I just got done reading a ton of posts similar to mine here, but the basic essence of the question still was not answered. S-o-o-o here goes:
I just put together a Unisaw this week and part of the effort involved
the installation of the guard and splitter.
It now amazes me even more that a riving knife has not been designed
for this saw. The hardware for the splitter and guard appears to be
much more involved and has more pieces than a riving knife and guard
(that could be mounted to the top of the riving knife) would have.
Has anyone ever talked to the Delta management to see what it is that
prevents the use of a riving knife on the newer designs?
There have been numerous design modifications to this saw in other
areas to both improve the design and lower the cost. I am going to
remove the blade guard after I tune the thing up and install my zero
clearance insert with an integral splitter which I find safer and more
convenient to use. A riving knife would be a nice addition. I have
not examined the trunion area sufficiently to see if it could be
modified in its design to use a riving knife.
Has anyone ever found an aftermarket riving knife (I DON’T mean the
numerous splitters of various designs by aftermarket people and
Delta).
It would seem that some enterprising person would have made at least a one-off.
Replies
Eric,
Can you explain to me the functional difference between a good splitter such as the Beismeyer and a riving knife?
Doug
A riving knife moves with the blade both tilt and height. It fits in close to the back of the blade - within about 1/4 inch is good. It stops the wood from contacting the "danger zone" of the blade which is the half of the blade above the table and back of the top of the blade. This zone is where the blade energy is up from the table and towards the operator. This is where a piece of wood will be thrown and if the hand pushing the wood is past the front of the blade will possibly be moved into the blade as the wood is thrown.
A stock type splitter doesn't move up and down with the blade and so must be positioned as high as the blade will go. So if you have the blade 1 inch above the table there is no protection at the danger zone of the blade and much danger for the inexperienced operator exists.
Most fingers are cut off when a hand is pushing a small workpiece past the blade and the piece shifts a little and catches the blade teeth in the danger zone. The piece pivots in an arc as it is thrown and the hand moves with it into the blade.
Edited 11/16/2004 11:26 am ET by Corners
Can't improve on that explanation. Makes you shudder to hear the explanation though, doesn't it?
Corners,
Thanks - that makes sense. Iwas in the process of researching a good splitter and now I may need to rethink my options. It also explains why the short fence is safer since it is designed to end at the arbor.
Doug
By the way. Still have not gotten an answer to my question. I hope that someone from Fine Woodworking is monitoring this post. Certainly they have talked to people at Delta and other companies about this. I can guess why nothing has been done to include riving knife technology on a US saw. The litigious nature of the US would tend to stagnate any development in safety. If I were a company, why would I stick my fingers into the rotating blade of the courts. I know, I have probably answered my own question, but I still would like to hear it from the "horse's mouth".
HOWEVER, if the Sawstop people can sell a saw for over 20% more than a saw without their safety feature of instantly stopping a saw when it encounter's flesh, why wouldn't the addition of a riving knife at no (or nearly no) additional cost not be a super marketing tool?
I have made a couple of them over the years. Just buy a second guard assembly and then drill out the rivets that hold the guard and the prawls in place (easy to do). You will be left with a flat piece of steel that is exactly the right thickness and has the correct attachment point. The only problem is on some models the piece of steel sticks up further then the blade top which means it gets in the way sometimes.
Doug,
I'm not convinced a short fence is safer. I like to have the fence control the workpiece until it's well clear of the blade.
My 2 cents.
I am firmly of the opinion that a table saw can be operated safely with current, common sense safety attachments. The biggest problem is that few owners of saws in the current wave of woodworking popularity have received any instructions from experienecd saw operators. They try to understand saw safety by reading forums such as this. I was fortunate to have had good instruction 30 years ago in high school and then in a production shop where I worked through college. The production shop back in the 60's had an owner that was continuously talking and showing safety - he was proud that there had been no fingers lost in 50 years of operation.
I would like to see the woodworking industry get into saw safety courses - I think this would cut accidents by huge numbers.
On another forum there was a story of a lady getting into woodworking and finding herself in fear of the saw she paid the price for a full day with a TV woodworker (David something if I remember correctly) to learn how to use her tools safely. She said after she no longer feared the saw.
