- Joined
- Jul 9, 2014
- Messages
- 613
On the eighth picture from the end of your run of photos , you have a shot of one of the gear retaining bolts sitting in the banjo C/W nut and washer ( almost dead in nthe centre of the picture ) . My lathe was missing one of these complete bushing sets ..ideally you need three to get a big range of gear trains /ratios as well as two of the alloy ferrules with the driving keys cast on them ( your eBay link )picture ).
I measured up one of the gear retainers & ferrule that was on the lathe then wrote down the dimension and recorded the measurements , checking them twice on the parts to ensure I hadn't made any errors ( A long dead old engineers tip ).
Using a 1/2 dia long shanked mild steel coach bolt , these have a square on the shank just under the domed head to stop the bolt turning when fastened in wood & that is ideal for our purposes .
I turned the unthreaded shank to the correct dimensions of the retaining bolt .... don't turn off the square shank .
Cut it at the correct length & threaded the end to the correct length , filing down the square of the coach bolt evenly on each side using a " hand safe edge file " , it has no teeth on one of the edge so it wont file from that face ).
Make sure it fits in the banjo's slot in all four planes by rotating it and testing the fit . Then I turned off some of the domed head to make the head the same size as the original bolt .. had to centre drill the dome and use a cut away dead centre to get the tool in to do it It was easier to initial dimension the bolt for the ferrule , threading & length using the chuck at the threaded end and the head in the dead centre. The full domed head was turned to a " 5/16 thick cheese head with a dome @ 9 /16 " dia "
Then the finished dome head was turned down with the new bolt end set close in the chuck , avoiding putting the threaded part in the chuck jaws . Had I given it any thought I could have done this whilst the bolt was still in chuck and held on the cut away dead centre as there was sufficient clearance .
The hollow top hat / ferrule / bearing was turned to the correct dimensions taking the last five cuts at a very fine cut & at a high speed then polished with a fine wet & dry . It was finally burnished with liquid brasso ( liquid stainless steel sink cleaner will work but it's not as good because there is no oil in it ) on some thick solid cardboard.
When making this ferrule make sure it will be long enough to work with all the gears . The first one I made was two thou too short and as a result a couple of the gears were nipped when I tightened the retaining nut on the anchor bolt whilst the gear was set in th banjo slot .... resulting in a semi solid gear instead of a free turning on . . You need washers on the bolt under the retaining nut to stop the gear coming off . Use the correct dimension washer under the retaining nut , make sure it is a true flat washer & not partially counter sunk or twisted , even if you have to turn them up your self .
Lubricate the ferrule inside & outside when assembling them in the gear and make sure that there is no crud on the anchor bolt that will cause the ferrule to bind .
When making up a gear train have everything finger tight and gently pull each set to be tightened towards the front of the lathe so it meshes easily but positively with the other gears then gently nip its retaining nut tight ( Don't do a gorilla job on it because the threads are quite thin ) .
Everything was now ready to build a desired gear train .
When I made up my 97 TPI train & had every thing set , meshed and tightened it was rather noisy to run so I used spray on ( rattle can ) white grease and copper grease out of a 1 pound tub . It was heavily spread on & into the gears with a long spatula of wood I'd cut on my band saw whilst the lathe was stopped , did this with the headstock casings gears as well .. it now runs amazingly quiet .
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