Workshop Fitting Out & Project Pages.
An Electric Chainsaw Mill (Part 1).
This article is on three pages. This first page
discusses the practical options and limitations when
considering using an electric chainsaw for milling, and
describes how the Oregon CS 1500 electric
chainsaw was fitted to a small 24" Royston
24" Portable Chainsaw ("Alaskan") Mill.
The second page
describes how a jig was designed and built to support
the chainsaw mill (with chainsaw mounted) as well as
safely supporting and securely holding the wood being
milled. Note that this jig although designed for the
Oregon CS1500 electric chainsaw, would be
equally usable with a small petrol driven
chainsaw/"Alaskan Mill" combination.
The third page
describes how the jig was assembled & operated.
Why consider using an Electric Chainsaw for
milling?
As a wood-turner and small-project woodworker, I obtain
a variety of hardwoods and some softwoods such as Yew
and Pine from tree surgeons, arborists, farmers, park
& estate managers who, when felling or pruning,
kindly look out for unusual timbers with attractive or
unusual features or figuring. Initially I successfully
converted such timber using a 1.9 Kw Bosch mains
(UK) powered electric chainsaw with a 16" (40 cm) guide
bar. Once cut to a manageable size, conversion is
completed using a medium sized bandsaw (capable of
cutting to a maximum depth of 190 mm (7½"), to
cut boards and circular turning blanks up to about 16"
(405 mm) diameter.
Instead of processing the wood by free cutting (which
produces a considerable amount of waste), I wanted to
use the chainsaw with a small "Alaskan Mill" to produce
more regular slabs of wood which are much easier and
safer to free-cut on a bandsaw and which will give a
higher yield of usable timber. The other major
constraint in converting this timber is working in a
residential area where the noise and pollution
generated by a petrol powered chainsaw is prohibitive.
The aim was to continue using an electric chainsaw both
for free cutting but also for mounting in a small
"Alaskan Mill".
The cost of so-called "Alaskan" chainsaw milling
attachments has come down in price. Currently (January
2018), It is possible to purchase a small (24"
capacity) well-made mill for less than 80 GBP. These
milling attachments are designed to be used with
powerful petrol (gasolene) driven chainsaws but this
article explores the possibility of occasionally using
an electric chainsaw with a small mill.
SO DOES AN ELECTRIC CHAINSAW HAVE THE REQUIRED POWER TO
DRIVE AN "ALASKAN MILL"?
The following table compares the required power ratings
for petrol powered milling to the available power of
electric chainsaws.
|
Minimum required power ratings for chainsaws
driving an "Alaskan Mill" with the chainsaw Guide
Bar lengths listed in column 1. (data adapted
from the Granberg International website.)
|
Guide bar length
|
Maximum Width of Milled Boards
|
Approximate Power Required for Petrol
(Gasolene) powered chainsaws.
|
Approximate Power Ratings for Mains Powered
* (UK) Electric Chainsaws
|
16" - 18" Guide Bar.
|
In an Alaskan Mill these will yield boards of 8" -
12"
|
50 cc, (about 3.2 hp or 2.4 kw) to 60 cc
(about 4.0 hp or 2.9 kw) is considered to be
the bare minimum for light to medium milling of
soft and hardwoods.
|
Electric chainsaws range from 1.8 kw (about 2.4
hp), to an absolute maximum of 2.4 kw (about
3.2 hp).
Most top-rated electric chainsaws have a maximum
guide bar length of 16" (40 cm) with a few
supplied with an 18" (45 cm) bar. Even a
top-rated 2.4 kw 3.2 hp electric chainsaw
will have a power rating equivalent to the
bare minimum of the recommended power
required to drive an Alaskan Mill.
|
20" - 24" Guide Bar.
|
In an Alaskan Mill these will yield boards of 14" -
20"
|
Not applicable as 18" (45 cm) is the
absolute maximum length of the supplied guide
bars and the required power (for bars in excess
of 18"), is substantially beyond that of an
electrically powered chainsaw using a domestic
supply.
|
28" - 30" Guide Bar.
|
In an Alaskan Mill these will yield boards of
between 22" - 26"
|
60 cc, (about 4.0 hp or 2.9 kw) to 64 cc
(about 4.2 hp or 3.1 kw).
