Manual grinding with disc bit on high-speed pneumatic micro-grinder

[PainAndMurphy]

before any of you jumps the gun (I hope it's the right expression since it's not my 1st language, so please pardon me..) -- I should mention that I have experience in craft/handy work, and when it comes to chain sharpening, I did a lot of reading & practicing -- since we don't have a table wheel grinder..

Couple of years I just happened to grab this high-speed PNEUMATIC micro-grinder that spins freely at about 60,000 RPM .. (just specs of the device, I didn't verify, and it doesn't matter to me since I lean to back off whenever I see even a glimpse of 'blueish' cast on MY cutters..)

For these last 2 yrs , I used diamond bits three common sizes for our chains: 4mm , 4.8mm and 5.5mm.

The ugly:
CHANGING BITS!! - whoever knows these cheap micro-grinders know.. I guess..

So, just a couple of months ago I HAPPENED (yes, it was by incident) to use the DISC BIT to lower the rakers' height............. and then I just felt like trying it out on the cutters.

I MUST MENTION -- I AM WELL PRACTICED WITH USING THESE KIND OF TOOLS ON DIFFERENT MATERIALS, AS WELL AS THE SAFETY MEASURES THAT THIS ACTIVITY DEMANDS. AND EVEN MORE -- I WOULD NEVER RECOMMEND THIS METHOD TO ANYONE ELSE WHO HAS A BETTER / SAFER METHOD THAT HE/SHE IS USED TO!!!! THIS METHOD CAN BE VERY DANGEROUS. Please understand that I'm just sharing..

Since I'm familiar with the factory numbers and angles (we're a small team that works a lot, but not super-heavy-duty, and though I'm the only chainsaw-hound there I'd rather sharpen it closer to standard, and not extreme..), and I also have my own 'corrections' for my own likes - I managed to practice enough (and I STILL am practicing it..) to develop my own method that allows me to repeat the angles on both sides too.

NOW I DON'T HAVE TO SWITCH BITS!! THIS DISC REMAINS ON THIS LITTLE SCREAMER AND SHARPENING IS NOW QUICKER THAN EVER -- AS WELL AS THE CUTTING SPEED !! (and the disc seems to last pretty long, and NEVER goes dull..)

I just wanted to ask the pro's here: is this method WAAYYYY bizarre , or it makes sense in a way that justifies sharpening like that so I can keep sharpening the chains while ON the chainsaw..?
(that's all it meant to be - sharpening without removing the chain - and back to work!)

Respectfully,


Jo.





P.S.
The picture was taken while I was fixing an abused, round-filed Full-Chisel 3/8" .050 Oregon chain, and thus the round curve against the flat disc.. I can later on post pictures of results from: STIHL .325" , STIHL Picco / Oregon 3/8" LP , and of course - the bigger 3/8" Oregon seen here in the photo.

 

[Philbert]

I just wanted to ask the pro's here: is this method WAAYYYY bizarre , or it makes sense in a way that justifies sharpening like that so I can keep sharpening the chains while ON the chainsaw..? (that's all it meant to be - sharpening without removing the chain - and back to work!)

Jo,

Please note: Your post is hard to read WHEN YOU USE ALL CAPITAL LETTERS AND BOLD TYPE! It 'sounds' like you are screaming.

As far as sharpening the chains while they are still on the saw, there are many methods that do this. The bottom line is getting the cutters on your chain to the angles and profile that you want. If this works for you, then that is fine.

The concerns I might have with your method (aside from any safety issues), are:

1. Getting each cutter on a chain loop the same, without using any type of guide. If cutters are ground to different lengths, or at different angles, the chain will not cut as smoothly or as effectively. If you have the skill to do this 'free-hand', OK.

2. 60,000 RPM is very fast, and your wheel in the photo is very small. This makes me concerned about overheating the cutters. In your photograph the cutter to the left of the one you are grinding, looks like it was 'burned'.

Again, sharpening the chain on the bar is fine, and if this method works for you, go ahead. If you are looking for other methods to sharpen on the bar, I am sure that some A.S. members can provide them.

Philbert

 

[PainAndMurphy]

Jo,

Please note: Your post is hard to read WHEN YOU USE ALL CAPITAL LETTERS AND BOLD TYPE! It 'sounds' like you are screaming.

As far as sharpening the chains while they are still on the saw, there are many methods that do this. The bottom line is getting the cutters on your chain to the angles and profile that you want. If this works for you, then that is fine.

The concerns I might have with your method (aside from any safety issues), are:

1. Getting each cutter on a chain loop the same, without using any type of guide. If cutters are ground to different lengths, or at different angles, the chain will not cut as smoothly or as effectively. If you have the skill to do this 'free-hand', OK.

2. 60,000 RPM is very fast, and your wheel in the photo is very small. This makes me concerned about overheating the cutters. In your photograph the cutter to the left of the one you are grinding, looks like it was 'burned'.

Again, sharpening the chain on the bar is fine, and if this method works for you, go ahead. If you are looking for other methods to sharpen on the bar, I am sure that some A.S. members can provide them.

