Need Help!- Stripped Threading Gear

[rawhite]

I have a TriPower. New to me but only 2 years old. I engaged the Y movement and heard a bad POP!! and CRUNCH!!!. I had issues the other day with the gear select for the Y jumping off of the cam and assumed that was the problem. I pulled the face plate off to see no issue. I opened the door to access the drive gears to see the smaller sprocket was chewed up. After further tear down I found that the Y ball screw had driven past the most + position and was locked up. After fixing that and cleaning everything up again. I replaced the bad sprocket with a size larger and it all seems to be working again.

Now I need a new sprocket. I think these are only sold in sets of 17 (or something like that). Is there any aftermarket parts for these?

Thanks,
Rick

[instructor37]

Originally Posted by rawhite I have a TriPower. New to me but only 2 years old. I engaged the Y movement and heard a bad POP!! and CRUNCH!!!. I had issues the other day with the gear select for the Y jumping off of the cam and assumed that was the problem. I pulled the face plate off to see no issue. I opened the door to access the drive gears to see the smaller sprocket was chewed up. After further tear down I found that the Y ball screw had driven past the most + position and was locked up. After fixing that and cleaning everything up again. I replaced the bad sprocket with a size larger and it all seems to be working again. Now I need a new sprocket. I think these are only sold in sets of 17 (or something like that). Is there any aftermarket parts for these? Thanks, Rick

Rick,
When you say " sprocket" I think you are referring to the change gears. These are the fine tooth gears with the 4 spline center hole. This is common with new owners who travel the power feed beyond its limits. We have done this a number of times. Usually the small 27 tooth gear gives up, but also will break it's mate as well. Carefully dis-assemble the gear train completely- making notes or a drawing of how it all goes back together- then clean all the gears and inspect them. You dont want to have a piece of tooth stuck in one when you start it back up. Also check the shafts that the gears ride on for straightness- sometimes the force of the jam can spread the gears and bend the shafts. JT keeps these gears in stock and you can order just the ones you need. Also, when doing the gear setup, have a small amount of backlash between the gears- too tight will grind them up, too loose will break the teeth.

[rawhite]

Yes on all assumptions. It was the 27. When the Y gear select jumped off of the cam, it was close to full through. After fixing the selector I manually ran the table back to 0. I did not check the drive at that time. When I broke it apart I found a thread at the end that had buckled and a bur on the brass. That was the causer. I filed the burs and ran a thread chaser on them. Everything is smooth again.

I pulled the gear stack assembly apart and washed everything. I rolled the shafts on glass to check for any distortion. I did not see any. I did polish all shafts before rebuild. I have talked with J.T. a couple of times. Seems like a very nice guy and knows his product well. I will give him a buzz on Monday.

Thanks,
Rick

[Tapered_Gib]

I usually machine freehand as I was trained early on to develop "feel". I only engage the gear box to do a finish pass or single point threading. And yeah, jeepers, watch my range limits.

One of my early, after high school jobs was delivering coal in an old Chevy dump truck out to residential customers. The coal elevators had a big bull gear that ran the elevator scoops up 80 foot high towers. That bull gear I bet was 4 feet in diameter and one day a couple threads stripped out. I took that gear in our delivery truck to a welding shop 50 miles away, that welded up the gear teeth and remachined them good to go.

In a pinch, I bet same could be done with your little gear but on a smaller scale.

I busted a cast iron horizontal cutoff saw's main arm, cracked it clean through pushing production, cutting off 6 inch diameter, D2 bar stock. I welded that arm back up and got it back into service no problem using Eutectic brand welding rods, stick weld and oxy torch pre-heat.

I don't know what the metal components of the gear are. If cast iron got to be careful of work hardening it and machining it would be close to impossible. If cast iron, maybe best to braze the teeth. Smallblock would know.

Another choice is to buy a Shoptask used and cannibalize it. The newer Shoptask look to me based on the early 1990's basic design. Wonder if the inner guts are the same? Used to do that with A.B. Dick printing presses.

Originally Posted by rawhite Yes on all assumptions. It was the 27. When the Y gear select jumped off of the cam, it was close to full through. After fixing the selector I manually ran the table back to 0. I did not check the drive at that time. When I broke it apart I found a thread at the end that had buckled and a bur on the brass. That was the causer. I filed the burs and ran a thread chaser on them. Everything is smooth again. I pulled the gear stack assembly apart and washed everything. I rolled the shafts on glass to check for any distortion. I did not see any. I did polish all shafts before rebuild. I have talked with J.T. a couple of times. Seems like a very nice guy and knows his product well. I will give him a buzz on Monday. Thanks, Rick