How much oil in lathe gear???

[Warlock]

I sold my old Atlas Lathe and purchased a new 10" x 18" gearhead lathe. The new machine has a oil level window for the gearhead and a vent hole in the cover plug. When I did the 20 minute per speed selection for the break-in no load speed run I found that at low speeds under 600 rpm there wasn't really any film of oil remaining on the gears but at 600 and over rpms there was some. I completed the run and drain the factory oil from the gearhead which looked nasty before starting. It looked they filled it with old used black motor oil. I refilled it to the halfway mark on the little indication window with some new synthetic 20 weight oil and still noticed the oil wasn't at low speed leaving a film so I thickened with some 75 weight. That drove the oil a little above the recommended mark but it is now leaving an oi film on the gears.

My question is with a splash lubricating system that has a vent hole in the cover is there any downside to adding oil to the gearhead to ensure that everything is always going to be partially submerged which I figure is about 2.5 times what is reccommended??

 

[Mike R]

My guess is that the sight glass is a bit too low based on you comment about it having oil on the gears with it just above the recommended mark, and some sight glasses seem to show more oil than the machine really has due to meniscus effect. You should maybe run with the oil just covering the sight glass, this would likely have zero negative effect.
My opinion on filling the gearbox (i.e. 2.5times normal volume): most likely effect is going to be a slight loss of power at higher speeds due to oil pumping losses. Also possible to have more leaks as oil is going to be splashed around more at places that probably wouldn't see much oil in normal circumstances. You should check if all shafts (shift levers etc.) coming out of the gearbox are sealed, if above the normal fill line they may not be and could leak.

 

[Warlock]

most likely effect is going to be a slight loss of power at higher speeds due to oil pumping losses. Also possible to have more leaks as oil is going to be splashed around more at places that probably wouldn't see much oil in normal circumstances. You should check if all shafts (shift levers etc.) coming out of the gearbox are sealed, if above the normal fill line they may not be and could leak.

Thank you, good points I will check as I want to run one more flush before starting to use the lathe. The first project is installing a 250-111 quick change tool post which means I have to make a new tool post bolt for the slide. The existing one is a 10 mm bolt with a oblong head that seats 3.56 mm into the slide and has a 15.84 mm shaft that is 17.60 mm long before dropping down to 10 mm diameter.

The new 250-111 wedge type QCTP bolt is also odd, I thought it was a 9/16", oh no that would to easy. I check the dimension with mics, taps and the best fit in either imperial or metric was a 14mm x 2.0 which was a little sloppy. I then went and checked online and the bugger is a non standard 13.5mm x 2.0. so I am either going to go with a 1/2" or 5/8 bolt and modify it to fit.