Author Topic: Holdridge Radius Cutter  (Read 12031 times)

Offline sshire

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Holdridge Radius Cutter
« on: November 10, 2015, 11:42:17 PM »
Last month, at the American Precision Museum's Model Engineering show, I made sure to be there early on set-up day. The advantage is that I can sit, like a vulture, as the used tool guy unpacks his wares.

I noticed a large wooden case with "Tool Room" painted on the top. Well, that's too intriguing to pass by. I opened the case and found an absolutely complete 4D Holdridge Radius Cutter in the (according to Holdridge) correct size for my 13" lathe.







This is a tool that I've always wanted but the price of a new one ($1000.00 plus) always stopped me.

(If you want more info, the manual/brochure is here)

http://www.modstest2.qpg.com/files/40871560.pdf



After a bit of haggling over price we settled on $200.00 and it followed me home.

Now, either Holdridge is incorrect ("fits 12-14 inch lathes") or my compound is higher than most. In any case, the toolbit center was .25" too high.  So, with the compound removed, I made a base to bolt onto the cross-slide.



The tool bits are all brazed carbide and the set comes with a sharpening jig to maintain the correct clearance angle. After looking at the tool bits closely, I realized that every one had been ground freehand by a less-than-accomplished person. Even worse than my freehand grinding skills. Without a T&C grinder, reshaping these was going to be a major project.

BTW, the radius is set with a depth mike and precision ground spacer bar.





Now, Holdridge makes indexable toolbits. For full range of radii, one needs all 3 lengths (2", 3", and 4") and once I realized that they are $90 each, there was nothing for it but to buy the inserts and make my own holders.

Stay tuned.
Best,
Stan

Offline Dave Otto

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Re: Holdridge Radius Cutter
« Reply #1 on: November 11, 2015, 12:32:35 AM »
Nice Score Stan!

Dave

Offline Don1966

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Re: Holdridge Radius Cutter
« Reply #2 on: November 11, 2015, 12:33:00 AM »
Nice buy Stan and you will enjoy making convex and concave radius and of coarse balls.  :ThumbsUp:

Don

Offline b.lindsey

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Re: Holdridge Radius Cutter
« Reply #3 on: November 11, 2015, 01:26:21 AM »
Great score Stan. I have one I bought years ago for my Atlas 12" lathe, which is still stored in my old shop along with the Alliant mill. As I recall it isn't Holdridge, but it is an American made brand. It looks very similar though and is set the same way.

Bill

Offline 90LX_Notch

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Re: Holdridge Radius Cutter
« Reply #4 on: November 11, 2015, 01:28:49 AM »
Nice score Stan.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline sshire

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Re: Holdridge Radius Cutter
« Reply #5 on: November 11, 2015, 01:38:54 AM »
Bill
Yours may be a Holdridge. A few distributors rebadged it with their name. Mine has a "Ralmike" badge and they also pasted a label over Holdrige on the instructions inside of the lid.
Best,
Stan

Offline sshire

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Re: Holdridge Radius Cutter
« Reply #6 on: November 11, 2015, 01:42:58 AM »
UPS just dropped off the inserts. A C1 and a C3. I do need to figure out the designation to avoid paying $20 per insert from Travers. They appear to be the only source for Holdridge.
I'm hoping they are a standard insert which I can get for less.
With the inserts in hand, I'll see if I can make a tool holder tomorrow.
Best,
Stan

Offline Lew Hartswick

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Re: Holdridge Radius Cutter
« Reply #7 on: November 11, 2015, 03:24:24 PM »
We use one at school for one of the projects. I did a little work with one to make some balls for repair of an antique transit. Had to "invent"
a new tool bit to make the required shape.  If any one wants more details I'll be happy to try and help.


   ...lew...

Offline Jo

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Re: Holdridge Radius Cutter
« Reply #8 on: November 11, 2015, 03:53:22 PM »
It does seem to have Mr Silky's name all over it. Whatever you do don't show it to him or I'll never hear the end of it  :-\

Jo
« Last Edit: November 11, 2015, 04:02:05 PM by Jo »
Enjoyment is more important than achievement.

Offline sshire

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Re: Holdridge Radius Cutter
« Reply #9 on: November 11, 2015, 04:41:31 PM »
Jo
We'll keep it under the Official Secrets Act.
😎
Best,
Stan

Offline sshire

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Re: Holdridge Radius Cutter
« Reply #10 on: November 11, 2015, 04:43:55 PM »
Lew
I was wondering how one got the toolbit in the rear undercut. Nicely done!
Best,
Stan

Online steamer

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Re: Holdridge Radius Cutter
« Reply #11 on: November 11, 2015, 06:06:01 PM »
Sweeeeet!!!!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline sshire

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Re: Holdridge Radius Cutter
« Reply #12 on: November 13, 2015, 01:40:54 AM »
The indexable holders are finished and “work a treat.”
A major difference in surface finish with the carbide inserts. (C1 and C3) is striking. I’m sure that with a T&C grinder to properly shape and sharpen the brazed carbide toolbits, I’d have been happy with the result, but 2 inserts at $20 each and some drill rod worked just fine.
When the setups were made, it was, as Marv says, trivial to make three: 2”, 3” and 4”. Three toolholders for a day in the shop and a few dollars worth of drill rod as opposed to $90 each. If I keep this up for about 50 years, the Bridgeport will have paid for itself.
The difference in the Holdridge as opposed to the Serepton is astonishing. The mass of the Holdridge dampens all vibrations as is evidenced in the surface finish, the long handle with adjustable drag and the centering adjustment are also very nice.





Best,
Stan

Offline b.lindsey

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Re: Holdridge Radius Cutter
« Reply #13 on: November 13, 2015, 01:51:18 AM »
OH yeah....nicely done Stan. I bet those look every bit as nice as the $90 ones too!!

Bill

Offline petertha

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Re: Holdridge Radius Cutter
« Reply #14 on: March 04, 2016, 07:39:52 PM »
Stan, thanks for posting the nice pics & details & sorry for digging up an old post. I've pretty much given up trying to buy one of these new or used & may try to make my own for the application at hand. A few things I wanted clarity on if you don't mind:

- how are 'axles' inserted & retained into the outer C-frame and then how does the chosen radius cutting post or C-frame rotate on them? For example one is fixed & other slides? Which one?
- are the axle holes bronze bushed or anything, or just straight axle into hole?
- assume the C frame components cast iron?
- you mentioned adjusting the height to suit your lathe vs. their nominal swing recommendation - is that adjustment occurring entirely with your modified mount plate on the compound? And now with that fixed its up to you to maintain center cutting location via the bit grinding themselves? (ie is there any adjustability in the bit holder hole or up-down adjustability within the pivoting frames themselves?)
- how exactly does your plate anchor to the compound? I'm visualizing the typical T like tool post, but it has a center bolt that engages a plate inside the T slot
- on insert cutters, is it basically the same geometry (relief) that one would select for conventional lathe tools?

 

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