For some time I have a question about the way woodworkers in the USA are using their table saw. Especially the adjustment of the fence. Now I have read the article about the table saw injuries and its was time to do so.
In the Netherlands (and I think in western Europe) we do ripping in a different way. Most important is the way we are adjusting the fence. The head off the fence should stop half an inch further then the place where the wood is cut, its absolutely forbidden to put it across the line where the shaft of the saw runs.
On all woodworking schools and courses this is what we are getting told by the instructor.
The theory is that the wood gets warm due to the friction of the saw and therefore can expand and can get stuck between the saw blade and the fence. Its obvious that this will lead to dangerous situations.
What’s your opinion about this
attached a rough sketch
Replies
schaaf,
that makes good sense. i have heard others say that they rip in a similar way.
just curious, maar waar in nederland leeft uw? ik was in tilburg geboren en wij ging naar america toen ik dree jaar out was. mijn hollands is niet zoe goed. eider een praat engls hier!
welcome,
eef
I'll give you another theory to throw at you instructors other than the one that mentiioned about the friction causing expansion and catching. If the fence extends beyond center line and you run into a piece of violent reaction wood (wood that has a high amount of built in tension that is released when severed) the stock can spread wide enough to hit the rear of a long fence and then rebound back into the back of the rear rising teeth which are the most dangerous as far as kick-back. A splitter or riving knife can flex under pressure so the fact that they are there may not help in that case.
The majority here in the U.S. use the long fence as opposed to your short fence and many don't use a splitter or riving knife which is personal choice. The riving knife has been made mandatory on all new design saws now here. But... all fences with the exception of the Uni-fence are long style. I learned from Richard Jones who is English apprenticed and now teaches in England at a college about the short fence and it made sense to me.
That was around 9 years ago and have been using it since. I simply made my own short fence that attaches to the face of my long fence which was about 30 minutes inversted... There are a few of us using the short fence now but the majority here still use the long fence as it has been around so long in the U.S;
I'm skeptical about the heat issue because it's moisture that makes wood expand, not heat. Wood movement due to internal stresses is an issue for sure, though. I learned of the short fence from Sarge and have played around with it a bit but most of the time, I just use a long fence. I am more comfortable having the fence boyond the blade to guide the wood safely past the blade.
It felt ackward at first to me also Chris... I took 10-12 pieces of wide scrap one Sunday morning and made about 300-400 practice rips for several hours. At that point if felt natural and has since. Some might argue that they don't have time to invest to get a good feel as that took several hours. My argument to that would be it took less time than many spend reading woodworking forums daily. ha.. ha...
Sarge,
Do you only use the long fence now?
Just the opposite Chris.. I use only the short fence. Click on and enlarge those three photos I posted. My long fence is white. So is my short fence but look carefully where the face attached short fence ends which is before mid blade. Do you see the blue clamps. They are the Rockler universals that hold the short to the face of the long.
If you look close in the last picture I went from all white UHMW to white phenolic as you see the white phenolic on the face of the black inner phenolic. Just look carefully and you will see where the short fence which is 3/4" thick ends and notice the free zone created from that point along the remaining long fence which is now 3/4" from the blade.
If you don't get if fully... let me know and I will get some better close ups tomorrow. OK!
Sarge,
If I ever heard of the short fence before it didn't register. This is a great idea, and it looks pretty simple to assemble.
Tell me, what are the devices you're using to the left of the blade?
--jonnieboy
J,
Virtually all Ypean TS have a two-piece fence that allows the working face to be slid back/forth and locked agin the main body of the fence. There is usually a set of T-slots on all the faces, which also allows one to mount wooden false faces, low-profile faces (for very narrow workpieces, allowing push-stick access) and hold-down or other devices to keep the workpiece from skewing or rising.
Like Sarge I set the working fence face to end halfway down the blade. The front of the fence-face sticks out the front of the saw table, so there is still plenty of fence length agin which to register the workpiece.
