11" Rockwell back gear trouble

B

BuffaloBill

Guest
Any ideas on where to purchase a spur gear?

The smaller gear on the moveable back gear is missing 2 teeth and an adjacent tooth is as good as gone. I've read about various methods of repairing and think I'd like to turn off the old teeth, purchase a new spur gear, boring the ID to fit over the turned-down area of the back gear hub (not sure what terminology to use here), and bond or silver solder it on there.

The damaged gear is straight-cut, has 35 teeth, an OD of 2.314". From that, I understand this to be a 16 pitch. Comparing the shape of the teeth to photos showing examples of 14.5 and 20 degree pressure angles, I believe my gear is 20 degrees. Also using a measurement method found online confirms the 20 degree PA. The width is 0.866"

I read posts that recommend Boston Gear. I didn't find on their site a way to inquire about a specific gear and I haven't phoned them yet. I did find on Rushgears site a way to request a quote. So I did so.

I asked for:
Cast iron
35T
16 pitch
20 degree PA
0.75" width

I received an email with quote within an hour and was totally shocked by the price. Where did I go wrong? I specified cast iron, should I have asked for mild steel instead? The price quoted for 1 piece was $1585!

I found a pdf of a Boston Gear catalog showing (stocked?) gears available. They show various tooth count in a 16 pitch 20 degree PA but not a 35 tooth. Is 35 teeth an "odd" number?

I was expecting the Spur gear to be maybe $50-$100. Am I dreaming?

Any sugestions? Thanks in advance.

Bill
 
Maybe this will help someone else. I just found the ametric dot com site. They show a steel 35T, 16 pitch, 20 degree gear for $17.54. I don't know what I'm getting for that price but I ordered a couple. I'll report back when it arrives.
 
If the gears you ordered don't work out Joe at Plaza Machinery has a gear repair kit with two rings you repair your existing gears with. $125 for the set. Pretty close to what you described you were looking for. Email Joe and be patient if you don't hear back right away. If you don't hear back in a few days to a week try him again. He gets busy but has always responded given time.

http://plazamachinery.com/RockwellBackGears-12-29-2014.html
 
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WSnyder said:
If the gears you ordered don't work out Joe at Plaza Machinery has a gear repair kit with two rings you repair your existing gears with. $125 for the set. Pretty close to what you described you were looking for. Email Joe and be patient if you don't hear back right away. If you don't hear back in a few days to a week try him again. He gets busy but has always responded given time.

http://plazamachinery.com/RockwellBackGears-12-29-2014.html
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Thanks for that tip. Joe's price is very reasonable. Nice to find someone offering support for the Rockwell.
 
Have good news to report:

The gear I ordered arrived the following Monday. I turned the bulk of the hub out grabbing it in the 4-jaw of my 12" Craftsman Atlas. Then bored a cavity in a block of aluminum that I lightly press fit the gear into, thinking that it would not squeeze the gear rim out-of-round. Indicated as best I could to 0 runout off of the ID of the aluminum block in the 4-jaw, and trued up the ID of the gear. Then turned between centers a shaft to spin the back gear on, using just a bit of taper such that I could use friction to spin the damaged backgear part. Taking light cuts I turned off the cast teeth to a diameter about 1.2 thousandths larger than the bored out gear. Then pressed it together with my beat up harbor freight press, using permatex sleeve retaining compound. Hopefully it won't come loose under load!

Did I mention the steel gear cost only $17.54 (plus shipping)? Attempted to attach pic below...

I tried to join the Rockwell group but have been unsuccessful thus far.
 

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Butch Lambert said:
How about having it tig welded about 4 different spots? I would worry about the press fit and Loctite.
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Now that's a thought Butch. I have a tig actually. I've tig'd steel, stainless, and aluminum but never tried cast. Would you expect the steel gear & cast to weld OK? I do think this cast is pretty decent quality. I did read when searching the web for gear tooth repair ideas, that someone tig welded material (nickel I believe) to build up missing teeth. Would you recommend adding filler material or just try and puddle the two together?
 
BuffaloBill said:
Now that's a thought Butch. I have a tig actually. I've tig'd steel, stainless, and aluminum but never tried cast. Would you expect the steel gear & cast to weld OK? I do think this cast is pretty decent quality. I did read when searching the web for gear tooth repair ideas, that someone tig welded material (nickel I believe) to build up missing teeth. Would you recommend adding filler material or just try and puddle the two together?
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I ain't a welder. Didn't know part of it was cast iron. Better get more opinions.
 
