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

[Coralillo Lo Pro]

Having trouble finding any decent condition real big bars for milling for sale anywhere at a decent price for my MS780/880, and new they're a small fortune. Hadn't really wanted anything beyond 60" but Left Coast Supplies seems to have some Husqvarna mount GB 72" bars for the ridiculously low price of $200. (Most all their other GB bars are sold out.) I know you have to mill out the slot from 9.0mm to 12.3mm and probably drill a new tensioner pin hole, but I was thinking even if a machine shop charged $50-100 to do it, it would still be a bargain. I could probably do it with my 20" Jet drill press, but I don't have any carbide burrs and I don't have an X-Y vise either, and would rather have it cleanly and professionally done. Any thoughts on the viability of this?

 

[SeMoTony]

Having trouble finding any decent condition real big bars for milling for sale anywhere at a decent price for my MS780/880, and new they're a small fortune. Hadn't really wanted anything beyond 60" but Left Coast Supplies seems to have some Husqvarna mount GB 72" bars for the ridiculously low price of $200. (Most all their other GB bars are sold out.) I know you have to mill out the slot from 9.0mm to 12.3mm and probably drill a new tensioner pin hole, but I was thinking even if a machine shop charged $50-100 to do it, it would still be a bargain. I could probably do it with my 20" Jet drill press, but I don't have any carbide burrs and I don't have an X-Y vise either, and would rather have it cleanly and professionally done. Any thoughts on the viability of this?

Two thoughts I have. One is a dual power cannon I have 72"/60" actual cut with helper handle wood be less than new, mounted once w/out chain. Another thought is the 72" Forester I got through Amazon was a bit more than $200 but mounts right on my ms-661. The other thought is 12.3 mm is smaller than ms-880? stud size but right for ms-460 or 661 IIRC
Mill safe & enjoy

 

[BobL]

Yeah I wouldn't use a drill press either. What I would use is a new grinding wheel in a table saw. While it needs to be a good fit it doesn't need to be super precise so clearly mark the amount you need to remove and use light swipes on the wheel to slowly remove the excess, as you get close to the final size you should stop and measure it with a caliper or template. Maybe even practice first on a regular piece of steel. check with a square to make sure the grind is square and if not flip the bar to square it up.


The adjustment holes can be drilled with a new or freshly sharpened masonry bit.

 

[Coralillo Lo Pro]

Two thoughts I have. One is a dual power cannon I have 72"/60" actual cut with helper handle wood be less than new, mounted once w/out chain. Another thought is the 72" Forester I got through Amazon was a bit more than $200 but mounts right on my ms-661. The other thought is 12.3 mm is smaller than ms-880? stud size but right for ms-460 or 661 IIRC

Ah yeah, the large size is 14mm and the regular is 12.3mm, is that right? Thanks for catching that. I've been fine with my 42" Forester I was milling with in Mexico, but just got the impression they weren't comparable quality to GB bars. Also they don't make them in the big Stihl mount, I don't think. I've been back and forth on double ended bars with helper handles, not sure if I want to go that route or not.

 

[Coralillo Lo Pro]

Yeah I wouldn't use a drill press either. What I would use is a new grinding wheel in a table saw.
The adjustment holes can be drilled with a new or freshly sharpened masonry bit.

Thanks, I may mess around with some scrap metal first. I have a 12" sliding chop saw with 12" DeWalt abrasive wheels I've been using for metal cutting til I get a dedicated metal chop saw. Seems like that would work well, I could clamp the bar down pretty tight and be fairly precise with it. I'll see how it works and if it seems easy enough to do, I might order the GB.

 

[BobL]

Thanks, I may mess around with some scrap metal first. I have a 12" sliding chop saw with 12" DeWalt abrasive wheels I've been using for metal cutting til I get a dedicated metal chop saw. Seems like that would work well, I could clamp the bar down pretty tight and be fairly precise with it. I'll see how it works and if it seems easy enough to do, I might order the GB.

I've tried a chop saw to modify and dress bars and found it to be too aggressive.
The linear speed of the outer edge of a 12" chop saw is too fast, one slip and you'll remove a hunk of metal.
A 8" or 5" wheel in a table saw will give a much slower linear wheel speed and remove a lot less metal per kiss.
I also found it easier to see what is going on by leaving the wheel in a fixed position in a table saw and finesse/kiss the bar gently up against the side of the wheel.

This is also how I dress my bar rails. With the wheel at right angle to the table its just a matter of moving the bar lengthwise back and forth and letting the bar gentle kiss the wheel all while adjusting for the curve of bar with each stroke

 

[Coralillo Lo Pro]

I've tried a chop saw to modify and dress bars and found it to be too aggressive.
The linear speed of the outer edge of a 12" chop saw is too fast, one slip and you'll remove a hunk of metal.