|
32" - 36" Guide Bar.
|
In an Alaskan Mill these will yield boards of
between 26" - 32"
|
70 cc, (about 4.6 hp or 3.4 kw)
|
42" - 48" Guide Bar.
|
In an Alaskan Mill these will yield boards of
between 36" - 44"
|
90 cc, (about 6.0 hp or 4.4 kw)
|
50" + Guide Bar.
|
In an Alaskan Mill these will yield boards of
between 50" - 52" +
|
120 cc, (about 20 hp or 14.9 kw)
|
|
*Note that battery powered
chainsaws are not considered here, as even the most
powerful models with 18" guide bars are rated at
about 1.2 kw, which is significantly below that of
the majority of mains powered models.
|
The specifications listed above clearly show why
serious electric chainsaw milling is not a viable
option. But from the table above it seemed that
small-scale milling with a 2.4Kw electric chainsaw
driving the chain round an 18" guide-bar was possible
and worth trying.
CHOICE OF PORTABLE MILL
I purchased a Royston 24 inch capacity "Alaskan"
Portable Chainsaw Mill. These so called "Portable
Chainsaw Mills" are much cheaper (Chinese made) copies
of the genuine Alaskan Mills first developed in the
1960's by Elof Granberg and currently manufactured by
the company that bears his name Granberg International. I'm not
sure how the copies compare in quality to the "genuine"
Alaskan Mills, but they are considerably cheaper (For
example a Royston copy 24" mill is 77.98 GBP as
against about 300.00 GBP for an equivalent genuine
Granberg Alaskan Mill, December 2017 prices).
The Royston (Chinese) copies seem reasonably
well constructed and to be a good option for an
occasional use mill.
(Click on image for larger view)
Royston Portable Chainsaw Mill ("Alaskan
Mill").
Photograph of an assembled 24 inch Royston
Portable Chainsaw Mill.
Choice of Chainsaw.
Of the two electric chainsaws at my disposal the
Oregon CS1500 was the only viable option.
The Bosch AKE 40-19 S chainsaw is
underpowered (rated at 1.9 Kw), has a 40cm (16") guide
bar with a gauge (thickness) of 0.043" (1.1mm). This
gauge is too thin to support the weight of the chainsaw
powerhead of about 4 kg (9 lb), which is what it would
have to do when mounted in "Alaskan Mill" mode. It
would be dangerous to attempt to use this saw with the
default bar in a mill.
(Click on image for larger view)
The Oregon CS1500 Electric Chainsaw.
The Oregon CS1500 has the following
specifications:
|
(Click on image for larger view)
Photograph of an Oregon CS1500 Electric
Chainsaw.
|
|
Model No:
|
CS1500
|
|
Guide Bar (effective) Length:
|
Advertised as 45 cm (18"), this is currently (2018)
about the maximum effective length of guide bar
available for an electric chainsaw. The guide bar
mount is A041 and the supplied bar is an
Oregon Double Guard 91, part number
180SDEA041, designed for Lo Pro ⅜" pitch chain
of 0.050" gauge with 62 drive links. It is described
as a lightweight, laminated reversible bar for the
occasional and hobby user. Small radius nose reduces
kickback. It has a maximum width of 2⅛"
(54mm) and can be reversed (can be flipped), by
unscrewing the chain tensioner and re-attaching on
the other side.
|
|
Power Output (kw):
|
2.4 kw (3.2 hp, currently [evaluated in 2018], the
maximum rating for a UK mains powered chainsaw)
|
|
Power Voltage Supply (UK Mains):
|
240 Volts ac
|
|
Total Product Weight:
|
5.7 kg (12.6lb)
|
|
Oregon chain:
|
The guide bar will accept any chain that's Lo Pro
⅜" with a gauge of 0.050" (1.1mm), with 62
links. However, the CS1500 chainsaw comes with the
Oregon PowerSharp® Chain and is unique in
having an automatic chain sharpener built into the
powerhead. Oregon part number 571037 (includes
replacement chain & stone which must be replaced
together), and Part Number PS62 (chain only). Note
that if chain other than the PowerSharp® is
fitted, the on-board powerhead sharpening stone must
be temporarily removed (unscrewed), as it is only
compatible with the PowerSharp® chain and serious
damage can result if used with a different chain
type.