Philbert

OK
Comment taken. I will change that! Thanks for notifying me about it, I had no idea. Said that it's not my best side.. it's only my 2nd language.. I tries to write it down carefully since I don't do it often, and I was trying to make sure I don't miss anything or misunderstood , so maybe that's the reason - I might have tried too much or too hard.. Please understand..

BTW, one Texan friend (as far as I know.. lol) who's a McCulloch person, always WRITES IN CAPITALS.. 100% CAPITALS. So maybe that's why I should speak to more people here.. LOL.. not just him.. you know? I got used to such writing as a non-screaming way..

I will improve!

Thanks again!!

Jo.

 

[PainAndMurphy]

1. Getting each cutter on a chain loop the same, without using any type of guide. If cutters are ground to different lengths, or at different angles, the chain will not cut as smoothly or as effectively. If you have the skill to do this 'free-hand', OK.

That's why I added the 'capslocked' part.. I am used to do precision (and even dangerous) work as such, and also do various kinds of practical arts (sorry if I don't have the right definition.. I try..) so I think I have much precision and control. I have learned from the best. I owe them a lot. I listen to the elderly, and to the experienced personnel.

2. 60,000 RPM is very fast, and your wheel in the photo is very small. This makes me concerned about overheating the cutters. In your photograph the cutter to the left of the one you are grinding, looks like it was 'burned'.

I meant that this is about the maximum speed, and between min' to max' - you have a sort of shaft-dial(?) that lets you freely set the RPM. I have mentioned that I did notice how it burns the steel from a certain speed and up, plus the duration of each continuous contact of the disc with the cutter/tooth. So - I have tested it and concluded that I start with half throttle and then fine tune so it has just enough power against the resistance, but not too fast to burn the cutter.

The cutter on the left (and the whole chain when this picture was taken) is just worn from rough cutting by a staff member. I'm trying to be much more careful than he is, and I usually don't wear the chains I work with like that.. not too quickly..

Thanks for your comment Philbert!

Jo.

 

[PainAndMurphy]

lil' samples

here goes nothing just another attempt..
when I grind chains like that it's like sculpting (spelled okay?)
like practical art.. I love sharpening the chain like that.. it's feels great when you can do it all with a single (and fast) tool for any gauge and pitch


OH! - and in this case, it's a 3/8" LP on a STIHL 020T that I did a complete rebuild, and found a very old but usable 12" bar for it. Did it a little treatment - and seems like it's gonna keep running for more than just a couple of hours

Sometimes contractors just throw away gear / parts / saws that have like 30-40% life, or even mint(!!) condition under a thick layer of oily sawdust......

Jo.

 

[LegDeLimber]

The drawback to free hand grinding is possible variations of angles.

Looking at the photos in your last post:
It appears that you have a negative angle on some of the top plates,
this would lead to it not cutting and excessive heat in the cutter.

I marked in red the *approximate* angle of your top plate
and yellow line to indicate the point where the angle should begin
and how it should be tilted forward.

This web page has some pretty good drawings of chain teeth and their angles.
It also has some explanations of how the wood flows across the cutting edges,
which should help to understand why they matter
and help with getting your chains cutting more efficiently.

0667-2805-MTDC: Chain Saw and Crosscut Saw Training
Course Student's Guidebook 2006 Edition

Figure 3-10: shows some of the angles.
Because of the way they are drawn, the side plate angle (at bottom of drawing)
shows the top angle more clearly.

Figure 3-9: shows the wood flow across the cutter, so perhaps
this illustrates why the top plate on your cutters will be a problem.

Do keep us posted with your results though!

 

[PainAndMurphy]

ha ha yes indeed! Thank you!!

The drawback to free hand grinding is possible variations of angles.

Looking at the photos in your last post:
It appears that you have a negative angle on some of the top plates,
this would lead to it not cutting and excessive heat in the cutter.

I marked in red the *approximate* angle of your top plate
and yellow line to indicate the point where the angle should begin
and how it should be tilted forward.

This web page has some pretty good drawings of chain teeth and their angles.
It also has some explanations of how the wood flows across the cutting edges,
which should help to understand why they matter
and help with getting your chains cutting more efficiently.

0667-2805-MTDC: Chain Saw and Crosscut Saw Training
Course Student's Guidebook 2006 Edition

Figure 3-10: shows some of the angles.
Because of the way they are drawn, the side plate angle (at bottom of drawing)
shows the top angle more clearly.

Figure 3-9: shows the wood flow across the cutter, so perhaps
this illustrates why the top plate on your cutters will be a problem.

Do keep us posted with your results though!

That's one of my earliest manual micro-grinding ever..

please note that though it looks pretty bad comparing to my recent work / performance , this is a Low Profile 3/8" with a round corner.. so there will never be a chance to get an arrow-sharp edge..

Agree? Am I wrong on that alone?


Jo.

 

[LegDeLimber]

If you come from this direction you'll have the wheel
in the same orientation as a machine grinder.
Then you will need steady hands and eyesight to hold the correct angles.

and a couple of pics, to give illustration to my words (hopefully).
I don't have the same thickness of stone as you have,
but this should give an idea of the positions.
It should give a sharp edge if you can hold everything steady.
The round tooth profile will not a problem.

