There is a special grease for worm drive saws called Hypoid grease.
Any decent industrial supplier should have it.
I have found it at power tool repair shops too.
Basically it is a tenacious grease that will cling to the worm gear.
I was looking for the same information some time ago and
found an online reference that said the Skil lubricant is
equivalent to the Mobil 600 series gear lubes. This makes
sense since this what is spec'd by Boston Gear for their
worm reducers. Unfortunately I don't recall which viscosity
to use in the Skil. Boston Gear uses Mobil 634, which is
much thicker than SAE90 gear oil--more like SAE140 gear
I'm quite sure I did find a Skil 77 manual online.
The tool repair house I bought replacement parts for my 77 told me their
manual specs standard gear oil, iirc it was 80 or 90 weight. I put Coastal
80w 90 in mine.
Heavy as a cinder block but much quieter running than any direct drive saw
With the saw flat and upright (blade perpendicular to the ground, body
parallel to ground) fill the gearbox until it runs out the fill hole and it
now has the proper amount of oil.
Do not, as another poster suggests, put lithium grease in it. I used
lithium grease in my lathe compound several years ago and it has turned into
a sort of concrete. The oil leached out leaving a really tough/hard deposit
of whatever else is in lithium grease. Maybe it reacted with the cutting
Skil sells tubes of the right stuff. Unless there's a leak, you
shouldn't have to do it again for a loooong while. I bought mine from
the local Skil service center. It's not a grease, it's something
similar to hypoid lube. If you can locate a local service center, it
might be worth having them check the beast out. They do develop
shorts in the motor and the brushes and commutator wear.
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