SCMS would like some advice on safe working

[TonyW]

Following a recent post asking for advice on the purchase of a SCMS I have just taken delivery today of a DeWalt DW707 and leg stand (free -leg stand that is!).
I have not yet had a chance to give it a try due to the time factor and the fact that I am quite tired (this a safety rule I try and observe!). In fact have decided to leave alone until back from a holiday - although I have had the saw out of the box and had a little play without actually running it.

I was a little surprised about 2 things. First no workpiece clamp supplied and second the fact that the blade guard does not automatically retract when blade lowered (don't know if this is a function that requires power)

I have only ever used a hand held circular saw so was interested to read the manual - main concern at the moment is safe working. After reading the manual I am now a little confused (or maybe just plain stupid) about certain points.

From the manual:
Additional Safety Rules for Mitre Saws
• Raise the blade from the kerf in the workpiece prior to releasing the switch.
I thought that it was recommended to let the blade stop before raising from the kerf

Vertical straight cross-cut
• Take hold of the carrying handle (3) and press the head lock up release
lever (2) to release the head. Press the trigger switch (1) to start the
motor. It is recommended to start the cut near the fence (fig. M)
• Press the head and allow the blade to cut though the workpiece.
Allow the blade to cut freely. Do not force.
• When the head is fully depressed, slowly pull it across to complete the cut.
I thought that you were supposed to move the saw towards the fence by gently pushing thereby keeping the work piece solidly against it.

Clamping the workpiece (fig. A3)
• In most cases, the action of the blade is sufficient to hold the material
firmly against the fence.
• If the material has a tendency to lift or come forward from the fence,
preferably use the optional material clamp (28).
No clamps supplied with saw. How can the action of the blade be sufficient to hold the material against the fence - particularly if pulling as described above?

Quality of cut
The smoothness of any cut depends on a number of variables, e.g. the
material being cut. When smoothest cuts are desired for moulding and
other precision work, a sharp (60 tooth carbide) blade and a slower,
even cutting rate will produce the desired results.
Ensure that the material does not creep while cutting; clamp it
securely in place. Always let the blade come to a full stop
before raising the arm. If small fibres of wood still split out at
the rear of the workpiece, stick a piece of masking tape on the
wood where the cut will be made. Saw through the tape and
carefully remove the tape when finished.
Seems to be some contradictions from earlier statements

Would appreciate your thoughts and comments.

Cheers
Tony

 

[Nigel]

There was a discussion about which way to cross cut at Steves bash where Waka brought along his new Festool saw,

when demonstrated most people were of the opinion that the saw was used like a radial arm saw ie the cut was made towards the fence

I asked the same question as you because my Electra Beckum saw instructions are the same as your Dewalt so Waka tried both ways with his Festool saw and the only difference was the dust collection was worse on his saw when sawing away from the fence,

sorry I cant answer the technical reasoning but i'm sure someone will be along to explain,

Cheers Nigel

 

[MooreToolsPlease]

I find that if I leave the saw in the cut whilst the blade stops there is some burning on the cut. I usually bring the saw up, and release the handle so that the guard is in place over the blade.
I do as the manual says for wide cuts, push the saw into the cut then pull it across, much as you would do with a radial arm saw.
If you are pulling the saw across the work piece then the rotation of the blade keeps it tight against the fence.
On site I have seen people cut with these things every which way imaginable.
I think its a question where you ask ten people and get 12 different answers.
A lot like the recent thread on table saw safety from the magazine article

 

[Andy Pullen]

Crikey thats a broad post you've made.
For a start squeezing the lever on the handle pulls the guard back.
If you pull the saw out and cut towards the fence it is safer because the saw wont try and climb cut but it is at the expense of poorer dust extraction, if cutting narrow pieces lock the head and just use as a chop saw and you will get the best of both worlds. Wood doesn't need to be clamped just held with your hands out the way of the blade but things like aluminium do, be sensible but don't be afraid of the machine. As far as letting the machine stop first before lifting the head I would suggest this only matters with small offcuts that the blade can catch and fling and another thing to bear in mind with cutting and pulling the blade towards yourself is that if cutting say melamine you would get a better finish on the top face because the blade is cutting in to it rather than cutting out, it will chip less on top.
The blades that come with this saw are superb and though you can get finer ones, i have a 48t, I rarely use it for general work and the finer the harder it will be to cut the thicker timbers, best to stick with what you've got for now maybe.
If you expect to do mainly 90' cuts you could fit a sacrificial fence which would improve safety by supporting the back of the cut better.
You've just reminded me how when I bought my last 707 a young chippie just out of his time borrowed it for one piece of architrave and mitred his index finger nail to the bone and ended up in Stoke mandeville.
You have bought a superb saw that will last for years, respect it but don't fear it.
Anything else?