But consistency, over all of the cutters,
will be the difficulty in hand held grinding.

 

[PainAndMurphy]

that's a good camera right there!

If you come from this direction you'll have the wheel
in the same orientation as a machine grinder.
Then you will need steady hands and eyesight to hold the correct angles.

and a couple of pics, to give illustration to my words (hopefully).
I don't have the same thickness of stone as you have,
but this should give an idea of the positions.
It should give a sharp edge if you can hold everything steady.
The round tooth profile will not a problem.

But consistency, over all of the cutters,
will be the difficulty in hand held grinding.

So, that's why I'd say this should become art! Did carving in wood not become art?

- AND I will keep posting more.. maybe tomorrow



Thanks for commenting people!

Jo.

 

[PainAndMurphy]

some more sample from the past month

note - I improved since those were taken.


=======================


EDIT:

1, 2 & 5 => STIHL MS240 w/ 16" .325 .063 Semi-Chisel
3 & 4 => STIHL MS200T w/ 12" 3/8 .050 round chisel

 

[LegDeLimber]

In the third pic, the cutter you show
still needs some help on the top plate angle.

considering the geomtery on the side plate,
I'm curious what the chips look like from cutting with this chain.

 

[PainAndMurphy]

Indeed the angle + sawdust

In the third pic, the cutter you show
still needs some help on the top plate angle.

Yea I know.. it's an older one, and on the MS240 it's more recent.

considering the geometry on the side plate,
I'm curious what the chips look like from cutting with this chain.

.....and you could guess already - after a day out.

Also, I had this urge to experiment myself if there's a benefit of this angle to 'ease down' the usage nature of a colleague here who likes to push.. on the other hand maybe it does the opposite if you put more thought into this.... yea, it might even stop more than having a steep razor sharp angle........ hmmmmm........

Jo.

 

[heyduke]

note - I improved since those were taken.


=======================


EDIT:

1, 2 & 5 => STIHL MS240 w/ 16" .325 .063 Semi-Chisel
3 & 4 => STIHL MS200T w/ 12" 3/8 .050 round chisel

Jo-

one problem that i see from your photos is a lack of radius in your side plate. when you sharpen with a file, grinder, or timberline burr, the "hook" in the side plate is a part of a circle determined by the diameter of your file or the dressed edge of the grinding wheel. you frequently see the same thing on chains sharpened with a grinder, when the operator grinds too far down into the cutter. one reason this is undesirable is that if you need to sharpen, in the field, with a file, the side plate won't have the correct shape to fit the file, unless you use a flat file. looking at the small grinding wheel on your die grinder, i can see that you need to "dress" a radius on the outside edge. that radius should be 5/64" (2.25mm) for lo-pro chain. note that the measurement is the radius, half the diameter of the required file. if you can find a stihl chain gauge, the one you use to set your depth rakers, you sill see two small half circles on the bottom edge. I believe these correspond to a 7/32" file but would probably be a good enough way to check your wheel dressing, infinitely better than your square edge. when sharpening, the grinding wheel should not go low enough to cut with the side of the grinding wheel. i also noticed in your photos that some of your top plate edges have a curve, indicating that your hand may not be as steady as you thought.

only other comment, i find your posts to be readable and often more clear than many of us that speak, and attempt to write, only one language.

good luck.

 

[rocketnorton]

:agree2:

Jo-

one problem that i see from your photos is a lack of radius in your side plate. when you sharpen with a file, grinder, or timberline burr, the "hook" in the side plate is a part of a circle determined by the diameter of your file or the dressed edge of the grinding wheel. you frequently see the same thing on chains sharpened with a grinder, when the operator grinds too far down into the cutter. one reason this is undesirable is that if you need to sharpen, in the field, with a file, the side plate won't have the correct shape to fit the file, unless you use a flat file. looking at the small grinding wheel on your die grinder, i can see that you need to "dress" a radius on the outside edge. that radius should be 5/64" (2.25mm) for lo-pro chain. note that the measurement is the radius, half the diameter of the required file. if you can find a stihl chain gauge, the one you use to set your depth rakers, you sill see two small half circles on the bottom edge. I believe these correspond to a 7/32" file but would probably be a good enough way to check your wheel dressing, infinitely better than your square edge. when sharpening, the grinding wheel should not go low enough to cut with the side of the grinding wheel. i also noticed in your photos that some of your top plate edges have a curve, indicating that your hand may not be as steady as you thought.

only other comment, i find your posts to be readable and often more clear than many of us that speak, and attempt to write, only one language.

good luck.

 

[PainAndMurphy]

yes..

:agree2:

I figured that out already.

until I find a suiting micro wheel - I'm BACK to using the round fine-diamond grinding bits, with all the different sizes we use: 4mm , 4.8mm , and 5.5mm (unless someone here tells me that the large 3/8 needs 5.2mm or something.. all stuff I read overtime + STIHL / Oregon / Husqy directions => all lead me to use 5.5mm on the large 3/8"..)

and thanks.


Jo.