As Sarge mentions, it is the bending from internal stresses in a workpiece, released as the front of the blade cuts the kerf, that cause the front end of that workpiece to attempt to travel into the rising rear teeth of the blade (which are wider than the blade body). But in my experience it is not pinch but opening of that kerf that is the worse potential problem. If the fence doesn't end before the back of the teeth, a widening kerf (and the consequent outward-bending workpiece) will see the fence push the workpiece into the rising rear teeth.
A pinching kerf does the same but in that case the fence doesn't contribute to the move teethward. Also, a pinching kerf becomes obvious quite early, as it begins to bind on the body of the blade before it reaches the rear teeth.
But the idea of the short fence is to remove also another potential cause of the workpiece hitting the rising back teeth. Even if the fence gets toed-in a little (accidentally) it is less likely it will itself try to push the workpiece into those rising back teeth if the fence-face ends well before the back teeth are reached by the workpiece.
As Sarge mentions, a blade-following riving knife doesn't completely remove the risk of kickback. The danger lasts for that brief period/travel when the workpiece is moving into/past the rising back teeth but hasn't yet reached the riving knife. The knife-design that allows the knife to move with the blade, always a mere 1/16 - 1/8" behind the teeth, reduces this risk greatly, compared to an American-style splitter (which may be 1 - 4 inches behind the blade).
If a riving knife has significant flex, incidentally, I would say it was unfit for purpose. Such flexible knives might well arise with very thin-kerf blades, as the knife needs to be 0.2mm thinner than the blade kerf. A 2mm thick riving knife is going to be significantly less stiff than a 3mm thick one.
But since there is a still a kickback risk, it is a good design of fence allowing the mounting of hold-downs and a pressure-finger to help keep the workpiece against the fence-face as well as offering supression of any kickback tendency that might arise. The Ypean two-piece fence design with T-slots and a movable face is, I believe, an improved design over the unadorned one-piece, full length fence typically found on American saws.
I can post pics if anyone is interested.
Lataxe
Sarge,
I meant "short" but
Sarge,
I meant "short" but wrote "long"! And I fully understand the concept. I, like ForestGirl, have a Unifence. It's not the easiest fence to build sliding jigs for, but I haven't yet felt the need to build such a jig. Love the Unifence.
Chris.. I tend to agree with your reply. But then again, I do not believe I have ever used a 'short' fence.. Maybe in a jig/fixture I have made for a special cut.
My opinion is that moisture 'inside' of the wood is the real problem. Could the blade friction make steam to make the problem more severe? I wonder. Wet wood is a killer!
I think most of the time it is 'reaction wood'. I use much Jatoba with wild grain. Sometimes that 'wild' grain is really dangerous to rip. I am in the habit to pay really close attention while ripping my Jatoba (or any wood) that the grain is not really straight. If my 'stick' seems to close up behind the blade, I stop and shut down the saw. I then put a wedge of wood in the previous ripped slot and then finish the rip. Stopping the cut is never a problem for me because I almost always rip a bit wide and finish the edge on my jointer.
I make up a bunch of wood wedges to have on hand that are a bit wider than my blade in use width is.
But, then again, what do I know?
I don't think thermal expansion is to blame. A six ft board ripped with the grain, if heated from 32 deg F to 212 deg F when milled would expand less than .035 inch. That is just a shade over 1/32 inch.
Here is the formula:
dl =(2.7*10-6in/in°F)*(6 ft) * (12 in/ft) * ((212 °F) – (32 °F))
2.7 e-6 is the coefficient of expansion.
Interesting problem, though.
Best regards,
Fred
PS I'll be in Amsterdam in mid March. Where is the best place to buy Cuban cigars?
Schaaf, I have an older Delta Unisaw that came with the Unifence -- it is an adjustable fence that can be slid toward the operator such that it becomes a "half-fence" -- what you describe as standard practice. It's a very desirable arrangement, IMHO, and one of the things I like the best about the saw. Biggest problem is remembering to adjust it, as I learned to saw on a standard fence that didn't adjust!
To all -
Off-topic observation:
I have trouble knowing who a response is targeted for. In the above exchange almost everyone address their reply to an individual. For example - "Sarge", "Chris" and so on. I will try to use that format in all my future posts.
