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4th Nov 2021, 11:28 PM #16Most Valued Member
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If he will still accept the parts returned i would at least try them, thats not the worst finish I've ever seen but thats definitely night shift material.
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4th Nov 2021, 11:56 PM #17Golden Member
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- Adelaide
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5th Nov 2021, 01:07 AM #18
Hi Eric,
I would send him a picture of your existing gears !
Point out that these are the quality you expect, particularly for the price paid !Best Regards:
Baron J.
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6th Nov 2021, 02:49 PM #19Golden Member
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I sent him video evidence that the gears were originally shaved, hardened then honed. Its actually this 14T/24T gear being made at 12 minutes and 2 seconds into this video https://www.youtube.com/watch?v=nQaA...&ab_channel=RH
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6th Nov 2021, 10:34 PM #20Senior Member
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- Mar 2013
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- Mt Pleasant SA
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Those teeth do look truly awful & I'd not accept the gears. However if truly involute, the shape is more important than finish, the contact being 'rolling' not 'sliding'. I dare say that finish would generate a bit of rumble which would likely get worse rather than better. I'm totally with you against lapping them with 'good' gears .. the grooves would tend to hold the abrasive & have more effect on the good than on the bad ..
Return them I say.
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7th Nov 2021, 10:54 AM #21Senior Member
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- Mar 2013
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- Mt Pleasant SA
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Hi again Llama. Looking at the cluster again, & not focusing on the teeth, it looks like they friction welded two gears back to back. Now you also say they're unhardened. How about taking your cluster (the gears) down to Hercus & discuss it with one of the Durdens, they're very nice people. You might get lucky & be able to assemble a new cluster with a pair of their stock gears, silver braze them together on a stainless steel mandrel ( suitably flame oxidised before-hand to prevent wetting by the silver). I'm not suggesting a custom job by Hercus, tho' you might get a quote & no harm done. Hercus stock gears are made in China & a far better finish than what you have. The rounding of the teeth is something you could also discuss with one of the Durdens .. they might be able to do it .. or you might be able to go so far with a flycutter concave grooved on end. The notch unavoidably produced in the 'hub' 'might' be something you could live with? Or just make a start with said flycutter & finish the root by file?
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7th Nov 2021, 11:17 AM #22Gear expert in training
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- Aug 2008
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- Melbourne
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- 34
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Gear cutting specialists and general engineers www.hardmanbros.com.au
Fine pitch gear cutting from 0.1 Module www.rigear.com.au
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7th Nov 2021, 11:19 AM #23Gear expert in training
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Can we get a pic of the other gears you bought that are good to compare them?
Gear cutting specialists and general engineers www.hardmanbros.com.au
Fine pitch gear cutting from 0.1 Module www.rigear.com.au
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7th Nov 2021, 03:43 PM #24Senior Member
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- Mar 2013
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- Mt Pleasant SA
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You're right, he DID say 'hardened' which I first read as 'unhardened', must be an age thing, & I interpreted that white line between the gears as a fin but now see it's probably where residual oil in the 'corner' protected the steel from oxidation. BUT I do wonder how long unhardened gears would last in that situation? Are they in an oil bath? Might be possible to have Hercus gears induction hardened after silver brazing together without melting the silver alloy since only the teeth are directly heated, maybe having them on a cooled, or at least copper mandrel for the hardening. Hercus stock gears are 1045 steel.
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7th Nov 2021, 07:15 PM #25Philomath in training
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What they did then and what we would do now are two different things -
If you watch the video that Eric has linked to, the teeth are hardened but not the whole gear. Only having the teeth hardened has some appeal as there should be no noticeable distortion that you might get if you quenched the whole gear cluster. It also means that welding the cluster together is quite feasible - in fact, the amount of time and material wasted by making it from one piece would be large.
The fork that goes into the space between gears is probably CI or Phos Bronze, so in a splash lubricated environment I can't see any problem with it run on 'non-hardened' steel. One thought I have had for a replacement is making the gears out of something like 4140, welding together and then nitriding or something to bring the hardness of the teeth up.
Michael
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7th Nov 2021, 08:29 PM #26Golden Member
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- Jul 2011
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- Adelaide
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The lathe has 8 gear ratios and a two speed motor so 16 speeds. The lower 8 speeds use a back gear style arrangement which is not used in producing the fastest 8 speeds. So by replacing only the three double gears I can replace all the wearing parts associated with gear ratios that produce noise on this lathe.
The dodgy gear that is the subject of this thread is the one on the drive shaft, the next gear sits on what they call the second shaft and I have attached a couple of photos of that. The final double gear sits on the spindle and that has not yet arrived but is new old stock from the colchester factory.
The gears are all induction hardened but I don't think it has been done a tooth at a time.
PXL_20211107_085407769.jpgPXL_20211107_085443252.jpgPXL_20211107_085430916.jpg
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