Good info. A table saw is the one major cornerstone of my new shop I haven't acquired yet, but soon. Makes sense to use the minimum size wheel possible to limit deflection potential and limit linear speed.

 

[SeMoTony]

Ah yeah, the large size is 14mm and the regular is 12.3mm, is that right? Thanks for catching that. I've been fine with my 42" Forester I was milling with in Mexico, but just got the impression they weren't comparable quality to GB bars. Also they don't make them in the big Stihl mount, I don't think. I've been back and forth on double ended bars with helper handles, not sure if I want to go that route or not.

I got one of the last 30" GB bars from Left Coast supplies. Like it enough to order a twenty inch that came today with two chains. I have about nine weeks to try it out to help me decide if I want a four foot bar. That is when Greg says the GB milling bars will be back in stock, June.
If I get a 48" narrow kerf bar & chain the 50" cannon will be up for sale.
CS milling 101 has excellent sharpening for milling instructions to get the most out of the equipment any of us have.
There is another option for fitting a smaller groove bar on to larger studs. I've read that turning the studs a 1/4 turn out and then grinding a flat on the bottom of the studs to fit and line up the oil hole.. Makes it easier to run either bar

Mill safe and enjoy

 

[Grande Dog]

Howdy,
The modified bar stud works well for adapting. I have changed Husqvarna 9mm slots to Stihl 14mm slots with a drill press and a carbide burr. You just need to have 14mm slot bar to use as a template. I clamp a piece of plywood to the drill press table. Clamp the 14mm bar to the 9mm with the 14mm on top. I used a 1/4" burr that has cutting surface with a shank that is the same diameter. Get the bar slot in position under the burr and drill through the ply wood to a depth where the smooth side of the burr runs on the template bar. When your looking down at the bar slot, you want to move the burr in a clockwise rotation around the slot. This uses the rotational cutting force to keep the burr against the template. It will usually leave the slot a hair tight but, a few strokes of the file and you're in business. When it comes to drilling the oiler and adjuster holes I prefer the template again. This time I'll stack 4 templates using a drill bit and drill press to line the holes up and clamp the pile. I do this because I've only met a few drill presses that can go slow enough to not anneal the bar. I then take a variable speed drill and use the stacked bars as a guide.
Regards
Gregg

 

[Coralillo Lo Pro]

Howdy,
The modified bar stud works well for adapting. I have changed Husqvarna 9mm slots to Stihl 14mm slots with a drill press and a carbide burr. You just need to have 14mm slot bar to use as a template. I clamp a piece of plywood to the drill press table. Clamp the 14mm bar to the 9mm with the 14mm on top. I used a 1/4" burr that has cutting surface with a shank that is the same diameter. Get the bar slot in position under the burr and drill through the ply wood to a depth where the smooth side of the burr runs on the template bar. When your looking down at the bar slot, you want to move the burr in a clockwise rotation around the slot. This uses the rotational cutting force to keep the burr against the template. It will usually leave the slot a hair tight but, a few strokes of the file and you're in business. When it comes to drilling the oiler and adjuster holes I prefer the template again. This time I'll stack 4 templates using a drill bit and drill press to line the holes up and clamp the pile. I do this because I've only met a few drill presses that can go slow enough to not anneal the bar. I then take a variable speed drill and use the stacked bars as a guide.
Regards
Gregg

This is why I come to this forum for answers. People have great recommendations from experience. That sounds like a very good technique. My Jet 20" drill press goes down to 150 rpm so I assume that's slow enough. I only recently started changing speeds and really taking advantage of all it can do, and was amazed to find it ran all the way from 150 up to 4200 rpm. Picked it up off a guy for $200 a few months back with nothing more than a missing column handle, one of my best shop buys yet. I've already got two Duromatic bars to use as templates. The burr is something I'll need anyway for doing minor machining like this so I'll order one up. I'll practice on some scrap metal I have first to see if I'm confident about doing it. I like the template idea so I can get an exact match.

 

[Grande Dog]

Howdy,
150 might still be a little to fast. If it makes chips instead of curls, you might get in trouble. I've had luck with carbide masonry bits at higher speeds. Bit's are cheap but, you'll need a diamond wheel to sharpen them before, and after you start using them. They also need to be sharpened on the outside edges. I've had the best luck leaving them fairly blunt. Just enough back angle so the heel doesn't drag.
Regards
Gregg

 

[BobL]

I used carbide burr in a die grinder and a drill press to shape an adapter bar segment to convert a sprocket to a roller nose.
The adapter is made from a table saw blade sandwich.