Ooops! Almost forgot to do it on this post.
Jerry
Good morning johnnieboy. The devices I use that you refer to are what I call a "spring-board". Simple to make from scrap ply and scraps strips of solid wood. In lieu of feathers the face is simply a solid piece that springs back when pressure is applied as feathers do when you set them up against the stock being cut.
I have two.. one that works in the stock miter slot left of blade and one that works in a miter slot I added to the left outer extension talbe. The standard slot handles pieces to be cut up to about 8" and the outer allows me to use the spring-board on pieces up to around 22" wide. If you want to see close-ups I can get you some as they are easy to build. Just a main board.. then glue two solid tabs on outer face.. then a solid strip glued to those.. then one wooden tab glued center.. then the final solid strip glued to it with the ends rounded over to prevent snag on entry and exit.
See how simple iit is? ha.. ha... may be a little confusing but a picture of the spring-board from directly over-head would explain in a jiff. If ya need them I will get a few shots as quite a number of people have private messaged me over the years to find out how I do it.
Sarge.. I would like to see your set-up.
I normally use a 'long fence' with a feather board set behind the blade. NO PRESSURE to the wood. Just surface contact. I can watch my fingers AND the back of the blade feather board.
I am NOT saying I am right or wrong. Just what I do. My saw does not have a riving knife. The 'splitter' that came with the saw never seems to fit the width of the blades I use. And it is always in the way for my common saw usage. Even if it fits the blade it will bend if given moderate preassure by hand. Maybe a hardened steel, not stamped, cold rolled ,would be alot better?
In my lifetime of woodworking I have been hit with kickback twice. I was NOT paying attention to what I WAS DOING.. I never thought that is was my saw's fault!
Here ya go Will. A better picture of the short fence which will slide to and fro by simply a couple of turns on the clamp screws... the short spring-board and an over-head view.. the long spring-board then over-head... Johnnieboy should get the idea of how if he wishes from those over-head views.
The only differnce in your feather method Will and mine is I do put a slitght amount of pressure on the stock. Just enough to cause a slight spring back which the empty space between tabs allows. Same reason feathers are made at an angle so they give somewhat.
I saw your photos of yoru spring board a couple of years ago and gave it a try.
What a lovely little piece of equipment it is! Mine's much cruder but I can't imaging ripping without it. Much better than a featherboard, IMHO.
Thanks Sarge,
Pete
My treat Pete... glad you are enjoying it as I also much prefer it over a standard feather-board.
Afternoon Jonnieboy.. I move the face of the shorter (and longer) spring-board so the leading edge corresponds to the leading edge of the short fence at mid blade. BTW... I used a 1 1/4" tall face on that one.. the long has a standard 3/4" tall face. You could move either SB back or forward if you wished and sometimes I do. I do it when making a trench in long grain (dado) to give support all the way through the blade as the cut of a dado is not finished until the stock entirely clears the blade. On a rip cut the stock is totatly severed when the tail of the stock clears about the 4-5 tooth "before" mid-blade. Take a look at a rip sometime and you will see that and the reason the fence needs to be no longer than mid blade. BTW.. I also remove the short fence on that cuit so the stock is also referenced on both sides for the whole lenght of the cut.
The long SB rides on a T track in the miter solt I added to the outer left of saw. But.. so does the short SB. There are slots in the SB so the SB can slide forward and back to adjust to the width of stock. But the same bolts that are in those slots go into a T track riding in the miter slot itself. What locks the SB to the track is when you tighten down on the handles. It not only locks the SB into position it locks the T track in the miter slot.
I use the T track from either Eage America or Rockler. I would have to look. You can get just the track that fits a miter slot or it and a miter track you can add yourself. The T track has 1/4 SAE threaded holes. You use star or T handle 1/4" male threade bolts that go through your jig slot and enter the T track. As stated when you tighten down on the knob on the bolt it drives the thread down and the T track lifts. The wings of the T track catch the T slot in a miter slot.
