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Mill Gearbox Lubrication and cutting oil

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Skarven11/10/2011 18:42:56
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93 forum posts
11 photos
Hi,
This is a LONG post, so if You have no interest in lubricating oils, skip it!

Having bought a Chineese mill Tongli ZX45 Super some time ago, I wanted to change the gear oil, and after reading the manual ended up with something like Shell SAE 68. This is obviously wrong, as the SAE numbers goes in 5's. After a little searching on the internet, I found it probably means ISO 68. That was not easy to find around here, so after a few phonecalls to Shell, Mobil... with no results, I went to a Petrol station where I earlier have found unusual things. The guy had never heard of an oil named xxxx-68, but while searching his store he suddenly shouted "Hi, there it says 68!" It was a 10 Litre can of Statoil CompWay 68. (You wouldn't believe the amount of dust on this can.) This is a special Air Compressor oil with the following characteristics:
 
CompWay 68 is recommended for all types of stationary
piston compressors. This oil has been approved by companies
such as Atlas Copco and meets the requirements set forth in
DIN 51506 VDL. Its approval per the Pneurop Oxidation Test
(POT) confirms its excellence in fighting carbon deposits.
ADVANTAGES
CompWay 68 is highly oxidation-stable and fights carbon
deposits.
 
The rest goes in a new post!

Skarven11/10/2011 18:47:45
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93 forum posts
11 photos
Link
http://www.statoillubricants.com/mar/lu/sto00131.nsf/UKProductsWeb/compway68/$FILE/Statoil_CompWay_68.pdf
 
Having no other options, I bought the can for about £50 and took it home and cleaned it
 
Further searching accidentally gave me the following table which made some of the standards for viscosity a little clearer.
I was not able to post the heading of this table, but theLink is:
http://www.tribology-abc.com/abc/viscosity.htm

Now, finally my question is: Should I use the Compway 68 compressor oil, or should I go for an engine oil of 20(if available) or a gear oil of 80W, which seems to have similar viscosity.
 
Anybody have an opinion?

mgnbuk11/10/2011 19:49:17
1394 forum posts
103 photos
Anybody have an opinion?
 
Well - from experience with lubrication of gearboxes in "full size" machines I would suggest hydraulic oil would be a good place to start. More machines that I have come into contact with have used hydraulic oil to lubricate spindle gearboxes than any other type of oil. I seem to recall the odd one that used slideway oil & one (a Brown & Sharpe VMC) that used ATF, but non spring to mind that specified a gear oil.
 
Viscosities vary - and some of the bigger machines use the lighter oils. Most large vertical borers (Webster & Bennett, Schiess, Froriep, Morando, OM) specify 32 viscosity oil. The Gildermeister lathes at my current workplace specify 46 viscosity hydraulic oil for the spindle boxes, as does a Kira VMC. A Dixi CNC borer I once worked on used 10 weight oil - like water ! I have seen the gears on vertical borers (I used to work for a CNC machine tool rebuild company) that had done over 20 years service (37Kw motors usually) that still showed the original grinding marks on the teeth, so ISO VG32 hydraulic oil seems to provide sufficient lubrication.
 
I don't have any experience of piston compressor oils, but suspect that they would be optimised for constant high temperature operation - maybe over extended periods. All piston compressors I have worked near have run hot. I suspect they would have similar characteristics to monograde engine oils.
 
My first preference would be to use a 46 viscosity hydraulic oil, but if no industrial suppliers nearby, then use ATF. I use ATF in the head of my Taiwanese Emco FB2 clone. ATF & hydraulic oils have added extreme pressure & anti-foaming additives and good viscosity stability with temperature change (think of the lubrication requirements of gear or piston pumps). Lighter weight oils will give the motor an easier time at start-up - higher viscosity may give better noise damping (maybe the reasoning behind a recommendation for 68 viscosity).
 
Other opions will, no doubt, be along in a momemnt !
 
Regards,
 
Nigel B
 
michael cole11/10/2011 21:35:57
166 forum posts
I also have a version of the zx45. The recommened oil is a hydraulic 32 . it cost about £25 for 20l from our local engineering supplies shop. Do not use a heavy gear type oil.
Mike
Bogstandard11/10/2011 23:38:08
263 forum posts
The importers of my geared head lathe recommend a 32 grade hydraulic oil, so it seems like a good bet that it would be fine in most other gearboxes on small machine tools.
I have been using Tellus 32 (or equivalent) for years in machine tool gearboxes.
 
John
Skarven12/10/2011 07:21:31
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93 forum posts
11 photos
Hi,
Thank you for the help.
It seems to me that I should go ang get some 46 or 32 viscosity hydraulic oil.
I know I can get the 46, because that was available at the same gas station. Maybe they will swap the Compressor oil 68 for the 46 viscosity hydraulic oil?
 
In all my troubles trying to post a Table of viscosity of different types I forgot my second question.
 
Can I use the same oil as a cutting oil?
 
I know there are special cutting oils, but all I can get here is the type that is mixed with water. I do not like the idea of water on my machines, so I would rather use an oil.
 
Up til now I have used a spray can of Cutting oil, WD40 or plain 10W-30 motor oil.
I does not seem to make much difference. My machines have pumps for cutting oil, and I think the finish would be better with a steady supply than the intermittent spray can method. At least I can see the uneven finish where the time between sprays were a little too long.
michael cole12/10/2011 17:21:17
166 forum posts
The oil for the gear box is totaly difference to cutting oils, Do not use any type of cutting oil in the gearbox.
 
As a cutting oil nothing wrong with using suds (soluble oil) . Different metals need differenct cutting/cooling liquids. WD 40 is good for AL . i wouldn't use motor oil as a cutting oil or in the gearbox. I do use it however on the slideways as any oil is better than no oil here.
 
Mike
Ian S C13/10/2011 09:07:06
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7468 forum posts
230 photos
If your machine has a coolant pump, suds is what you need there. Use it for steel And most other metals, the stuf I use indicates that its OK for aluminium too, but most use kerosene (parafin) for that. I'v been using this stuf for the last twenty years or so with no rust or staining problems. I only apply the suds with a squeeze bottle, last time I used a lathe with a suds pump was in the early 1960s, at school, that sometimes caused some fun! Ian S C
Dave Martin14/10/2011 09:02:25
101 forum posts
11 photos
Posted by Skarven on 11/10/2011 18:42:56: ......after reading the manual ended up with something like Shell SAE 68. .......
 
I wonder if there is a confusion over the purpose for the oil.
 
The reason that I ask is that "68" is very familiar - but not for gears!
 
I use Mobil Vactra no. 2, which is rated at 68 - but that is the slideway lube - not for transmission.
 
Dave

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