Edited 11/16/2004 3:38 pm ET by Corners
Edited 11/16/2004 4:09 pm ET by Corners
Nice overview, but you are not suggesting that the splitter and guard that is on the saw as delivered is the answer, are you? I will admit, if everyone used the standard equipment for through cuts of average width (say, 2 inches wide and above), the saw standard safety equipment would be sufficient. However, I find myself with a much wider variety of tasks than that. It is a pain to remove the blade guard and put it back on. I found myself devising a splitter in the insert and pushsticks that tended to hold the piece down on the table back of the blade.
Your first post that described the rotation of the piece after kickback started made me think that a version of the Gripper push stick might be worth pursuing.
However, a safety system that worked with a cabinet maker instead of getting in his way is what should be standard in a saw of today. The standard blade guard is fine for an old shop that just used a standard blade for standard lumber performing all through cuts.
The as supplied splitter and guard - no thanks.
I have a unisaw with Uniguard overarm and splitter, in fact 2 splitters, one with pawls and one without.
For some cuts a Gripper is a great idea.
For other cuts another idea may be better.
I would like to see woodworkers understanding how to make each different cut safely - there are lots of safety accessories avalable.
Corners,
I replied to you, but this comment is directed at the hundreds of posts I've read over the years that blame table saw accidents on the operator. Work smart and presto you won't get hurt. The FWW article says that there were 33,114 table saw injuries in 2002. Did those injuries happen to people who considered themselves inexperienced, improperly equipped, or at any meaningful risk of injury? Probably not. I bet that the vast majority of them happened to people who considered themselves reasonably experienced, working on appropriate equipment, and not at risk. With over 30,000 out there, I also bet that a good number of accidents happened to people who really ARE experienced, capable, and prudent.
There is no safety silver bullet. Proper safety training is important. Cautious and alert work habits are vital. Every improvement in the effectiveness and convenience of safety features should be celebrated. None of these should be looked down upon, ridiculed, or ignored.
When SawStop decided to design their own saw they realized that safety is more than just an innovative blade brake. The saw also has a true riving knife and blade guard that provides a good view of the work while allowing rips as narrow as 5/8". Both of these are built solidly and insert quickly. The starter is magnetic and has a removeable safety key. The start/stop paddle can be operated with a knee or hip in an emergency. The unusually wide and deep top allows workpieces to balance more easily. The saw's base has a toe kick to allow better operator balance while reaching over the blade. I don't have any problem with these features, and will not criticize anyone who chooses to buy the saw because of them.
BTW, I have one of the saws on order. I looked closely at a production sample at IWF in Atlanta. It looks like a good saw despite the safety features.
Regards,
Dave
I too saw the Saw Stop at the Atlanta show. In looking it over, I wonder if they are doing themselves a disfavor in pushing the safety factor nearly exclusively? The saw has quite a few engineering innovations beyond the saw stopping capability. I did notice that they are using a ribbed flat belt to transfer power from the motor to the blade. The matched 3 belt system used by most manufacturers seems so archaic and it wastes so much power. I too hope that the $2,200 price tag does not stop it from selling.
I agree. It is unfortunate that the FWW review focused almost exclusively on the saw's safety features. That would be like Car & Driver wrecking a car during a test and only reporting on how well the airbag worked. Safety alone doesn't sell. A safe saw that is also a good one would do much better in the market. The SawStop cabinet saw may be an excellent all around saw as well as a safe one, but you wouldn't be able to figure that out from the FWW article. I had been hoping to get more general information about the saw and how it compares to competing North American style cabinet saws. Did it unpack and set up easily and precisely? How flat is the top? What is the runout figure? What is the apparent quality of castings, materials, and workmanship? Does the fence move smoothly, lock square, and withstand abuse? Does the integral dust collection shroud keep the cabinet interior chip-free? I understand that threaded adjusters allow easy alignment of the miter slots with the blade. Are there other innovative features? How does the machine operate and cut in comparison with long-standing North American style saws like the Unisaw, PM66, and Jet cabinet saw? Is the saw to a good dollar value?
It would be good to hear more from FWW on the saw, but there isn't much chance of that because it was a loaner. The saw is no longer in their posession. I expect that other woodworking magazines will review the saw. Maybe they'll do a more thorough job.
Well that's just grand... I just made up my mind to purchase a new cabinet saw and now this has thrown a wrench into my plans. Never heard of a riving knife... Note to self, inquire with manufacturer about a riving knife.
