Radial Arm Saw as alternative to table saw and track saw? - Page 2 - Woodworking Talk - Woodworkers Forum
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post #21 of 58 Old 09-21-2019, 07:55 PM
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Quote:
Originally Posted by epicfail48 View Post
Not quite, as far as the blade physics go. In a sliding miter saw, youre pushing the saw against its direction of rotation. The blade cant really feed itself into the wood as youre forcing it to go in the other direction. The saw would have to ride up the workpiece and force your arm back

With a RAS, youre pulling the carriage in the direction of rotation, so instead of pushing against the saws movement, youre pulling with along with it. In that case, if something goes wrong you have to completely reverse the direction of your force, while the carriage is pushing against you. Picture trying to push someone out of the way and having them suddenly start moving the direction youre pushing
I agree 100%.
In fact, I've found that with my particular saw, I can start the cut (towards me) and with 1/4" luan, the saw will make the cut "automatically" towards me without a problem, and without my hand on the saw. If I cut anything thicker or 'harder', the saw will grab and... well.. things get nasty. At that point, I go from pulling to pushing. Not a natural way to cut wood.
NOW... Yea, I realize this is the TOTAL wrong way to do it, however, that speaks of how the saw works, and the fact it will 'feed' itself through the wood.
I've learned to bring the carriage to me, feed the wood into position, turn the motor on, then cut it as I push the saw away from me (the 'normal" direction saw blades need to cut).
Hope that helps.
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post #22 of 58 Old 09-21-2019, 10:01 PM
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My 1957 Dewalt ras had a 5 hp 220 motor on it and with a 16 inch blade spinning wide open it never did ride up on top of the materials. I guess the motor was so heavy it didn't get much of a chance to lurch forward.

I really did like my ras but my shop now is way way too small for one so I had to sell it along with several other large tools.

I tried ripping with a ras one time, didn't try again.

Bill, no way would I even try to turn a 10hp shaper on. I had a 3hp 220 shaper and it sounded like a jet warming up, I was really afraid of that thing, sold it and all the cutters for a song.

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post #23 of 58 Old 09-21-2019, 10:23 PM
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"On a RAS, the workpiece is pushed between the fence and the blade when ripping. The blade's teeth are pushing down on the workpiece at the rear so, no rotational type of kick back. Warped material is likely to kickback regardless the type of saw."


When ripping on a RAS the blades teeth are pushing up, hence causing kickback where as on a table saw when ripping the teeth are downward into the stock
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post #24 of 58 Old 09-21-2019, 10:35 PM
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Originally Posted by Bob in St. Louis View Post
I don't have much to add, other than you need to know to buy SPECIFIC blades for a RAS.
They're not just "regular saw blades".
Bob



How so? I interchange blades on my table saw and RAS all the time.
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post #25 of 58 Old 09-21-2019, 10:45 PM
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It's not hard you just go slow with the cut, push back a little, I really can't image with what I'm doing without a RAS, it makes so many things easier.
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post #26 of 58 Old 09-22-2019, 03:21 AM
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Quote:
Originally Posted by Bob in St. Louis View Post
I agree 100%.
In fact, I've found that with my particular saw, I can start the cut (towards me) and with 1/4" luan, the saw will make the cut "automatically" towards me without a problem, and without my hand on the saw. If I cut anything thicker or 'harder', the saw will grab and... well.. things get nasty. At that point, I go from pulling to pushing. Not a natural way to cut wood.
NOW... Yea, I realize this is the TOTAL wrong way to do it, however, that speaks of how the saw works, and the fact it will 'feed' itself through the wood.
I've learned to bring the carriage to me, feed the wood into position, turn the motor on, then cut it as I push the saw away from me (the 'normal" direction saw blades need to cut).
Hope that helps.
Technically not proper technique, but honestly safer that way

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How so? I interchange blades on my table saw and RAS all the time.
Can doesnt mean should. The teeth on your average saw blade have positive rake, makes them dig into the wood for a slight more aggressive cut. More aggressive cut means higher chance of the saw deciding to self-feed. RAS's are recommended to be used with either a zero or negative rake blade, for safety

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post #27 of 58 Old 09-22-2019, 09:01 AM
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This is your sliding miter saw, right?

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Originally Posted by Bob in St. Louis View Post
I agree 100%.
In fact, I've found that with my particular saw, I can start the cut (towards me) and with 1/4" luan, the saw will make the cut "automatically" towards me without a problem, and without my hand on the saw. If I cut anything thicker or 'harder', the saw will grab and... well.. things get nasty. At that point, I go from pulling to pushing. Not a natural way to cut wood.
NOW... Yea, I realize this is the TOTAL wrong way to do it, however, that speaks of how the saw works, and the fact it will 'feed' itself through the wood.
I've learned to bring the carriage to me, feed the wood into position, turn the motor on, then cut it as I push the saw away from me (the 'normal" direction saw blades need to cut).
Hope that helps.

