Offsetting Tablesaw Splitter?
Hi All,
In another discussion, the idea of offsetting the tablesaw splitter came up. It seems like there is some difference of opinion here. If it actually works, offsetting the splitter would be a good safety enhancement to tablesaw use. I’m interested in hearing from more people and getting to the bottom of it, if I can.
Here’s the concept: you offset the splitter a little towards the rip fence. While ripping a piece of wood, the splitter actually forces the keeper portion of the stock towards the rip fence, providing a moderate feather-board effect.
It appears that the stock splitter is too flexible to offer a feather-board effect (it would just bend out of the way under stress). But there is an after-market splitter available called the MJ Splitter. It has different configurations. One of the configurations allows the user to offset the splitter towards the rip fence. Go here to see what I’m talking about: http://www.microjig.com/MJ%20Splitter.htm
So…
— Is it safe to do this?
— Does the concept actually work?
— Is the stock splitter on your tablesaw stiff enough to do this, or do you need to get a stiffer after-market splitter?
Thanks everyone
Edited 2/19/2005 9:49 am ET by Matthew Schenker
Replies
I use the micro jig and love it. It does provide the feather board effect. I like that it is adjustable. The degree of offset from center is adjustable in increments (1 increment per side of the tab). You receive multiple tabs to insert. Each tab has two values that indicate how many thou away from the blade the material will be pushed. I also like that the pressure is applied to keep it against the fence. I generally use the ++ side (.002). The critical part to this jig (IMHO) is the initial set up. The jig comes with good instructions, and I had no trouble setting it up with a zero clearance insert and the template that is provided. The template also will hold the spare tabs when not in use. I also love the Grippr that micro jig sells. I use a couple of them and they help keep even pressure on both sides of the blade and glide right over the splitter. I like having my digits above the blade if you know what I mean. The gripprs are not cheap, but then my digits are priceless. Sales team are pretty good too. I had contacted them back in the early summer and wanted a thin kerf version (for the splitter). They indicated it was still in R&D and if I wanted it, he would take my name and let me know when it hit the market. He called back a few months later and even let me have a discount for waiting.
Matthew, interesting follow-up to your earlier thread. Here's my take.....
"Every action has an equal and opposite reaction." If there is a force, however slight, pushing the wood more firmly against the fence after the wood has passed the blade, what's the "equal and opposite reaction?" The other end of the board is going to move toward the blade. At the very least, I'd think there would be a possibility of burning on the fence side of the cut and/or some unnecessary roughness.
I suppose you could prevent the back end of the board from moving by using a featherboard, but I don't like the idea of any part of a board being trapped both fore and aft.
If your feeding technique is correct and, if needed, you use a featherboard on your side of the blade, you don't need help from the splitter. If your feeding technique is incorrect, counting on the splitter to help you out is, IMHO, dangerous in and of itself. I speak with great confidence about incorrect feeding technique because I have so much experience with it, LOL!!
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Not only is there a possibility of the board turning(how much depends on where the side load is in relation to the pivot point) there's the problem with binding. Depending on the weather, higher or lower humidity will also change the way the splitter fits due to friction and wood swelling. The turning can be eliminated by maintaining the board's contact with the fence at the rear.I recently found a shop that sharpens blades and planer/jointer knives, makes bandsaw blades from bulk, does welding/machining/machinery repairs and various other metalworking. I have some 1/8" x 6"steel from when I removed a wall and installed a beam in my house, so I'm going to make a riving knife for my saw. I'll post whatever I make with info on how well it works. I'm making this because the splitter/guards that come with almost all saws are either useless, cumbersome or do too much damage to the wood in the process of being what I said before. Since I work with a lot of sheet goods, an arm mounted on the right side would be in the way a good portion of the time. Otherwise, I would use one of those.
"I cut this piece four times and it's still too short."
"an arm mounted on the right side would be in the way a good portion of the time." Just to mention an alternative, the PSI guard/collector can be ceiling mounted. You probably knew that, didn't you? LOL!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
I do know it can be ceiling mounted and have seen your photos. The problem is that my equipment is in my garage, it's not drywalled and my walls are 9'. This means that the stringers are 9' at the bottoms and I also need to park in there. I position the TS based on what I'm cutting. If I need to cut from the length of a sheet of plywwod or MDF, I need to move it toward the overhead door. OTOH, I never put my hands directly behind the blade when I am pushing stock through. I have roller stands to support the stock after it goes through, but thatwill change soon as I'm going to make an outfeed table that can fold down.
"I cut this piece four times and it's still too short."
Offsetting Tablesaw Splitter
Proper feeding technique is not the issue here. It is a given (as is sobriety) when using a table saw.
That said, the 'equal and opposite reaction' part of the equation is tension relief; a tendency of the wood plank to spring back against the cutting blade after the cut. "The other end of the board is going to move toward the blade" is not a valid statement because it's YOU guiding the wood into the blade.
