|
Carving
Tools (1)
Chainsaw Carving Bars. |
The
pictures below show two carving bars both 16", one a "dime tip"
on a Stihl MS170 (left) and the other a "quarter tip" on a Stihl
MS200. These bars are extremely useful accessories for anyone involved
in large scale woodcarving. In the hands of someone well used to handling
chainsaws, this bar can be manipulated in a very delicate manner. It can
cut fairly tight curves and rout out deep, comparatively tight holes.
One can write using the tip of the bar in a way that is impossible with
a standard bar. There is virtually no kickback making them extremely safe
to use in comparison to a standard guidebar. I also use a 12" version
of either bar for close up, more controlled, detailing.
As
a word of warning however, it is not advisable to start using a carving
bar as a complete novice in the handling of chainsaws. If anyone was to
attempt to try this, then subsequently try to use a standard bar, they
run a serious risk of being caught by surprise and injured by kickback.
Below is a close up of the tip of my 16" carving bar, it has a radius of about 12mm (quarter tip). The 12" bar has a radius of about 8mm (dime tip). These bars are made in North America and are very well engineered. They are made from one piece of steel (rather than being laminated), the rails are triple induction hardened and the tip has a sizable section of stellite welded into it (as can be seen in the photo). They are solid nose bars and the gauge of the bar groove is 0.050". When first put to use it is advisable to run the chain relatively slack (i.e.hanging down with the tie straps just off the bottom bar rails) compared to the standard tension used with a solid nose bar. Initially there is a tendency for the bar to heat up a lot while both bar and chain are bedding in. This causes the chain oil to burn black which is then thrown off onto the carving making black lines. This passes after a few days of carving, then the chain can be run a little tighter and the black lines get fewer (as long as the saw oiler is working efficiently).
The choice of chain is also important with these carving bars. A friend
of mine Ed Robinson,
a chainsaw carver based in Northumberland (who sold me my first carving
bar) reckons that a 3/8" pitch chain works fine on the Quarter tip
bar as long as it isn't one of these consumer chains with the bumper tie
straps. He works mostly in softwoods and generally does all his work with
the carving bar from beginning to end. I originally tried my bar with
the 0.325" pitch chain but found that it didn't cut very smoothly
and didn't bore into the wood very effectively in the timber I used, which
was mostly Beech and Sycamore. I decided to order the special 1/4"
pitch chain from America which is recommended for the carving bars. It
has no anti-kickback features on it as it doesn't require them for such
a narrow nosed bar, which means that it cuts and bores into the wood relatively
well (hardwoods that is). I don't believe it's possible to obtain 1/4"
pitch 0.050" gauge chain without anti-kickback features in the U.K.
any more unless you can find a dealer with some old stock.
The
"Dime tip"carving bars must be run with 1/4" pitch chain
as the nose of the bar is far too small for the larger pitch chain to
get round. The drive links would probably all bundle up against each other
at the groove tip as well.
In
order to run this type of chain it is essential to have the appropriate
sprocket conversion to 1/4" pitch on the chainsaw. The sprockets
are sold according to the make and size of saw, the list being given by
the supplier Baileys-Online.
They only fit a certain drive shaft diameter, that of the smaller saws.
I found that the model of Husqvarnas I used all had press fit bearings
in the sprockets they were supplied with, so when I received my 1/4"
sprocket, the bearing would not fit it. I had then to order a bearing
for the sprocket from Baileys. Though the small Sthils seem to have the
loose bearing that works with the 1/4" sprocket as well as the sprocket
supplied with the saw. If in doubt, remove the sprocket from the saw and
see if the bearing slips out easily. If it does and it comprises of a
little plastic cage with the needle bearings captive in it, then there
is a good chance that it will do for the new 1/4" conversion.
Tooth Modification on Chains for Carving Bars
The
carving bars currently available have two tip sizes, the Dime and the
Quarter. They are so called because the radius approximates that of the
two USA coins of the same name. The Quarter tip has a radius of approx
12.5mm and the Dime, a radius of approx. 8.5mm. Both of these guide bar
tips offer an extremely tight curve for the chain to follow, as well as
cut. All of the chains available, that are recommended for these types
of guide bars, fail to cut efficiently at the nose of the bar. The reason
for this is that the chains in question have been designed for bars with
a far bigger radius at the tip as compared with carving bars. The top
plates of the cutting teeth on all of these chains are too long for the
radius of curve/cut dictated by the carving bars.
Shown here is a scaled up picture profile of a new quarter inch pitch cutter from a saw chain as it would sit on the carving bar while travelling around the tip of the bar. The path the cutting edge takes is marked in green; the path the heel takes is marked in red. The tooth is shown as it would be on the Dime Tip. The dimensions and the paths taken by the same tooth on a Quarter Tip are also indicated.
It
can be seen that the path the cutting edge takes is within that of the
path of the tooth heel. This would result in the failure of the tooth
to bite into the wood. It would therefore be incapable of achieving a
plunge (boring) cut. In order to rectify this problem the shape of the
tooth must be modified.
By removing the rear portion of the tooth (heel), the cutting edge is able to actually contact the timber. This enables it to cut far more efficiently and with considerably less friction. The figure of 35% of tooth to be removed is a minimum. It might also be beneficial to reduce the depth gauges of the chain slightly more than that recommended by the manufacturer (DO NOT REMOVE THE DEPTH GAUGES).
These modifications relate only to the use of chains on carving bars and
should not be made to any chain used on standard chainsaw guide bars.
Bumper drive links do not seem to adversly effect the "bite" of teeth on a carving bar. However, bumper tie straps (as can be found on chain supplied to the consumer market) do interfere. Consumer type chain should not be used on carving bars.
Bumper drive links do not seem to adversly effect the "bite" of teeth on a carving bar. However, bumper tie straps (as can be found on chain supplied to the consumer market) do interfere. Consumer type chain should not be used on carving bars.
A supplier of carving bars and associated equipment is: