Tree 2UVR Sight Glass Replacement

[Flyinfool]

I have an old Tree 2UCR Mill. The sight glass is so dark on the inside that I can not tell the oil level so I have been over filling to be sure it was not under filled. This leads to oil leaking out thru the spindle and all of my work shirts having a horizontal oil line across the chest from oil slinging off the spindle.

The current sight glass is .875 Dia pressed in type. I can not find a source for a replacement, all of the readily available sight glasses are NPT thread mount. A 3/4 NPT could be tapped into the existing .875 hole but I am afraid of the chips that will end up inside of the gearbox. The other thought was to make an adapter that will press into the .875 hole and have a 1/2NPT inside thread. It woiuld be a fairly thin wall from the 1/2NPT to the .875 OD of the adapter so the sight glass may actually expand the adapter to help lock and seal it in place. It looks like I could start with a brass 3/4 to 1/2 brass bushing and the 3/4 thread should clean up completely at the .875 dia.

Anyone have a better idea or a source for a .875 Dia press in sight glass. I am hoping to do all of this without actually opening up the head if I possibly can.

 

[ddillman]

you can put grease on the tap to help catch chips. or maybe a vacuum while tapping

 

[Flyinfool]

I have used the greased tap method before on spark plug threads.
I am not sure if the wall thickness of the head casting is thick enough to support pipe threads. I am guessing it is about .250 thick But I will not know for sure till I pry the old glass out, and then I am committed to doing something because the old glass will be destroyed in the process.

 

[mksj]

You can get a through the wall oil sight glass and back it up with a washer and sealant. Alternative would be something similar to what you suggest, I probably would make my own adapter, thread the portion going through the headstock with something like a 7/8-14 UNF and you can buy a thin backing nut. You could do an 0-ring seal on the front or just put it in with automotive engine sealant. Then do a press in on the front. Since you will have an exterior lip, just turn to fit a standard a press fit glass site window. Also press it i with a little sealant to prevent future leaks. Otherwise just do two press fits and use sealant.

I looked for a 7/8" press fit and the closest I could find was a metric 22.2 mm, seems to be an odd size. I would be afraid to use pipe tap on the current hole unless there is sufficient material. Wouldn't be worried about chips if you plan to drain the oil and can clean out the chips.