Problem arises when lumber leaves the blade and that is the subject of this discussion. A pinched blade must be avoided to avert kickback. That is accomplished by the splitter. As to whether or not the MJ Splitter is safe, practical, etc has already been addresssed in these posts.
BTW: If I was to design a splitter it would resemble the wedge on a splitter used for firewood. Entry point would be sharp/fine to accept the the cut work. Then, after say 5mm the splitter would assume a uniform dimension that is slightly thicker than the teeth (widest part) of the blade. This accomplishes a) counter-acting wood tension described above and b) exerting a slight pressure against the fence FOR PRECISION.
I use the MJ splitter, in combination with an overarm guard, and I'm pleased with it. I think I have it in the "+" position, which is offset something like 0.003" toward the fence.
As far as offsetting an original equipment splitter to achieve the same effect, it's not going to be easy. Stock splitters are usually metal stampings that aren't particularly flat, and they don't adjust very precisely. When I used one, I counted myself lucky to get the splitter somewhere in the kerf, and approximately parallel to the fence. If you do try it, you'll probably want to file a bevel on the leading edge of the splitter to avoid hang-ups.
[edit]
Edited 2/19/2005 2:57 pm ET by Kent
Matt
I think the better solution is what the Euros use. My MiniMax has a riving knife just slightly narrower than the blade (<.01"). The closeness in width of the riving knife keeps the stock tracking correctly as the blade cuts.
Additionally, since the riving knife is approximately 0.115", it will not twist if the stock is run misaligned.
_________________________________
Michael in San Jose
"In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted." Bertrand Russell
Michael,
I'd also prefer a European machine, with a riving knife, but it's way beyond my budget! I held back for a long time in buying a table saw, because of this issue. But I finally had to have one.My purpose here is to learn as much as possible about how to make an American tablesaw safer.I have noticed that the stock splitter on my saw is aligned with the center of the blade near the back, but it is twisted toward the fence near the top. This makes it difficult to determine it's aligment! However, as I slide a piece of wood through, the splitter seems to set straight with the kerf.The MJ Splitter might be a good upgrade. Maybe it's worth replacing my stock splitter with one of these? With the cost so low, and so many people giving it such high marks, it might be a worthwhile experiment, at least.
If you have a Jet, Powermatic, General or Delta cabinet saw, look into a Biesemeyer add on splitter. http://www.biesemeyer.com/safety/splitter.htm
I had one on my Jet cainet saw and it worked very nicely. Cost about $130._________________________________
Michael in San Jose
"In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted." Bertrand Russell
Matthew,
I also use the MJ Splitter, and like it a lot. But I found that with anything other than the non-featherboard-effect setting - i.e. - no "+" on the splitter, I was getting a good deal of resistance and in a couple of case actually pushed the splitter out of it's seating. I should say that on setup I had to shorten the lengths of the front and back "legs" that fit into the front and back holes on my ZCI in oder to get the splitter to sit flush against the ZCI. That could be my problem... I'd be interested to know if anyone else has experienced the need to do that.
In any case, featherboard effect or not, I like having the splitter and not having my boards bind up past the blade...
Mitch
"I'm always humbled by how much I DON'T know..."
Mitch,
You're the first one I've heard report that problem with the MJ Splitter. I would think that if you shortened the stems that are plugged into the throat plate, you would cause problems.
Agreed. I think it had something to with the throat plate ledge being under one of the splitter pin holes, but I can't remember; I think it's early Alzheimer's...Mitch
"I'm always humbled by how much I DON'T know..."
Perhaps this is an over simplification, or a whole different concept, but would angling the rear of the rip fence a few thou be just as good?
Ing,
I don't claim to be a woodworking expert, but why would I ever want to have anything other thana rip fence that's parallel to the saw blade? That would guarantee a different width at each end of the board. I think if you really want a "featherboard" effect, there are a bunch of other ways to do it with out taking your fence out of square and parallelism.
Regards,Mitch
"I'm always humbled by how much I DON'T know..."
Mitch,
I was thinking the same thing.I've read many times about people angling the back end of their rip fences away from the blade. I understand that the goal is to keep the wood clear of the blade, but I don't see how this technique accomplishes that without creating a tapered cut.Lots of woodworkers use this technique, so there must be SOMEthing I'm missing here.PS: To achieve the same goal, Euro machines use a short rip fence that ends just a few inches from the rear of the blade. That makes sense, because the fence is still parallel to the blade.
Matthew,
Every time I've seen a demonstration of a cut that required the blade to be very close to the rip fence, a sacrificial fence was added.
I must say, I've never read about angling a rip fence. It's certainly possible I missed it, but it just doesn't make sense. I'm not even sure what the objective is. If you want a taper, use a taper jig, right? And if you know you're going to get close to the rip fence, protect it with a sacrifical fence.
