# Radius turning tool project



## John Conroy (Nov 17, 2018)

I have been thinking about building a radius turning tool for a while now. I have been working on plans in my head for a couple of weeks now and got to work on it this weekend. My lathe has t-slots on the cross slide so I machined some t-nuts and a mounting plate for the body of the radius tool. The compound does need to be removed to use it but the cross slide stays more centered in it's travel so I chose not to mount it using the compound bolts. I copied a design I saw on another forum but added a second bearing. It has a tapered roller bearing on the top and a thrust ball bearing on the bottom. The bearings are packed with grease and slightly preloaded which makes for very smooth stable turning action. The cutter head is mounted to an adjustable slide that is secured from one side with four m8 set screws. The cutter head can be mounted 2 ways to provide more options for different size radii. It can machine  a ball up to 3.125 inches in diameter and can be adjusted to make a large range of concave radii as well. I made a couple of balls, one for the handle of this tool and 1 for the spindle clamp on my mill. They came out pretty smooth and didn’t need much polishing to be made shiny smooth. It uses a TCMT insert which has a 6 degree positive rake.


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## DPittman (Nov 17, 2018)

VERY NICE! I really like your ball bearing set up.  I made a ball turning tool myself but didn't really know how to do the ball bearing thing. I ended up using a non tapered bearing but it's not quite right.

I was showing my wife my newly completed project and she asked what I needed a ball turner for and I told so I could make a ball for the handle of the ball turner!


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## YYCHM (Nov 17, 2018)

Well done!!!!  Can you provide a better image of how the tool is mounted. Please.


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## YYCHM (Nov 17, 2018)

DPittman said:


> I was showing my wife my newly completed project and she asked what I needed a ball turner for and I told so I could make a ball for the handle of the ball turner!



LOL..... I have encountered books that suggest projects that require the project itself to complete.


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## DPittman (Nov 17, 2018)

YYCHobbyMachinist said:


> Well done!!!!  Can you provide a better image of how the tool is mounted. Please.


 Click on one of the pics and you get a whole album of awesome pictures!


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## DPittman (Nov 17, 2018)

YYCHobbyMachinist said:


> LOL..... I have encountered books that suggest projects that require the project itself to complete.


Oh ya I forgot to tell you the first half of my funny story...
So I was first working on making a milling attachment for my little lathe and my supportive wife asked what I needed that for and I told her so I could do some milling for a "radius turner" project... "oh I see" she says...


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## PeterT (Nov 17, 2018)

I like it! Your design actually looks more solid than a Holdridge C-frame sitting up on the compound.  You'll probably find many uses for this. A lot of machinery accessories are just nicer looking with ball ends or even simple round-overs & maybe a bit safer too. I like looking at older machines with their fengshui elliptical blended profiles that pleasingly fit the hand. Or you can be the first kid on your block with egg-shaped motorcycle bar end weights! LOL. Good project.


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## Dabbler (Nov 18, 2018)

very nice work!


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## Everett (Dec 5, 2018)

That's a very nice build.  Well done!


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## YYCHM (Dec 9, 2018)

Been considering building one or purchasing one as well.

This one looks easy  to make

https://littlemachineshop.com/products/product_view.php?ProductID=1970&category=

For this arrangement how does one advance the cutting tool?


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## DPittman (Dec 9, 2018)

You make a mounting block to fit your lathe and advance with the cross slide if mounted there or your compound (if big enough) and if mounted there


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## DPittman (Dec 9, 2018)

Most common I've seen is mounted into your toolpost


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## YYCHM (Dec 9, 2018)

DPittman said:


> You make a mounting block to fit your lathe and advance with the cross slide if mounted there or your compound (if big enough) and if mounted there



Advance the cross slide?  I must not understand how this thing is mounted on the lathe.


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## DPittman (Dec 9, 2018)

Here Tubalcain will explain all much better than I. He has a few examples of turners.


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## YYCHM (Dec 22, 2018)

My lathe only has 2 1/4" clearance between the cross slide and the center of the chuck, so a horizontal swivel base approach is not practical as far as I can tell.   I drew up some plans for an over the top ball turner (same as the LMS offering I posted) and am now wondering what orientation the tool needs to be.  I assume 90 deg clockwise (from normal) such that the cutting edge intercepts the oncoming metal as it turns into the tool at the top of the swing (am I making any sense here?).  This affects how high the support arms need to be when using a standard carbide insert tool.  Also affects where the tool holder hole needs to be positioned on the swing arm.  Am I on track here?

Also, forgive me father but I am about to sin and go to MSM to source the materials I need.

Base - 1/2" X 2" X 6"
Supports - 1" X 1" X 5" (will suffice for both)
Swing - 1" X 3" X 3 1/2"

Anyone want to suggest an appropriate steel for this project?


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## PeterT (Dec 22, 2018)

What I'm not too crazy about on that LMS configuration is if you happen to go too far over towards the chuck to make a more complete ball, your hand & the handle is in the kill zone of the spinning chuck. If you happened to slip or drop the handle on that side of the lathe into the chuck, that would get ugly for the machine. Maybe there is a stop I'm not seeing but anyway, that's my armchair engineering assessment.

Then there is the 'turnado' which seems just slightly less yeesh, but when you watch the video seems ok on light cuts & soft materials.
https://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=37&Itemid=108

I've had some ideas in my head of a 'duplicator' to make replicate curvy or profile parts from a 2D template but it will probably take a specific project to bump it up the que. I have a round tip carbide parting tool & was just mucking about cutting into material like a parting blade & I thing it would be perfect for this kind of application. It would never be as smooth as a pivoting radius mechanism, so leave that to the radii ball makers.


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## YYCHM (Dec 22, 2018)

Horizontal or over the top arrangements have is the same chuck collision issue.


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## PeterT (Dec 22, 2018)

You're right. I just thought about that after I clicked Reply. I guess you have to either have more arbor stickout from the chuck or maybe use one of those hocky stick bent cutters to keep the swivel away from the chuck.


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## YYCHM (Dec 22, 2018)

New thread in order.... Sorry OP for stealing your thunder...


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## John Conroy (Dec 22, 2018)

Good discussion guys.  I tapped a few different hole locations for my handle to keep my hands away from the chuck but I think the safest way is to use a collet chuck hence my recent 5C chuck purchase.


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## John Conroy (Apr 14, 2019)

My new lathe doesn't have t-slots in the cross slide and the top of the cross slide is about 1/4" higher than my old lathe so I had to rework my radius turner. I measured the center height of the spindle and machined the material off the bottom of the tool bit holder to get the height correct. That gave me a chance to break out my vintage Browne and Sharp height gage. The base will now have to be bolted down using the same studs that hold the tool post so I'll have to make something to keep the swarf out of the openings. I haven't had a chance to try it out yet but here's some pics.


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## PeterT (Apr 14, 2019)

_JC>My new lathe doesn't have t-slots in the cross slide and the top of the cross slide_

I didn't even notice that before. Is your cross slide dovetailed on the sides (arrows) to hold things gib style or is it 90-deg square?
I always thought I would be mounting things to my T-slots but so far haven't had a solid requirement. A pseudo-travelling steady is brewing in my brain though.


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## John Conroy (Jan 21, 2020)

Sorry Peter, I somehow missed your question and lost track of this thread. The cross slide has no slots of any kind.


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## Marc Moreau (Jan 21, 2020)

DPittman said:


> Here Tubalcain will explain all much better than I. He has a few examples of turners.


Real nice I will try to do this . Thank you for the video


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## buckbrush (Jan 21, 2020)

nice job.


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