Andy

 

[Andy Pullen]

There was a discussion about which way to cross cut at Steves bash where Waka brought along his new Festool saw,

when demonstrated most people were of the opinion that the saw was used like a radial arm saw ie the cut was made towards the fence

----------------------------------------------------------------------------

A radial arm saw should be pulled out and fed in towards the fence, mainly because the machines we use aren't like the huge industrial ones and arent heavy or powerful enough to cope with sawing by pulling towards yourself. They will just bog down and try to climb out of the wood, most dangerous IMO.
Andy

 

[Sawdust]

There was a discussion about which way to cross cut at Steves bash where Waka brought along his new Festool saw,

when demonstrated most people were of the opinion that the saw was used like a radial arm saw ie the cut was made towards the fence

----------------------------------------------------------------------------

A radial arm saw should be pulled out and fed in towards the fence, mainly because the machines we use aren't like the huge industrial ones and arent heavy or powerful enough to cope with sawing by pulling towards yourself. They will just bog down and try to climb out of the wood, most dangerous IMO.
Andy

Are you sure about that. I have a RAS which I have used for years and never cut towards the fence, always away from it. I'm happy to be told I'm wrong but I just can't see how you could use a RAS any other way.

For example, cutting a 10foot long plank in half. I would have to pull the blade out, slide the wood in from the side, turn the saw on, push it back to the fence to cut. With a SCMS, you can pull the blade towards you above the cut, turn it on, push down and then forwards. You can't do that with a RAS.

I'm puzzled ???

Cheers
Mike

 

[Andy Pullen]

You'll be familiar with it fighting against itself aswell. I know people do it that way, mainly because they have seen huge wadkins etc that are up to the job used that way but light dewalt's etc arent and they become jerky and erratic in use, even light industrial ones have the same problem.
You should pull the saw out put the timber betwen it and the fence then feed back towards the fence, more awkward but safer and easier on the machine.
Andy

 

[NeilO]

surely you cut towards the fence, given the rotation of the blade...

the teeth points towards the fence, each tooth acting chisellike to remove the wood from the cut..

the other way, drawing the blade backwards, you are not only getting an inefficient cut but you are inducing the chance of the blade riding the workpiece :shock: , and effectively pushing/dragging the work AWAY from the fence and any support it was giving....

 

[Sawdust]

You'll be familiar with it fighting against itself aswell. I know people do it that way, mainly because they have seen huge wadkins etc that are up to the job used that way but light dewalt's etc arent and they become jerky and erratic in use, even light industrial ones have the same problem.
You should pull the saw out put the timber betwen it and the fence then feed back towards the fence, more awkward but safer and easier on the machine.
Andy

Yes, it can tend to climb but that is something you learn to get a feel for and deal with. It is scary the first time it happens though. But I have never seen a RAS used the way you suggest. I'm not saying you are wrong, it's just not how I've ever used it!

Also, what about wide boards - surely you would pull cut them rather than push?

Mike

 

[Andy Pullen]

surely you cut towards the fence, given the rotation of the blade...

the teeth points towards the fence, each tooth acting chisellike to remove the wood from the cut..

the other way, drawing the blade backwards, you are not only getting an inefficient cut but you are inducing the chance of the blade riding the workpiece :shock: , and effectively pushing/dragging the work AWAY from the fence and any support it was giving....

Climb cutting away from the fence usually amounts to an arm locked at the elbow trying to control a series of jerky cuts from the radial arm saw head, not at all pleasant or particularly safe.
Andy

 

[DaveL]

To help reduce the blade biting on a climb cut on a mitre saw they should be fitted with a negative rake blade.

 

[Sawdust]

surely you cut towards the fence, given the rotation of the blade...

the teeth points towards the fence, each tooth acting chisellike to remove the wood from the cut..

the other way, drawing the blade backwards, you are not only getting an inefficient cut but you are inducing the chance of the blade riding the workpiece :shock: , and effectively pushing/dragging the work AWAY from the fence and any support it was giving....