Other compatible (non PowerSharp®) chains
include Oregon low kickback chain (Part No.
91P062E), Oregon Lo Pro Ripping Chain (Part
No. 91R062E), Stihl PMX Ripping Chain (Part
No. 3614), Granberg Ripping Chain ⅜"
Lo Pro .050. (part No. G729-2).
|
Fitting the Oregon CS1500 to the Royston 24
inch Portable Chainsaw Mill
The CS 1500 has one of the maximum power ratings for an
electric chainsaw (2.4kw), and is one of the few designed
to operate with an 18" effective length (0.050" gauge)
guide bar which is certainly robust enough to support the
powerhead when mounted in an "Alaskan Mill". The problem
lies in the 54 mm width of the bar. The narrow bar width
is not wide enough to extend outside the width of the
"Alaskan Mill" clamps. This is shown in the photograph
below.
The Oregon CS1500 Chainsaw Guide Bar is too
narrow!
(Click on image for larger view)
The Oregon Double Guard guide bar as supplied
with the CS1500 Chainsaw. Note the two holes of 6 mm
& 7 mm diameter drilled through the bar near the
nose. These holes (an original feature of the bar),
facilitate the attachment of a PowerSharp®
sharpening jig to the guide bar to enable chain
sharpening when the saw is running. The 7 mm
diameter hole was subsequently used (in part) for
attaching the guide bar to the Royston Chainsaw
Mill clamping system (See description below).
(Click on image for larger view)
The problem of clamping the CS1500 Guide Bar in an
"Alaskan Mill" clamp.
The guide bar is too narrow for the clamp jaws which
would pinch the rails. The running chain could also
impact with the jaws of the clamp, especially if there
was any slippage of the guide bar in the clamp jaws
when the "Alaskan Mill" was in operation.
Would a wider guide bar be the solution?
One possible solution considered was to replace the
existing bar and use something like a WoodlandPro
18" ArborMAX® Chainsaw Bar (Part number WPA 18 UM50).
The specification is:
Effective Length 18" (45 cm), Pitch Low Profile (⅜"
Picco), Gauge 0.050" (1.3 mm), Drive Link Count 62, Nose
Sprocket 9 Teeth, Weight 1.40 lbs (0.64 kg).
The description states:
"The wide contour body and large radius
nose makes this bar much stronger and longer lasting
than standard consumer bars. These bars are made of three
silicon manganese alloy steel plates that are
electrically welded together. The center plate has been
hollowed out to reduce weight. Rails are induction
hardened for a long life. Sprocket nose tip contains high
quality Swiss bearings held in place with 4 sturdy
rivets."
(Click on image for larger view)
The WoodlandPro Arbormax Chainsaw Guide
Bar.
The broader form of this bar and sturdier construction
would make it much more compatible with the clamping
system of an "Alaskan Mill". Unfortunately these bars are
currently unavailable in the UK. Also the downside of
using a broader bar, is that it would diminish the
performance of the electric saw, requiring more power to
drive the chain effectively.
THE OPTION OF BOLTING THE EXISTING CHAINSAW GUIDE BAR
TO THE PORTABLE CHAINSAW MILL
I decided to abandon conventional clamping and try an
alternative method of attaching a chainsaw guide bar to
an "Alaskan Mill" by bolting it in place instead of
using clamps. This is a tried and tested method as
shown on this Instructables; Chainsaw Mill Build, Use
& Tips N Tricks very informative and helpful
website.
The author of Chainsaw Mill Build, Use & Tips N
Tricks argues strongly against using clamps for the
following reasons:
- Clamps add weight.
- Clamp on systems are more complicated and have more
bolts that could potentially come loose.
- They take longer to attach and remove from the
guide bar because you have to carefully position them
while tightening the screws.
- In contrast bolt-through attachments self-align the
mill onto the guide bar.
- Clamp-ons are usually more bulky, and take up more
room. And they necessarily pinch the bar so tightly
that they can't be anywhere near the nose area or they
would jam up the sprocket. This means the effective
cutting width of a given guide bar is much reduced.
- And lastly but importantly, clamps prevent you from
quickly removing and replacing your chain, while the
saw is mounted in the mill.
