# Holdridge 8D Radii Tool



## Starlight Tools (Mar 11, 2011)

Well in a moment of temporary insanity, ok maybe not temporary, I hit the Buy Button on a Holdridge 8D Radii cutter. It arrived today, a little worse for wear on the box, but otherwise looks to be a good tool.

That thing is HUGE. Now my lathe is a 14" lathe and both the 4D and 8D are supposed to fit lathes of that size. but don't try to get that thing over the saddle.

Will pick up some 3/4" stock and fit a Tee nut to the compound then try it out. May have an issue as the minimum centre distance is 1.625" and turns out my lathe is 1.575" OH well, I am sure I can adapt it.

Walter


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## Starlight Tools (Mar 11, 2011)

Is that better?

Figured if 4" is good, then 8" will be even better. Might try making bowling balls LOL

Walter


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## Starlight Tools (Mar 12, 2011)

Pete

Thanks for the compliment. As I have said before to others, my hobbies and work are very much comingled. The machining side is more the hobby and has gotten greater in what I do over the past few years.

I figure that is Princeton not Priceton where you live here in Beautiful BC?

As for new pricing, $1975.00 USD for a new one and $2050 for the power head, yup scary.

I make sailboat stands and one of the features is a ball on the end for the pad to swivel. They can be turned by hand, whcih I have been doing up until now, but I am looking for a "more better" route that will give consistant balls. The socket is easy as it does not need to be curved but see where I go with this. 

Walter


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## Starlight Tools (Mar 12, 2011)

Pete you are welcome, been through Princeton many times in the past many years.

Have not been that way for awhile though as I am not leaving Kootenays much these days. Truck is old and tired and do not trust it to drive long distances.

Walter


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## Starlight Tools (Mar 14, 2011)

OK so I snagged a chunk of 3/4 x 3 FB and made a Tee Nut for the compound rest, actually made two so I have an extra, got the Radii cutter mounted and noticed a wee problem. It is too high.

Now I figured it might be about 0.050" high as the specs said in the manual that it was good for 1-5/8 to 1-3/4" centre heights, but I am getting more like 0.140" high.

Not sure if I should just mill the bottom down by that or try to figure out some form of offset tool holders.

Walter


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## Starlight Tools (Mar 15, 2011)

Ok so I had a discussion with Ellery from Holdridge today, I had emailed them last night and he replied first thing this AM.

His options were for me to make up a Plinth, but that would reduce the ability to machine u shaped grooves in parts such as making bending dies or round bottomed pulley grooves.

The other option is that he offered to mill 0.150" off the bottom of the frame mount, for no cost to me. Now this has to be done just right as it is the main reference for the whole set up. My only cost would be shipping to and from California. this is the most that can be taken off without compromising the strength of the frame.

They have a milling fixture that the frame is dropped into and then they can mill it "lickety split".

I have been looking at that part trying to figure out how to clamp it properly, and will not be an easy task, nothing is flat, everything is slopped in some way.

The third option is to make custom cutter holders that drop the cutting edge by the 0.140" and that may be a royal pain.

So I am leaning right now at shipping the piece to Holdridge and taking them up on their offer to do a quick adjustment to the frame.

Walter


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## Starlight Tools (Mar 16, 2011)

Ok so Holdridge Radii Cutter is modified, set it up on the mill and took off the 0.150"

The cutting time was minimal, although I did only cut 0.010" per pass, but the set up time, now that was fun!

It is now dead on centre.

Walter


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## Pontiac Freak (Mar 16, 2011)

Forgive the ingnorance, I am completly new to this and trying to wrap my mind around how all this works. Could you post some pics or video of this in action so I can comprehend how this works?   Your setup in the mill to get it flat is amazing!


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## Starlight Tools (Mar 16, 2011)

http://www.holdridgemfg.com/

Here is the link to the manufacturer of this ball turning tool. They have 4 sizes, and also a series of over-the-top sherical turning tools that mount in an Aloris style QCTP. 

The 3S and 3D, (D being deluxe) that fits smaller lathes where the compound rest height to centre line is 1"

The 4S and 4D which will cut up to a 4" dia ball. Compund height to centre line is 1-5/8 to 1-3/4" 

The 8D which will cut up to an 8" ball, compound height to to centre cine is also 1-5/8 - 1-3/4"

and the 12D for lathes larger than 15" and will turn a ball that is 12" dia. The compound height to centre line is also 1-5/8 - 1-3/4"

These units will cut internal or external ball shapes and will cut half round internal or external grooves around the OD of a cylinder to make bead rollers or tubing bending dies or rope sheaves etc. See the manual on the holdridge site for pictures and more details.

Now even though my lathe is a 14" the centre line to comppound height is 40 mm or 1.5748" so it was too low for the 4, 8 or 12" units without this modification which have a minimum distance of 1.625".

At the factory they have a jig that is made up to allow them the machine the frame quickly and easily. It locates the part and allows the operator to be cutting off that face in minutes. With my setup, it required trying to make a setup that would hold the part in alignement so that the bottom could be squared off, and maintain that hold even though a fly cutter set to about 3-2/4" diameter was attacking it and trying to knock it out of square.

The main alignment was with the Tee Nut for the lathe with a 1" diameter rod in it that is used to mount my Tool Post Grinder. this would have been better if the rod was longer and centre drilled to catch the pivot pin in the lower leg of the frame, but even as it was it allowed me to move the frame up and down and clamp it to the 1" dia rod. I backed this up with a machinist screw jaclk and a step clamp over top to hold it solid. The Tee Nut that I made to clamp down the Radii cutter was used as a jack screw set up with two 1/2" carriage bolts on the top of the swivel vise jaws, which allowed me to support and level out the flat area. A toolmakers vise was clamped in the main vise and and another clamped in it to lift my clamping point. Parallels were used to space them so that the upper support was clamped straight. I used a lay up of parallels between the tool maker vise and the frame to make sure that it was aligned so that as the fly cutter passed along the Y axis of the mill it stayed parallel with the initial cut that had been made on the frame.

I used a 6" Starrett #98 level to align the face of the frame in both X and Y axis, which works well as the mill is leveled. Should have dialled it in, but this seemed to work OK.

Overall, I was pleased with the way that the setup worked out and the frame was cut flat to within tolerance.

Walter


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## MisterT (Oct 11, 2013)

I've got a holdridge radii cutter model 12-d. It is absolutely like new and was only used ones. All the cutters but one is still in wax. No corrosion and in orginal box. I'll make someone a smoking deal. My email is tayloraircraftservice at yahoo.


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## oldgoaly (Oct 13, 2013)

I had the opposite problem I had to shim up mine 


good tool! 
I've adapted insert tooling to it, a cheap set from Shars
got a deal on mine a damaged box 8D for 850$ delivered.


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## KBeitz (Jul 12, 2018)

Made mine...


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