Tutorial: make your own raker depth gauge supported by software tool

jrs_diesel

jrs_diesel

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I just picked up some 1/16" (1.5875 mm) aluminum to make one of these gauges this weekend. I'll post my measurement from a new loop of Oregon 91PX.
 
waynedb

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I managed to get a gauge made yesterday. Took less than 20 mins in total. Very straightforward - if you can handle a square, marker, vice, grinder and file you can make one. Main steps in photo sequence below.

upload_2019-12-11_10-46-37.png

I filed the slot carefully so that it slips easily but snugly over the tie straps; this way the gauge sits there by itself and wobble is minimised. In pic 4 above you can see I still need to square off the end of the slot, but it doesn't affect the function of the gauge.

Below is a sequence that shows the gauge in use - works well. The camera angles are a bit deceptive - the gauge is sitting on the third rivet to the right of the raker in question. I like that the gauge gives the finished raker an angle rather than the flat top you get with the standard gauges - apparently this makes for smoother cutting and allows the raker to "dig-in" slightly allowing the cutter to be more aggressive.

upload_2019-12-11_10-50-35.png

My (imperfect) measuring of the final raker depth was about 40 mil, which on this chain, with 100 mil wear calculates to around 6.7 degrees raker angle. About right I guess, although the theoretical figures calculated by Hannes' program using the gauge thickness and new chain measurements and what I measured on my type 2 gauge-filed raker don't match exactly. Quite likely down to measuring inaccuracies - I may be a bit ham-fisted with calipers and a straight edge. I'm happy with the slightly higher angle, supposedly CSM calls for this anyway.

I'm heading back down the gully on Friday to do some more milling - will report back. Pending actual cutting performance, I'm chalking this up as a win for the nerds! :reading:;)
 

Del_

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I managed to get a gauge made yesterday. Took less than 20 mins in total. Very straightforward if you can handle a square, marker, vice, grinder and file you can make one. Main steps in photo sequence below.
===

I'm heading back down the gully on Friday to do some more milling - will report back. Pending actual cutting performance, I'm chalking this up as a win for the nerds! :reading:;)

Thanks for the great illustration!

It got me to thinking that maybe a measuring gauge could be made and then adjusted to specific parameters experimentally by precision bending.

Using no math at all. Just use a gauge like Waynebd had made, use it on a chain, take it to the woods, bend accordingly. Repeat.

Perecise bend.png
 
waynedb

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I did wonder about this when making the gauge...

My plates weren't entirely flat off the guillotine - I spent a bit of time hammer-tapping and hand-bending them as flat as I could.

It wouldn't be hard to tweak a slight bend in the gauge to either raise or lower it relative to the raker. Not sure what that would do to the linearity of the angles over the life of the cutter, but I think it would be fine to allow a bit of adjustment in the field.
 
hannes69

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I made one of these too, for .325 chain and it works well.
Nice, so there is confirmation that the gauge works for pitches different from 3/8. :)

I have made 1 for each for 3/8LP, 3/8 & .404.
So all common pitches (leave alone 1/4) seem to work with the gauge design. I assumed that, but wasn´t sure because of the lack of practical experience...

All of the gauges I made were fabricated from 1" steel banding used to secure packages of 21' steel pipe.
Out of curiousity what´s the thickness of this material and how do you flatten the material assuming it´s bent?

What I am proposing is a gauge with a slot that would capture the depth gauge similar to Hannes's design but would have a horizontal stop on the bottom side The stop would be 90 degrees (right angle) to the slot for the depth gauge as well as the tie straps.
[...]
I know it would be easier if I post pics. of what I am talking about but I will be working on a prototype to test functionality in the near future. If I can make a workable design I will take some pics. then to post.
Yes, a pic or illustration would help, I can´t quite imagine your approach. Pics of a prototype woul even be better, including your experiences with it :)

