Is this idea worthwhile?
I was thinking about featherboards and it occurred to me that if a table saw had a pair of fences and the table could
hold the stock, there could be no lateral movement and no sideways force.
Anyone have an opinion?
Have you ever been shot in the belly by a piece of wood that the saw kicked back? Huge risk of increased kickback if you try that. You now have two pieces of wood that you are trying to safely pass by the saw blade. With just one fence the waste can lay on the table or fall off the table with marginal risk of getting tossed back by the blade.
If your wood is not parallel you have chances for even more adventures in kickback and binding.
NO!!!!! HORRIBLE IDEA!!!!!!
You're begging for binding, kickback, and all kinda' bad things.
Make a sled with hold-downs.
-Zz
Rockler has a similar set up on its cove making jig. I really don't see the purpose on that jig but the fences you are talking would have to be perfectly parallel, "perfectly". If they were not perfectly parallel there would either be no purpose of the extra fence or the fences would pinch the stock.
Actually, I have a homemade sled that is almost perfect for my needs.
The homemade fence quickly locks to the sled with a pivot clamp and it happily sits vertical and it is parallel the blade.
Since I know how easy it was to make, I can make another one fairly quick.
My sled has a forward stop for safety.
It will always stay parallel to the table and it uses underside slides to prevent tilt and lift-off when fully extended.
My intention is to employ hold downs and a push handle far from the blade.
Like a deli slicing machine!
I will forget about the dual fences.
Yeah.. put your head between your knees and kiss your ass goodbye..
You would be almost forcing kick back, IMO.. Feather boards work because the have flex in them and let things move in one direction.. A fence on each side of the work would let the piece of wood being cut move either to the back or FRONT of the table..
Also, most folks only use feather boards before the blade... I think a 2nd fence might close the kerf and cause kickback, but not sure..
All in all, it sounds dangerous..
mac
Please remove splinters before emailing
If you don't believe all of the other posters who described terrible kickback, please film the tests.
Trapped wood is never a good idea on a table saw.
Cove cuts are not through cuts. Cuts that aren't through don't get the same pressure against the rising teeth.
Think crosscut dadoing with stop blocks. You can use the stops for dadoing, but the same stop in a full crosscut is an invitation to disaster.
I've done coves with one and two fences, and prefer two when the angle is such that the wood wants to walk away from the fence. I can take a slightly deeper cut with two rails.
Sat, Feb 2, 2008, 2:41pm snipped-for-privacy@doesthisblockpork.mindspring.com (Jim=A0Behning) doth posteth: Have you ever been shot in the belly by a piece of wood that the saw kicked back? Huge risk of increased kickback if you try that. You now have two pieces of wood that you are trying to safely pass by the saw blade. With just one fence the waste can lay on the table or fall off the table with marginal risk of getting tossed back by the blade. If your wood is not parallel you have chances for even more adventures in kickback and binding.
If you stand out of line of the blade you won't get hit by kickback. When I was in high school shop class the teacher showed use what kickback was. He then told us not to do that. And I never hav
I don't see a problem with two fences, if they are parallel to each other and the blade. I also don't see the need.
JOAT - who does not welcome thread question e-mails..
10 Out Of 10 Terrorists Prefer Hillary For President - Bumper Sticker I don't have a problem with a woman president - except for Hillary.
Here's another idea based on your post.
I have a sled.
Using clamps the board is fixed.
The sled has a stop.
Why not stand on the other side and pull the sled instead of pushing it?
The 'kickback' would go away from you.
Completely safe?
Sat, Feb 2, 2008, 6:09pm (EST-3) snipped-for-privacy@aaronj.com (BoyntonStu) doth queryeth: Completely safe?
I do not believe I know of 'anything' that is 'completely' safe.
JOAT - who does not welcome thread question e-mails..
10 Out Of 10 Terrorists Prefer Hillary For President - Bumper Sticker I don't have a problem with a woman president - except for Hillary.Stu, Like others have mentioned, dual fences would be hazardous when used for ripping on a table saw but you can run paralle fences when making cove moldings on the TS. In this instance, the fences are not in line with the blade and you are not performing a through cut. Also, a hold down is highly recommended. Just wanted to mention that there is a variation of a two- or parallel
- fence set up on a table saw. Marc
And if there IS anything that's "completely" safe, I suspect that it wouldn't be much fun.