I've found they are slightly different in operation than a radial arm saw. I think this is because you can also control the depth of cut as you push the saw, unlike a RAS where depth of cut is predetermined. I always PULL my RAS carriage into the work from behind the fence.



Pushing a RAS would be a "climb" cut, that is feeding with the direction of rotation. You would NOT feed a table saw from behind the blade for a rip for this reason and some unwitting operators attempt to feed a RAS from the wrong direction which results in an expulsion of the workpiece. You should always feed the work INTO the direction of the rotation of the cutters/blades, and this is especially true on a router table.
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post #28 of 58 Old 09-22-2019, 10:49 AM
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Quote:
Originally Posted by redeared View Post
How so? I interchange blades on my table saw and RAS all the time.
Hard for me to explain, but I found a video that does a pretty good job.
But honestly, I don't believe you're supposed to do what you're doing. I could be wrong.
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post #29 of 58 Old 09-22-2019, 12:26 PM
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Lightbulb It's about th ehook angle of the teeth .....

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How so? I interchange blades on my table saw and RAS all the time.

A table saw cuts up from the bottom of the board, pressing the board down towards the table ...at least at first. A RAS cuts from the top down, lifting the board off the table ...at least at first. Table saw blades have a "positive" hook angle or rake, so there's no problem. The RAS will also cut with a posiitive hook angle, but its a very aggressive cut and will tend to self feed into the work. That's why you have to use a firm control when using a TS blade on a RAS!


A proper RAS blade, now available with a "negative" hook angle, however those were not made back when they initially came out with the home shop versions of a RAS. People were not aware of the self feeding issue and made mistakes which sometimes resulted in injuries.
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post #30 of 58 Old 09-22-2019, 12:39 PM
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The reason radial arm saws get such a bad rap is because they are not set up with the proper blade, not adjusted as they wear and are not used as intended.

It is virtually impossible for a blade to run across the top of a board if the carriage bearings are set properly, this seems to be particularly important with Craftsman saws.

Self feeding will be practically eliminated when using a blade designed for the saw with a negative hook. I have personally seen a demonstration where a cut is made part way into a board, the carriage is stopped and let sit running without being held, (do not try this at home).

Imagine if someone advised you to feed a board into a table saw from the other end, you would likely dismiss them immediately as a crackpot.

For Craftsman saw owners there is an online manual here that covers adjusting the carriage bearings:
http://vintagemachinery.org/pubs/222/2238.pdf
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post #31 of 58 Old 09-22-2019, 02:32 PM
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The reason radial arm saws get such a bad rap is because they are not set up with the proper blade, not adjusted as they wear and are not used as intended.

It is virtually impossible for a blade to run across the top of a board if the carriage bearings are set properly, this seems to be particularly important with Craftsman saws.

Self feeding will be practically eliminated when using a blade designed for the saw with a negative hook. I have personally seen a demonstration where a cut is made part way into a board, the carriage is stopped and let sit running without being held, (do not try this at home).

Imagine if someone advised you to feed a board into a table saw from the other end, you would likely dismiss them immediately as a crackpot.

For Craftsman saw owners there is an online manual here that covers adjusting the carriage bearings:
http://vintagemachinery.org/pubs/222/2238.pdf

On my RAS, the pin didn't align perfectly for the 90 degree stop so I took it off intending to adjust it later. I was home on leave from the USAF when I did that, a while later I hear about my brother trying to rip a 2x4, he fed it into the rotation of the blade, the motor pitched up, and launched the 2x4 through a cement block in our basement where I had my shop


He said it happened so quick he didn't even know what happened. lucky it did if he would have fought it, it very easily could have pulled his arm into the path of the blade


I have since adjusted the pin stop
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post #32 of 58 Old 09-22-2019, 04:13 PM
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BigJim, You should have at least one shaper. They are so versatile. For a small investment you can setup to grind your own knives, make curved moldings, precisely machined "to width" stock on & on. If you had one of the light duty shapers I can see why you thought they sounded bad. They are awfully floppy. A nice 5 hp industrial grade machine purrs. Well, until you put an 8" cutter block on it and spin it a bit too fast. I've got 6 shapers from a nice SAC 5hp to a Gomad tilt at (7.5 hp ??), all with feeds. The big Gomad weighs over 2,000#s, smooth as silk. Try it, you'll like it :>)
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post #33 of 58 Old 09-25-2019, 09:13 PM
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On a ras, the wood is not lifted off the table, if set right.
If not the trailing edge of the blade could touch the kerf, and lift the wood.
With a powerful enough (no Craftsman saws) motor, and a sharp blade (regardless of how) you should have very little, if any.
Learned after having a number of old Craftsman, DeWalt 9" and Red Star 10".
Big difference on DeWalt 7790. 12" saw, running 10" positive hook blade.
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post #34 of 58 Old 09-26-2019, 12:33 PM
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To the poster's original question, I'm of the opinion a table saw is central to a woodworking shop. If the budget is limited, then I would say any table saw is better than none.