You do have to purchase a T handle or Star handle bolt that allows thread the lenght of the thickness of your jig.. and the thickness of your T track thread. You can purchase long and cut them to lenght if necessary.
The short lenght of board you refer to is called "crown gaurd" and it common on most Euro TS's that has a taller riving knife that one can be attached too. Contrary to what many think all riving knives are not the same. Some go below a blade.. some taller so a crown gaurd can be mounted. And yes.. in this case the crown is mounter to the splitter with two machines screws after I drilled holes in the splitter to accomodate them.
I won't hesitate to modity any machine I have to make it better so drilling holes means nothing to me. ha.. ha.. I can think of no WW machine I have I have not modified with the exception of my 20" planer to improve this or that. Any more questions ask and if ya need more pictures just shout!
Thanks on ther TS compliiment. Its a Steel City 5 HP Industrial I got by working with Steel City demonstrating their machines at the International WW Show in Atlanta in 2007. I worked 90 hours and in lieu of cash... got that saw for nothing as I loaded the show floor model on my pick-up and took it home. I sold my Uni-saw 3 HP for $800 . Love that saw and it is built like a beast.
Sarge,
Thanks for the great reply. That answered my questions very well.
When you talked about jig knobs I wondered if you'd ever seen these from Lee Valley
http://www.leevalley.com/wood/page.aspx?c=2&p=60934&cat=1,43455,61994&ap=1
They claim the bolt "snaps-in," but I've found that they fall right out. Still, it's worth it to me to have a bunch on hand and use any length bolt I need. Sometimes you just don't know which length is going to work. I just epoxy it in place once I find the length I need.
And yes, that saw is one mighty beast! She gleams!
Talk to you soon, Sarge.
--jonnieboy
The "wood expanding from the
The "wood expanding from the heat" explanation is interesting but wrong, the small area heated by the blade and the very low expansion of wood with a temperature rise wouldn't cause nearly enough expansion to cause binding.
The short fence is only safe to use if the saw is also fitted with a riving knife. If the riving knife isn't there, the wood can easily pivot in the open area past the end of the fence and get caught and thrown by the blade.
"The short fence is only safe
"The short fence is only safe to use if the saw is also fitted with a riving knife."
John, that seems to imply, because of what I suspect you probably inadvertantly didn't say, that you're perhaps suggesting ripping with a US style long fence without a riving knife (or splitter) is somehow either safe or safer. Can you expand on your thinking there? I can't see how a long fence and an absence of a riving knife and crown guard makes this style of working any safer than a short set fence and similar absence of guards.
I found that when I worked in the US with US style saws that I still preferred ripping with a short set fence as I found it safer, even if a riving knife was absent (as they always were because riving knives weren't fitted to US saws in the 1990s and early 2000s), and further, even if there was no splitter or overhead blade guard (items that were as rare as hen's teeth in the US workshops I worked in or visited). Slainte.
Slainte,
I didn't imply anything about long fences with or without riving knives or splitters.
The style of fence, while still important for safety, is far less critical than whether or not there is a proper riving knife in place. A splitter is not an ineffective substitute for a riving knife.
Without a riving knife in place, ripping using a short fence is at best only slightly safer than ripping with a long fence. With a short fence, you do reduce the chance that the stock will get pinched against trailing edge of the saw blade, but with a short fence there is also a slightly greater chance that the stock can pivot and get kicked back because the stock isn't being stabilized by the fence as the board is pushed to get it past the blade at the end of the cut. If there is a riving knife the stock can't pivot into the back of the blade at the end of the cut, hence my comment that a short fence needs a riving knife to make it truly safer than a long fence.
John, thanks for your clarification. My only slight disagreement with your analysis of the movement of wood after the cut when using a short fence is the likelihood of the material to pivot into the upward cutting rear teeth of the blade. I don't think it's much more likely with a short fence than with a long set fence if other guarding is absent.