I use about 120 RPM on a drill press with masonry bits, lots of coolant and high pressure and shape/sharpen as per Greggs post on the diamond wheel I use to sharpen big tips. Co dill bits work on some bars.

 

[Coralillo Lo Pro]

Bob, the first time you mentioned masonry bits, like many I scratched my head. But after Gregg chimed in and after reading up on it, it seems to be a well known trick among amateur machinists. This begs the question - if it's the best way to drill hardened steel, why doesn't anyone manufacture bits just like that for hard steel drilling? Then again, being a diehard fisherman, I could ask the same about why hook manufacturers never make hooks sharp enough out of the box. I gather the manufacturing process can't produce something with a sharp enough edge and it requires hand sharpening to get it to where you need and that's obviously not cost efficient for most manufacturers.

 

[BobL]

Bob, the first time you mentioned masonry bits, like many I scratched my head. But after Gregg chimed in and after reading up on it, it seems to be a well known trick among amateur machinists. This begs the question - if it's the best way to drill hardened steel, why doesn't anyone manufacture bits just like that for hard steel drilling?

They do - well my local big box hardware stores do. The ones at the hardware look like masonry bits but have a different shaped tip and the tip is soldered to the shaft with a higher temp solder. They are a bit more expensive than basic masonry bits. I think dewalt make these bits.
There are more professional units like the http://wlfuller.com/html/drills_for_hardened_steel.html - I used one at work and they worked really well. For these they recommend "Heavy Pressure and low R.P.M.'s recommended. Cutting oil should be used. Recommended for use in drill presses". Pretty expensive though.
I also have a set of hole saws with TC tips For about 5/8 to 1 1/4" specifically for use in steel.

 

[Coralillo Lo Pro]

Ah, okay, I saw a Bosch one at a big box store, the Bosch MP06 1/4" bit - "Bosch Daredevil® Multipurpose Drill Bits help users make an impact in metal and masonry, as well as other materials. Its upgraded multi-grind head is metal tough, providing up to 85% faster drilling in metal than standard bits, making it a true all-in-one bit. For the ultimate versatility in multiple materials, these impact-rated bits have hex shanks, for use with hammer drills or impact drivers. The bits handle thicker metal such as angle iron, as well as sheet metal, aluminum, masonry, brick, block, tile, wood and PVC. They feature steep flutes with ribs for fast dust removal, as well as tips designed to reduce bit-walking for clean holes. The bits are manufactured to Bosch's exacting specifications and are made with innovative tungsten carbide tips, for up to 9x life in multi-material applications than standard bits." Now do those still need sharpening from new?

 

[Dub11]

Hello all, I'm just a hack here and I know your looking for a pro finish but after playing with the Bridgeport at my work I had the best luck drilling a hole to my final size on each end of the slot then taking a cut off wheel on an angle grinder and removing the rest of the material in between the two holes.

 

[BobL]

. The bits are manufactured to Bosch's exacting specifications and are made with innovative tungsten carbide tips, for up to 9x life in multi-material applications than standard bits." Now do those still need sharpening from new?

The make it sound like TC has only just been invented but its been around for years. I have only every tried one one of those bits regular steel and from new it cut fine.

 

[Coralillo Lo Pro]

The make it sound like TC has only just been invented but its been around for years. I have only every tried one one of those bits regular steel and from new it cut fine.

The "innovative" bit is a wild bit of marketing excess. It's like, hey, we just watched youtube videos of what people have been doing with our regular masonry bits for years, tweaked the design a bit and charged a little more, and pretended we invented TC. My shop partner in Mexico, who was born in Australia and grew up in Canada, is still dubious that this works til he tries it but I sent him a video of an Aussie on youtube drilling a small hole in a spanner with an ordinary little masonry bit to convince him.

 

[Dub11]

The "innovative" bit is a wild bit of marketing excess. It's like, hey, we just watched youtube videos of what people have been doing with our regular masonry bits for years, tweaked the design a bit and charged a little more, and pretended we invented TC. My shop partner in Mexico, who was born in Australia and grew up in Canada, is still dubious that this works til he tries it but I sent him a video of an Aussie on youtube drilling a small hole in a spanner with an ordinary little masonry bit to convince him.

It works! What have a problem at my job "printshop" of snapping allen head wrenches flush with the screw head. The local machine shop told us about the masonry bit trick.

I'll take some pics Monday if I remember.

 

[bigblazer]

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.