Why? Because you simply cannot beat a table saw for precision and consistency. Hands down, only the best commercial grade radial arms can compare in this regard.

The common RAS's for homeowner use are not reliable machines. The settings are easily disrupted. For example, one bump of the arm will require a recheck for 90.

IMO they are one of least safe machines because they are so prone to self feeding and binding. I would never even attempt ripping on one. Sliding miters have largely taken their place.

That said, I have one and use it a lot. 95% for rough crosscuts. I use a miter saw for precision miter cuts and small pieces of wood, etc.
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post #35 of 58 Old 09-27-2019, 06:10 AM
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Basic physics for circular saws ......

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A table saw cuts up from the bottom of the board, pressing the board down towards the table ...at least at first. A RAS cuts from the top down, lifting the board off the table ...at least at first. Table saw blades have a "positive" hook angle or rake, so there's no problem. The RAS will also cut with a positive hook angle, but its a very aggressive cut and will tend to self feed into the work. That's why you have to use a firm control when using a TS blade on a RAS!


A proper RAS blade, now available with a "negative" hook angle, however those were not made back when they initially came out with the home shop versions of a RAS. People were not aware of the self feeding issue and made mistakes which sometimes resulted in injuries.
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To the poster's original question, I'm of the opinion a table saw is central to a woodworking shop. If the budget is limited, then I would say any table saw is better than none.

Why? Because you simply cannot beat a table saw for precision and consistency. Hands down, only the best commercial grade radial arms can compare in this regard.

The common RAS's for homeowner use are not reliable machines. The settings are easily disrupted. For example, one bump of the arm will require a recheck for 90.

IMO they are one of least safe machines because they are so prone to self feeding and binding. I would never even attempt ripping on one. Sliding miters have largely taken their place.

That said, I have one and use it a lot. 95% for rough crosscuts. I use a miter saw for precision miter cuts and small pieces of wood, etc.

I have probably done more ripping on a RAS than anyone on this forum. I have done a whole lot of ripping with a circular saw over the past 50 years. I have done a lot more ripping on the table saw than either of the other 2 saws, probably several thousand linear feet. I know what I'm doing.


I also know what happens when a rotating circular saw blade enters the wood and starts to cut and that depends on the type of saw being used.


Let's start with a hand held circular saw, a very common tool that just about everyone has used. The saw has a base plate to support it's weight AND to press against the top of the workpiece, very important. You would NOT just freehand hold the saw above the work and attempt to saw with it! As the rotating blade enters the work the teeth are rotating upwards, pressing it against the base of the saw. You can now control the forward motion and continue cutting with no issues, including no kickback. Depending on the material, plywood or lumber, the saw kerf may close up and bind the blade, stalling the motor. Plywood will NOT do this because it's homogeneous, lumber will because it's grain varies within the wood.


Now what happens when a miter saw is used? As you start the cut you are pushing down. The saw blade is entering the material from the top, BUT you need to hold it down against the table and the fence with your left hand. You can't just lower the blade without a secure grip on the workpiece or it will tend to lift up because that's the direction the teeth are rotating.


Now what about a RAS? It's very similar to the miter saw in that the rotating blade is above the workpiece, except you are pulling the saw towards you from behind the fence. As the teeth enter the material from ABOVE, it's being pressed down into the table and against the fence, BUT you still need a firm grip on both the material AND the handle on the saw. Depending on the hook angle of the blade it may self feed aggressively into the material. Here's where a negative hook angle blade is the best type to use on a RAS.



What about ripping on a RAS? It's a lot like a circular hand saw, BUT there is NO base plate to keep the material pressed down while the blades teeth rotate upwards, lifting the material. This is where the blade guard/cover must be used to prevent the material from lifting upwards! This is very critical and often not done. It's the main reason for kickbacks and lack of control of the material! I used a roller located right above the material when I ripped several hundred feet of Cypress for this barn door project:
https://www.woodworkingtalk.com/f2/evil-machine-28461/










The roller prevents the workpiece from rising upwards due to the upward rotation of the teeth entering the material.


