Thread: Whats the diagnosis Dr BOBL? (chain surgon )

i reckon as a chain surgeon bobl gone past the doctor part and as a highly qualified expert in the field he should be refered to as Mr bobl. i don't quite understand how it works in the medical profession,but as a bloke starts out and climbs the ladder they end up being caller Mr. All a bit weird to me but bob's got my vote when you need to know something

Originally Posted by Krunchie

Want to ask you Bob,
Hows this chain look?
Have got to the end of a felling job and am now in to the grubby end of the deal, (stumps and fire wood) the bar and chain had been running curves through the logs with all the pushing and dirt digging getting the stumps down (not to mention all the ant crap in the stumps) so I dressed the bar and took the rakers down a bit with a basted file (for some extra bite) and now I cant stop her she just cuts and cuts and well cuts. I don't have to push the saw through the engine stays at about 85-90% load.

Any Who whats the diagnosis Dr BOBL?

FWIW I have a PhD in Nuclear Waste Disposal. Satisfaction guaranteed or dowble your wubbish back!
Don't believe me - look here - I'm the author of this web site.

OK lets look at your cutters.


The Key Performance Factor (KPF) is the ratio of the length of the RED line divided by the length of the blue line, or gullet width divided by raker depth.

The nominal ideal KPF is 10. if the value is greater than 10 the chain will make more powder - if it is less than 10 it will make more chips, and if it is much less than 10 it will be a lot grabbier.

In your case the Red/Blue ratio is 9 which would put it into the "more chip" range BUT all this assumes your rakers are rolled over as per the green line and yours are not, so your real working ratio is the purple line divided by the yellow which is ~13 so that puts it back into the "less chip" range.

To get yours cutting like a new chain you need to roll those rakers right over like this.


I think you will be even more surprised when you do this.

BTW I think you should be a little kinder on dressing the bar. It looks like you have used an angle grinder? There are a lot of chips taken out if the edge of the bar. It's better to keep the bar rails as smooth and chip free as possible. Small chips are birth places for bigger chips. I have seen a small chip grow within minutes into a big enough chip to total the bar.

Originally Posted by charlsie

i reckon as a chain surgeon bobl gone past the doctor part and as a highly qualified expert in the field he should be refered to as Mr bobl. i don't quite understand how it works in the medical profession,but as a bloke starts out and climbs the ladder they end up being caller Mr. All a bit weird to me but bob's got my vote when you need to know something

Thanks Charlsie - that's a bit of a turn around from what I usually get called, eg "mongrel bob" or TBB (That bastard bob)

[/QUOTE]
BTW I think you should be a little kinder on dressing the bar. It looks like you have used an angle grinder? There are a lot of chips taken out if the edge of the bar. It's better to keep the bar rails as smooth and chip free as possible. Small chips are birth places for bigger chips. I have seen a small chip grow within minutes into a big enough chip to total the bar.[/QUOTE]


This is a second hand bar (i swear i never touched that bar with a grinder)(I have a stihl bar dressing tool works a treat) that was "just" stuck on with the saw which was bought for about $70 just over a year ago i have put up with the bar for the sake of learning how to make a f**ked bar work ok and how to keep a good bar working best as for the chip ratio i was seriously impressed with the result i was getting so far and i had used the raker gauge as pictured but it kinda got to a point that wasn't giving me any more umph i guess you would say not to mention all the #### i was pushing the bar and chain in to cutting the stumps down to the ground.

i will give some more pics of the next episode of fire wood and stump cuttin

Thanks Dr BOBL or should i say MR

Bob what do you think of the side plate angle



could it have a bit more hook? along with the rakers being more curved rather than 'flat topped'?

Originally Posted by Sigidi

Bob what do you think of the side plate angle , could it have a bit more hook

Yep I agree, if he was cutting clean green wood.

For really dirty wood and stumps he is probably about right. The amount of hook he has is consistent with his new file size 3/16" file which means his chain stays sharper longer. I'd be looking to maybe try 13/64 file at least - or my wierd combo below.


**** WARNING - ULTRA GEEKY FILING STUFF FROM HERE ONWARDS *****

By sheer accident I discovered that using a 13/64" file (that's half way between 7/32 and 3/16 file) in a 5/32" file guide/holder works very well on 3/8 chain in very hard wood.

A 13/64" file produces more hook than a 7/32 but since the file is slight higher up in the guide/holder than it should be, some of that extra hook is lost and this enables the cutter stay longer in harder wood. This combo produces a very slightly different cutter profile than going direct to a 3/16" file

Unless you are really good at freehand filing you cannot get this level of finesse with a file alone. Also getting this level of finesse with a grinder requires making sure the wheel is properly dressed and by making changes to the side plate angle setting.

Well as you guys know, my knowledge on chains isn't anywhere near Bob's so I'm trying to get a feel for 'good looking' chain.

Dunno about it being ultra geeky Bob???

will be doing some more work with this chain next Monday so will take some more photos and give some more feed back

Has been an awesome response to such an integrable part of our work as saw operators be it a cutter or a fella

Cheers MR BOBL
and Cheers surgical offsiders untill next episode

Stay safe and stay sharp

Rob

Originally Posted by Krunchie

will be doing some more work with this chain next Monday so will take some more photos and give some more feed back
Has been an awesome response to such an integrable part of our work as saw operators be it a cutter or a fella

Onya Rob!

Originally Posted by Sigidi

Well as you guys know, my knowledge on chains isn't anywhere near Bob's so I'm trying to get a feel for 'good looking' chain.
Dunno about it being ultra geeky Bob???

"geekiness" is a relative thing. Some people think that if you sharpen your own chains you must be a geek!

Originally Posted by BobL

"geekiness" is a relative thing. Some people think that if you sharpen your own chains you must be a geek!

Bob you made me think back to my other life as an Exercise Physiologist, most people thought you where a freak if you exercised more than twice a week or a total of more than 3 hours a week...

Originally Posted by Sigidi

Bob you made me think back to my other life as an Exercise Physiologist, most people thought you where a freak if you exercised more than twice a week or a total of more than 3 hours a week...

3 Hours a week - that is freaky! I limit mine to 2.5 hours a week

Now - if you want to see some geeky racing chain have a geezer at this technical article by oregon on racing chain
http://www.madsens1.com/pdf/RacingTechfacts_93099.pdf

This is actually pretty conservative compared to what some racers do but you don't see to many pics of racing chains because people like to hide their mods.

BTW I don't recommend doing this to your milling saws.

bob, you copped a MR from rob so that puts you at the top of the chainsaw guru's list of all time greats congrats

Originally Posted by charlsie

bob, you copped a MR from rob so that puts you at the top of the chainsaw guru's list of all time greats congrats

Thanks charlsie! Please remember that although I've been around chainsaws for 50 years I never really got serious about milling till about 3 years ago and I didn't quite appreciate a really sharp chain until I have to mill really hard wood. Maybe I'm just a quick learner, or after slabbing up 20 tons of big spotties I guess I either had to work it out pretty quickly or go mad, or maybe a bit of both! I learned a lot from other people like my dad and his mates, on this and other sites, and just from my own analytical training, but still reckon I have way more to learn than I know. Someone once told me, " . . the more you know, the more you realize how little you really know. . . "