Chainsaw milling dense tropical woods

[ZachAK]

My shipwright buddy has asked me to take a 2" slab off of a huge 1600 pound purpleheart timber. I'm looking for any guidance on chain or other adjustments. It's an irreplaceable, expensive piece of wood, so I have to get it right the first time.

I've only ever milled softwoods, this being Alaska and all. Here are some pictures of the latest milling I did last week. A yellow cedar, about 28" DBH.

I'm building a bench for the local chapter of the Society of American Foresters to honor a member who passed away. First I found a nice windthrown yellow cedar and cut the stump off the tree. The stump laid back upright.



Then I pulled the bucked logs with a Griphoist into position, and set it up so the log would be downhill. Thank you, Bob for the great tip. Gravity is our friend!


I like slabbing with a 2X12 for up to 3' logs.





Finally, I had to slide the slabs downhill, past a cliff, and into my skiff at the beach. Here's the skiff ready to be unloaded on the beach below my house.


Thanks, everyone!

 

[BobL]

Purpleheart has a similar density and hardness as Spotted Gum which is the most common tree I mill.

If you know about progressive raker setting and are already running a high raker angle then you may need to reduce that angle by a degree or two.

I believe it exudes a lot of resin if heated which will gum the chain so increasing the flow from the Aux oiler and keeping the chain sharp is important or the chain will overheat and gum up. Touch up every tankful of mix and the rakers every 3/4 tankfuls.

To keep the resin build up under control a hand pump spray of diesel to spray on the chain when you stop will help remove the gum that has stuck onto the chain.

 

[ZachAK]

@BobL Thank you, Bob! You've given a tremendous amount of knowledge to this forum. You've made me a better miller with your years of advise.

If you were a bit closer to Alaska, I'd love to buy you a beer or two!

 

[808fish]

Purpleheart has a similar density and hardness as Spotted Gum which is the most common tree I mill.

If you know about progressive raker setting and are already running a high raker angle then you may need to reduce that angle by a degree or two.

I believe it exudes a lot of resin if heated which will gum the chain so increasing the flow from the Aux oiler and keeping the chain sharp is important or the chain will overheat and gum up. Touch up every tankful of mix and the rakers every 3/4 tankfuls.

To keep the resin build up under control a hand pump spray of diesel to spray on the chain when you stop will help remove the gum that has stuck onto the chain.

Good idea to spray diesel to remove chain resin build up. Will have to give it a try

 

[Cease232]

Purple Heart is very abrasive as It contains a lot of silica. I've never milled it with a chainsaw but it's very hard to work with from a woodworking standpoint. It will dull blades, router bits, and decimate sand paper very quickly. My guess is that you will have to sharpen more frequently then every tank. Good luck. Post pics.


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[ZachAK]

Purple Heart is very abrasive as It contains a lot of silica. I've never milled it with a chainsaw but it's very hard to work with from a woodworking standpoint. It will dull blades, router bits, and decimate sand paper very quickly. My guess is that you will have to sharpen more frequently then every tank. Good luck. Post pics.


Sent from my iPhone using Tapatalk Pro

You're right! I don't much care for purpleheart. It's a miserable wood, but rot resistant and hard, so shipwrights continue to use it.

I will post pics!

 

[ZachAK]

Thanks, Bob! The progressive raker setting is pure genius. At 6 degrees the saw bit in like a hungry animal. Pretty much self-feeding until things dulled a little. If I had to do it again in purpleheart, I might back off to 5 degrees with my 066. A bigger saw would have been perfect at 6 degrees.

The timber was a 12" X 18" X 16'. That's a 2X12X20' on top of the timber. It weighed 1600 pounds and cost $3500 bucks. It's going into a big old wood seiner (fishing boat) as the bow stem—which is the timber right at the front of hte boat that both cuts the water and has a running rabbet on the trailing edge that all the planks attach to.


I really wanted to do more homework before potentially screwing up such an expensive timber. It went beautifully. By pure chance, the Alaskan mill depth was perfect from the last cut I made on a yellow cedar log. Here's stopping to gas up.


It was raining, and everything in the area was covered in wet purple sawdust. My shipwright buddy jokingly sang Purple Rain.


