Mac 640 From Brian

[Ax-Man]

This is what is confusing in Gary's thread. He has a geardrive Mac with .404. Most if not all of those old buggers ran 1/2 pitch. I have a couple of those old Macs that I refuse to work on. Lets just say I tried and gave up only because I didn't want to go through the hassle of finding parts. The saws have very good 1/2 in chain and sprokets on them. If I ever come across one of those old geardrives that will work without putting much time into it at least I will have a supply of chain.

 

[Cut4fun]

I got a .040 file gauge if anyone wants to trade .

 

[Al Smith]

Indeed most of them were 1/2" chain but they made a .404 spur for them which few ever used .It's a rarity to even find one of those spurs .

As far as the Macs they are just about the easiest saw ever made to work on .Nothing really ever goes bad on them except maybe a set of points needs cleaned or one of those screwed up flatback carbs .Occasionally an oiler doesn't work from sitting for 25 years unused but a good dose of kerosine usually cures that problem .

On the other hand a geardrive is not what you would use on an every day bassis .Just something to fiddle with now and again .

 

[GASoline71]

Spent about an hour hand filing that chain. It'll prolly cut better now. I should just get a new chain spun up for it.

Larry... any of those old buggers you wanna get rid of... just let me know.

Gary

 

[Al Smith]

Well you're not going to use that saw that much anyway .If it's sharp you might not need a file job again for a long while .On that I have a loop of Stihl .404 chisel on a Mac super 44A that I've never filed in 7-8 years because that saw sees very little action .Those old Macs if you fire them up a couple times a year and maybe run half a tank through them ,they start and run like they were used every day .

 

[woodworkingboy]

My 090G is set up with half inch chain. It's classical for sure. I thought I'd be smart and make up my own sprocket for 3/8" chain, a somewhat elaborate process, since none are available to fit the saw. I never thought a sprocket could completely disintegrate like that...within two minutes too! I've since decided that the big chain is pretty cool.

 

[Al Smith]

You have to use some pretty good steel for a spur gear ,I think it was either 4140 or A2 that I used for one of the Macs and heat treated to boot . It has to be around 55-60 Rockwell C .Too hard it breaks,too soft the chain drivers cut it up like butter .

 

[woodworkingboy]

Too hard was probably the case, and it didn't help that the guy who used some laser set-up to cut a key way in it also put a hairline crack in. I didn't notice it until I got back to my shop. I thought about taking it back ant getting some refund, the cut wasn't cheap, but I figured he gave it his best effort, but it wasn't meant to be. What bothered me most is that he didn't say anything, I'm sure he saw the crack if he bothered to examine his work. It quickly blew out to tiny bits of metal, jammed the whole thing up.

 

[Al Smith]

Old trick on keyways for the amature machinest .Take an old tap,grind the teeth off one fluke ,leave about a 7-10 degree postive rake on the very end .Take that thing and use it as a brooch in a drill press ,mill or whatever to cut the keyway .You just use the quill as kind of a light duty arbor press and just "nibble " at it .You might have to file a tad bit but it works .

 

[woodworkingboy]

Nice trick, but in my sprocket's case, a file wouldn't touch it. Some hard azz stuff given to me by a local machine shop.

 

[Al Smith]

You're pretty much SOL in that case unless you normalize it first then reharden .