Below are the measurements from my Carlton 3/8 .063 semi-chisel skip chain and a screenshot of what the raker angles will look like with a 47 mil (1.2mm) thickness gauge (all seem reasonable?)
Average of 5.5 degrees is perhaps a touch low...? 39 mil (1.0mm) thickness plate brings the average to 6.5...
My (imperfect) measuring of the final raker depth was about 40 mil, which on this chain, with 100 mil wear calculates to around 6.7 degrees raker angle. About right I guess, although the theoretical figures calculated by Hannes' program using the gauge thickness and new chain measurements and what I measured on my type 2 gauge-filed raker don't match exactly. Quite likely down to measuring inaccuracies
Thanks for the measurements! The measurements are certainly within reasonable limits. Not so easy to measure are the lengths B and D and the angle alpha. Some small errors here and there sum up quickly in the end result. What counts: Your gauge seems to work in practical life, you get reasonable and expected cutting angles. Your 6.7 degrees at 100 mil wear are similar to the calculated 7.0 degrees at 100 mil wear for my Stihl 3/8 chain. So I can probably assume, that the gauge principle seems to work well for different brands.


I managed to get a gauge made yesterday. Took less than 20 mins in total. Very straightforward - if you can handle a square, marker, vice, grinder and file you can make one.
[...]
I like that the gauge gives the finished raker an angle rather than the flat top you get with the standard gauges - apparently this makes for smoother cutting and allows the raker to "dig-in" slightly allowing the cutter to be more aggressive
Thanks for your report! :)
And yes, it´s a nice side-effect of the design, that you get a slightly angled raker. Of course you can trim the raker further after using the gauge, leaving the tip alone, and ramp it even more.

I just picked up some 1/16" (1.5875 mm) aluminum to make one of these gauges this weekend. I'll post my measurement from a new loop of Oregon 91PX.
Ok, another 3/8 low profile chain I think, and a different manufacturer. Soon we can make some conclusions about different pitches and brands.
I´m not so sure your material for the gauge is appropriate. Aluminium is weak and soft, you can only use it for measuring, certainly not using a file onto it.
With its thickness you´ll get very small cutting angles. When your chain has similar measurements like my Carlton low profile chain, then you´ll end up with angles in the region of 3 - 4 degrees.

It got me to thinking that maybe a measuring gauge could be made and then adjusted to specific parameters experimentally by precision bending.
Using no math at all. Just use a gauge like Waynebd had made, use it on a chain, take it to the woods, bend accordingly. Repeat.
It wouldn't be hard to tweak a slight bend in the gauge to either raise or lower it relative to the raker. Not sure what that would do to the linearity of the angles over the life of the cutter, but I think it would be fine to allow a bit of adjustment in the field.
I thought about this possibility as well :)
I made some simulations with such an approach.
The linearity is harmed - the more you bend it.
When you don´t have the proper material thickness at hands, you can bend too thick material down - or the other way round bend a too thin material up.
When looking at the numbers of gauge design 2, you´ll see, that there is a small bump of the values of cutting angles in the middle wearing region. So you start with a brand new chain with a normal desired cutting angle of 6 - 6.5 degrees. This value climbs up a bit to 7.0 degrees in middle wearing state and then falls down to 6 degrees at the end of life point. When using 1.2mm material and not bending.
Let´s take the example of the 1/16 inch alumium material given above. You can bend it down, so you have you normal cutting angle of 6.3 degree at the beginning, with my Stihl RM chain example.
Compared with the 'normal' 1.2mm setting, the following happens: The angles rise up in the middle up to 8.5 degrees and then fall down to 7.5 degrees at the end of life point. So the small bump from above gets now a larger (higher) and wider bump. You´ll get cutting angles in the region of 7.5 to 8.5 degrees most of the time compared to 6.0 - 7.0 degrees in the original design, so more or less an average of 8.0 degrees compared to 6.5 degrees.
But maybe in this example it would be better to bend the gauge not completely down to match the starting raker depth of 25 mil but stay a little bit higher for compensating the given overshoot.
The better approach is to use a material in the right region, so that you can take it without bending or leaving only a small need for a slight bending.
The 1.2mm material is in the sweet spot without the need for bending and assuming common 'normal' cutting angles.
The 1/16 inch material (1.6mm) seems a little bit too thick to me. On the other side I wouldn´t go below 1.0mm material, it becomes unstable and you´ll soon get very large cutting angles.
Material in the range of 1.0 to 1.4 mm (40 to 55 mil) should be fine.
When using the 1.2mm material and looking for the common cutting angles, I would second Del_´s opinion, use it, leave the math alone and bend it slightly if needed ;)
Like mentioned above, it´s questionable if 'ham-fisted' and 'precision bending' are a good couple ;)


