The blade and the internal reciprocating mechanism in the machine are
rigidly connected via the chuck. While the body of the saw vibrates
as a result of being connected to this reciprocating combination
How could one end of this reciprocating combination of parts move,
and not the other ?
I haven't snipped or chosen to ignore the remainder of the points
which you make to which I'd be happy to return. However to save
any further misunderstandings I think it best to proceed one
point at a time.
So how could one end of this reciprocating combination of parts -
the blade and the mechanism move, and not the other ?
It can't - it must obey the laws of conservation of momentum.
if you simplify it to two connected masses - the saw on one end and the
blade on the other. The saw is alternately pushing and pulling on the
blade - accelerating and decelerating it. It having a low mass will
accelerate quickly. There will be a matched reaction in the movement of
the saw body, but it will be at a much reduced velocity due to the
substantially greater mass of the saw.
As you add load to the blade, you are increasing its effective mass and
inertia. So the velocity of the matched reaction of the saw will
increase (i.e. increasing the vibration level).
So if you take this to its ultimate conclusion where you add enough load
to the blade to in effect fix its position (say lopping a tree branch
that closes on the blade), then you have the mass of blade plus a tree
on one side, and only that of the saw on the other. The vast bulk of the
movement will now be the saw body itself - causing substantial and very
uncomfortable levels of vibration.
Take the example above when cutting a branch. Assuming the blade is
still free to move, you get most movement in the blade, and some in the
saw. If you now push the saw's rest against the branch you are coupling
the mass of the saw to that of the branch. So the momentum equation has
blade and friction "mass" on one side, and saw body + tree on the other.
So you have massively increased the inertia of the saw body, and thus
reduced the velocity of vibration.
(Also for half of the cycle (the "pulling stroke") you now have closed
system where the pull on the blade is exactly matched by the push
against the saw's rest - eliminating acceleration of the saw body in one
Indeed. This is the normal vibration I've been talking about
In other words where the blade snags or sticks in the work, a possibility
you suggested earlier. A situation which is fairly easy to replicate simply by
taking hold of the saw, clamping the blade in a bench vice, and squeezing the
trigger. Whereby it's the body of the body of the saw which oscillates violently
back and forth in the hands of the operator against the blade, which is held
firmly in the vice. Causing as you say "substantial and very uncomfortable
levels of vibration"
But any and all of which would of course be brought to an immediate halt,
by the simple expedient of the operator simply releasing the trigger.
So that, if you're seriously suggesting that vibration from this source
represents a very real problem as compared with normal vibration, or
any sort of problem at all for that matter, then its necessary for you
to come up with some sort of satisfactory explantion as to why,
following that initial kick, any operator of that saw would be
foolhardy enough not to release the trigger. Which most certainly
would be the instinctive reaction I'd have thought.
Or leaving instinct aside, why would they ever think of doing this
(not releasing the trigger) a second time ?
As with the blade firmly stuck in the work, the whole weight of
the violently oscillating saw, as held in hands of the operator,
is now supported at the point where the blade enters the work.
Greatly increasing the likelihood that it would snap-off at this
point; making the subsequent removal of the broken tip from the
work all the more difficult.
Why would anyone ever want to do this ? Why wouldn't they simply
release the trigger at the first opportunity ?
Indeed. In such circumstances the combined mass of the saw and the
branch/tree would easily dwarf the mass of the oscillating blade and
would thereby clearly reduce vibration by a substantial degree. Were
it possible that is, to clamp or otherwise securely attach the shoe/guard
or any part of the saw body to the work. Although not in this
case with the aforementioned bench vice, unfortunately
As it is however, in order to keep the vibrating body
of the saw in close contact with the work requires considerable effort
on the part of the operator. In fact it amounts almost to a form
of torture. Slacken your effort in any way and the vibrations
will get a lot worse, an awful lot worse, and we don't want
that, do we ? So push!
This is the reason why using such saws for any length of time is
so very tiring, and why other means short of clamping the saw to
the work - using counterdirectional shafts or damping the shaft at
either end of its travel - have been sought in order to lesson
the normal vibration which is the real bugbear of such saws.
As I originally said; and to which you took such exception
for some unaccountable reason, which is yet to be fully explained.
