Mini Lathe Change Gear Specification?

Does anyone know what spec the gears are? I've found them listed online as module one, 8mm face width, 12mm bore, with a 3mm by 1.4mm keyway, but I've printed one and it doesn't fit, mine appear to be 7mm wide, with a 4mm by 2mm keyway.

I'm just going to run with those numbers for now, but if anyone can help, please let me know - I presume either different manufacturers use different ones, or they've just been changed somewhere along the line, these machines have been in production for over 15 years now I think.

Thanks,

Russ

Interestingly, the spacer behind the leadscrew gear is 8mm wide, seems even the manufacturer couldn't make their mind up - the shaft is 14mm long, so with the 8mm space it doesn't quite fit properly! I wonder who decided to shave a mm off the gears and all the little shafts - typical chinese money saving mentality perhaps.

On my minilathe, a Clark CM300, made by Sieg, the gears are Mod 1 with a 20 degree pressure angle ( see: http://mikesworkshop.weebly.com/change-gear-pressure-angle.html). The gears are 8 mm wide and they are bored 12 mm. The key is 3 mm square. However, the Real Bull minilathes (Chester, Warco, Amadeal), I am told have 4 mm keys.

I hope this helps

Mike

I thought I'd replied but perhaps I forget to hit send!

The gears ARE 8mm wide (7.8mm actually), but the plastic 80T are relieved around 0.75mm on one face (presumably to stop them rubbing) so they appear to be 7mm wide across the tooth. The small 20T are 8mm wide and steel.

They have a 4mm key not 3mm which is perhaps the only real defining feature between the Sieg and RealBull as Mike's mentioned.

Interestingly the shaft on which the gear and spacer sit on the leadscrew is too short but its closers to 15mm than 14mm (I was struggling to measure accurately with a steel rule)

I've made the gears Module 1 with a 20 deg pressure angle and nominal 0.075mm backlash/clearance and they mesh and fit nicely (better than the original gears which are a very close fit on the shaft and hard to remove!)

If anyone ever wants the 3D files for the gears or any of them printing, just let me know as I've got the design adjusted to accurately print to tolerance but this will only really apply to my printer, they're all slightly different (mine prints about -3% on internal holes and 0% external with the material and settings I use for function stressed parts)

I've got a 3D printed gear on my big 11" swing Myford as the primary gear and it's been running for 18 months now, so they are quite robust. I printed it in Nylon and being hygroscopic it was completely dry straight off the printer due to the temperatures (250c). I submerged it almost straight in ISO32 oil overnight hoping it would soak up that, rather than atmospheric moisture, seems to be doing very well, but I'm not sure if that's the oil dip or just generally because they're surprisingly durable. I might do a test next time because I would expect nylon to swell if absorbing moisture/oil as is normal for Nylon, so if submerged in oil straight off the printer, the bore should reduce in diameter if it's absorbed anything. The inside of the gear is slightly hollow so there's also room for it to retain quite a lot of oil if the air can escape.

Edited By Russ B on 01/05/2017 12:37:21

As Mike says there are two manufacturers, Real Bull and SIEG. When measuring keyways, only half the key is in the gear so Mike's 3mm figure makes sense.

I think the Chester machines are SIEG but I won't swear to it.

Neil

My Chester 'conquest' is a 'Real Bull' machine....