I forgot to bring the spray bottle, so I just ran the saw to see if I got resin build up. It wasn't bad, but here's what the bar looked like after:


The milling was flawless, much better than the circular saw pattern on the outside. That new Alaskan mill with the milled bar ends is great. My trusty old 066 ran like a champ. What a great feeling to have everything go so smoothly.
Moving the timber to a sawmill would have been very difficult, so the other option would have been to chunk up that upper 2 inches in little pieces with a skilsaw. Would have been a terrible shame, and likely taken all day.


All around, an easy job. The mill more than paid for itself again. Thanks Bob for getting me on progressive raker sharpening. I can't wait to try it on softwood. I'll start at 6 degrees and then work up to see what angle works best for different species.

 

[BobL]

Thanks, Bob! The progressive raker setting is pure genius..

Dunno about genius, but I'm glad it worked out for you.

At 6 degrees the saw bit in like a hungry animal. Pretty much self-feeding until things dulled a little. If I had to do it again in purpleheart, I might back off to 5 degrees with my 066. A bigger saw would have been perfect at 6 degrees.

If you drop the raker angle too far, even with freshly sharpened cutters the chain will just make a lot more fine dust and slow the cutting speed
Before you reduce the raker angle, what hook (top plate cutting angle TPCA) are you using?
If this is too low this generates a less supportive cutting edge which is why the cutters will dull faster. For chains that seem to go dull quickly I've found its better to maintain the same raker angle and increase the TPCA a touch. The saw won't self feed as easily BUT to regain that. put the log on more of a slope.
If you sharpen with a grinder this is easy - if you use a file let me know and I will tell you how to do this with files.

All around, an easy job. The mill more than paid for itself again. Thanks Bob for getting me on progressive raker sharpening. I can't wait to try it on softwood. I'll start at 6 degrees and then work up to see what angle works best for different species.

A few years back a member by the name of Mtngun cut all the softwood lumber for a decent size barn using an 066. He and I were experimenting with progressive sharpening at the same time. Using Lopro chain he was using up to 9º raker angle (this is extreme) on small softwoods and about 8º with regular chain.

 

[ZachAK]

Thank you, Bob for your response. Much appreciated.

I hand sharpen exclusively...though I could be talked into using one. I generally run a chain right out of the package and then sharpen down to about 10°.

I always try to mill downhill when practical, thanks to your suggestion.

I'd love to hear your thoughts on hand sharpening the top plate angle.

 

[BobL]

I'd love to hear your thoughts on hand sharpening the top plate angle.

Top plate "filing" angle or top plate "cutting" angle?

I assume you meant "filing angle? if so no problems hand filing although I do use a file guide with 10º marked on the guide.

 

[d1hamby]

I understand everything in the above diagram except the difference between the "Top Plate Cutting Angle" (TPCA) and the "Side Plate Angle" (SPA). Isn't the TPCA and SPA the same thing? How would they differ. I'm doing more research.

 

[ZachAK]

My apologies, Bob. I meant Top Plate Cutting Angle. That's where I usually go for about 10 degrees. This is the angle you see when looking straight down on the cutter, right?

Am I correct that the Top Plate Filing Angle is the small angle upward (relative to dead level) when filing? I've never given that angle much attention...I'd say I just copy what is usually there. The file tells you if you mess that up. That's a harder angle to name, but I would guess 5° from level. I've always filed the same for regular cross-cutting and for milling.

Again, thank you!
Zach

 

[BobL]

I understand everything in the above diagram except the difference between the "Top Plate Cutting Angle" (TPCA) and the "Side Plate Angle" (SPA). Isn't the TPCA and SPA the same thing? How would they differ. I'm doing more research.

The SPA seems to be a self generating angle depending on chain type, and the way the chain is sharpened, which is why I rarely talk about it.

The way I interpret it is as follows.
TCPA is the angle on the cutter edge.
SPA is the angle on the side plate immediately below the cutter edge

If you use a disc type grinder these angles will be the the same.
If you are sharpening square ground chain using the so called "goofy" file the SPA will be determined by the TPCA and the cross sectional profile of the file.
If you use a round file or sharpening tool, SPA will depend on the height of the file above the cutter and the radius of the file.
Chain manuals like the Oregon Chain Maintenance and Safety manual (Which is where I got that diagram from) show these angles for all their chains with some TPCAs and SPAs the same - many are different.
The 33 page Carlton Chain Guide document doesn't even mention SPAs.