Eric,
This was discussed about a year ago here in Knots. I explained why a riving knife can't be fitted to a typical American saw in posting #15603.54 with a further comment in #15603.66.
Basically building a saw to take a riving knife would require a complete redesign of the arbor and trunnion assembly. You would think that some manufacturer might break down and do this after building the exact same saw for over 60 years, but there are few industries slower to innovate than woodworking power tool manufacturers. We should be grateful that the same lack of innovation doesn't exist in most other industries or we would still be living in the stone age.
I am really frustrated by this lack of innovation when DeWalt, Jet, Ridgid, and probably some others, have released entirely new saw models and they still kept the old arbor and trunnion design that won't allow using a riving knife.
AND, as long as I'm on a rant here, when will some manufacturer make the huge leap to manufacturing jointers with the same type of disposable knives that are used on benchtop planers?
John W.
Whoa! I hear you on your second topic, but I would like to stay on topic because I would really like to have someone at one of the company's pick up the gauntlet here. If the focus of this is muted, I don't think that will happen.
I went back and read your posts. I don't think it is necessary to have the saw come up on ways. It may ultimately be better so that a guard would be easier to design into the product, but I would (I think) be satisfied to have the riving knife attached to the casting that holds the arbor. Granted, a guard attached to the riving knife attached to an American arbor would be trickier to design since the riving knife would tilt backward and forward as well as go up and down when the blade was raised and lowered. If we wanted to keep the casting assembly unmodified, possibly the riving knife could be controlled by a linkage, however, I don't want to kill this idea by suggesting a Rube Goldberg design.
I didn’t notice this thread picking up the technical reason that a riving knife cannot go on a Unisaw. It is because blade height changes on the Unisaw, and other North American style table saws, is effected by pivoting the arbor/motor assembly around a large shaft that is placed horizontally and located near the underside of the saw’s top close to the operator. The assembly tilts (clockwise when viewed from the saw’s left side) as it rises. This rotation prevents a true riving knife from being flush with the top of the blade at all height settings. The knife would start below when the blade is low, and rotate to be above as the blade is raised.
A true riving knife requires the motor/arbor assembly to travel straight vertically, which in turn requires a more expensive mechanism. The SawStop cabinet saw’s motor/arbor is mounted to a massive cast iron elevation plate that rides vertically along two large bronze bushing linear bearings. The blade height adjustment wheel turns a bevel gear that in turn rotates a large acme thread rod to move the assembly up and down. The weight of the motor, arbor, and elevation plate is somewhat offset by a spring loaded strut. This construction may well have added more to the cost of the saw than the blade brake did.
I look forward to reading the FWW review, though I hear that it focuses on the blade brake without making much mention of the saw’s many other design advances. Might be in my mailbox as I write this.
I don't believe it is necessary to redesign a table saw so that the blade height adjustment is vertical. If there was a modification to the current cast iron mandrel housing so that a riving knife could be attached a simple linkage back to where the usual splitter attaches could be designed to move this riving knife in a suitable pattern of movement as the blade rises and falls through it's arc of travel.
I would prefer this approach because it could lead to a retrofit for the millions of old saws we all have.
Edited 11/16/2004 3:25 pm ET by Corners
I made a riving knife / splitter for my Delta saw from a piece of 1/8" aluminum. It curves to match the curve of the saw blade. It is mouted in the same mounting clip as the OEM splitter and tilts with the blade. I beveled the leading edge (like a knife) so that wood would not catch on it. As I recall, Tage Frid in one of his books has a similar design except that he mounted a block of wood on top, presmably as a shield.
We just got two new Laguna tablesaws that are equipped with just the kind of riving knives you're describing. They're great saws.
If Delta and others don't get their act together soon, the sales they lose to companies like Laguna will take an increasingly larger chunk of their market share.
The same thing happened to American automobile makers back in the 70's - they ignored emerging trends and consumer demands while Japanese car makers ate their lunch.
When Delta doesn't make a tablesaw that has the safety features I want, I buy from someone else. If Delta doesn't catch on and change their behavior, they'll continue to lose market share - but not if we gripe while we continue to buy their products!
What I don't understand is why we, as consumers, continue to reward unresponsive companies by purchasing their products while wringing our hands in dismay. Why not just buy the product that meets our needs and let market forces "inform" manufacturers?
Caveat manufacturer.
-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
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