___________________________________

Nice to see that some life got into this thread and the theory landed finally in the practical field :)
 
waynedb

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..reporting back as promised...

The weekend milling session went well - I used the gauge a few times to touch up the rakers; it worked great, quick and easy to use and the chain seemed to cut nicely. As mentioned, I'm milling some quite dry Aussie hardwood, so that is slow going and pretty dusty regardless. I did do one crosscut on a ~4' redgum log - went through like butter - nice chips!

I do think I could perhaps go a touch more aggressive for milling and take the rakers down a little bit more - perhaps a thinner gauge material might be worth an experiment. The next thinner available thickness is 0.9mm (compared with 1.2mm currently) which would give a theoretical average of 7.1 degrees raker angle - worth a try.

Thanks again Hannes for gifting such a nice little tool.

Without wanting to hijack the thread, here are a few pics...

upload_2019-12-17_7-35-10.png
 
hannes69

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I did do one crosscut on a ~4' redgum log - went through like butter - nice chips!
:) :) :)

I do think I could perhaps go a touch more aggressive for milling and take the rakers down a little bit more - perhaps a thinner gauge material might be worth an experiment. The next thinner available thickness is 0.9mm (compared with 1.2mm currently) which would give a theoretical average of 7.1 degrees raker angle - worth a try.
You could try it, but I would consider: Your theoretical average would be 7 degrees taking your measurements, but you already mentioned, that your real results were more similar to my Stihl 3/8 chain (what I would expect, I think that the results regarding the cutting angle should be very similar between different brands when taking the same pitch), so your real cutting angle average would maybe be more in the range of 8 degree with highest values of 9 degrees. A cutting angle of 9 degrees with hardwood (and I have read that redgum seems to be very hard) is very demanding. The saw has to deliver the power to get this to work and beside that wear of the chain, the bar, the rim and so on rises up. I made some tests with an old chain with very short teeth (let´s say 40 mil next to the end of life marking on the tooth) and using very aggressive cutting angles in that region of 9 degrees. The result was that the chain soon lost some of the teeth - even when only cutting softwood. Ok, when very short, they break as well regardless of the cutting angle, but not so many in such a short time like in my test.
What I want to say: There is an upper limit for a useful cutting angle. Going beyond that some unwanted side effects start to rise.
Maybe you could get 1.0mm material (it´s quite common here in Germany) or bend your gauge slightly down or try to lower the material thickness in the filing region with a file or sand paper (should be fairly easy to take away 0.1mm to get to 1.1mm thickness, and if necessary and possible take another 0.1mm away for 1.0mm thickness).

Without wanting to hijack the thread, here are a few pics...
Nice setup :) And an interesting material, this kind of wood...
 
arathol

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Meh, seems like a lot of effort to re-invent the wheel. I just went to Lowes and bought one....
UiWFy0Hl.jpg
 
arathol

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Yeah that picture was just to show how it works....and it does work very well. But yeah the chain did need some work...
FEiIq4Sl.jpg
 
Huskybill

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When the chain teeth are sharpened so much the rakers are almost flush and it's cutting saw dust and not big square chips making two passes with the flat raker file will will bring the rakers within spec. If not make three passes on each raker. It's no big thing. When I file the teeth I make the exact same passes on them too. I never had a problem sharpening chains.

to check the raker depth look down the front of the bar due balling the teeth and takers depth. We're talking a spark plug gap space.
 

SEAM

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In this day and age some people need a computer-derived formula to get their a$$ wiped properly...

A good eye and common sense will usually get the job done (I am referring to the filing issue here).
 

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