what is this knob on my chainsaw?

[paulmars]

I found this old craftsman electric chainsaw in a garbage can. Chain was beyond dull. Got new chain and except for oil leak while sitting on shelf, it works great. However, there is this knob (red arrow) and I don't know what it does. I asked sears and they don't know and don't have the user manual and I cant find it online. It's not for chain tightness adjustment. Im sure you all already know that based on where it is, but I need to say that now to save me from having to respond to someone who might suggest that.

It can be turned in either direction as many times as you want. It never stops or gets tighter. It's got mild resistance which never changes when turning it. It is attached with set screw. I removed the set screw and knob and you can see the retaining clip below that.

I can't see any thing related to that knob by looking into the oil filler when its cap is removed. Even when looking at angle w/flashlight to try and see below the knob.

Black arrow is a spring loaded push button, below the oil filler cap. What is that for? Someone suggested it's to prime the chain after it's filled, if it ran out of oil. I doubt that.

power-sharp
model number 315.34170
sears roebuck and co
simpson-sears LTD.

 

[blades]

could be a control for the amount of oil being dispensed. A lot of those older electrics were manual oiling.

 

[paulmars]

saw is automatic oiler, but push for extra oil in HD use. Black pin to hold missing chain sharpener button in position. missing the two buttons for the sharpener, which i dont need. This tool is more powerful then my other nevver ele chainsaw.