Radius cutting attachment for pen ends

[Amihai]

Hello, question for the kitless makers here:
I have the Proxxon radius cutting attachment for their PD400 lathe.

I want to cut a radius at the end of the pens I turn, to give them less of a "square" and more professional look. However, I don't seem to get the positioning of the tool right.

Is there some sort of formula or method to find out where should I position the tool to get the closest to perfect of half a sphere around the axis of rotation while moving the tool?

Pictued are my setup and the kind of end I want.

Thanks,
Amihai Fishman.

 

[hooked]

I have ground cutting tools to form the radius. I have also tried mounting a radius milling bit in the tool holder. I even bought a micro mark jig to do radius ends. By far, the easiest and quickest way I have found for pens is to move the pen to a wood lathe and do it by hand. If you don't have access to a wood lathe, the homemade radius cutter gave me the best cone-shaped result. The problem with the raius jig is that it is hard to get something other than a "ball end"

This video explains what I mean by making a cutting tool to form the radius. It also shows the operation of a radius cutting jig, but a much larger one.

 

[Chriscb]

Afternoon, I'm with Hooked - I also move the pen onto a wood lathe and form the end using hand tools. Although I have come across this video which shows the use of the tool you mention. I fear that it will only enable you to cut a constant radius, rather than the shape you want. Either way, you'll learn a new skill.

Chriscb

 

[d_bondi]

I'm with Hooked and Chriscb, I do it all on a wood lathe and shape the ends with hand tools.

 

[Amihai]

I don't have a wood lathe, unfortunately...

 

[GFHWoodWerks]

I don't have a wood lathe, unfortunately...

There are those that add a tool rest and turn with wood lathe tools, in a metal lathe. It can be done with some creativity.

 

[rherrell]

I made my own radius cutter using a metal lathe boring head...

The difference between mine and yours is mine cuts at a different angle, 90 degrees from yours. The principle is the same so if you still need help PM me and I'll try and explain how to set it up.

 

[Mortalis]

I want to cut a radius at the end of the pens I turn, to give them less of a "square" and more professional look. However, I don't seem to get the positioning of the tool right.

I don't have a wood lathe, unfortunately...

Thanks,
Amihai Fishman.

You could use a rasp to rough out the shape and then finish with sandpaper.
Watch some YT videos of how woodturners turn beads. They use the spindle gouge and/or skew and accomplish very good results. That would mean you would need to somehow replicate the setup of a rounded tool rest to move the tools along. Once you get the hang of it (it doesnt take long) it goes pretty easily.
The attachment shows my very first attempt to turn a "bead" after practicing for a very little time. The original is on the left and my attempted copy on the right.

 

[Penultimate]

On a metal lathe you can create a series of stepped cuts then finish with a file. It's a little tedious but it works OK once you get a good work flow. I attached the spreadsheets I use. There was an article in Home Shop Machinist also describing the process. He said Blondihacks did a video on making rounds with a step function.
My Dad was a machinist and could free hand radius cuts. It's fun to try because you have to coordinate turning both hands at once.
I watched a program on craftspersons and a woman was making bowls on a large Southbend lathe turning the saddle and cross slide hand wheels.
Good luck, contact me if you have questions.

 

[manik]

I ran across this jig a while back. I have not tried it, was a bit pricy. It might give you the control you are looking for. You could also create a template and follow the template to recreate the same look on any pen.

Turnado - Turning System

 

[Aurelius]

If you are looking to just radius the ends of pens and do not have a need for the range of radii that you would get from either the Micro Mark jig or the tool Rick made, take a look at Micro100 . That link takes you to their carbide cutters with various radii. you can also cheat a bit and use different radii in conjunction to get more of a tapered shape but that takes a bit more experimenting.

 

[Penultimate]

If you are looking to just radius the ends of pens and do not have a need for the range of radii that you would get from either the Micro Mark jig or the tool Rick made, take a look at Micro100 . That link takes you to their carbide cutters with various radii. you can also cheat a bit and use different radii in conjunction to get more of a tapered shape but that takes a bit more experimenting.

Thanks for the link I didn't realize they made radius bits. I have their boring bars

 

[Aurelius]

Thanks for the link I didn't realize they made radius bits. I have their boring bars

No problem, it's only like 4 pages in the print catalog and you would totally miss it unless you were looking for it on their site.
As long as you don't get too aggressive with feeding it in, they work very well. If you feed to fast, they are a spectacularly effective way to shatter a blank. (Ask me how I know )

 

[Paul in OKC]

You need to start with the pivot point of the tool at 'zero' straight under the axis of the blank. Then put it even with the end of the blank. Then move the tool roughly the amount for the radius toward the chuck. Lock it there, then move the cutting tool up to touch the blank, either on the diameter or the end, and swing it around. Hope this makes some sense.