Offset machining work

[Jacktegla]

Just wondering if people would be intresred in giving opinion just to settle a "debate"

So I'm not machininst i dabble, I'm fitter by trade but the machining and welding comes with the trade now I don't like to argue too much with thep professional machinist only being 23 but...

I have two offset shafts need making in work, 105mm diameter overall, stub ends machined down to 60mm od. Ofset of 40mm, overall length of 1400mm.

Now he's saying this is a massive job to machine and struggle to fit in lathe especially with all the weight bla bla bla, all excuses under the sun.

In my head though it's machine centres on both end on 90 head on mill, setup in 4 jaw and tailstock, go nice and stead and hey presto. I know not that simple but am I missing something or is he just a bit of a wet lettuce m

Thanks

 

[Bouledogue]

I'd guess that bar is getting on for 100kg. How big is your lathe? And how big is your machinist...?

 

[Martin-Sy]

Assuming steel @Bouledogue is damn near right. I make it 95kg.
Also the figures don't add up. If the bar is 105mm dia and you want a stub 60mm dia with 40mm offset the bar needs to be 140mm to start.
Or maybe I'm not understanding what you're after.
Can't the stub be made as a separate part and bolted/welded on?

 

[indykid]

What's the tolerance on diameter, surface finish and straightness on the ends? How long are the turned ends?

As above, to keep 60mm ends, you can only offset 22mm, but even still, the centripetal force at 200rpm is 965N and even at 100rpm, it's 240N so I'd say you'd benefit from some bobweights attached down the length, but it feels doable without as long as you're not chasing microns and mirror finish on the end journals. Watch some Keith Fenner on youtube and it'll soon look trivial at any rate.

(NB: I'm an Engineer and hobby machinist, not a professional machinist)

 

[Seadog]

60mm stub offset 40mm from the centreline of the shaft fits within 105mm.

 

[indykid]

60mm stub offset 40mm from the centreline of the shaft fits within 105mm.

You have 52.5mm radius. The stub has a radius of 30mm. You only have 22.5mm left til you're back on centre.

You can have 40mm stroke, but not 40mm throw