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Making arbors to fit Van Norman 'C' spindle?

shaggy

Hot Rolled
Joined
Sep 29, 2010
Location
Oakland CA
VN 'C' taper tooling being virtually unobtainable on the used market, I'm trying to figure out the best way to go about making or improvising some arbors.

I have a full set of VN 'C' collets up to 3/4", and the nose of the spindle is slotted for a pair of drive dogs to match the original VN horiz. arbors.

I was thinking to make a collar with matching dogs that could be pinned to a suitable horizontal arbor, reduced in diameter and the taper 'adjusted' to the VN spindle. I figure the drive dogs would do the work, w/ no harm to the spindle taper (and/or collet, if say I used the same idea around a collet and straight-shank 3/4" dia. arbor.)

Any thoughts on type of steel (for dogs and collar), heat-treatment, whether to case-harden or not? I do not have a cylindrical grinder, and am but a simple (though decent) mechanic :)
 
VN 'C' taper tooling being virtually unobtainable on the used market, I'm trying to figure out the best way to go about making or improvising some arbors.

I have a full set of VN 'C' collets up to 3/4", and the nose of the spindle is slotted for a pair of drive dogs to match the original VN horiz. arbors.

I was thinking to make a collar with matching dogs that could be pinned to a suitable horizontal arbor, reduced in diameter and the taper 'adjusted' to the VN spindle. I figure the drive dogs would do the work, w/ no harm to the spindle taper (and/or collet, if say I used the same idea around a collet and straight-shank 3/4" dia. arbor.)

Any thoughts on type of steel (for dogs and collar), heat-treatment, whether to case-harden or not? I do not have a cylindrical grinder, and am but a simple (though decent) mechanic :)

I had an a abundant amount of Weldon R8 tool holders that I turned and ground to fit the “C” spindle. This also allowed for a larger than 5/8 that the “C” limits out at .... just my 2 cents


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Anything R8 can be easily turned down to VN C. Shank gets turned, angle face changed and the woodruff keyslot has to be cut. Make up a new drawbar out of threaded rod and an adapter to go in the spindle in place of the VN tubular drawbar. I've converted shell mill arbors, slitting saw arbors, drill chuck arbors, etc... when I had the 6 at the museum and my 12 at home. Do several while you are set up.
 
Anything R8 can be easily turned down to VN C. Shank gets turned, angle face changed and the woodruff keyslot has to be cut. Make up a new drawbar out of threaded rod and an adapter to go in the spindle in place of the VN tubular drawbar. I've converted shell mill arbors, slitting saw arbors, drill chuck arbors, etc... when I had the 6 at the museum and my 12 at home. Do several while you are set up.

Thanks Mike, that's encouraging! I'm probably going to try that eventually.
For now I've got a couple of straight shank stub and shell cutter arbors for the 3/4" (Hardinge 5V) collet, and want to figure out a good way to drive them with the (soon to be) existing spindle drive lugs (although for light work I guess they'd be OK as-is).

I also need to replace the missing VN woodruff key and just went over the whole machine Ezy-Outing a bunch of broken studs, including both spindle drive lug screws. Then I've gotta make a whole new x-axis travel limit/auto-stop setup from scratch... Old machines eh? :)
 

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I made the woodruff key by turning a rod to diameter, bandsawing it a little off center, sawing that piece off and filing to fit. Wish I had pictures, but that was over 20 years ago before cell phone cameras. The straight shank and drive lugs isn't a bad idea. Might do the job without ever having to go further.
 
That's a good idea, thanks.

Yeah, I'm glad mine has the drive slots. Short of modifying the spindle for a larger taper (not possible with the 12, I realize), I figure they should allow working the machine close to it's power limit without danger of spinning a collet, or other potential damage.

I'm still considering throwing a 3 hp motor on when I come across the right one. What do you think about that?
 
A 3HP motor on a #12 is probably OK if you only use peak HP occasionally. I would not plan to maximize material removal based on the textbook figures for cubic inches/HP, though!
 
A 3HP motor on a #12 is probably OK if you only use peak HP occasionally. I would not plan to maximize material removal based on the textbook figures for cubic inches/HP, though!

I'd only be doing it if there was reason to think the machine would overall run more efficiently. That is, if say too much was being asked of the 1-1/2 hp motor, whereas a 3 hp could be loafing along at the same speeds and load, drawing the same or even less current. But maybe I'm just dreaming.

