Chain filing angle ??'s..

[realzed]

We all try our best usually to sharpen our chain teeth to match the etched angles that are imprinted onto each tooth top surface, no doubt..  
If I recall most regular Stihl chains are supposed to be ideally set to around 30 degrees, but possibly that changes with the type of chain and tooth configuration - but my own knowledge of chains aside from regular RS type is admittedly very limited.
My question is: if one files the teeth to an angle less than the 30 degree mark - what will it do for the cutting performance and are there a lot of downsides to trying to do this?
I'm not saying to try and make the angle of cutting edge anywhere near '0' degrees - but what would be the result cutting-wise, if it were done to say 15 or 20 degrees instead, and are there a lot of downsides to even trying to get the angles 'custom' depending on the type of powerhead or wood hardness one is dealing with?

Thanks - Randy  

PS: from the number of replies, probably either an inane or totally noob question - but I may be just showing how naïve I am about chains and cutting different types of wood, but..
Figured Willard would be one of the first to respond - but even he may figure it is just too stupid a series of questions to bother with.. :D  

[Al_Smith]

You can get as many opinions about how to file or grind a chain as the ongoing and ever present ,nonstop great oil debate .Being a simple man I just figured whoever the chain manufacture was  had already figured it out .Why complicate something as simple as that ?
However without mentioning names a former sponsor of this site at one time had discounted a certain brand of chain that turned out not to be a bargain .It was ground incorrectly and didn't cut well after about two filings .So on occasion it can get messed up .

[Grandpa]

In my experience chain angles are a compromise. What it amounts to is the pointier the working corner is the more aggressive the chain is. The less pointy it is the more durable it is. This applies to both the top plate angle and the amount of hook. 

[bandmiller2]

I have found the top angle to not be real critical. I usually do my round ground chisel to 20. Really anywhere between 20 to 30 just get them all the same. Frank C.

[ladylake]

 My grinder has been set at 30  60  0 for 40 years.  Steve

[ButchC]

Its not a bad or improper  question in any way.  Al, Grandpa and Bandmiller have pretty well nailed the answer. As far as I am concerned a few degrees of chain angle isn't as important  as some make of it unless your racing saws or getting paid by the tree to fell.  My suggestion is on some nice fall day you  get a log up on some bunks at a comfortable height and get your saws out and play with your file angles while cutting it up into cookies. Get a raker file and depth gauge and play with that too, Personally I play with raker depth more than file angles but be careful using a saw with rakers lower than .020. One last thing.  Leave the stop watch in your pocket, if it takes a stop watch to know the difference, there aint no difference in the field;)

Steve, my grinder settings also, only for less years ;)

[HolmenTree]

Randy realzed, not a dumb question at all.
Sawchain filing and depth gauge jointing hasn't changed much since the old hand powered swede saw days.
Hardwood, softwood , frozen wood settings.
Standard settings on the chain box pretty will cover it all but a little refining can be done.

I've  been filing chain long before  witness guide marks were put on the cutters so I don't even look at them.

I like blunter angles on my top plate like 20° versus 30° for all round cutting.
More durable working corner.