Drill it and pin it. To weld cast you need it extremely hot with a cast rod stick style. It welds to cast well if allowed to cool under sand or lime for a day or so but it doesnt weld to other metals well at all. If you hit it with tig itll almost disappear with porosity. It may can be brazed with a proper flux covered brass rod but it wont do anything but sit on the surface. It would need a relief cavity to fill. Id drill at an angle and dowel it together
 
There is a good Youtube series on this very subject

Look for Keith Fenner on Youtube. He has a series on repairing a gear like yours as well as fitting a new one. He has some great stuff on his site. He is an expert welder as well as machinist.

Pete
 
I'll check out those youtube vids, thanks Pete for letting me know about them. I just finished pinning it so I,ll save what I learn from Keith for the next time!

I went ahead and pinned it like you suggested Dusty, although perhaps not at an angle. I went in with an 1/8" end mill then drill bit parallel to the axis of rotation, centered on the mating surface, and drove in roll pins. I have read that with an interference fit and Loctite 648 it was probably not going anywhere. I couldn't find 648 locally so went with Permatex high temperature sleeve retainer. The spec sheets and instructions are very similar. This one's said to give 3000psi "holding power". I've got about 4.5in^2 surface area at the joint, so can I equate that to 13,500 lbs? The radius to the middle of the teeth is about an inch, so should it hold a torque of 1125 lbft? No matter how big that number is I still do feel more confident having a couple pins in there. Pic below, but not easy to make out the one roll pin in view.

Butch,

I too really like this lathe. Like you've said, with spiders at each end you can work on short barrels. Mine is missing the shoe material that runs against the back side of the v-belts, a part of the "safety" mechanism to prevent spindle gear changing when in motion. I have no trouble being patient and careful with gear changes so it's not a problem with this not working, but it would be fun to have it work as intended. Does yours have that puck? What sort of material is in there? I was guessing it was rubber.
 

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Thanks guys. I put it back together and it runs in back gear with a consistant sound now, no clunking.
 
BuffaloBill said:
Mine is missing the shoe material that runs against the back side of the v-belts, a part of the "safety" mechanism to prevent spindle gear changing when in motion. I have no trouble being patient and careful with gear changes so it's not a problem with this not working, but it would be fun to have it work as intended. Does yours have that puck? What sort of material is in there? I was guessing it was rubber.
Click to expand...

It's a fiber reinforced piece of rubber. It probably doesn't need to be fiber reinforced. Fairly stiff durometer. It's glued on. Without looking I'd say it's about 1/8" thick.

I'll agree with Butch in that they are a nice gunsmith lathe. Another problem area you may have to deal with (if someone hasn't already) is the bushing in the floating pulley in the Reeves drive. They were a composite bushing of some sort. Sort of a phenolic with bits of what looked like embedded bronze fibers. Mine was coming apart (as they all seem to do), I replaced it with a shop made bronze bushing.
 
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WSnyder said:
It's a fiber reinforced piece of rubber. It probably doesn't need to be fiber reinforced. Fairly stiff durometer. It's glued on. Without looking I'd say it's about 1/8" thick.

I'll agree with Butch in that they are a nice gunsmith lathe. Another problem area you may have to deal with (if someone hasn't already) is the bushing in the floating pulley in the Reeves drive. They were a composite bushing of some sort. Sort of a phenolic with bits of what looked like embedded bronze fibers. Mine was coming apart (as they all seem to do), I replaced it with a shop made bronze bushing.
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I thought I'd try gluing in a piece of flat belt material.

I believe my drive pully bushings are ok. I didn't dissassemble them completely, but when I had the belts off the sheeve slid nicely w/o being sloppy on the shaft. Maybe the've been replaced already. A guy needs more than one lathe so he can make parts for the one that's tore down!
 
I love my Rockwell! BTW, DON'T try to clean old grease and crud out of the quick change gears with a toothbrush and WD40 while the lathe is running!!! Thank God the gear I stripped was the finest threading one, when it ate the brush. Had to braze in and file 2 teeth on the other(idler?) gear. :eek: Compared to my old Atlas, it sounds like a Lexus versus my Grandpa's Model T hay wagon.
 
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