Photographer: "Bongo Drummer" (Click on image for
larger view)
LARGE CHAINSAW GUIDE BAR BOLTED TO AN "ALASKAN
MILL"
This is a modified photograph from the Instructables website of a
Stihl MS440 petrol driven chainsaw with the
guide bar attached using two bolts (one at each end
of the bar), into the aluminium frame of a custom
built "Alaskan Mill". The M8 bolts are made of high
tensile steel and tapped into the frame of the "mill"
to a depth of 50 mm. The actual length of the
Stihl Rollomatic ES(uper) guide bar is not
given but the top and bottom aluminium rails of the
"mill" (in the photograph), are given as 900 mm
(35½") long, so a guesstimate of the effective
length of the bar might be 28" (710 mm).
Photographers pseudonym: "Bongo Drummer" (real name
unknown so a proper acknowledgement can't be made)
For the Oregon 18" Double Guard guide bar the
bolting modifications were done in three steps.
Step 1 was to drill one 6mm diameter hole near
the tail of the chainsaw guide bar (as a companion to
the existing 7mm diameter hole near the nose of the
guide bar).
Step 2 was to drill two corresponding 6mm and
7mm diameter holes in the front and the rear clamps of
the Royston Chainsaw Mill (one hole in each).
This would then allow the guide bar to be bolted to the
mill front and rear upper clamping plates.
Step 3 was the assembly of the CS1500 chainsaw
guide bar to the Royston chainsaw mill"
STEP 1: DRILLING THE CHAINSAW GUIDE BAR
The unmodified Oregon Double Guard chainsaw
guide bar (Oregon Part No.180SDEA041).
(Click on image for larger view)
The Oregon Double Guard guide bar as supplied
with the CS1500 Chainsaw. Either of the two
(PowerSharp® sharpener mounting) holes of 6 mm
& 7 mm diameter passing through the bar near the
nose, could be used for bolting to the Portable
Chainsaw Mill, but the 7 mm diameter hole, nearest
the nose of the bar was used, thereby maximising the
potential cutting width in the milling process.
A new hole was drilled (See photograph below),
towards the tail of the bar to enable a second point
of attachment by bolting.
(Click on image for larger view)
MARKING THE POSITION OF A REAR BOLTING HOLE IN THE
CHAINSAW GUIDE BAR - 1
This shows how the position of the second (rear) 6mm
diameter bolt hole was marked out. With the chainsaw
guide bar plus chain fitted to the saw, the
rear clamp (25 mm wide), of the Portable
Chainsaw Mill is positioned on the guide bar just in
front of the spike bumper (with about 5 mm to spare),
and a pencil line drawn across the front edge.
(Click on image for larger view)
MARKING THE POSITION OF A REAR BOLTING HOLE IN THE
CHAINSAW GUIDE BAR - 2
Measure back from the first line, half the width of
the Portable Chainsaw Mill clamp (25 mm ÷ 2 =
12.5 mm), and draw a line parallel to the first line.
Draw another line to intersect this at half the width
of the chainsaw guide bar (54 ÷ 2 = 27 mm).
Where the two lines intersect on the guide bar is the
position of the additional bolt hole.
(Click on image for larger view)
DRILLING A REAR BOLTING HOLE IN THE CHAINSAW GUIDE
BAR
This is best done with the guide bar clamped to the
table of a drill press. Use Cobalt twist drill bits.
A centre-punch was used to mark the position of the
hole at the intersection of the two pencil lines (to
ensure the drill bit registered in the exact
position). The drill press was set to its lowest
speed and a 2 mm pilot hole drilled. The hole was
then widened in increments of a millimetre to the
final diameter of 6 mm. Oil was added whilst drilling
to lubricate the drill bits. Drilling this single
hole was the only modification made to the guide bar.
(Click on image for larger view)
DISTANCE BETWEEN THE TWO BOLTING HOLES IN THE
CHAINSAW GUIDE BAR
For the benefit of anyone replicating this adaption
(using this Oregon 18" 180SDEA041 guide bar), the
distance between the existing (nose) 7mm hole and new
(rear) 6mm bolt hole is 355mm (14"). In the
Royston Chainsaw Mill, this gives an effective
maximum cutting width of 320mm (12⅝").