I must however declare that all my woodworking methodologies are European, so although I have used American style saws quite extensively I still usually 'tweaked' them by doing something to make the fences a 'short' style-- those long fences on saws in the US (and the absence of all guarding in most cases [probably discarded into the dumpster long ago]) generally just doesn't suit the way most Europeans work, ha, ha. Slainte
John.. I am still a bit confused with your statement.... "A splitter is not an ineffective substitute for a rivining knife"..
Did you mean effective? If so... do you consider the fact that I do use a short fence with a splitter more dangerous than using a long fence because the splitter is on board and not a riving knife. I do understand your comment about the chance of pivot if there is no riving knife and I agree with it totally. But.. you did not menton splitter in any way other than in-effective substitute for a riving knife. If the operator uses the push stick and puts pressure toward the blade the tail of the stock can pivot coming off the short fence. Agreed!
But.. with that said I have probably made over 30,000 rips using a short fence and splitter. I also use a springboard to the left. The only time I don't use a spring board to support on the left side of blade is when I rip rough stock that has been straight line ripped on one side and has the tree's original taper on the other side.
But.. even then I have never had a problem with pivot as I put the push stick pressure toward the fence to pin the stock on it. When the tail of the stock is finally severed I re-direct the push stick pressure to center line and push the severed stock straight through... not to one side or another.
So.. are you implying that a short fence is more dangerous to operate if you use a splitter in lieu of a riving knife?
First of all I made a typo and I can't correct it. The sentence should have read as you suggested, "A splitter is not an effective substitute for a riving knife." I will try to find out how to get in and correct the error.
Yes I do think that ripping with any fence, long or short, is less safe with a splitter than with a riving knife because a riving knife does a much better job of keeping the stock away from the rear of the blade. However ripping with a splitter is much safer than not having anything behind the blade.
Thanks John.. that totally clariffies your thoughts and exactly what I wanted to hear. I do agree as the riving knives I had on one of my TS's years ago would adjust to within 1/16" behind the blade. A typical splitter will not get that close and gets farther away from the blade as you lower it. The reason I always run my blade at maximum height. I do use a plastic shield over the blader so the high position closes the gap somewhat.
But... with that said I just spoke to Lee Styrone who fabricates the Shark Guard and I intend to design a spliiter for my saw that closes the gap even farther in the high blade positon. I diid the same thing with my Uni-saw before I moved up to a 5 HP as Lee fabricated the splitter for me. He uses a thicker blank than a normal splitter also as stock splitters are just to thin. Some of the stock riving knives I saw at IWF are too thin for that matter.
Yep.. the gap can make a difference IMO. What many that have riving knives don't realize is even with a riving knife there is a small window of opportunity between it and the blade. If you do enough ripping that tiny window is going to shut eventually as the odds can catch up with you. So... the bottom line is the riving knife is just one thing that contributes to over-all safety. Not the holy grail by any means and certainly not 100% sure fire for preventing the stock from touching the back of the rear rising teeth. So.. never lose fact of it could happen so pay attention at all times.
Again... thanks for clarification!
Regards...
While I appreciate the concept behind the short fence, I'm still in the long fence crowd. But, my "push sticks" are shaped more like planes of various widths, resting on top of the board and having a short cleat at the back to catch the trailing corner of the stock. All have raised handles for firm control of the stock, and a combination of an abrasive strip and a slightly-protruding pin at the front, sharpened to a tiny wedge, parallel to the blade, giving good lateral control of the stock. For me, the long fence provides a reference surface until the end of the stock is well clear of the rising teeth at the back of the blade. A short fence would eliminate that reference surface and rely only on my dexterity. I trust the fence staying put more than I trust myself.
hi ralph,
a few months ago a friend of mine went to reach for the 3/8x3/8x8" off fall to the left of his running t-saw blade. the back corner of the piece caught the back of the blade and fired the little stick into the end of his left index finger. the damage looked as if he'd been shot, point-blank, in the end of the finger. if he had had a riving knife...
with regards to the long fence, i too use one and for the same reasons you do. i have sometimes used a short fence and greatly fear the tail end of the board tipping left, into the blade as i push it clear of the rear of the fence. (does that make sense?)
eef
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