johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most.

Tag: gear repair

Installing the lathe gear

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I neglected to take a photo of the completed gear.  In this shot it is almost finished.

I intended to reassemble the spindle and its cluster of gears, spacers, and taper roller bearings myself, but after talking to an expert on the topic (Swen Pettig), I realised that sometimes it is better to leave surgery to a surgeon.

I gratefully accepted Swen’s offer to help.  In his working  life Swen had performed this task on many, many occasions.

Firstly Swen reinserted the taper bearing outer races in the headstock.  The lathe spindle is approx 80mm diameter and 800mm long so it is heavy.  After careful cleaning, it was fed into the headstock, progressively loading the bearings, gears, spacers, clips and nuts, and moving and tapping them down the shaft as it was moved into place.

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Note the photo prints to remind us of the order of reassembly.  Board to protect the lathe bed.  Repaired gear laying flat.  Surgeons’ towels blue rags.

when it was all reassembled and tightened, the retaining disk at the chuck end was loosened, sealed with liquid gasket (Loctite product- cannot remember the name), and retightened.

Then Swen went through a lengthy process of checking the end play, using a dial indicator, tapping each end of the shaft with a copper hammer, and finally settling on 0.01mm of play.

Then we had a short test run at low speed, and he tested the end play again, with no change.

Then we set it running at 200 rpm, and went and had a cup of coffee for 20 minutes.  Came back and checked the bearings temperatures.   All cold, all good.

I reinstalled the external gears, the cover, etc, and took some decent cuts in some cold rolled bar.

All good.  Oil change soon.

 

Preparations for gear cutting

Almost ready to cut the lathe gear.  It is 237mm diameter, 25mm thick, with a new rim Loctited and Scotch pinned to the old hub.

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I borrowed the 6-12″ Mitutoyo micrometer from a GSMEE member.  Thanks Rudi.  I had to learn how to read an imperial micrometer.  The rim is glued and pinned to the original hub.

And today I made a tool holder for the new-old gear cutter which I purchased from Russia.  It was meant to have a 27mm bore, but when measured was closer to 27.1mm, so I made an arbor to match.

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The cutter on the new arbor.  It required 2 attempts to get acceptable dimensions. It will be held in the vertical mill with an Er40 collet chuck.  It runs true.   Not bad for an ex gynaecologist hey?   Might need to sharpen the teeth on this old-new cutter.

Meanwhile, on advice from Swen, another GSMEE member, thinking ahead, and setting up to trial fit the new gear after it is cut.   Here is Swen, making some steel temporary bearings to try the new gear on the shaft, after the gear is made.  Tapping out the old taper bearing races.   This is what Swen did for a living when he was in the work force.  I have learned heaps just watching Swen doing his stuff.

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I admit that I would not have been brave enough to do this.  “Piece of cake” says Swen, tapping out the race with a copper drift.

Broken Lathe Gear – Update.

I searched the lists of stock spur gears from international suppliers but I could not find a supplier of a 77 tooth, module 3 gear.  77 teeth is apparently unusual.  Plenty of suppliers for 76 and 78 tooth gears, but none for 77.

I did find an Ebay seller who had some old new stock of rotary HSS gear cutters and I  considered making a new gear.

But meanwhile, after airing the situation at a GSMEE meeting, I had a recommendation to try a local gear maker.   Well, fairly local.   He is 1 hour up the freeway.   But the phone calls were unanswered, repeatedly.  Another fellow GSMEE member also required a gear cut, for a telescope mount (a BIG telescope…. another story), and it was on his route home, so he called in, prepared to bang on the gear maker’s door.    Despite the industrial turn down in Australian manufacturing, the gear maker is so flat out with work, that he has stopped answering the phone.  But he received Frank very cordially, and was also very friendly and helpful to me when I turned up 2 hours later.

I took the broken gear and its shaft, and he is preparing a quote.  His initial recommendation is that the gear be replaced entirely, rather than repaired, or a toothed ring shrunk on.  So I am waiting for the quote.  But frankly, the lathe is unusable the way it is, so I cannot imagine rejecting the quote, unless it is so high that I am pushed back to making a gear myself.  I will post this when I get the quote.   Meanwhile, a photo, and a plug for the gear making business.

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This is Johnny, the owner manager of Sunshine Gears

Johnny proudly showed me around his factory, and we discussed the options for my job in detail.  He has many (~40) gear hobbing machines, lathes, mills, and jobs in progress.  He is just about to get his first CNC machine, a lathe.  The  machine in the photo was making a gear cluster of 6 or 7 different sized gears.

Sunshine Gears is at 14 First Avenue, Sunshine, Victoria.  Telephone 0393117152.   Probably best to just call in rather than telephone.

Post script.   After considering the quotes I have asked Johnny to make me a gear which I will attach to the original hub.  It should be ready for me to pick up when I return from my UK trip.   It saves several hundred dollars to do it this way, rather than getting the entire gear with hub made from scratch.

By the time this post is published I should be in the air…..