Or if you don't want to take my word for it, it's safe to assume
I'd imagine that all the people who've been using such saws on a
regular basis for protracted lengths of time since the 1950's can't
have all been mugs. Similarly the competing manufacturers of such saws.
And that had there been some simple solution to this problem as might
be suggested nowadays on websites, but formerly perhaps in articles
in DIY magazines and the like, then this would have become standard
practice decades ago.
You seem to be trying to put words into my mouth... I use the blade
jammed illustration simply as an example of one extreme of the various
possible scenarios. The other extreme being saw held and braced, with
the blade in free space. One will result in the minimum level of
vibration likely to be experience, and the other the maximum. Normal use
will be somewhere between those two extremes.
Of course. (lets ignore the trigger lock "on" situation for the moment).
Well having got the blade snagged, you now need to free it. Most I would
expect will do as I do, adjust the position of the blade in the cut (if
possible) and re-apply power.
They are IME quite difficult to break - certainly for wood blades
anyway. It does depend a bit on how long the blade is and where along
its length its snagged.
You said that above.
Well you *could* do that in the vice example, although the saw is going
to be might unhappy!
I have not found this to be the case. Remember we are dealing with
"normal" operation here - not a jammed blade. Applying similar levels of
force against the rest as you are applying in the direction of cut is
often adequate (in fact you can play one off against the other).
This is exactly the same situation as using a jigsaw - you get much less
vibration if you keep the sole plate firmly in contact with what you are
cutting. The moment you lift it away from the surface and try to cut
with the body of the machine unsupported, you get a significant increase
in vibration transmitted to the operator.
As with any tool, there are some use techniques that get better results
than others. Personally I don't find it difficult to use in such a way
as to control the vibration to a reasonable extent.
Now don't read into this that I am suggesting that these are
particularly sophisticated or smooth cutting tools. I would not want to
use one all day and every day.
I am a little confused by this... my initial comment on the subject was
"The trick to controlling vibration on a recip saw is to make sure you
push the blade guard firmly against the thing being cut"
That (to my internal voice at least) does not in any way amount to "such
Whoa horse! You are now romping off at a tangent having your own
argument. By all means do, but don't pretend its with me.
I have at no point suggested you don't get vibration from this kind of
tool. I am also fully aware that vibration is harmful, especially with
prolonged exposure. (read the power tools faq which I wrote many years
ago - its a topic I pick up on frequently). I have spent many years here
encouraging people to select better quality power tools, even if for
occasional use, because you usually get a better quality result and more
I gave a simple tip that helps reduce the impact on the user. I mention
it because it does not appear to be self evident to some users IME.
For example, some years ago when de-tialing a roof. I passed a mains
powered recip saw to my friend to cut down a row of tile battens nailed
to the rafters. A good application for such a saw since its fairly blade
hostile environment, and you want a cut flush to the side of a rafter -
a recip saw will do it quickly and easily - and if you kill a blade in
the process then who cares?
However he (an experienced builder) was struggling - the saw would snag
quite often as not all the tile battens were well fixed - they could
flex and pinch the blade. He was frequently getting the lions share of
the reciprocation through him and not the wood. He passed it back to be
and said "I have never been able to use those things". So I took over,
and did the job with no drama simply by the expedient of doing what I
suggested - engaging the rest against the top of the batten and applying
some forward pressure, and cutting with the bit of the blade closest to
the tool, rather than trying to use the end of the blade as he had done.
This resulted in no snagging, and way less vibration for me.
Well this *is* standard practice and advice. You can read it in the
handbook that comes with the saws, but then who reads those eh?
I am also not disputing that the more refined saws can better help
control vibration than the cheap ones (especially that which results
from the translation of rotational work to longitudinal, and balancing a
somewhat variable blade mass). Floating and spring loading the mechanism
also helps, as do vibration dampening grips.
However, the operator can still do a huge amount to influence the
experience with any recip saw by their choice of technique.
The previous version included a graphic element inadvertently
pasted from the Makita website which might lead to its rejection
on some NewsServers.
There are two different things being discussed here.