What about ripping on the table saw? Now the rotating blade is entering from BELOW the material. The teeth are pressing the material downwards, at first as they begin to cut then under feeding pressure. As the kerf is opened up there is some tendency for the material to be lifted up at the rear of the blade, BUT not much because it's not cutting, just friction on the sides of the blade. If the kerf closes because of the internal stress being relieved, the friction is greatly increased and that's when the material will lift up and either stall the motor or cause a kickback. A splitter or riving will prevent this from happening, it's is a critical table saw safety feature and should always be used when ripping.



So, some basic physics is needed to understand what's happening when a rotating blade enters the material from above AND whether there is a means to prevent it from lifting upwards, like a base plate on the circular saw, OR a blade guard/cover on the RAS.
Table saws are different since the material is resting on the table initially and is being pressed downwards as the cutting begins. There is only sideways friction if you stop feeding the material forward.



A bandsaw has a much smaller blade contact area and the teeth are offset leaving the remainder of the blade in the kerf, therefore with much less friction. The material is being pressed downwards onto the table the same as the table saw, however. Bandsaws will not kickback because unlike a circular saw the width of the blade plane is so much smaller. For this reason on a table saw, any rotation of the workpiece away from the fence at the rear while the blade is cutting will bind and cause a kickback.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

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post #36 of 58 Old 09-27-2019, 12:50 PM
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I have probably done more ripping on a RAS than anyone on this forum. I have done a whole lot of ripping with a circular saw over the past 50 years. I have done a lot more ripping on the table saw than either of the other 2 saws, probably several thousand linear feet. I know what I'm doing.

Perhaps, I know I have done some of the best ripping on a radial arm saw..... some say I have probably ripped more than anyone else......I do beautiful ripping but the fake members here won't give me credit for it......
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post #37 of 58 Old 09-27-2019, 03:57 PM
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Yep, you are always ripping into something ....

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Perhaps, I know I have done some of the best ripping on a radial arm saw..... some say I have probably ripped more than anyone else......I do beautiful ripping but the fake members here won't give me credit for it......
Or someone about something, but how much actual "ripping" have you done ON a RAS? It doesn't matter really, because if you know what you are doing, it's perfectly safe. If you don't know what you are doing and feed from the wrong direction for example, bad things will happen.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #38 of 58 Old 09-27-2019, 04:22 PM
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Or someone about something, but how much actual "ripping" have you done ON a RAS? It doesn't matter really, because if you know what you are doing, it's perfectly safe. If you don't know what you are doing and feed from the wrong direction for example, bad things will happen.
I guess some people really need to be taken seriously.

I have actually ripped many lifts of plywood, 1 1/8" and 3/4", a month for spiral stair case treads and risers for several luxury condo projects, so yes I have a bit of experience ripping on a radial arm saw.
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post #39 of 58 Old 09-27-2019, 05:44 PM
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I'm sorry ......

I thought you were being facetious .........





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I guess some people really need to be taken seriously.

I have actually ripped many lifts of plywood, 1 1/8" and 3/4", a month for spiral stair case treads and risers for several luxury condo projects, so yes I have a bit of experience ripping on a radial arm saw.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #40 of 58 Old 09-28-2019, 11:07 AM
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My one adventure into ripping on the RAS was an immediate "not for me!!"


For those considering embarking on such an adventure, I suggest doing some research beyond this forum. Lets just say there is wide agreement among ww'ers that this is not the "go to" machine for ripping, for several reasons.


My comments are directed toward the consumer type saw like the every present Craftsman pictured above. I have owned 3 such machines in 35 yrs of ww'ing the only one I would consider acceptable was an old DeWalt with cast iron arm.

The biggest issue is accuracy. On most any consumer saw, there is flex in the arm when lateral force is applied. To me, the thing about RAS' is "set it but don't forget it". They are notorious for losing their settings. Just a bump on the arm is enough to require a full check up. Setting one up for ripping is probably not going to be just a matter of rotating 90. The blade still has to be checked parallel to fence and 90 to table. Then when its put back to cross cut, the same checks need to be done. Lot of hassle for no realistic advantage.


Power is another factor. I know this is saw-dependent, but consumer type saws such as the one pictured have their limits. From experience, I couldn't imagine ripping 8/4 hard maple through a radial with the typical "2 1/2HP" motor.


When ripping on either machine, if there is no riving knife or splitter much care has to be taken to keep the material against the fence. With a saw kerf in the board, this isn't an east task.


I apologize for the length but I feel I should bring up the points for consideration for those thinking its a safe, easy, accurate task rather than reading a post and assume its easily done and a good alternative to a table saw (which I hope I have shown it is not).

Not intending to start an argument here but felt the need to respond as many people will read something in a forum and assume it is totally correct. So I'll stick to my table saw for ripping.Like many things related to ww'ing to each his own what works for one might not for another.
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