Horizontal Milling Arbor

kb3guy

Active Member
Registered
Joined
Mar 29, 2017
Messages
26
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.



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.


Sent from my iPhone using Tapatalk
 

Silverbullet

Gold
Registered
Joined
May 4, 2015
Messages
3,520
Shouldn't be a problem if you use cold roll you can always case harden the piece to give it some extra strength .
 

benmychree

John York
H-M Supporter - Gold Member ($25)
Joined
Jun 7, 2013
Messages
3,868
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.
 
C

cg285

Guest - Please Register!
Guest - Please Register!
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
 

benmychree

John York
H-M Supporter - Gold Member ($25)
Joined
Jun 7, 2013
Messages
3,868
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.
 

kb3guy

Active Member
Registered
Joined
Mar 29, 2017
Messages
26
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-C-Collet-Horizontal-Arbor-Milling-Machine-5V-Machinist-Shop-Made-ASIS/282962250691?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!
 

Hawkeye

Active User
H-M Supporter - Gold Member ($25)
Joined
Jun 17, 2011
Messages
1,902
If the 7/8" arbor isn't overly hardened, you could reduce it to 22mm and rethread it.
 

john.oliver35

Active Member
Registered
Joined
Apr 26, 2014
Messages
138
Probably an impractical option, but can you dial the gear cutter in on the lathe and grind the ID with a toolpost grinder?
 

kb3guy

Active Member
Registered
Joined
Mar 29, 2017
Messages
26
Probably an impractical option, but can you dial the gear cutter in on the lathe and grind the ID with a toolpost grinder?
I actually thought about doing that! Unfortunately, a toolpost grinder isn’t in the budget either, at the moment.

If I had to choose between grinding the import cutter bore and modifying my OEM arbor though, I probably would go for the cutter, since it’s more easily replaced. I think I’ll give building the mild steel arbor a shot, and see if it develops runout after a few cuts.
 

benmychree

John York
H-M Supporter - Gold Member ($25)
Joined
Jun 7, 2013
Messages
3,868
Your soft arbor should work fine, and even hard arbors sometimes (more often than not) do run out a little, but it does not make much difference in cutting a gear. I have ground the hole in metric cutters out, and also made thin bushings for the larger size metric cutters, for them, I cut a piece out to accommodate the key.
 

bfd

H-M Supporter - Sustaining Member
Staff member
H-M Platinum Supporter ($50)
Joined
Sep 9, 2016
Messages
434
can you open up the gearcutter to 7/8 grind it or bore it with carbide I have turned down the od of endmills by using carbide tools worth a try bill
 

kb3guy

Active Member
Registered
Joined
Mar 29, 2017
Messages
26
Well, here’s today’s progress. Pinned, forge brazed and rough-turned between centers. Need to take everything down another .010 or so and do the threading, nut, and spacers.

This is the first time I’ve turned between centers - I like it! Minimal fuss.










Sent from my iPhone using Tapatalk
 

kb3guy

Active Member
Registered
Joined
Mar 29, 2017
Messages
26
Well, I got this thing tidied up and working. Cut my first gear with it - a 24-tooth, 16dp gear. I did make a mistake in indexing, so the first one is scrap, but I'm satisfied that this arbor will do the job. I ended up changing the threads on the retention nut to take the nut from the 7/8 arbor since they're so close in size, and borrowed some spacers from it too (which wobble up and down a bit on the video, but their end faces are still parallel for keeping the cutter vertical - that's the important bit, right?) Thanks again for all the help and suggestions, it's been an educational project.

2018-05-28 21.23.03.jpg
2018-06-10 02.35.42.jpg
2018-06-10 02.09.37.jpg

Here's a short video of the machine cutting a tooth:
 
Top