To keep things simple assume inside the saw is a rod (attached to the free
moving blade via the chuck) which moves forwards 1 inch, stops, and then
moves backwards 1 inch, and then stops at say 2,000 times a minute. In
simple terms this causes the body of the saw to vibrate; while in holding
on to the saw, rather than allow it to move around on the bench
the operator will absorb some of that vibration.
That is the normal vibration (A) associated with reciprocating saws where
the operator absorbs some of the vibration.
In addition if the blade is trapped, the entire body of the saw will
move forward 1 inch, stop, and then move backwards 1 inch, and then stop
say 2,000 times a minute. Which is (B). In this case its impossible for the
operator to absorb any of this movement or more technically
vibration. All that will happen should this be attempted is that the weakest
link in the chain will malfunction or break, be it the saw blade, the chuck,
the internal linkage, the motor, or the operator him, or her self
So the trigger is pressed rather than released.
However on the basis of your claim that (B) is such a common occurrence
"the problem many seem to have with recip saws", I'd imagined there might
have been a reluctance on their part to lock the trigger. Even if at
the cost of losing the odd millisecond here or there,
What I meant was if they didn't stop the saw, and thus subjected themselves
to a good dose of (B) the first time around, once having experienced (B)
why would they do this a second time ?
In other words you stop the saw.
Previously you claimed if you remember that B) vibrations, those resulting from the
entire body of the saw moving forward 1 inch, stopping, and then moving
backwards 1 inch, and then stopping say 2,000 times a minute was a major
problem. Whereas if you've immediately stopped the saw in such
circumstances then clearly it isn't.
Indeed. Whereas in fact they don't. As you've just explained they stop
the saw so (B) isn't as big a problem as you previously suggested it was.
Quite possibly but not enough to compensate for the fact that a
reciprocating saw vibrates four times as far/much/whatever - 22 m/sec?
when cutting chipboard as does a chainsaw 3.9 m/sec? Rear Grip
5.2 m/sec? Front Grip (task unspecified) . All Hitachi figures
This is the original point from Theo which I was responding to
"Out of interest, what would be a suitable alternative for cutting trees?
Having a similar portable, relatively safe, battery-powered form factor -
where a full chainsaw is not appropriate "
All I was seeking to point out, was that while with a chainsaw its possible
to let the saw do the work some of the time, given the weight of the bar
and the chain. IOW that it's not always necessary to apply maximum force,
even if this is inefficient and will prolong the job to some degree.
(here we go!) Whereas with a reciprocating saw which is usually suggested as
the closest alternative, this simply isn't possible. Not only is it
necessary to apply constant force on the blade but as I suspected
and confirmed by the figures above, the level of vibration is
considerably higher even in the most capable hands. So one must
assume at least. Making reciprocating saws correspondingly that more
tiring to use over extended periods
Taking into due consideration all those facts having any bearing
on the matter in hand, the position you currently find yourself
in, and the almost inevitable result should you choose to continue,
were I called upon to do so, this is exactly the advice I would
have given myself.
Try and move on, and put it all behind you; and in a while you'll
most likely have forgotten all about it.
If it is only relatively small stuff do you really need a power tool?
The speed and simplicity of use of such things as bowsaws provided they
have a good quality blade is something that seems to have been forgotten in
recent times, its got that almost no task can be done unless a power tool
Ah, many years ago the only time in my life when I've attended accident
and emergency at the local hospital. Using it to cut logs and on the
first cut the saw bounced out and cut into the back of two of my
fingers. I can vouch for the fact that the blade is sharp - there was a
lot of blood.
There's sometimes quite a lot of relatively small stuff, such that the human
battery gets depleted, and recharging it is a bit trickier than plugging
into a car charger.
The Ryobi One style of saw looks interesting, thanks. I was also a bit
dubious by the batteries on some of the other tools like the Bosch - 10.8V
1.5Ah, which surely can't last for very long.
I have a small recip saw which I mainly use for plumbing and some
Its good at getting into tight corners where a hacksaw is the only
option, and its very quick for lopping off things like 40mm wast pipe
and even trimming 110mm soil pipe. It also shares batteries with my
small drill driver / ID combo.
If I stick a "green wood" blade on that its not bad for a quick bit of
pruning - you only get 10 mins or so of work out of a battery, but the
batteries are small enough to have a spare in your pocket.
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