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quicksnail
30-08-2010, 06:57 AM
i try to build a small rotary (4th axis) for my router...
already i got the materials for tailstock... but my little lathe crossed my imaginations...

the first issue was the gears... for feed and thread cutting... when i tried to change gears, i discovered theres no 127... the reason lack of room for...
getting on the net i find a few website about this nifty machinery... they talking about the 21 teethed gear

so first looked for the whole problem what can be done on simple way...
on the first picture you can see the original part, made of 3.5 mm hotrolled sheetmetal...
you can see the design ""ignored"" the necessity for gears and modified to the available room for...
so first i cutted a testpart, which one worked better...

some more study on this, and find out the part has more room on the front... new design, and it is close what i would like...

next issue was the gear...
the inch-mm require the 127/120 ratio... even i moved the part to the front, still the room is not enough for... (due to the maximal teethnumber can be applied)

the first test of this was a 51 teeth gear... actually it would require about 0.8 mm dia endmill, but i had only 1.23 dia... so toothroot has a little undercut, but it doesnt reach the main circle..

127/120= 1.0583 the necessary
21/20=1.05 error 0.0083
51/48=1.0625 error 0.0042

might be next week i will get from ebay the right endmill.. already ordered, just it takes time...

thank you

quicksnail
30-08-2010, 07:22 AM
the next issue is the rest... some website sells for, but originally i purchased from harborfreight, and they don't have this time...
so i gave a try on this weekend for...

it is made 1 inch thick aluminum billet.. first i cutted a paper template, which one not really worked.. so i just measured the tailstock..
after dimensions were in hand, i drew it up in cad, andd cutted contur on the router, and slots were made on my mini miill.. a rongfu 45, 29x9inch tablesize...

it is openable what like really, because the saddle can be leaven on its position and the jaws also not necessary to release...

it is not ready yet, might be next weekend i have time for again...

and some picture about the gear i tried... the steelgear is original with the lathe..
i checked the dimension, on five teeth, but i could compare only with the caddrawing... i can't calculate involute a...


thank you

GeorgeD
30-08-2010, 07:47 AM
Hi QS welcome to MYCNC.

I'm sorry but you have lost me on what you're doing or asking? making gears out of Aluminium is not the way to go as ally is too soft a material for a machine ie lathe orientated,reason being they get chewed easily and chip at the finer points ie the teeth.

Have you looked at this site for all manner of spares for all models of the mini lathe?

http://www.littlemachineshop.com/products/product_category.php?category=5&First=H&Last=K

quicksnail
30-08-2010, 08:13 AM
my post rather informative...
since all gear made of nylon, or some similar plastic on this lathe, i think aluminum is suitable... i was thinking to cut of corian...
also the sdpi website has ready gears, but those only 6mm thick and this lathe has 8 mm thick gears...

thank you for link, in the recent days i discovered many similar site... i found one item i might buy that is the longer bed... theirs longer by 4 inch...

the gear, i felt no comfortable with the 21... still it is just a very substitutive solution... very possible i have to shift for a larger lathe, which ones are has better solution like this mini lathe...

GeorgeD
30-08-2010, 08:29 AM
I think the C6 has the biggest bed 21.65 between centers.

John S
30-08-2010, 12:33 PM
Very interesting and practical. Thanks for posting.
You could get away with a 6mm wide metal gear on these lathes as the loading is very small.

.

Swarfing
30-08-2010, 01:19 PM
Quicksnail i don't there is anything wrong to use aluminium but a better proposition would be to use tuffnell as this is what the big boys use to make their plastic type gears. hard enough to take the abuse but at the same time very easy to cut. it will mesh with the metal gears and the plastic very well.

GeorgeD
31-08-2010, 07:45 AM
Brass isthe better option if steel is out of the question? Ally just gets chewed over time.

John S
31-08-2010, 10:09 AM
So the original plastic gears are harder than aluminium ?

GeorgeD
31-08-2010, 10:33 AM
The point is Plastic and Aluminium gears are not suitable material for machinery and if the shipping wasn't so hefty from the states I'd change them on my own Lathe for metal ones.

Swarfing
01-09-2010, 12:04 AM
or maybe he is righ?t in that case i will start making nuts for my leadscrews out of brass as it obviously is a good material to use no? because plastic nuts on aluminium leadscrews would not be a good idea either and bronze would definitely not???????????????? (am joking here just in case it is taking literally)

George i am not sure where you get your facts from as google has the monoply on the answers. For an informed view checkout what the pros do please? servo's (the type in model aircraft) have been meshing aluminium and plastic gears for years.

Jonathan
01-09-2010, 12:32 AM
servo's (the type in model aircraft) have been meshing aluminium and plastic gears for years.

Indeed, servos with aluminium (or other metal) gears are considered much better than their plastic equivalents. The model cars I use use aluminium and plastic gears and they're fine. I should think the pressure on the gears in this application is greater than that on a lathe...48dp aluminium gear with 500W going through it!

Anyway, I'll be interested to see this 4th axis in action when it's done. Have you considered keeping the original lathe motor so you can use it as a CNC lathe should the need arise?

quicksnail
02-09-2010, 11:21 AM
dear people

my post was informative... who want to use anything of this... i'm glad...

yes, for industrial environment, working in 3 shift on a lathe need cast iron gears.. or similar that not sensitive for the not accurate positioning like machinist set manually on lathes...

but it is a hobbymachine, even it is wellmade, it is for hobby, you can't expect from this little machine like one built for machineshops with 3phase motors, and you can cut thread all day long reversing motors thoushand times 24 hour...

another point, i don't have hobbing machine, don;t even want to buy set of gearcutters...

i have small router, also not industrial and have some scrap aluminum got from recycling place by trading sodacans :-)

so.. why i should order ground hardened gears, just because they are standard in a production environment?
to order a set gear for this little machine might resulting 1-3 K bill from a machine shop...

what i expect, to cutting a few couple of metric thread, i believe it could be a solution...

i did work in factory... there were several type of gear cutter... mainly hobbing machines, but also was klingelnberg and oerlikon type... but the factory did not produced gears for handdriven drills...

so with this funny example i try to pointing, everything need to be affordable... for me this time this was affordable,,,, as george mentioned he wanted to buy gears, but stamps on mail are too expenses... i guess the next machineshop more expenses :-)

so everything is just as affordable really...

hopefully this weekend i can have more process on this...

best regard