Horizontal Milling Arbor

kb3guy

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I’d like to cut a few spur gears on my VN16 mill, which takes “C” collets. Also, I have inexpensive Chinese gear cutters with a 22mm bore - just slightly too small to fit on a real 7/8 arbor. I’m not about to turn down my VN brand arbor to fit import tooling, so I drew a new one up I’d like to turn on the lathe.

9d6e3e88700fa08ed7dd94ffab6493af.jpg


I’m looking to turn this between centers, and make it out of mild steel. Does this plan have any glaring issues? I’m slightly concerned about the stiffness of the material, but I’m also not looking to buy a big chunk of high-carbon steel for this.


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Shouldn't be a problem if you use cold roll you can always case harden the piece to give it some extra strength .
 
The fact is that hardness has no effect on stiffness; the modulus of elasticity is the same, hard or soft. The only thing about case hardening is that it would make the arbor less likely to get scratched up, but the downside is that it would have to be ground to finish all over due to distortion in hardening, The only advantage in through hardening is that if something hung up, the arbor would likely spring back instead of being bent permanently. As to a choice of material, if you wanted to go beyond CRS, stressproof would be a good choice, it is easy to machine, it has an elevated hardness and it does not distort while being machined; the next ratcheting up would be 4140 heat treated, a bit harder and harder to machine.
 
The fact is that hardness has no effect on stiffness; the modulus of elasticity is the same, hard or soft. The only thing about case hardening is that it would make the arbor less likely to get scratched up, but the downside is that it would have to be ground to finish all over due to distortion in hardening, The only advantage in through hardening is that if something hung up, the arbor would likely spring back instead of being bent permanently. As to a choice of material, if you wanted to go beyond CRS, stressproof would be a good choice, it is easy to machine, it has an elevated hardness and it does not distort while being machined; the next ratcheting up would be 4140 heat treated, a bit harder and harder to machine.

i've never used stressproof. i make some parts from etd150. how does that compare? (machining)

op: what does 1y.822 mean? 36.822"? one big arbor
 
i've never used stressproof. i make some parts from etd150. how does that compare? (machining)

op: what does 1y.822 mean? 36.822"? one big arbor
ETD 150 is more like 4140 HT, except it is higher in tensile rating and machines easier; Stressproof is softer, and machines more freely and is the go to material for shafts with long keyways (won't bend) and such things as lead screws with coarse acme threads, it is quite stable when a lot of material is removed from one side of a part.
 
You might want to check eBay. There are several horizontal arbors up for sale including a couple for Van Norman C collets. One is $125.00 or Best Offer and includes a number of spacers, the retainer nut, and free shipping.

https://www.ebay.com/itm/Van-Norman...250691?hash=item41e1dd4bc3:g:y5EAAOSwcB5ZOH6N

Thanks for the suggestion. Size is the main issue here - I need a 22mm diameter arbor for my particular cutters (7/8 is too big, I tried), where VN-manufactured stuff is all imperial/inch based (they made 7/8”, 1”, and 1.25”.) Also, I could use the practice with some lathe work!
 
If the 7/8" arbor isn't overly hardened, you could reduce it to 22mm and rethread it.
 
Probably an impractical option, but can you dial the gear cutter in on the lathe and grind the ID with a toolpost grinder?
 
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