Leaking sightglass

[bevinp]

Hi,
The oil from my lathe headstock is leaking passed the sight glass which is not damaged or cracked. The leak is from the poor fit of the sight glass into the cast iron headstock.
Would like advice on which sealant/glue I should use to fix the leak. And perhaps how to clean the cast iron hole before applying the sealant.
Bevin

[simonl]

Hi Bevin, If it's like my lathe then the sight glass is rather poorly fitted and just a push in affair. For a simple fix, I would drain the headstock, clean the hole and surrounding area. Then perhaps use a silastic form a gasket type of sealant. Any sealant that is designed to replace a gasket will probably do. You won't need much. Alternatively, if you are brave, you can purchase a new sight glass on ebay. They are available with a thread (ie M20 etc) then tap a matching thread in the existing hole and screw in the new sight glass. These screw in sight glasses seal with an O ring. Edit: I should also mention that a small weep from these sight glasses is pretty much normal too. Cheers, Simon

[Steamwhisperer]

Hi Bevan,
I use this stuff at work with success.
http://www.henkelna.com/product-search-1554.htm?nodeid=8797928488961
I doubt you will ever get the cast iron to give up any or all of the oil it seems to get impregnated with.

Phil

[Ropetangler]

Bevin, if your sight glass fits into a housing which is bolted to or screwed into the head-stock, I would remove it from the housing and then clean the housing with solvent, and / or paint stripper, and to get as much oil and contaminant out as possible, heat the housing as much as you feel comfortable in doing, and then drop it into lime or cement powder to extract any remaining impregnated oil by capillary action. Even better would be to sit the housing in its container of lime/cement on the dying embers of your evening fire, if you still have one, and the heat combined with the wicking ability of lime or cement powder will extract nearly all the soaked in oil. then you can clean it up and re seal the glass into it using the original sealing materials and method. Then re install the housing with glass onto the head-stock.
All the above assumes a cast iron or steel housing, if yours is aluminium, then keep it away from strong alkalais, including most paint strippers, caustic soda etc, and obviously watch the heat, - you could use a domestic oven, (if your domestic goddess allows) but keep it out of the fire, and be extremely careful of any flame heat source. Aluminium has a much lower melting point than C.I. or steel, and turns into hydrogen in the presence of strong alkalais.:doh::o

If the glass is installed directly into the head-stock housing, your job will be somewhat trickier I think, as it will be harder to get all the oil out from the sealing surface. Again for C.I. I would use solvent, start with Kerro, then try thinners or spray gun cleaner, lots of clean paper towel or clean rag, and keep cleaning till no trace of contaminant can be seen on clean white rag/towel. Then if everything is in good shape, re-fasten the glass using the original method and materials. Good luck,
Rob

PS I see that Simon and Phil have also replied before my slow typing was complete, and both are on the money. I use Loctite master gasket which is in the same family of products which includes Phil's suggested fix. If your glass is the real problem because of poor fit, most glazing firms or even amateur stained glass enthusiasts could grind a small glass in no time if need be.
Rob.

[kwijibo99]

G'day Bevan,
I've found Stag Jointing Compound to be the best all round sealant for this sort of thing.
If you can get the old sight glasses out in one piece give the contact surfaces a wipe with a rag to remove any oil then give them a final clean with metho.
Apply a bead of the Stag compound to the contact surface of the sight glass then push or thread it home.
I usually buy it from Repco but I'm sure there are any number of other stockists around, it's about $12.00 a tube from memory.

This is the stuff: https://www.autobarn.com.au/stag-jointing-paste-200-gram-tube-sg200

Cheers,
Greg.

[Oldneweng]

I recently topped up all the oil reservoirs on my CY lathe. Main gear box, feed/thread change gear box and the apron. There is also a fill cap on the outer end of the feed, lead screw and shift rod shafts bearing housing, but this appears to be just an oiling location.

The sight glasses are all rather discoloured and hard to see thru. I used a temp dipstick to get close and then a torch to see better. Once the oil was in the glass it was visible, just. I would like to replace these sight glasses.

The other problem is a leak on the apron. There is an oil pump that is pulled out and when it goes back in it pumps oil to the various parts of the apron. This leaks. I presume the shaft seal is worn. It loses quite a bit of oil over time. The oil is below the sight glass now. I try to remember to put a plastic take away container underneath to catch the oil and prevent a puddle on the floor.

Dean

[bevinp]

[QUOTE=Ropetangler;1820217]
If the glass is installed directly into the head-stock housing, your job will be somewhat trickier I think, as it will be harder to get all the oil out from the sealing surface. Again for C.I. I would use solvent, start with Kerro, then try thinners or spray gun cleaner, lots of clean paper towel or clean rag, and keep cleaning till no trace of contaminant can be seen on clean white rag/towel. Then if everything is in good shape, re-fasten the glass using the original method and materials. Good luck,
Rob

Hi Rob,
Yes the sight level is in the housing. About five years ago, the level was leaking and I did the same "thorough" cleaning as you suggest above. I don't remember what sealant I used then but clearly it wasn't a permanent fix. About three years ago I found the feed screw gearbox had a leak from its sight level. So I did the same multi solvent cleaning and then used "Sikaflex-Pro Multipurpose Highly Flexible Polyurethane Formula", a label that inspires confidence but the leak has returned there as well.

But in fairness to whatever sealant I used, I think the problem is the inability to thoroughly remove the oil from the cast iron. So I guess I will have to acknowledge that replacing the sealant is just another maintenance item and to view it as another opportunity to experiment with sealants.

Stay tuned for a followup post in about five years (or less).

And thanks to all the other posters.
Bevin
PS. Both sight levels are plastic push in. Yes the lathe was made in Taiwan.

[malb]

A lot of mid sized compressors have a site glass to check oil level. The one on mine looks to all intents to be a threaded ali housing with the background and glass inserted. It isn't, it's a nasty bit of soft injection moulded plastic. Strange that the only leak in a 15yo comp is the sight glass thread. You may well find similar on the lathe.

[Ropetangler]

Well Bevin, perhaps the answer lies in a combination of ideas presented here. Simons' idea of drilling and tapping the HS to take a screw in sight glass, and Malb's thoughts on plastic sight glasses might mean finding a metal one or even fabricating one from brass or aluminium, and using Loctite or Stag or an "O" ring to seal in a proper glass. If you have an "O" ring seal, it could be easy to remove the glass for cleaning should it be necessary, or to replace an "O" ring should it become damaged due to exposure to oil over time. I know if I had a leaking sight-glass it would annoy the hell out of me eventually, so a permanent fix sounds good.
Rob

[OLCDOG]

Hi Bevin,

I inherited a similar problem with a leaking sight glass (plastic) on the used RF45 mill I bought.
The sight glass once removed could be carefully pulled apart and the insides cleaned so that it was once again possible to see the oil level in it against the white background.
It's a push in type of sight glass but has quite a bit of depth to it.
After thoroughly cleaning the cast iron mill housing with acetone and the sight glass with Shellite, I was able to seat the sight glass with a O ring seal at the back and then filled the remaining cavity out to the face of the sight glass and the mill housing using Loctite 'Grey Maxx' RTV silicone gasket maker. It's formulated for use on things that get hot and oily.
I masked the face of the sight glass and the mill housing face around the hole to avoid getting silicone over everything.
Turned out very well and hasn't leaked since.
Hope this is of some help.

Alan