Penturning DIY Bushings

[chipmunk]

Just a quick question for you experienced penturners.

I've just bought a Sierra kit as a one-off and since I have a metalworking lathe it seemed silly money to buy the bushings to go with it. So, I have made a set and sized them so that the largest outside diameter matches the diameter of the nib and cap that abuts the wood. Is this right?

Both the bushings are therefore bang-on 12mm (0.472"). Elsewhere though I have read that the Sierra kit has two different bush sizes (Nib .522 & Finial .550") which is very different from my measurements.
http://www.penturners.org/wiki/Bushing_Size_Chart

The drill size is 10.5mm so my wall thickness is only about 0.75mm at the ends with 12mm bushes.

Am I making the bushes too small?

Any advice gratefully received.
Thanks
Jon

 

[Neil Farrer]

The bushes are a guide only - I make around three thousand pens a year and there is not one pen which I turn down to the bushes, always slightly proud. From memory the sierra bushes are 12.15mm and I have never heard of them being different. Most sierras, and there are several manufacturers that have strayed from the Berea design, have a double bead at the top of the pen which hides the difference with a large margin anyway. But the critical dim is that which will adjoin the nib assembly. The finished wood dim will also need to account for the finish you apply, a CA finish will enlarge the barrell whereas a sealer and friction polish finish will not appreciably.

Being pedantic, the drill size is 27/64 regardless of what the suppliers put on the instructions.

So to answer your question, no the bushes are not too small, you just need to monitor the dimensions of the blank anyway. The critical dimensions are the ID of the tube so that the tube and blank dont rattle on the mandrel. If you're turning it between centres you dont need the bushes anyway.

 

[Naxie]

If they are the same size as your kit you should be fine. To be honest bushes are only really a guide, you need the diameter with a vernier caliper.

I also use a 27/64 bit.

I never use bushes for the sierra, just turn between centres, far better and you don't have to worry about a wobbly mandrel. :wink:

Hth,

Kind regards,

Ed

Edit: I see Neil beat me to it!

 

[chipmunk]

Thanks guys - Responses much appreciated.

27/64 is 10.72mm but the 10.5mm hole seems plenty big enough for the tube so I'll not be enlarging it.

Thanks again though.
Jon

 

[jpt]

Standard Sierra bushes are the same size it is only the Sierra circuit board pens that has the two bushes different sizes.

john

 

[Inspector]

If you are only doing one pen then skip the bushings altogether and turn between centres and measure to size as you turn. A 60 degree dead centre in the headstock and a 60 degree live in the tailstock is all you need and you likely have that stuff for your metal lathe if not for the wood lathe too.

Pete

 

[paul-c]

I make around three thousand pens a year

wow =D>
i haven't got around to making 1 yet
i would love to see some of them.
cheers paul-c

 

[Neil Farrer]

Paul,
heres one afternoons work:

 

[SteveF]

Paul,
heres one afternoons work:

Hi Neil

nice looking pens
what brand\model are they ?

Steve

 

[Neil Farrer]

Steve,

They are the Orion from Woodturningz.com

 

[paul-c]

hi neil
they are awesome, lovely looking pens and a nice mix of timbers - thanks for showing us your pens.
i am absolutely in awe that that is one afternoons work for you - that really is very impressive. =D>
i am even more ashamed i haven't got around to making one
thanks paul-c