But I'm interested in some of the applications you've read about we're experienced woodworkers used the technique. Do you have any links you point me to?
Thanks,Mitch
"I'm always humbled by how much I DON'T know..."
Mitch,
People angle their rip fence away from the blade for safety reasons. This method is meant to help prevent kickback because if there is any stress-related bending in the wood, it will take place away from the blade.This is my understanding of it. But I have never done this. Perhaps someone who has done it can clarify here...
People angle their rip fence away from the blade for safety reasons.
I was taught that technique 40 years ago, but abandoned it fairly soon. I think it came from using those old "Jet-Lock" type fences where you had to measure at the front and the back of the saw table every time to get the fence straight. People figured that they didn't want the blade to pinch, so to be safe, they made sure to err on the safe side. With Biesemeyer type fences you don't have that problem. If you really want to avoid kickback when ripping, use a short fence like the industrial rip saws and the Euro saws do, or get the same effect with short board attached to your fence
Michael R
Matthew,
Actual featherboards, splitters, kickback pauls and blade guards are the appropriate tools, IMHO, for dealing with any issue with the structure of or stress upon the wood. But that's one person's opinion...
Regards,Mitch
"I'm always humbled by how much I DON'T know..."
Where is the cut being made? At the leading edge of the blade. Not in the middle, not at the rear. Since the blade and fence aren't moving, the distance from the inside edge of the blade to the fence is the determining factor in how wide the board will be after the cut. The inside edge of the waste will have saw marks on it because it is crossing at a very slight bias through the blade so the teeth will hit as the wood passes the rear of the blade. Cutting a cove on a tablesaw is a very extreme version of setting the fence at an angle, going away from the blade. That doesn't taper, does it? Nope.
"I cut this piece four times and it's still too short."
There are dozens of references "out there" that recommend positioning the rip fence 2 or 3 thousandths away from the blade at the far end. If your feed technique is proper, it won't produce a tapered cut, but will theoretically take a little pressure off the stock, decreasing the liklihood of the wood catching rising teeth of the blade.
The main reason I don't like this technique is that it prevents me from moving the fence to the other side of the blade when needed. I tried it for a short time, and hated it. Realigned my fence and just concentrate on proper set-up and technique. forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
forestgirl,
I agree! For me, proper set up of the tablesaw is enough to think about, without worrying about offsetting the fence. Maybe in another 10 years, I'll say something different, but for now I'll just keep everything aligned.
Any idea what a .002" or .003" offset amounts to in width differences on a 8 foot board?Mitch
"I'm always humbled by how much I DON'T know..."
Mvac, I think you're assuming that in feeding the board, you'd be keeping it snug against the entire length of the fence. Not! If you feed the board with pressure against the fence on the operator end of the blade (e.g., a featherboard placed on the infeed side, a little in front of the blade) the board will not have a taper. If you stopped in mid-cut and put a feeler gauge at the outfeed end of the fence, you should find a tiny gap between the fence and the stock.
If you were to have the pressure equal all along the board, you would end up with burning on the side of the wood opposite the fence and quite possibly a roughened cut. You never should be putting pressure on a board on the outfeed side of the blade.
I've learned this (repeatedly, LOL) when cutting plywood. If my pressure (force) is too much toward the back of the fence, the cut gets very screwed up. I had to learn to envision arrows going from my hands following the force of my pushing, as in the diagrams in tablesaw books. Too much sideways force at either end of the fence will skew the cut.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
"If you stopped in mid-cut and put a feeler gauge at the outfeed end of the fence, you should find a tiny gap between the fence and the stock."
Sorry, but I have to disagree with this technique. Allowing the workpiece to drift away from the fence is risky (even if the fence is angled). The feeding force should be mostly parallel to the fence, with a slight bias toward the fence.
When you observe, "if my pressure (force) is too much toward the back of the fence, the cut gets very screwed up," I suspect what's really happening is that you're deflecting the fence slightly. As the fence moves away from the blade, burning occurs on the offcut side. When you release pressure, the fence springs back and you get burning on the keeper piece.
Yet another reason to use a full-kerf splitter!
Mitch
Angling the fence a couple of thou's will not give an angled cut, but the cut will be very slightly coved, top to bottom.
FWIW, I believe everything should be exactly parallel or perpendicualr to the blade for safe and accurate cuts._________________________________
Michael in San Jose
"In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted." Bertrand Russell
Angling the fence will not produce a tapered rip. Think about the geometry - the width of the ripped piece is determined by the distance between the cutting edge of the blade and the fence (measured perpendicular to the fence, if you want to be exact about it). There's no way that the board can get wider again after it's passed the blade!
Personally, however, I set the fence parallel to the blade.