STEP 2: ADAPTING THE ROYSTON 24 INCH PORTABLE
CHAINSAW MILL
This required two new holes (6mm and 7mm diameter) to
be drilled in the front and the rear clamps of the
Portable Chainsaw Mill (one hole in each). This allowed
the chainsaw guide bar to be bolted to the mill front
and rear upper clamping plates
In addition, one of the rear curved metal fenders
(shown on the top right of the photograph) had to be
shortened by sawing off with a hacksaw to allow a
spanner to be inserted into the box section to tighten
the new M6 fixing nut and bolt.
(Click on image for larger view)
THE POSITIONING OF NEW ATTACHMENT POINTS IN THE
PORTABLE MILL CLAMPS
Two new attachment holes in the upper parts of the
mill rear and front clamps were drilled to enable the
CS1500 chainsaw guide bar to be bolted on instead of
being clamped.
(Click on image for larger view)
DRILLING A NEW ATTACHMENT POINT ON THE UPPER PART
OF THE MILL REAR CLAMP
The position was marked with a centre-punch (to make
a registration point for the drill bit). It was
impossible to mount on the drill press, so was
clamped using a Workmate portable bench vice
instead, and drilled freehand. A 2 mm diameter drill
bit was used to make a pilot hole (low drill speed),
and was widened in increments of a millimetre to the
final diameter of 6 mm. Oil was added whilst drilling
to lubricate the drill bits. The procedure was
repeated for the front clamp but drilled out to a
diameter of 7mm (to match the pre-existing 7 mm
diameter hole in the toe of the guide bar). Set the
drill speed to slow and use Cobalt twist drill bits
which are designed for drilling through metal.
STEP 3: ASSEMBLY OF THE CHAINSAW GUIDEBAR TO THE
ROYSTON 24 INCH PORTABLE CHAINSAW MILL
With the modifications completed to the chainsaw guide
bar and the clamps of the mill, the next stage was to put
everything together by bolting the chainsaw guidebar to
the Royston Chainsaw Mill clamps.
(Click on image for larger view)
COMPONENTS FOR ASSEMBLY
All the components are shown here. The large penny
washers ensure that the narrow guide bar and chain are
kept well clear of the metal of the mill clamps.
(Click picture for larger animation)
|
Animated overview
This animated sketch shows how the front
fastening bolt was secured with the M7 nut &
bolt inside the square tubing of the mill clamp.
(Click thumbnail image for larger animatiom)
|
(Click picture for larger view)
|
Sketch of assembled components
This sketch shows in detail how the front
fastening M7 nut & bolt secured the front of
the chainsaw guidebar to the square tubing of the
mill clamp. The same technique was used for the
M6 nut & bolt fastenings securing the rear of
the guidebar to the mill clamp.
(Click thumbnail image for larger picture)
|
PUTTING IT ALL TOGETHER
The most difficult part of this operation was locating
and tightening the M6 & M7 nuts in the square
tubing of the mill clamps. Details are outlined below.
(Click picture for larger view)
|
Components laid out on a workbench, ready for
Assembly
Tools needed include a double-headed long reach
spanner with a ring at one end to fit a 10 mm
headed (M6 bolt), and an 11 mm ring at the other
end to fit over the head of an M7 bolt. It was
essential that both ends of the spanner would fit
inside the clamp box sections (20 mm width). A
shorter normal sized double-headed spanner (also
10 mm & 11 mm capacities) and 2 wooden wedges
helped to guide and keep the long reach spanner
(and cradled nuts) in position within the box
section. These were used when inserting the bolts
through the chainsaw guide bar, penny washers and
through the top of the box section to engage the
nuts within the box section. The way that this
was carried out is shown in the following two
video clips.
(Click thumbnail image for larger view)
|
thmb.jpg "[Bolting the chainsaw guidebar to the mill - part 1 - click to view video]")
(Click picture to view video)
|
Bolting the chainsaw guidebar to the mill - part
1
Video demonstrating how the front end of
the chainsaw guidebar was bolted to the chainsaw
mill.
(Click thumbnail image to view video)
|
thmb.jpg "[Bolting the chainsaw guidbar to the chainsaw mill - part 2 - click to view video]")
(Click picture to view video)
|
Bolting the chainsaw guidebar to the mill - part
2
Video demonstrating how the rear end of
the chainsaw guidebar was bolted to the chainsaw
mill.