I thought that's why negative raked teeth were used in RASs? - to keep the tooth angle correct while pull cutting?

If it does snatch, it's not pleasant but it doesn't throw the wood out, it just pushes it harder into the fence.

You guys now have me worried as I think I have been using my saw the wrong way for years!

Cheers
Mike

 

[NeilO]

Mike, I think the original question was about a SCMS, not a RAS...but honestly I cant see the difference, you wouldnt try to feed wood on a TS from BEHIND the blade?????? :shock:

 

[Andy Pullen]

If it does snatch, it's not pleasant but it doesn't throw the wood out, it just pushes it harder into the fence.

You guys now have me worried as I think I have been using my saw the wrong way for years!

Cheers
Mike

Theres the rub, it jerks a spinning blade towards you in an erratic fashion, a negative tooth blade will keep the material pinned to the table whatever way you feed but you will have a spinning blade that you cant control properly jerking towards you, not good.
Any way lets get back to this chaps new chop saw.

 

[Sawdust]

Apologies for dragging this off-topic - I have started a new thread

Thanks
Mike

 

[Scrit]

A radial arm saw should be pulled out and fed in towards the fence, mainly because the machines we use aren't like the huge industrial ones and arent heavy or powerful enough to cope with sawing by pulling towards yourself. They will just bog down and try to climb out of the wood, most dangerous IMO.

I think I'd disagree with that one, Andy. A RAS, even a lightweight one, is designed to have a home position at the rear of the saw, behind the fence. Most recent saws either come fited with or have available a spring return device which will ensure that the motor/blade/yoke assembly is returned to the home position should the operator release the handle. If you were to start buy pulling the head out, positioning the timber, then making the cut towards the fence then you have quite a few problems. Firstly if your saw is (rightly) fitted with an auto return mechanism you'd need to hold the motor/blade/yoke assembly in the outboard position with one hand whilst shimmying the timber into position with the other - an interesting proposition with a 12 x 2in section lump of oak some 8ft long, I'd say. Secondly, if you experienced a problem during the cut from outboard to inboard to inboard releasing the handle would result in the motor/blade/yoke assembly being drawn into the timber, potentially resulting in an accident as the blade spins down whilst bumping into the timber. That is not good! In this mode the blade is cutting upwards and to the rear leading to much increased potential to lift and throw the workpiece, especially if the back fence is very low:

Contrast that with the correct way to use a radial arm saw, namely with the head retracted behind the fence position the timber firmly against the fence. Next use the left hand to hold the workpiece, ensuring that it is well clear of the cutting path. Finally switch on the machine, draw the motor/blade/yoke assembly out gradually and at the end of the cut return the motor/blade/yoke assembly to the home position. In that instance the biggest danger is from climb cutting, as you rightly say, but part of the cure for that is to use sharp blades, don't pull across too quickly and use a negative rake blade. In this method of use the cutting action is downwards and to the rear of the machine and generally much safer.

The major difference between a RAS and a SCMS is that the SCMS is designed in such a way that in the event of the user releasing the handle the spring counterbalance in the arm will always pull the motor/blade assembly upwards and away from the workpiece., something which does not happen with the RAS.

Scrit

 

[mailee]

Well Scrit I am in total agreement with your views. I would add though that negative rake blades are not just for a RAS but also for a SCMS as this action as you have so perfectly described holds the work to the fence and base preventing it from being pulled up into the back of the blade. On a table saw a postive rake blade has the same effect but holds the timber to the table as it cuts through with a downward motion. To get back to the point in question that was originally asked, yes with a SCMS you should lower the spinning blade into the timber from the front and work to the rear and only allow the blade to stop in the downward position when cutting small pieces that may get caught in the blade. As has also been mentioned gripping the handle and or lowering the blade should release the safety guard around the blade. Well that's my two penneth done. :wink:

 

[Scrit]

I would add though that negative rake blades are not just for a RAS but also for a SCMS as this action..... holds the work to the fence and base preventing it from being pulled up into the back of the blade.