Kent,
"Angling the fence will not produce a tapered rip. Think about the geometry - the width of the ripped piece is determined by the distance between the cutting edge of the blade and the fence (measured perpendicular to the fence, if you want to be exact about it). There's no way that the board can get wider again after it's passed the blade!"
Don't think me obtuse (although you wouldn't be the first), but this doesn't make sense to me, and I don't think it makes sense geometrically. The reason is this: Unless I make rip cuts different from everyone else, I hold my work tight to the fence as I slide it toward the blade. The blade enters the work at the angle at which the piece approaches it - the distance from the blade to the fence is different from the front to the back, because the fence is angled.
The only way to achieve a parallel edge on a ripped piece is to have the fence parallel to the blade; any other case must by definition produce a taper, or angled cut (This assumes of course that the opposing edge of the piece is already parallel to the fence).
Were this not the case, taper jigs couldn't produce tapers, because according to your logic the width of the piece would be determined by the distance between the cutting edge and the fence, and not by the angle of approach of the work to the blade.
If my logic is flawed, I'd be very interested in understanding how. I'm not a rocket scientist, but I think I know angles and basic geometry well enough to make the case.
Btw, as ForestGirl mentioned earlier, we may only be talking about 2 to 3 thousandths of an inch difference between fence front and back - that's still an angle, however small.
Regards,Mitch
"I'm always humbled by how much I DON'T know..."
You just highlighted another reason to keep your fence straight.
When your fence isn't aligned with the blade and you hold the wood tight against the fence, the blade, being solid and fairly long, resists non-parallel movement and wants the wood to run parallel to the blade instead of following the fence. This makes the wood want to ride away from the fence in back, and tends to burn the wood on the offcut side.
A taper jig holds the wood at an angle to the direction of feed, but the feed motion itself is parallel to the blade, being controlled my the slots in the saw top.
Hope that is halfway clear.
Michael R
OK, Michael, I think you just cleared it up for me. Angling the fence could result in burns because the blade wants the wood to go one way and fence wants it go another - i.e. - it's stressed. But it can't taper because if the fence were angled enough to attempt to create a discernible taper, the blade wood lock up from the stress of forcing the wood's motion to stay straight while the operator is trying to literally push it laterally - a physical impossibility.
The taper jig explanation - that it in fact keeps the wood moving parallel to the saw blade, was what opened my eyes.
And so, Kent, it would seem you were indeed right, and I am indeed getting old.
Thanks for your tolerance, and Michael, thanks for a very illustrative and intuitive explanation.
Regards,Mitch
"I'm always humbled by how much I DON'T know..."
Mitch,
Although I am new with tablesaws, I am not so new with geometry. As I thought about it more, the angled rip fence started to make sense, at least geometrically.With both the angled rip fence and the taper jig, what matters is the ENTERING angle of the wood.Correct me if I am wrong, but with a taper jig, the stock rides along the "fence" at an angle throughout the entire distance. In other words, the wood ENTERS the cut at an angle and that is the key here. What comes after the cut makes no difference, even with a taper jig. In theory, I suppose a taper jig could end with the back of the blade and you would still get a taper.With an angled rip fence, the stock ENTERS the cut straight and exits possibly at an angle, or perhaps with a gap between the stock and the fence. But again, what comes after the cut makes no difference. In theory, you could have a rip fence that stops after the back of the blade and it would still be a straight cut.I'm only speaking geometrically here, as I have little experience with tablesaws and no experience with tapering jigs.With that said, geometry is less comforting to me right now than having a parallel rip fence, so I'll keep my fence straight!
Re: angling the fence. While that will tend to prevent the wood from binding between the blade and the fence, it will also tend to cause the wood on the other side of the blade (the side not between fence and blade) to hit the outfeed side of the blade. This is still a kickback risk.
If y'all take my example of ripping a piece of stock using a featherboard it should be pretty clear that you're not going to get a tapered cut. Between the fact that the board is pinned to the fence at a specific spot in front of the blade and the fact that you are only talking about .002 - .003" over a, what?, 30" span, you're not going to get any discernable "taper."
I hate arguing this side of the debate, because I don't toe my fence out! ROFL!!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Angling the Fence
Angling a few thou - away from the blade. Correct?
Built-in tension in lumber tends to close the kerf. You want the splitter to keep the kerf open to avoid blade pinch. Ancillary advantage gained by a slight offset is to gently goad the keeper part of workpiece to continue to hug the fence. [Part that slides against fence is considered the keeper while the free end is termed 'waste']
Offsetting Tablesaw Splitter
To achieve the featherboard effect all you need is a 'nudge' effect, not a 'push'. So, the stock should perform as well as the MJ.
Actually, the MJ has only a couple of nubs featherboarding the keeper while we have a full length metal object with the stock splitter - exerting a wee bit of pressure. Of course, neither is foolproof in that a twisted piece of lumber has its own mind :)
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