If a round sharpening tool is used it seems near impossible to measure or set a specific SPA which is why I never bother to set a specific SPA and just accept whatever SPA is produced by an optimised TPCA.

My apologies, Bob. I meant Top Plate Cutting Angle. That's where I usually go for about 10 degrees. This is the angle you see when looking straight down on the cutter, right?

Look at the diagram again. Looking straight down from above, the angle of the cutter edge from the line perpendicular to the bar is the TPFA and is usually set at 10º for milling.

Am I correct that the Top Plate Filing Angle is the small angle upward (relative to dead level) when filing? I've never given that angle much attention...I'd say I just copy what is usually there. The file tells you if you mess that up. That's a harder angle to name, but I would guess 5° from level. I've always filed the same for regular cross-cutting and for milling.

Oregon call "the small angle upward (relative to dead level) when filing" , as the "file guide angle" - Look on the diagram.
Oregon recommend 10º for this angle for 3/8 and 404 ripping chain, but 0º for 0.325 chain.

Of the 30 chains listed on the Oregon chain manual ~2/3s specify a 10º angle, and the rest are 0º - these are mainly for smaller chains.
I don't fuss too much about this angle but I do try to keep it above zero i.e. have the file guide at a slight angle.
I do this even for the Lopro chain for which 0º is recommended - doesn't seem to slow it down any.

Oh yes and back to your original question on hand filing, well I haven't put any of my chains on a grinder to sharpen them since about 2012 so this might answer your question.

 

[ZachAK]

Thank you again, Bob! I'm finally following all the bits here. I'm following on the difference between TPFA and TPCA.

I see why the SPA and TCPA are so rarely talked about.

I'm headed out later to mill another couple inches off that purpleheart timber on the narrow face. Thanks again for all of your help.

 

[BobL]

No Worries Zak

I see why the SPA and TCPA are so rarely talked about.

SPA I agree, but TPCA (or "hook") should be talked about a bit more than it is.

And just to confuse you have a look at this.

The TPCA works in conjunction with the raker depth and together they determine how deep the cutter rocks into the wood lifting the chain off the bar before chain tension snaps the chip out.
In other words together they determines the size of the chip bite and hence cutting speed.
This pair of cutter parameters also determines how much the saw self feeds.
Too much of both and the power head will just bog down.
Too much TPCA and not enough raker depth will make a lot of dust and not feed
Too much Raker depth and not enough TPCA may still feed but will make a lot of vibe and will more prone to kickback, although kickback us not relevant when milling.
To get a saw that cuts fast and self feeds requires a bit of fiddling of the raker depth and the TPCA.

The other thing that the TPCA affects to a small extent is how quickly the chain goes blunt - to small a TPCA leaves less metal supporting the Cr cutting edge allowing it to break off easily. Slightly higher angles leave more metal behind supporting the edge, In really hard wood it may pay to raise the angle slightly, you will get more vibe bfs

Most folks just set their grinders and rakers to the manufacturers spec. TPCA and raker is arrived at by manufacturers assuming an "average" size bar and power head so the chain does not not make a lot of vibe and minimises the possibility of kick back. In theory a lower TPCA can be used on a larger power head especially On most chains except square ground chains and ripping chains the recommended TPCA angle is 60º.

On Ripping chains the recommended TPCA is 50º but Will Malloff who mills withe an 090 recommends 45º!
Not many operators who use files know how to change the TPCA with a file especially when using just a file does not even file a flat surface.
In fact talking about a TPCA as a constant/fixed "angle" is somewhat meaningless as the surface is a circle and so not a constant angle anyway.
This is why I prefer to use the term "hook" - a general term that takes into account how "pointy" the cutter edge is.
More "hook" means more "pointy".

The hook is changed when using a file, by slightly changing the amount of file that shows above the cutter.