I concur with that, Alan. I suppose one difference that people don't understand is that an SCMS is designed to allow cuts to be made where the finish surface is up or down. If you are scoring across on an SCMS to allow you to chisel out a housing then you'd want to do a pull cut rather like that on a RAS. Doing the pull cut would ensure that any reaction to the cutting action is downwards and to the rear and that (upwards) spelching on the face was minimised. Conversely cutting a coving would probably be done with the visible face downwards on the table using a pull-out, drop and push cut action to ensure the best possible cut quality - although this technique generates up lift on the workpiece and is why SCMS should have hold-down cramps. Your comments about keeping the blade in the down position until it stops spinning is also a very cogent point. I've occasionally been a bit hasty and had small offcuts ejected past my hand - the "bang" the waste makes is normally enough to wake you up!

Scrit

 

[TonyW]

Thanks to All for your comments

For a start squeezing the lever on the handle pulls the guard back.

I know it was a dumb thing for me to say its just that with all I had seen to date after release the blade guard retracted automatically as the saw lowered.

The blades that come with this saw are superb and though you can get finer ones, i have a 48t, I rarely use it for general work and the finer the harder it will be to cut the thicker timbers, best to stick with what you've got for now maybe.

Due to my broad post was saving this for another day. Most posts I have seen recommend ditching supplied blades and replacing with Freud or CMT. From your comments I am now hopeful that I will get a good finish from the supplied blade. In the future I may want to try finer blades - so I will be back 8)

You have bought a superb saw that will last for years, respect it but don't fear it.

Did you smell the fear in my post . My experience to date has been with hand held circular where obviously both hands hold the tool well out of the way of the pointy bits! It just struck me that the potential for mischief with this tool far greater and therefore I needed to be made aware of safety pointers. Just joking about the "fear" bit - but certainly need to have a healthy respect.

I would add though that negative rake blades are not just for a RAS but also for a SCMS as this action..... holds the work to the fence and base preventing it from being pulled up into the back of the blade.

I concur with that, Alan. I suppose one difference that people don't understand is that an SCMS is designed to allow cuts to be made where the finish surface is up or down. If you are scoring across on an SCMS to allow you to chisel out a housing then you'd want to do a pull cut rather like that on a RAS. Doing the pull cut would ensure that any reaction to the cutting action is downwards and to the rear and that (upwards) spelching on the face was minimised. Conversely cutting a coving would probably be done with the visible face downwards on the table using a pull-out, drop and push cut action to ensure the best possible cut quality - although this technique generates up lift on the workpiece and is why SCMS should have hold-down cramps. Your comments about keeping the blade in the down position until it stops spinning is also a very cogent point. I've occasionally been a bit hasty and had small offcuts ejected past my hand - the "bang" the waste makes is normally enough to wake you up!

The saw and manual state about using negative rake. Scrit pointed out that people do not understand that SCMS is designed for finish surface up or down. I certainly was one of those people - thanks for the explanation.

If you can stand it just one more question. I would like to have the option of hold down cramps, cannot find DeWalt type (for 707) any suggestions for alternatives?
Thanks again
Cheers
Tony

 

[Scrit]

The saw and manual state about using negative rake.

It is often not appreciated that negative rake blades for the RAS and chop saws were really an invention of the late 1970s. Prior to that time zero or even slightly positive rake blades were often used which were much less forgiving.

I would like to have the option of hold down cramps, cannot find DeWalt type (for 707) any suggestions for alternatives?

I see no reason why a QR cramp such as the Wolfcraft couldn't be pressed into service should a cramp be required, after all you won't need it for all cuts.

A couple of things you might like to consider for safety. When cutting narrow pieces of a wide moulding, such as the "step" cornices on a breakfront cabinet, it is often safer to cut the short pieces off the end of a longer piece, but do not cut through completely - leave a few small tabs holding the short cut on the end of the longer piece and then finish the cut on the bench using a fine-toothed back saw. That way you'll risk of being hit by "shrapnel".

Secondly very fine mouldings are rarely adequately supported on the standard SCMS bed, so consider the need to buils an L-section bed comprising base and sacrificial back fence to provide extra support. This is easily done by glueing and pinning a couple of strips of MDF together. Don't forget to adjust the depth of cut so that it doesn't cut through the entire sacrificial table and also remember to screw this sacrificial bed in place to prevent it moving.

Finally some cornice mouldings are more easily cut by building a U-profile box to hold them at the angle they will be installed. Some of the larger SCMS around actually have cornice stops and high back fences incorporated for that very reason.

Scrit