BTW I just checked again -- with some effort got the machine into high speed (1500 rpm), and (including idler motor) is drawing a total of 2500W off the wall (12+ Amps) and that's at 'idle' (ha-ha) :eek:

(btw, sorry for mixing up topics -- I've got at least three threads running on this machine now, and they seem to want to run together(!)
 
Back in the day I had my vn12 it was only 2 hp. It was a big motor, physically, but still only tagged two.


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The 1-1/2 hp looked big at first... till I got a 3 and then a 5 hp for the RPC idle motor. I sure do like the way that 5 hp feels when it starts up, and it only draws 300W at idle. Can't help wondering how it'd go on top of the VN12 (even run off just the static converter). Loafing along, even under a cutting load, is how I imagine. Of course I know there's no 'free lunch', but... :)
 
I'd try it, as is, before I made any motor changes. I never felt lacking for power on either the 6 or the 12 with the factory motor. In horizontal mode, you'll probably be running at low speeds due to cutter diameter and that's where the geared reduction does its job giving GOBS of torque. Small endmills at high speed don't pull much load. The designers at Van Norman laid these machines out very well.
 
Thanks - you're probably right. 70 thru 500 rpm run fine (1000 rpm in a pinch) and will cover pretty much all I need. I'll put it on the back burner for now
and get back to making new drive lugs, etc.
 
I doubt making arbors or holders is any big deal.
Just make them from any steel at hand, as good as reasonably practical.

Final fitting of tapers can easily equal the best high $$$$ toolholders of today,
and runout near 1 micron is fairly easily achieved.

Endless hobby guys do better with model engines and telescopes every day, mostly without good dtis or machine tools.
Rigid brass/alu laps and diamond paste, 30$ or so.

Drive dogs etc. are a machining exercise that does not seem to need any particular precision.

I would expect about 20 work hours to achieve a reasonable work flow to about 0.01 mm in gross dimensional size.
And near 1-2 microns in taper sizes and TIR error.

After the 20 hours, making maybe 3 gages for top and bottom end each, and everything else, I would expect about 3 - 4 parts per hour, turning only.
With extra setup and jigs and planning, and work, the production could probably be 6-8 parts per hour.
On pre-cut slugs center drilled.

High end:
Much better than the mill in question, or Bridgeport or R8 stuff.

It´s perfectly possible to make tooling arbors or toolholders with external tapers and internal bores highly concentric.
Anyone *can* learn to do it, if motivated.
But is is *very hard* to do properly well.

Speaking from my experience, past 10 years.

It´s easy to get 0.01 mm TIR at bore of hole and at taper mouth.
Getting the bore to be concentric with the taper, 100 mm out, and maintaining 0.01 mm TIR and concentricity on both, is hard.
About 100x harder to maintain 2 bores 100 mm out at 0.01 mm than a 0.01 mm TIR at mouth of part.

This is about as good as most high dollar tools today.
200$ collets and 200$ toolholders and 200$ tools would typically be about 0.01 MM TIR 100 mm out of the spindle.
This is what the better kennametal stuff will do, as-is, buying everything from them.
A single tool is 200 holder + 200 collet + 200 tool == 600$.

The very best toolholders and tools can achieve about 2 microns TIR 100 mm out of the spindle.
Big kaiser, perhaps some regofix, some HSK spindles and their spindle/collet/tooling.
The pricing is higher than kennametal, but not much.
Maybe around 1000$ for a single tool, vs 600$ for kenci / kennametal (or sandvik).
 
"I doubt making arbors or holders is any big deal.
Just make them from any steel at hand, as good as reasonably practical. ..."

Thanks, will do. Not too worried about a few microns ;)
 
If you want insane accuracy, mount a lathe compound and toolpost on the table and bore your endmill holders, turn your arbor shafts, etc... with the tooling in the mill spindle.
 
Great idea. Funny, as I've just been thinking about all the ways this mill could be set up. Say as a large-swing lathe, w/ aux. compound and toolpost, as you suggested, or as a vertical lathe, by motorizing my 15" rotary table. Motorize the knee to do boring, etc. Line boring on the table, with a 90-degree drive off the spindle, or maybe a BP spindle on the o/head support.
Imagination (or sanity) is probably the limit :)
 








 
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