He's now offering machined steel (maybe aluminum?) keys. That's what I got, but have yet to install.
Jonsered Chainsaws
- Thread starter briantutt
- Start date
Help Support Arborist Forum:
https://www.ebay.com/itm/1755782711...zCCk5zuRd6&var=&widget_ver=artemis&media=COPY
Nice example of an ol-workhorse !
Ernie
Nice example of an ol-workhorse !
Ernie
- Joined
- Feb 17, 2009
- Messages
- 16,685
- Reaction score
- 15,915
- Location
- Beautiful Rockbound Coast of Maine
That is a nice one!!!!!
Love mine.....smoothest running saw I have. Once warm...pull the recoil out halfway and it starts. Only saw I ever had to do that. 32" bar, .404, full-skip Oregon chisel chain. She aims to please! Besides my 2094, the saw with the second most amount of paint left.
Kevin
The offset key should be made of steel like the OE. All keys, whether for a chainsaw or lawnmower, have a shear strength figured in. B&S for example makes sure you have to fit their key. That way they ensure their designed shear strength.
Nylon or aluminum won't do that. Now if the OE key were aluminum, that would be another matter. Not seen any keys in chainsaw crankshafts that weren't steel. Those keys are probably pretty mild steel, but that's different than aluminum. It's not gonna hurt anything being aluminum, but will shear easier than steel.
Kevin
Please don't take this as me being obstinate, I'm just curious. He machines them from 7075 aluminum, and just as an example the woodruff keys I just got from McMaster are 316 steel. 7075 is often used in aircraft construction. I don't know all the engineering and physical properties that are relevant but here is a comparison and more specs here.
Speaking of woodruff keys, the keys I ordered from McMaster to replace the keys on my 451 are not tall enough. I measure my old keys at 2mm x 9.7mm x 4mm (WxLxH). The McMaster ones are 2mm x 9.7mm x 3.7mm. When I placed them on my shaft they barely stuck out past the keyway, certainly not enough to index the flywheel or clutch. Major bummer. Larger bummer is that I'm having a difficult time locating the exact dimension keys I need. The size I got from McMaster seems to be a standard. Local stores only carry SAE.
Anyone know where else to look?
Yeah torquing flywheel onto crank taper really provides most of the holding force. I work on snowmobiles all the time and the clutches they use are just fitted to a tapered crank with no key at all. Some turbo 4 strokes are making in excess of 300hp and clutches don't slip.
In the age-old battle of aluminum versus steel....in this case, corrosion resistance and all the other factors are irrelevant other than shear strength. That's the key's only function, to shear when things go south. But like mogulmasher says, the taper of the shaft and the torque of the fastener do most of the work. Anytime I've seen a sheared or damaged key, the flywheel was offset just a small amount. Not like it goes spinning off and launches through the cover. So if he's using 7075, maybe that's strong enough for this purpose? But don't try to sell me on nylon....
I guess you're going to have to find metric key stock....i.e., the differences between that and SAE must be enough to cause size issues. I've always had extra keys from dead saws so admittedly, I've never had to search for any. Or find some metal stock the same thickness and shape with a Dremel etc......lacking machine shop tools like most of us. Or, if the thickness is the same, just buy a larger key and Dremel it down....those keys are just punched out of a machine anyway using the appropriate steel stock.
Kevin
I think you're right, I'm gonna have to buy something bigger and Dremel it down. The McMaster key is nearly flush with the shaft, there maybe 0.1 mm of key above the shaft, it's barely perceptible with a finger.In the age-old battle of aluminum versus steel....in this case, corrosion resistance and all the other factors are irrelevant other than shear strength. That's the key's only function, to shear when things go south. But like mogulmasher says, the taper of the shaft and the torque of the fastener do most of the work. Anytime I've seen a sheared or damaged key, the flywheel was offset just a small amount. Not like it goes spinning off and launches through the cover. So if he's using 7075, maybe that's strong enough for this purpose? But don't try to sell me on nylon....
I guess you're going to have to find metric key stock....i.e., the differences between that and SAE must be enough to cause size issues. I've always had extra keys from dead saws so admittedly, I've never had to search for any. Or find some metal stock the same thickness and shape with a Dremel etc......lacking machine shop tools like most of us. Or, if the thickness is the same, just buy a larger key and Dremel it down....those keys are just punched out of a machine anyway using the appropriate steel stock.
Kevin
I just ordered 2x5x12.7 that I'll try to Dremel down. I think the flywheel and clutch can handle the extra height, so I'll only have to shave the length. Any tips on how you guys would go about this?
I clamp the key in a vice and use a flat file to shape it. You will have to flip it to do all areas you need to.
Check by taking measurements of the key slot so you now what dimensions to shoot for.
To make sure you never shear a key, make sure there is zero oil on the shaft and flywheel tapers.
Most saws take somewhere between 18 and 22 ft lb torque on the FW nut if you can't find a listed torque.
Thanks, someone on a thread I created in the in the main chainsaw forum pointed me to a Husqvarna p/n that I wasn't aware of for the 451. I ordered a set from eBay and I hope this will do it.
Yes, the key on a chainsaw is just for timing. And for the steel vs. aluminum argument, the key on a lot of newer saws is cast as part of the flywheel.
Yeah, you see that on small engines a lot now. I've also seen them shear pretty easily on lawnmowers when they hit something.
Tim's no oil on the tapered shaft and the flywheel is spot on. The tendency for many is to oil it or put on anti-seize. Great way to split your flywheel and ruin it.
That's one way to look at it; the key is mostly for timing. But it's also to protect the crankshaft from a sudden, abrupt rotational torque force.
Kevin
- Joined
- Feb 17, 2009
- Messages
- 16,685
- Reaction score
- 15,915
- Location
- Beautiful Rockbound Coast of Maine
- Joined
- Jul 19, 2019
- Messages
- 4,258
- Reaction score
- 8,521
Got some cool stickers in the mail today- a thanks for finding a guy a Dolmar oil pump he had been hunting for a long time. Were some PARTNER ones as well- but these are the cool ones.
I can't believe I didn't check their site.
I have been searching for an intact clutch-side “semi pro” decal. It would be the finishing touch to my 49 SP
Attachments
I can't believe I didn't recommend them....one of the three I traditionally recommended for used parts.I can't believe I didn't check their site.
Kevin
- Joined
- Feb 17, 2009
- Messages
- 16,685
- Reaction score
- 15,915
- Location
- Beautiful Rockbound Coast of Maine
So.........does anyone in here have or know anyone that has any 751 parts??
