RAS Push Cutting Myth

[Jim O'Dell]

I'm glad to see this post. I've always been told and read on forums that you always pull cut with a RAS. The handful of times I push cut with it I felt like I was doing something bad and someone might be watching.

And I've always felt that, even with a negative hook blade, that the saw wants to come straight back at me during the pull cut. So when I'm cutting thick stock or something like maple, I'm pulling back but I have to tense up and be ready to push back on the saw to control it. If that makes any sense...

Should a negative hook blade or positive hook blade be used when push cutting?

Matt, I feel exactly the same. In fact, I had a couple instances with my original RAS of the climbing phenomenon actually stalling the motor. I'm sure the wood moved and put the blade in a bind that stalled the motor, but I didn't like it. It was always a work out cutting big boards because of having to stay so tensed up when pulling the the blade slowly through the cut.

Yeah Joe, it's the same issue when trying to explain positive and negative camber. The you get in to the discussion of off camber for a corner and you watch the eyes glaze over. Jim.

[Jerome Stanek]

I cut a lot of extruded aluminum and use the push to get a good cut.

[John McClanahan]

Personally I liked the way he kept slamming the blade into the saw so hard that it made the entire saw jump up and backwards. We don't need no stinking safe or best practices. I need folks like that. My wife needs customers in the operating room. She needs to pay off that new Volvo.

I did that to demonstrate that even with a positive hook blade and gross over feeding, the board doesn't rise up. The saw wasn't jumping backwards. I moved it under the overhead light for the video and didn't fully adjust the leveling feet.

John

[John McClanahan]

I don't think I would try that with thicker stock........the thicker the stock, the more the blade will tend to lift.

Lee, you are probably right.


John

[Pat Barry]

The way you have the blade setup, what you call positive hook, means the blade is cutting from the bottom up and that is unhealthy, unwise, and potentially very unsafe. With that setup you'd be better off pull cutting. Or am I missing something?

[Rick Potter]

No myth, manufacturers recommendation.

As I understand it, the saw is designed to have the blade parked behind the fence for safety. The makers recommend you use a pull cut and return the saw to the parked position. This avoids having your hands near the blade when it is running.

Watching the video shows your hands reaching around the moving blade to adjust your cuts, when it would be safer to have the blade in the parked position. I am sure, John, that you are very carefull while doing this, but are you sure you are comfortable recommending that a novice woodworker do it this way? It is akin to saying it is ok to reach around the back of a table saw blade while running. If the novice accidently bumps the handle while his hands are back there the blade is going to move.

I am sticking with the manufacturers recommendations. Make like a chicken and pullet.

Rick Potter

PS: Quotes from the DeWalt 790 owners manual.

1: Return carriage to full rear postition after each crosscut.
2: Never reach around moving blade.
3: Place material on work table, against guide fence, draw saw blade across for the cut just far enough to sever wood.

Note that #3 is saying that you don't need to have the blade out in the full extended position where you could get your hands around it.

[Steve Peterson]

My miter saw specifically mentions in the manual that it is best to bring the blade in front of the work, then lower it into the cut and push to the back. This is not possible on a RAS (unless you want to crank the handle 100 times for every cut).

Steve

[Chip Lindley]

=johnny means;2046905]What's the RAS push cut myth?

Reply by Rich Riddle: It's unsafe to cut wood with the push stroke with a radial arm saw instead of cutting the wood on the pull stroke. You have to insert the wood after you have pulled the blade toward you (even if the saw isn't running).

That is my take exactly! After 30 years of RAS usage, first with a Sears 10" for too many years, and now a monster Rockwell 7.5hp (max. 18" blade) but using a 14" blade and 14" guard. I do not want that huge amount of gnarly blade staring at me as I insert the workpiece! Without appropriate "hold downs" the push stroke can and will lift a board off the table and into the guard. This is not much of a problem with a powerful saw which refuses to bog down, even croscutting 3" stock. Much more of a problem on an under-powered saw such as the Craftsman, if the blade should bind in the least. But that exposed blade before each cut is still an alarming problem for me.
.
On the other hand (if you still have 5 fingers) the pull stroke can also have it problems. The blade can overfeed to jam into the stock, even with a negative hook blade. Neg. hook is not the "end-all panecea" by any means. It can also be abused to jamming. I have found that controlling the rate of feed with a stiff forearm makes for successful but tiring use of an RAS.

