basic MC900 wood lathe and used a 7mm mandrel with standard bushes.

I decided to get a better wood lathe and started shopping around checking every wood lathe that I could. Almost without exception the tailstock on these did not line up with the headstock when I put a dead centre in the headstock and a live centre in the tailstock. One in particular also had enormous runout on the headstock spindle (there are a couple of threads about this quest).

I finally settled on a wood lathe that was more accurate than most, and no it wasn't one of the most expensive ones!

Next on the list was getting a collet chuck and collets, again an improvement.

I then started looking at a metal lathe, not with the idea of turning pens but for turning bushes and other pen paraphernalia. The thing that really opened my eyes here was the way these metal lathes were constructed. The bed was constructed very accurately and beautifully finished, unlike most wood lathes where the tailstock has heaps of side to side play.

What surprised me even more was that the very accurate metal lathe I finished up buying was actually cheaper than the wood lathe I bought!

Next step in this process was making some No Mandrel Bushes and turn between centres, one barrel at the time.

I finally got the sort of results that I was after.

Now the whole point of this long winded story is that there is no single "fix" for out of round pens.

We have to start with a lathe where the headstock and tailstock line up accurately each time.

We need a way of holding the blank on the tubes concentrically, mandrels and cheap factory bushes don't cut the mustard here.
The further out we go from the headstock, the more potential for runout we have, so single barrel turning is the go.

Never forget that pen turning, although scoffed at by the "real" wood turners, is a precision process where we are attempting to match a piece of wood to a precisely (usually CNC) manufactured metal part and fingers can detect very small differences and certainly pick up out of round barrels.

So accuracy at each step of the process and the macinery and tools used is very important.

This includes very sharp tools, if you can bend a barrel whilst turning a pen blank then you are using too much force and your tool isn't sharp enough.

There are quite a few threads here and on IAP about out of round pens and how people overcome this problem, in fact this subject is one that frequently pops up.

Hey mate

I got sick of mandrels so I got some of Fred's aka Bigshed bushes to go between a dead center and live center and I have never looked back D I only have a Sierra set but still worth it

Ian

And here I was thinking that I was the only one suffering this issue by having a cheap $200 lathe and a set of $50 turning tools.
I have been battling this issue for a while with mixed results.
Alignment issues with the tailstock, bent mandrel, over tightening tail stock etc etc etc.
I can get then turned perfectly round and the next one is out. Very frustrating.
I am a perfectionist but have started to learn that 99% of people cannot pick a flaw.

My most popular tool for turning - sandpaper.
Still learning every pen and still have NFI about sharpening properly and a skew thats something out of alignment

I've virtually kicked bushes altogether and only TBC using callipers for sizing and are getting much better results, it does add a little time to each turning but thats what works for me. I dont do a lot of slim/stream lines anymore but if the occasion arises I turn one barrel at a time on an adjustable mandrel using a mandrel saver and I seem to get virtually no out of roundness. I have also with the use of shims got the alignment on the woodfast pretty good with minimal play in the tailstock.

Greg,
Go buy one or the other of these, on the left a 60 degree wood counter sink, the right a 60 degree pilot hole/counter sink for metal.
The wood one is available from almost every wood working shop, the right side is from a machine shop, cost about $3.00 American, because the stock bushings are soft metal, either one will work.

Mount your bushing in the 3 or 4 jaw chuck, use the Jacobs chuck and counter sink a bevel in the rear of the bushings, if you don’t have a spare Jacobs, use the one from your drill press, it has a #2MT and will fit your tail stock.

Lastly, take the live center that came with your lathe and toss it in the nearest trash bin, they are junk, with several thousands of an inch run out and can deflect when you apply pressure, both when you tighten it up and when you apply pressure with a cutting tool.
Get one of these, it is massive, has a 60 degree cone to match the bevel you just cut in the rear of the bushings, it has top quality heavy duty bearings and the one shown, after 6 years of hard work, has zero deflection or run out.

By adding the bevel to the rear of the bushings, they seat better against the stock drive center of almost all lathes, which has a 60 degree point, Because the head or cone on the live center is big and heavy, it also dampens any vibrations, and with the snug fit to the bevel in the bushings, you get no deflection.

With the better live center in the tail stock, if the tailstock is centered properly, you will get zero wobble turning between centers.
If you have difficulty finding the metal pilot/countersink let me know and I will see what I can come up with.