Crashed the lathe when threading!!

[D.sebens]

Ughhh. I was making good progress on my project. Needed to make a 7tpi thread. Slowed the machine down and engaged the half nuts. The carriage moved in to the tailstock until it stripped a gear. Stupid me forgot that I had the reversing gear engaged for the last thing I was doing! I tried to disengage the half nuts but they were bound up. The good news is that it only damaged one gear. The lead screw still turns nice and the carriage moves when manually turning the lead screw with the half nuts engaged. I feel so dumb for this. I know this was just a mistake it just makes me feel bad it happened.

Now that being said, this is on my old sheldon. The gear is a 62T gear. 16 DP and I think 14.5PA. Gear is .485” wide. Center hub boss is raised .310” on one side .110” on the other. The bore is 7/8”(0.875”).

Please give tips for repair or replacement!
Lathe is a sheldon 11” WW2 era lathe.

 

[D.sebens]

To make my measurements about the boss more clear, I gave accurate measurements but I don’t think they mean much. The gear teeth are wider than the gear body. I measured off the gear body. One side of the hub boss is .200” wider than the teeth. The other hub boss is recessed .085” from the face of the gears.

 

[Uglydog]

Several options:
Do you have a mill an a dividing head?
Looks like three sheared teeth?
Options include repairing this one or making one new.
Either are doable.
Spur gears are fun and easy.
However, your first attempt(s), like every other machine project, may require a learning curve.

If you'd like I could (or others here) can make you a gear.
Or, if you want to travel to Minnesota, you can make your own gear on my mill. I've done that before for people.
This includes repairing this one or starting new.

I really like teaching.

Daryl
MN

 

[D.sebens]

I have a mill but no dividing head. I’m having one 3d printed by a friend for now and also to verify the pressure angle is correct. I may take you up on the offer. I thought about repairing with braze but I wasnt sure how to get the tooth profile correct. I was thinking that I could use the 3d printed one to copy the pattern? This gear is a little rough. It’s got another section that was repaired, looks like it was welded.

My friend is just making a plain gear and I will make spacers to get it in correct location. If I take you up on your services I will have to get better measurements since you won’t have the part in hand to verify.

 

[Uglydog]

Let me know.
She is either a 14.5 or 20. Likely already have the cutter.
Am serious about the offer of you doing it yourself on my machines.
Given prior problems. Perhaps you want to make a new gear. Or the printed one may be the long term solution.

 

[D.sebens]

I would love to come by there but that is much too far away from me. I’m looking at purchasing a rotary table. Is that not precise enough for a gear? Ive only seen people use a dividing head for it. I’ll let you know about the gear when I get the printed one.

 

[Uglydog]

RTs are good.
I've not used one for gear cutting.
One with plates and a tailstock may be just fine. I don't know.

 

[benmychree]

All the change gears that i have seen are 14 1/2 deg PA.

 

[OTmachine]

You can use the existing / remaining teeth of the gear with a round, tapered, stop pin to set in between the gear teeth and enable indexing without a dividing head. Grind a flycutter to the tooth profile to machine the welded up teeth to size. Done this a few times in a pinch . Works.

 

[Uglydog]

All the change gears that i have seen are 14 1/2 deg PA.

Seriously doubting 20. R
Regardless, it's one or the other.
I recall my first gear cut. Totally lost. Completely.
You can likely find an old thread here at HM.
Wherein many were very patient with me....