I'll stick to things that have just a hint or two of "unsafe" to them...let's me know that I'm still alive by getting me to think "If things go bad, where do I need be that will allow me to TALK about it later?" And hoping that nothing DOES go bad.
Mike
Unsafe for other reasons, such as the mechanics of reaching long distances, but safe for other reasons I'll mention below.
The bottom line: You don't understand kickback. The key to safely and successfully using machine tools is a solid understanding of the physics involved in each operation and using them to your advantage. Fear based "safety" workarounds usually have unintended side effects, at the minimum destroying accuracy or speed of work.
Boards clamped to sleds are not the same as boards trapped between a fence and the rising back teeth of a saw blade. You need three conditions for serious kickback:
Ripping a board that's short and wide, or using a miter gauge and rip fence together (without extra room to the side of the blade) can also get ugly in a hurry.
You can prevent kickback by eliminating at least one of the conditions above. For example, a splitter prevents the cut wood from pinching or being grabbed by the rising teeth. A properly adjusted fence eliminates the slop. Without traction (as on the clamped sled or the offcut side of a rip), the possible force of kickback is greatly reduced.
Here's a decent demo that looks like it's filmed in a school shop:
Some teachers will demonstrate the same thing using foam.
Yes, I do stand to the side.
My high school shop teacher was a room monitor. I do not recall any teaching but that was over 30 years ago. I do recall the college shop teacher teaching but I do not recall any lessons besides pull down on the disconnect handle mounted 14 feet up on the ceiling before servicing equipment. Oh, he also said no power sanders allowed. I do not recall a lesson on the use of scrapers. One last lesson from the college instructor. Two parts. Do not drop tools on the floor. Do not stick your foot out to prevent a chisel from hitting the floor. Better the floor and teacher wrath than a trip to the hospital.
Lucky you. At least you knew what "sharp" was like. Wasn't until I started doing my own sharpening that I found out that you don't try to catch a chisel with your foot.
DANGER DANGER Will Robinson Kickbacks ahead!!!!
Good video.
Comments:
1> The kickback was away from the fence and it flew in rotation like a frisbee..2> If another fence was on the other side of the board, how could it fly off the table?
3> A hold down near the fence would prevent lift.4> A slide table push fence would not allow the board held against it to frisbee rotate.
Conclusion: Sliding tables are inherently safer than bare table saws. BTW My slide table stops sliding before your hand can reach the blade. Use a hold down next to the fence as close to the lifting blade as possible. Install a splitter if possible (harder on a slide table) A second fence not even touching the board or a feather board would help.
Sun, Feb 3, 2008, 11:00am snipped-for-privacy@cox.net (J.=A0Clarke) doth sayeth: Lucky you. At least you knew what "sharp" was like.
It's all relative. I took shop starting in the 4th grade, mandatory until the 8th grade. I took 4 years of it in high school, where it was optional. Started using power tools, unsupervised, in th grade. The wools were demonstrated, and then we were expected to se them right, and not hurt ourselves. We listened, and no one sufferred injuries that a bandaid wouldn't fix. Except for the idoot jock that was horseplaying and shoved an arm thru the shp door window, cutting an artery - he survived. We learned woodworking, welding, some mechanics, drafting, forging, sheet metal work, metal lathe and milling machine, and even a big of electricity, and probably one or two things I don't recall just now. However, I graduated high school in 1958, age 17. Oh yes, attended schoo in two different small countryschools, in the same school distric, in rural southern Michigan. .
JOAT - who does not welcome thread question e-mails..
10 Out Of 10 Terrorists Prefer Hillary For President - Bumper Sticker I don't have a problem with a woman president - except for Hillary.Sun, Feb 3, 2008, 10:17am (EST-3) snipped-for-privacy@aaronj.com (BoyntonStu) doth sayeth: =A0BTW My slide table stops sliding before your hand can reach the blade.
Yeah, sure, right. All it takes is one time of putting your hand in the wrong place, and your friends will be calling you "Stumpy".
JOAT - who does not welcome thread question e-mails..
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