Baaa Black sheep!

[Delphi]

Hi all,
I have an interesting Mandrel conundrum, no, the sheep are okay, as I am trying to replicate a tapered cylindrical wooden cigar shape objecst. from 1" to 3" long, preferably 50 of each size.
Briefly, has anyone come up with a design for a straight rod mandrel for pen turning from 2.5mm to 5mm roughly, for use with collets, rather than a morse taper?

However, the internals are the problem going from 2.5mm ID. to 4.5mm ID. max, and this is essential, as I have used 6mm ID before, and it is pretty bad.
Not having many options I researched a reasonable pen lathe, without realising that the mandrels here are 7mm, which I found unusual as what Biro insert would need that.
So I bought a Proxxon Lathe, DB 250 wood turning lathe and ended up with a right rough mess using between centres, gently.
Even an ordinary lathe with a morse taper mandrel is of little use.
So how did these people make these things in 1850?

I then bought steel threaded rods 2.5 mm to 5mm which were too soft and bounced, with the aluminium frame, holders under too much wear, when used lightly.
I then bought steel rods, made up spacers etc, but the flex is too much, even at minimum speed.
Now I am an old rusty codger who barely uses this laptop, but I can think, and I reckon a trick was missed here when the internals had to be 7mm, and how that limits tremendously fine pens, taper,s and curves.
Somebody must have thought it too limiting for no good reason.
Presently I am looking at HSS (high strength steel)) steel, threading them, but that has limitations too with dies, so far.

So I would appreciate any comments with a direction to solve this one.
If I do find a process to overcome this conundrum I reckon it would be helpful to many of you, who seem to be limited in diameter.
Kind Regards,
Black Sheep, no wool.

 

[flexi]

Have you tried using a lathe steady? That might take the whip out your turning....or as its tapered how about making a box/sled and running a router over it whilst turning.....

 

[Doug]

When I make pens from biro nibs with ink tubes I simply drill a 3mm hole the length of the blank for the tube, enlarge the hole one end to suite the nib & then turn the blank between centres to the size I need using callipers to achieve the required size.
This one is laburnum



I can’t see how you‘d achieve this on a mandrel certainly not in compression as the components would be too small, you could try adapting your lathe so any mandrel was held in tension but I still can’t see that being successful.
Personally although you require a fair number I would drill your blanks & turn them between centres, at between 1-3” long they are pretty small & a simple jig could be made to hold against the turning to ensure it’s the correct finished size.

good luck.

 

[flexi]

That must be fun drilling a 3mm hole that long!

 

[Doug]

That must be fun drilling a 3mm hole that long!

Just a 3mm long reach bit drilled on the lathe, just take it steady & keep clearing the waste

 

[Delphi]

Have you tried using a lathe steady? That might take the whip out your turning....or as its tapered how about making a box/sled and running a router over it whilst turning.....

Thank you for this one, looked it up. Might run out of room, thanks.

 

[Delphi]

When I make pens from biro nibs with ink tubes I simply drill a 3mm hole the length of the blank for the tube, enlarge the hole one end to suite the nib & then turn the blank between centres to the size I need using callipers to achieve the required size.
This one is laburnum

View attachment 51829

I can’t see how you‘d achieve this on a mandrel certainly not in compression as the components would be too small, you could try adapting your lathe so any mandrel was held in tension but I still can’t see that being successful.
Personally although you require a fair number I would drill your blanks & turn them between centres, at between 1-3” long they are pretty small & a simple jig could be made to hold against the turning to ensure it’s the correct finished size.

good luck.

Many thanks for this one, I am beginning to identify fundamental issues here. First is aluminium extrusion and tensioned screws on a Proxxon DB 250, even with light passes, then the live centres are poor, so I will see about fixing the first, but not too many options on the second, so I will use 3mm holes and try again. Thank You.

 

[Delphi]

That must be fun drilling a 3mm hole that long!

Smoke came out from my head when I realised I was getting nowhere and had promised a few people I would have plenty of these for them as it looked so easy- what could go wrong, and this is only the beginning stage.