It works for me....but its YOUR shop and your health!

~~Chip~~

[Rich Riddle]

It works for me....but its YOUR shop and your health!

~~Chip~~

Chip, you said it best. I hear horror stories about tools from my wife on a very regular basis, stories involving serious injuries, trying to reattach body parts in surgery, or at times unexpected amputations. None of the stories involving power saws is every minor. As often as she discusses those injuries, it keeps power tool safety at the top of my mind.

I like many old tools, but some of the newer safety features far surpass what former machines could offer. When dealing with old tools, at a minimum I follow their recommendations regarding use and safety. I wish all woodworkers well no matter what safety choices they make.

[Mark Bolton]

I always thought the issue was actually the Pull-cut issue with the cheaper RAS? when the user had their hand/arm near the cut, pulled the saw into the work, the saw then "rode up" onto the work piece (like a tire on a car driving down the road) at which point the flexure in the cheaper saws allowed the blade/head/arm to bend and the blade would lay over at an angle and cause the arm to rotate/swing while the saw (car) was driving over your work piece (and your arm) and when the process was complete you would be left with a RAS motor free-wheeling at the end of the arm, clear of the work piece, an arcing slice on the work piece (which was suppose to be a straight cut/dado) and a freshly severed human arm laying atop the work piece.

There is always the issue on the push cut (just like a slider) of the piece lifting up into the blade but I always interpreted the "radical harm saw" as the fact that the pull cut is a climb cut and with cheaper saws (craftsman) there was a lot of bloodshed/potential bloodshed.

[John McClanahan]

I guess I should point out that this is not a "How To Use Your Saw" video. It is only to demonstrate that the blade isn't lifting the stock. The alignment of this saw was recently checked, and the blade is running true. If the saw was out of alignment the results would probably be quite different.

I should also ad that this is not how I use my saw.

I didn't hold the board during the cutting, and only moved it an inch or so for the next cut. I also never let go of the saw. When finished, the board was 13" long. If you hold stock in the miter gauge of your table saw, your fingers may get closer to the blade than this.

When I pull the carriage out all the way and start the motor I have nothing to fear, as it is as close to me as it can get. The only way it can go is farther away.

For everyone that prefers to pull cut, continue to do so. I'm not out to change your ways.


John

[johnny means]

I don't see how cutting that way is any more dangerous. But, I wouldn't want to position my work piece behind the blade like that. This would be especially hairy with a larger RAA. Imagine reaching across a 30" tablew trying to position a door behind a 20" blade. IMO, the video shows poor shop habits.

[Mark Bolton]

John,
I dont see anything wrong in your video whatsoever. Its likely the EXACT procedure for cutting with any slider on the market today. Our slider has warning stickers on it clearly visible to the operator that say to place your work, draw the slider back, lower the saw head, and push through the work. These are much flimsier saws than your slider.

I have several times had issues with pieces lifting into our slider. No different for a RAS. Its just something that can happen. Dull blade, short piece, rushing, nasty grain, on and on.

Procedure, and procedural over thinking can often be a bad thing....

My thoughts are always just stay on your toes and the rules are a little pliable..

10 and 10 here..

Mark

[Joseph Tarantino]

pull cut, postive hook angle blade, workpiece unsecured on RAS table top (this is not how i normally work!!!)



what's all the fuss about? i have, when dadoing 4x4s for deck posts, stalled the motor if i wasn't careful about the feed rate. with almost 3/4" of dado cutters and chippers spinning around, they are bound to grab the material if the saw carriage isn't carefully controlled and attempt to "move" towards the operator. easily controlled if operator's paying attention. but, that aside, since the blade is spinning down into the table, the workpiece shouldn't lift off the table.

[Joseph Tarantino]

The way you have the blade setup, what you call positive hook, means the blade is cutting from the bottom up and that is unhealthy, unwise, and potentially very unsafe. With that setup you'd be better off pull cutting. Or am I missing something?

hook angle refers to "the angle formed between the tooth face and a line drawn from the center of the blade across the tip of the tooth."

http://www.rockler.com/articles/saw-blades-101.cfm

it has nothing to do with the position of the blade relative to the workpiece.