Gear between carriage and rack on Hardinge TL

[W6PUG]

Hi Guys. Have gotten some good posts back - great info - during the restoration of the Hardinge TL (thanks Jim!), and it is going together very well ... hope to have first chips within next week, however one thing that is being hard to over come is the gear that runs between the carriage and the rack .... it has broken somewhere along the line and the previous owner put a 12 tooth little gear where the original 11 was. It works - turns things great ... a little bit of backlash but livable, but I think when I start threading, that extra tooth is going to throw off my feed rate, so I still need to figure out how to get that gear replaced, either from a salvage or from someone who can cut one. I did find out that there are a couple of other guys who are also facing this, so if anyone has any sources or thoughts I am sure we would all appreciate it who have the same problem. I will get some new pictures of it within next few days. the machine is 1944 and the experts I have been in contact with thus far are skeptical if we can find this out on a net anyplace (and I am sure we are all scouring every resource we can find!) This is not something that I have to do right now, but it is going to be there until I get it fixed, and as I said, I think it will cause me problems in threading (??) ....thanks in advance for any/all help/thoughts.
Doug W6PUG (I am also a ham radio operator and we have a houseful of pugs, so that is where that came from).

 

[Weldingrod1]

Doug,
It looks like Hardinge likes 20 degree pressure angle gears and 22 diametral pitch.
This will sound crazy, but you could have this gear 3d printed in metal. I am currently printing a special pair of gears to let me cut an 8 TPI thread on my TL-10. I'll let you know how that comes out. If you are interested in trying this route, I can generate the STL file you will need. In order to make the file I will need to know the shaft diameter, keyway dimensions, and confirm the number of teeth and diametral pitch.
Of course I don't have the change gear quadrant OR the change gears... Argh! If you happen to have the standard quadrant or metric quadrant, I would love to get a scan/copy of both sides of them with a precision ruler in the picture!
Regards,
Rod

 

[Weldingrod1]

Doug,
Hardinge change gears are Fellows 22/29 stub pitch, 20 degree pressure angle.
Both of the sketchup involute plugins make standard teeth. I might be able to build a single tooth in Autocad and copy it...
I don't know if they use stub teeth on the carriage; probably not, but it needs checking.
Does this gear mesh with the rack, or some other gear I can get at to measure? I have gear tooth calipers and a Hardinge TL-10.
FYI, the 3d printed plastic change gears worked!
Regards,
Rod

 

[W6PUG]

Sorry to be so slow to respond - things are weird at work right now and time is nonexistent, so I did not see this ....
This is the gear that actually meshes with the track ... the guy who had it before me put a 12-tooth in its place and it sorta works but I cannot help but think it will not track speed right, which in most cases probably would not make a lot of difference - until you try to cut threads or something! Then I think your spin versus your linear speed will be off, and your thread will be off by the extra tooth angle .... I am obviously not a machinist at your level but the logic seems to fit here ....

I will need to get some help to take the compound off if you need to see it, but I am going to dig through some of the old pix I had when I got it and send you what I have / if I can find the broken gear, I might even be able to send it, but that has been a year ago and I am not sure where I might have put it.

You have a 3D printer!! Wow! That is so over the top to me that I can't even comprehend it. Let me see what I can dig up in photos and hopefully find the broken gear ... God help me on this one!

Thank you for the followup .... and again I apologize for being so slow to respond.
Happy Holidays and thank you again! doug

 

[Weldingrod1]

Doug,

Having the wrong number of teeth meshing with the rack gear won't have any effect on threading; that's controlled by the lead screw.

I can measure the rack pitch on my lathe, and make sure it isn't stub tooth like the change gears. I will see if I can see in and count teeth on the drive gear.

Regards,
Rod

 

[Weldingrod1]

Doug,

At the bottom of this page is a photo of the pinion gear that drives the carriage. It is integral with the shaft, and it looks like the large gear is too.
http://www.mycncuk.com/forums/lathe-build-logs/566-renovating-hardinge-hlv-h-3.html
Its not obvious to me that you could even put in an incorrect gear at all!
Halfway down this page is a picture of the insides of an HLV carriage; our should be pretty similar to this.
How did you decide you had the wrong gear in there? How much backlash do you have? 0.01" is a good measurement.
Rod

 

[W6PUG]

Hi! I really appreciate you digging into this ... I have looked for a replacement gear for months.
The original gear is 11 tooth; it was broken and was a replaced with a piece of 12-tooth commercial gearstock that was cut - I still have the remnant ... Obviously parts for this lathe are not available now ... I even contacted Hardinge and they said there was not even any manual or reference available in their arachives wo I am SOL.
It runs ok ... but that is part of the tracking across the whole bed way, so I was trying to find a replacement. The guy I got it from knew the story behind it and showed me as we were putting it together ....
Cannot answer about the backlash ... you are right .... I need to measure it ....
I also have been told that this TL is same gearing config as T-10 ... but I could not verify that if my life depended on it. I am newly getting back into hobby machining after 30 year absence, so I have discovered what I don't remember is huge ....
Afraid I do not have any more info that I know of (doesn't mean I don't have it - I just don't KNOW if I or Billy has it!
Thanks again! OBTW - Merry Christmas! Hope the Spirit of the Holiday is in your house!
doug

 

[W6PUG]

I JUST realized something ... I should have started this thread in the Other Lathes section instead of the milling section - I was so excited to see someone with a Hardinge label that I totally missed that ... please forgive.
I have not had much time on the machine lately - working to upgrade some of my welding resources the job had me overseas for a couple of weeks - I will get back to this and see where I am in it all.
Should I stay here or reopen the thread in the Other Lathes section?
Thanks Guys!

 

[Bill Gruby]

Would you like it moved or left here, your call.

"Billy G"

 

[W6PUG]

Would you like it moved or left here, your call.

"Billy G"

Bill - I am ok with it as long as someone else does not get bent out of shape .... but I should have paid a little more attention ... will be more careful next time ....but I also want to thank everyone who has been HUGE help with me using this lathe - Jim S and Rod and others have been very encouraging and very very helpful. This is a great forum and I am privileged to be a part of it. Thank you. Doug