Thoughts on converting a 72" GB bar from Husqvarna to big Stihl mount?

[Coralillo Lo Pro]

I have changed Husqvarna 9mm slots to Stihl 14mm slots with a drill press and a carbide burr.

Gregg, I only now figured out you were the same person I was buying the bar from who was giving me advice. Slow on the uptake. It's out on the UPS truck for delivery today. I might have gotten confused on machining terms, and bought a 1/4" four flute end mill last week instead of a burr. When I was about to run it in my drill press yesterday, I looked up info on drill press milling again and saw everyone advised NOT to use a drill press due to side loading the bearings, the chuck maybe coming free, etc. I had to mill a key out of a gear sprocket for my obsolete 15" Grizzly "portable" planer made of unobtainium, to make a free spinning idler sprocket, and found the 1/4" end mill I bought worked fine at max speed of 4200 rpm as long as I was careful and only shaved a little at a time. Finished it out with a stone in my Dremel as the shaft size was fractionally different between the idler shaft and the gear shafts, and needed a bit more opening up. Are burrs okay to run in a big heavy duty drill press but should end mills be avoided at all costs? I gather that in milling, unlike drilling, high high speed is your friend thus die grinders seem to be favored. I can either get a cheap die grinder at this point, or a 1/4" burr for the drill press, or both.

 

[Coralillo Lo Pro]

I was thinking of doing the same to run one on a 660 for milling. Anyone have experience with a 72" bar on a 660? What chain would you use, skip? I currently run a 41" cannon with regular milling chain with zero problems. Thanks.

My buddy in Mexico wants to run one of these on his 660. Last I checked the price went up $50 for the Husky mount ones, so not quite as screaming a deal, but still a good $200 less than a 72" Cannon at that price. The hyperskip - either Oregon 27RX or Woodland Pro 46RPS - seems like it would really come into its own at that length, but would require choosing the .404 tip and changing out your sprocket. Then there's the question of whether the lesser load from the less teeth of the .404 hyperskip and better chip ejection would offset the greatly increased load of the .404 chain/sprocket combo. As hyperskip is relatively new and mainly designed for the Lucas Slabbers, the jury seems to be out still on experimenting with it in other applications much and just how much it cuts down on your power requirements. In standard chain applications people have lost a lot of RPM's and cutting speed trying to use .404 on an MS660. It was clearly designed for high RPM cutting with 3/8". People have gotten away with 72" bars before on an MS660 for the odd job where it was all they had to work with, but it was painfully slow cutting. My understanding has always been that the MS660 stands out in milling in the 20-36" bar (and can do 41-42" just fine) range but 42" and up really is the province of the MS880 (or double ended milling with a pair of 660's), no matter the new innovations in hyperskip and lopro long bars and the like. I honestly would have preferred to go with a 60" bar for my MS780/880 as I just about never have any call to mill something wider than 48", but the price of the 72" was too good to pass up. I'm pairing it with a 60" mill because even with the spikes off my saw, I'd guess I could get a maximum milling width of 60-62" out of this 72" bar. I think the max cut width of a 60" mill is about 56". Even my hardnose 36" Duromatic bar I can clamp right at the end, I only get a 29" max cut out of it. It only has 32" of useable cutting length outside a mill. Everyone (including Oregon in one of their FAQ's) strangely parrot the line that bar length is from where the bar exits the powerhead to the tip of the saw, yet manufacturers rarely size their bars that way. All my Stihl Duromatic bars and my GB 72" bar seem to be sized from a midpoint between the mounting studs to the tip of the bar. Yet I do have a Husqvarna 20" bar for my 455 Rancher that actually is 20" of useable cutting length. There's absolutely no consistency in useable bar length vs stated bar length in the industry as far as I can tell, which I've found makes choosing number of drive links a headache unless you have the manufacturer DL specs for that particular bar.

 

[Coralillo Lo Pro]

Need to order a 1/4" carbide burr instead of the 1/4" four flute end mill I mistakenly bought. Grabs and bucks too much to be used in anything hand held like a die grinder when dealing with hardened steel or titanium alloy. Here's what I set up to do it before figuring out the end mill was a disaster. (I had tested it on a scrap steel bolt and it ground right into it fine but it was jumpy as hell on the titanium GB bar.) I clamped a 1/2" piece of wood between the two bars because I needed some space between the smooth edge of the shank and the cutting edge when operating something like a die grinder that I couldn't maintain in an exact fixed vertical position, so I didn't inadvertently cut up into my guide template, the Stihl bar. So will wait for the burr to arrive and try again.

 

[Coralillo Lo Pro]

Okay, got it done. Turned out I needed both the end mill and the burr. The burr was ridiculously slow on the titanium GB bar, but good for getting my first groove started without bucking around. Then I was able to switch to the four flute end mill and make more headway but that GB titanium is ridiculously hard. Took hours of work but finally finished. The end product was fairly smooth looking but unfortunately oversized. Not the end of the world, but would have liked the tolerance to be a lot tighter to the studs. The fatal flaw in my way of doing it was the wood spacer between the bars which I used so I could keep plenty of separation between the cutting edge of the end mill and the smooth part of the shank running along the template bar. That spacer made it so that when I tilted the die grinder past 90 degrees - hard to keep dead straight while hand holding it - it took too much off of the bar. Kind of defeated the accuracy of using a template by introducing that much room for slop, if the bars had been clamped directly together, that couldn't have happened. I think I could have used the end mill in the drill press perfectly well if I had an X-Y drill press vise. That's the only way to mill it really accurately. Just have to make sure to mill real slow with titanium. The bonus of the end mill was that when it came to drilling the holes, I didn't need any masonry bit sharpened into a hardened metal cutting bit. The end mill is an excellent 1/4" carbide drill bit that drilled the holes easily.

 

[BobL]

Nice Gloves George.

 

[Coralillo Lo Pro]

And the hyperskip came in today too - finished product all mounted up and ready to slab. So it takes up half of my garage, so what....

 

[Rosss]

Interesting thread. Thank you everyone.

So the oil holes line up ok, modifying a husqvarna bar to go on a large mount stihl?

 

[Coralillo Lo Pro]

Interesting thread. Thank you everyone.

So the oil holes line up ok, modifying a husqvarna bar to go on a large mount stihl?

Good you asked about that. I was a bit confused about oil holes and only just now made sense of the comparative locations (the one on my Duromatic 36" bar is so small I barely noticed it). Measuring from the rear of the bars, the oil hole on the Duromatic Stihl bar is about 3/4" further forward than the one on the Husqvarna mount GB 72" bar. Not sure that's going to line up with the oiler slot, it's close, will depend a lot on where the tensioner puts the bar with my chain setup. Was going to run an auxiliary oiler with that bar anyway.