[4]

Changing tailstock quill taper

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

dtsh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Sep 22, 2017
Messages
119
Likes
132
#1
My old 1903 Seneca Falls 10" lathe happens to have a #5 Jarno taper in the tailstock. It's not in terrible condition, but tooling to fit it is hard to find and when it can be found, it is invariably expensive. I've modified a few bits of tooling to fit the Jarno taper, but it's a hassle setting it up to cut a taper everytime I want to add a new tool. I've been thinking for some time that reaming the Jarno to MT2 would be the most expedient solution, but before I destroy an otherwise working lathe it seems prudent to get some advice. I'm not at all concerned about keeping it original, it's a tool and anything that makes it a more useful tool for longer is great in my opinion.

Jarno #5
large end: 0.6250
small end: 0.5000
length: 2.50
Morse #2
large end: 0.7000
small end: 0.5720
length: 2.56

I'd appreciate advice and warnings from those of you who have been down this path before.

Thanks in advance.
 

Whyemier

Active User
H-M Supporter - Gold Member ($25)
Joined
Jul 11, 2014
Messages
495
Likes
404
#2
Machine a new quill, keep the original...in case.
 

dtsh

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Sep 22, 2017
Messages
119
Likes
132
#3
Machine a new quill, keep the original...in case.
I feel pretty foolish as I'd considered this before and promptly forgot about it.
 

Whyemier

Active User
H-M Supporter - Gold Member ($25)
Joined
Jul 11, 2014
Messages
495
Likes
404
#4
Don't feel foolish. I've remachined bits and parts then realized I needed the original and had to machine it new. Duh!
 

bfd

H-M Supporter - Gold Member
Staff member
H-M Supporter - Gold Member ($25)
Joined
Sep 9, 2016
Messages
418
Likes
242
#5
my lathe (old one ) came with a # 2 mt and I wanted a #3mt so I measured the od of my spindle and on vacation went to grizzly tools and measured theirs found one .001 larger than mine and ordered one from grizzly. then I changed the whole spindle. maybe you can do this. worked for me bill
 

Bob Korves

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Jul 2, 2014
Messages
5,535
Likes
5,848
#6
My old 1903 Seneca Falls 10" lathe happens to have a #5 Jarno taper in the tailstock. It's not in terrible condition, but tooling to fit it is hard to find and when it can be found, it is invariably expensive. I've modified a few bits of tooling to fit the Jarno taper, but it's a hassle setting it up to cut a taper everytime I want to add a new tool. I've been thinking for some time that reaming the Jarno to MT2 would be the most expedient solution, but before I destroy an otherwise working lathe it seems prudent to get some advice. I'm not at all concerned about keeping it original, it's a tool and anything that makes it a more useful tool for longer is great in my opinion.

Jarno #5
large end: 0.6250
small end: 0.5000
length: 2.50
Morse #2
large end: 0.7000
small end: 0.5720
length: 2.56

I'd appreciate advice and warnings from those of you who have been down this path before.

Thanks in advance.
The differences in diameters between the sizes is really too much to ream, so it will have to be bored, which is possible. It is not particularly easy to get great results in producing a machine taper that is to the correct size, the correct taper, and concentric to the lathe axis, with a nice surface finish, all at the same time. Make sure you are up to the challenge.
 

derf

Brass
Registered
Joined
Oct 3, 2015
Messages
606
Likes
690
#7
This seems to be a common problem with Seneca Falls lathes. I recently ran into the same problem with a 12" Seneca Falls, but it had a taper closer to a #2 Morse. A #2 stuck out quite a bit and didn't quite seat right. I first bored it, then finished up with a #3 Morse reamer.
I might add, that I did this on another lathe... not the one I was correcting.
I first put a #3 Morse sleeve between centers and swept it with an indicator and adjusted the compound to follow the taper. I did have to bore the depth slightly deeper (cylindrically) for the tang area. Once I bored the taper, I had it very close and was just going to lap out for a final fit, but that's about the time my buddy showed up with a new MT reamer ( it was his lathe) so about a dozen turns and we were golden.
 

benmychree

John York
H-M Supporter - Gold Member ($25)
Joined
Jun 7, 2013
Messages
2,339
Likes
1,768
#8
Yes, either make a new one, or bore out and ream the old one; I'd do the latter if the old one was still a snug fit in its bore. The Jarno made a lot of sense on its dimensional calculations, but came to late in history to be adopted as a standard for anything except cylindrical grinders.
 
[6]
[5] [7]
Top