SawStop Router Tables


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16 hours ago, wtnhighlander said:

One would think a router table is the next logical application for the SS "flesh sensing" technology. A lift could easily be designed to yank the bit below the table when fired off.

Yeah trouble with that, it would take a massive amount of force like a gunshot to work fast enough that you'd basically have to use a gun. I don't think blade retraction was the initial goal with the table saw. It was just used because the forces involved with stopping a blade from what 4,000 rpm to a dead stop created far to much force to keep the blade above the table.

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3 hours ago, Chestnut said:

Yeah trouble with that, it would take a massive amount of force like a gunshot to work fast enough that you'd basically have to use a gun. I don't think blade retraction was the initial goal with the table saw. It was just used because the forces involved with stopping a blade from what 4,000 rpm to a dead stop created far to much force to keep the blade above the table.

Piggy backing on Chestnut, I have a healthy respect for routers and would love to see some sort of flesh sensing technology implemented in their design. I am sure it can be done but the engineering and the tooling would be costly. My main focus would be reliability. Having a spindle that spins upwards of 20k RPMs retract and come to a dead stop would be hell on internal parts. I think a better option would be a router lift that retracts the tool. But then you need a hell of a beefy router table to withstand the forces of the router being pulled down. Even this option wouldn't be that great. I cutter spinning at 20-25k RPMs will still take quite a chunk before it retracts below the table. There's also the chance of pulling a finger down with it.

 

I know we have a few engineers here, me included, but do we have any patent lawyers? We could put a design group together and shoot for the stars!

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10 minutes ago, MattF said:

Piggy backing on Chestnut, I have a healthy respect for routers and would love to see some sort of flesh sensing technology implemented in their design. I am sure it can be done but the engineering and the tooling would be costly. My main focus would be reliability. Having a spindle that spins upwards of 20k RPMs retract and come to a dead stop would be hell on internal parts. I think a better option would be a router lift that retracts the tool. But then you need a hell of a beefy router table to withstand the forces of the router being pulled down. Even this option wouldn't be that great. I cutter spinning at 20-25k RPMs will still take quite a chunk before it retracts below the table. There's also the chance of pulling a finger down with it.

 

I know we have a few engineers here, me included, but do we have any patent lawyers? We could put a design group together and shoot for the stars!

Yeah so a router spins max lets just say 20k rpm for easy math. That means that on a 2 flute bit you have .5 revolution to get the bit out of the way before the 2nd flesh strike would happen. That gives you .0015 seconds to move the router down. Lets say you have a 1" bit above the table the acceleration would need to be 150,000 ft/s^2. We're talking router table so assume the all popular PC 7518 at 19.1 lbs or .6 slugs.

F=ma we have the mass and acceleration that leaves us with a needed force of 90,000 lbf to move the rotuer out of the way. Divide by 12 to get the energy to move the router 1" and you get 7,500 ft-lbs. The muzzel energy of a 50 BMG is 11,000 ft-lbs and a lapua mag is 5,000 so yeah a heck of a lot of force.

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2 minutes ago, Chestnut said:

Yeah so a router spins max lets just say 20k rpm for easy math. That means that on a 2 flute bit you have .5 revolution to get the bit out of the way before the 2nd flesh strike would happen. That gives you .0015 seconds to move the router down. Lets say you have a 1" bit above the table the acceleration would need to be 150,000 ft/s^2. We're talking router table so assume the all popular PC 7518 at 19.1 lbs or .6 slugs.

F=ma we have the mass and acceleration that leaves us with a needed force of 90,000 lbf to move the rotuer out of the way. Divide by 12 to get the energy to move the router 1" and you get 7,500 ft-lbs. The muzzel energy of a 50 BMG is 11,000 ft-lbs and a lapua mag is 5,000 so yeah a heck of a lot of force.

Huh?? How about I just take your word for it and keep my hands away from the spinning bit, my head hurts just reading that LOL

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32 minutes ago, Chestnut said:

Yeah so a router spins max lets just say 20k rpm for easy math. That means that on a 2 flute bit you have .5 revolution to get the bit out of the way before the 2nd flesh strike would happen. That gives you .0015 seconds to move the router down. Lets say you have a 1" bit above the table the acceleration would need to be 150,000 ft/s^2. We're talking router table so assume the all popular PC 7518 at 19.1 lbs or .6 slugs.

F=ma we have the mass and acceleration that leaves us with a needed force of 90,000 lbf to move the rotuer out of the way. Divide by 12 to get the energy to move the router 1" and you get 7,500 ft-lbs. The muzzel energy of a 50 BMG is 11,000 ft-lbs and a lapua mag is 5,000 so yeah a heck of a lot of force.

I'm glad you did the math, I didn't want too. Been stuck on a factory floor at our contract manufacture all day and am exhausted. 

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I think if SS or anyone else went the router table route (sorry), it woyld be a purpose-built machine, not an add-on for a conventional router. The SS tablesaw is obviously not just a retrofit design, but an entirely new machine.

I also think having a divot taken out in the time required to drop the bit is far better that grinding away an entire digit. Also, stopping the spin isn't nesessary, Bosch proved that with the Reaxx product. Even if it were, a purpose-built design would break the shaft away from the motor armature, so only a fraction of the mass has to stop. In fact, that might be more effective than lowering the bit. It is adaptation of a break-away clutch design commonly used in heavy industrial machines.

Imagine a motor with a hollow shaft, having internal splines, and rigidly mounted below the table. A splined drive shaft could slide through the motor shaft to provide vertical adjustment of the cutter. A hydraulically adjustable clutch (mini version of the "SafeSet" used in my industry) below the collet causes the bit to stop turning when overloaded, and a brake mechanism between the clutch and collet provides the overload when detecting a touch. 

Of course, the brake mechanism could also kill power to the motor, but it can wind down on its own.

Voila, SS router table. 

I call dibs.

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I'm seeing this as a perfect accessory for the SS tablesaw. If added as a wing of the saw, it is even feasible that the same set of electronics could be used to trigger either brake. The hydraulic coupling I mentioned above would allow ONLY the bit to be stopped. A 2" bit should have similar mass as a 10" blade, and if spinning at 20k rpm has almost exactly the same linear speed at the cutting edge as a 10" blade at 4k rpm.

Someone check my math, I'm getting sleepy.

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