(Click thumbnail image to view video)
|
Note that this method of attachment by bolting
results in the lower parts of the mill clamps not being
needed.
COMPONENTS ASSEMBLED
(Click on image for larger view)
|
Bottom view of assembled chainsaw with the
Royston 24 inch Portable Chainsaw
Mill
This photograph shows the CS1500 chainsaw attached
to the Royston Mill by means of two (M6
& M7) bolts through the guide bar to the clamps
of the mill. It's crucially important to ensure
that when the nuts & bolts are tightened, there
is no pinching of the rails or impairment to the
rotation of the nose sprocket or anything else to
cause impediment to the free circulation of the
chain round the guide bar.
(Click thumbnail image for larger view)
|
(Click on image for larger view)
|
Side view of assembled chainsaw with the
Royston 24 inch Portable Chainsaw
Mill
In this photograph, a side view of the attachment
shows how the penny washers give a safe separation
between the cutting chain and the clamps of the
mill. This also shows the maximum cutting width of
the guide bar when mounted in the mill which is 320
mm (12⅝"). (Click thumbnail image for larger
view)
|
VIDEO OF A DUMMY RUN OF THE CHAINSAW WITH THE
ROYSTON 24" PORTABLE CHAINSAW MILL.
Having completed the assembly of the Chainsaw to the
Royston Mill, the next step was to run the saw
to ensure that the chain ran freely within the
framework of the mill. Note that the shield guarding
the tip of the guide bar is fitted for this test. For
reasons of safety, it is very important to ensure
that this is fitted whenever the "Mill" is operated.
(Click on image to view video)
What type of chain to use?
Having completed and tested the assembly of the chainsaw
to the Royston Mill, before using the mill it was
necessary to decide which sort of cutting chain to use. A
number of available choices include:
-
Oregon Powersharp® chain (as supplied with
the chainsaw), (Part No. PS62)
-
Oregon low kickback chain (Part No. 91P062E)
-
Oregon Lo Pro Ripping Chain (Part No. 91R062E)
-
Stihl PMX Ripping Chain (Part No. 3614)
-
Granberg Ripping Chain 3/8 Lo Pro .050. (part
No. G729-2)
Note that although the Oregon CS 1500 chainsaw
can be used with any of the chains listed above, the
on-board chain sharpening system can ONLY be used with
the Powersharp® chain and under no circumstances
should it be used with any of the other chains
listed.
Ripping Chain Description
This refers to a special purpose semi-chisel saw chain
with shallow angle cutters that is only used in chainsaw
mills to make planks. The cutter angles (are usually at
10o, whereas with conventional chain the
cutter angles are 25-35o), enable the chainsaw
to cut smooth planks with a good quality finish to the
cut timber. The rip cut is along the grain; essentially,
"ripping" the wood apart, like splitting it with an axe,
except the cut is straighter as some of the wood fibres
are sliced. The rip cut has a tendency to bind the
cutters of the chain as the wood fibres relax. Ripping
chain is ALWAYS semi-chisel.
As the milled wood will be used mainly for producing
turning blanks, speed of cut has a higher priority over
quality of finish. The crucial question is whether
ripping chain eases the load on the chainsaw when
milling? I cannot find a definitive answer to that
question but one quote stated "If speed of cut
rather than quality of finish is the aim, then full
chisel normal chain will do the job fine, and cut
faster". On the basis of that quote I therefore
decided to begin milling using the default Oregon
Powersharp® chain, possibly experimenting with
ripping chain at a later date.
The other big advantage of using Powersharp® chain
is the on-board sharpening system which makes sharpening
the work of a few seconds!
DEVISING A JIG TO SUPPORT THE PORTABLE CHAINSAW MILL
AND THE TIMBER BEING MILLED
The next step was to design a jig to support the
Royston Mill (with chainsaw mounted) as well as
safely supporting and securely holding the wood being
milled. Note that this jig although designed for the
Oregon CS1500 electric chainsaw, would be
equally usable with a small petrol driven chainsaw
/"Alaskan Mill" combination.
The design and construction of this jig is described
HERE
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