In the image below the LHS red circle show how lifting the same size file slightly above its previous position reduces the hook.
The circles on the right shows how when at the same position relative to the top of the cutter, increasing the file size increases the hook

Changing the vertical position of a round file just slightly and consistently in an already shaped cutter is very hard to do by hand and is why I use an Oregon type file guide for all my touch ups.
Using a file guide also allows for the use of "different size files" in "file guides designed for different files".
Using a file e.g. a 3/16" in a file holder designed for a 7/32" file, this lifts the 3/16' file slightly further above the cutter edge and reduces hook.
Using a 3/16" in a file holder designed for a 5/32" file, this drops the 3/16' file slightly further below the cutter edge and produces more hook.

Unfortunately there are not a lot of file sizes and file holder sizes to play with and, for example, there is no Oregon type file holder for 13/64" files.
Pferd does have a 13/64 holder but it also includes a second file that does the rakers and it does them too shallow for my setup. I suppose I could use one without the raker file in it.
Mostly I use a 13/64" file in a 7/32" holder, this reduces the hook just a touch and reduces the cutter blunting effect when milling really hard woods. Sometimes use a 13/64" file in a 3/16" holder when milling softer woods.

The advantage of finessing the TPCA is it can be done at touchup stage simply by using different files in different file holders, whereas changing the raker depth down means if you go to far you have to remove a lot of cutter to effectively bring the raker up again.

 

[ZachAK]

Bob, That is an excellent explanation. Heck, even I followed!

At this point I just don't do enough milling to experiment with more than one variable, so I'll focus first on the progressive raker setting. That makes perfect sense about the hook using a smaller file. I would guess (wildly) that softwoods are fine to cut with a standard fairly sharp hook.

Years ago I ended up with a file that was a touch too large and the overly sharp hooked edge sure didn't hold up, though to my memory it was crazy sharp at first. Once I realized my error, it was a turd to get it filed back to where it should be with a correct-sized file.

I really appreciate how you've made me think about how each cutter works. I've spent my entire 25 year career working wood, and I never gave the cutting action of a chain much thought—which is ludicrous!

I better get ahold of Will Malloff's book again for some Winter reading.

 

[BobL]

Bob, That is an excellent explanation. Heck, even I followed!.

Great.

At this point I just don't do enough milling to experiment with more than one variable, so I'll focus first on the progressive raker setting..

Good move.

That makes perfect sense about the hook using a smaller file. I would guess (wildly) that softwoods are fine to cut with a standard fairly sharp hook..

Yep

Years ago I ended up with a file that was a touch too large and the overly sharp hooked edge sure didn't hold up, though to my memory it was crazy sharp at first. Once I realized my error, it was a turd to get it filed back to where it should be with a correct-sized file.

That's why I still use a file guide.

I really appreciate how you've made me think about how each cutter works. I've spent my entire 25 year career working wood, and I never gave the cutting action of a chain much thought—which is ludicrous!.

See if you can get hold of the Carlton chain manual. It is the only document that I have seen that really explains how chains work properly. After reading it it changed the way I looked at chain and so I decided to start more or less from scratch and it took me a while to really come to grips with it. At the time I had just started to cut really hard wood and it was timely for me to have all this info and was able to put all my experimental science training to use - try this, measure that, change this, go back to square one, move to square two, jump a couple of steps etc. Suddenly I hit "the zone", self feeding saw, improved cutting speed, reduced blunting of cutters and I knew I was getting somewhere.

I better get ahold of Will Malloff's book again for some Winter reading.

Good idea. I don't quite agree with everything in the book but otherwise its a very useful book.

 

[ZachAK]

Thanks, Bob! You've inspired me to try a file guide again.

I found the Carlton Chain Manual if anyone wants to look at it online. A great read:

http://www.carltonproducts.com/pdfs/carltonsafetymaintmanual_en.pdf

Best wishes from Alaska,
Zach

 

[d1hamby]

On page ten it shows to sharpen some chain, like K1L, at a 10° angle instead of a 90° angle perpendicular to the bar. Sharpening at a 10° angle would almost be straight up and down, parallel to the bar. Shouldn't it be an 80° angle?

 

[BobL]

On page ten it shows to sharpen some chain, like K1L, at a 10° angle instead of a 90° angle perpendicular to the bar. Sharpening at a 10° angle would almost be straight up and down, parallel to the bar. Shouldn't it be an 80° angle?

The reference position is usually the line perpendicular to the bar so all the 90º values should be 0º.