US Government is About to Change Table Saws FOREVER!

[chiroindixon]

https://www.youtube.com/watch?v=kb6LRfGhr_g

Guys,
Something for us to keep on eye on. How and what effect of this will have on ShopSmith could be massive..

Doc

[RFGuy]

Doc,

Thanks. Very interesting. IF, the CPSC does go through with this, it would be the end of the Mark 7 and effectively Shopsmith. I don't see how they could incorporate any kind of blade stop technology since the arbor is fixed and the table moves around it.

[edma194]

This process was initiated by SawStop. The video has links to documents from CPSC. I've taken a quick look at them, need to spend some time examining them in detail but it doesn't look anywhere near a done deal yet and lawsuits from table saw manufacturers not names SawStop will likely put this to sleep for years at least.

I don't think it's impossible to implement injury protection on a Shopsmith but there are patent infringement issues and it would further increase the price of an expensive machine.

[RFGuy]

I agree it may be a slim chance that the CPSC takes action on this, but then again who knows. With enough pressure from insurance companies, as discussed in the video, it could happen. Out of curiosity, I went back and checked on this 3 year old thread (link below) where a retrofit solution (SawStop alternative) was detailed. Remember SawShield? Website no longer works, so I don't know what happened to them. Either not enough interest to make the company viable or the threat of litigation took them out. The core technology of both the Bosch Reaxx and the SawStop is a mechanical brake that stops sawblade rotation in a very quick time duration to limit injury. Doing so requires a robust table and the ability to quickly have the arbor drop down when the brake is engaged into the blade. Shopsmith tables are too dainty for such an adventure and since the arbor is fixed, the table would have to swing up and away. How exactly would that work??? Could you imagine a trigger event causing the table and your workpiece to come up and at you? Yikes! In contrast, if Shopsmith could come up with a way to identify the hand getting close to the blade and changed the DVR motor to have an effective e-brake then yes it is possible Shopsmith could have a future should the CPSC rule in favor of this. Very slim chances of Shopsmith making this work IMHO.

viewtopic.php?p=277724#p277724

[edma194]

I don't think it's necessary to put a brake on the blade. It just has to drop down below the table. That might decrease maximum blade depth with the safety system engaged, but the SawStop has modes where the system is disabled and Shopsmith can do the same. To drop the blade requires the arbor be attached to the spindle with a clutch which disengages when the blade is dropped. Because the blade keeps spinning there is no torque from instant braking to deal with and the motor can just spin down.

I think it will cost way to much to implement and what counts here is the detection mechanism that SawStop has locked up in their patent. Don't get me started on the patent system, but the CPSC has already noted that they have to avoid giving SawStop a monopoly. Doing that brings up a truckload of legal issues and one is soon coming to a head in the SCOTUS where the power of agencies like the CPSC to regulate outside of congressional involvement is being considered.

[RFGuy]

Ed,

Well, they are trying to stop a sawblade from cutting more than 3.5mm into skin when an accident occurs. I really doubt that a clutch system as you describe, where the blade can still be spinning would decelerate fast enough that it wouldn't cut into a finger by that much if blade contact should happen. Now you are saying you need a clutch to disengage the blade and a mechanism to force this blade + clutch under the table to avoid contact. Not sure exactly what that would look like mechanically. For sure without headstock changes that would mean a tablesaw table much higher than existing on a Mark 8 or whatever you want to call the new thingie from Shopsmith that survives the CPSC. And you thought the Mark V table height was tall for TS mode now?

I really don't see that costs have to be that exorbitant for any manufacturer provided patents and licensing can be reasonably worked out. Remember Bosch brought this out in their Reaxx system and that was on a contractor TS so budget friendly Similarly Saw Shield had a system for retrofit on certain model tablesaws. Honestly, this has been a long time coming and every manufacturer should have something like this. Think of how much safer woodworking would be if every company sold something similar to protect the woodworker.

Yes, there is a very important ruling coming for SCOTUS soon that may impact many government agencies.

[edma194]

There's plenty of room to drop a saw blade below the table. It might be tight at maximum blade height (lowest table height) but no need to raise the table for any other reason. Dropping the blade can happen just as fast as a brake. A brake could be added also but seems unnecessary. Unlike common tilting table saws it's always easy to drop the blade straight down on a Shopsmith.

There's no way they can make SawStop the standard for a safe table saw, other equivalent means have to be acceptable. Because of all the bureaucratic issues that arise I don't think this goes anywhere, but watching the process unfold could prove interesting.

[RFGuy]

Ed,

With the waytubes, carriage and the lower saw guard, etc. I am having a hard time seeing how the blade has plenty of room to drop down on a Mark 7 arrangement but maybe I am missing something. Honestly, an electric brake, i.e. e-brake seems like the easier engineering solution for Shopsmith since they already have a DVR motor and just need to implement a drive system and monitoring to ensure that it comes to a rapid deceleration to protect the user when triggered. IF one could do this quick enough you could even argue that the blade could stay in place, i.e. still above table. Provided the detection is always made and the blade stops in time, then that is all that is required. SawStop's solution is highly effective but also highly destructive, by design.

[edma194]

According to Scott Markwood rapidly stopping a Shopsmith blade was tested for some reason, not necessarily for this purpose, and they found that the torque could tip the saw over. Being taller than most table saws with narrower footprint front to back that seems likely to me. Perhaps simply disengaging the blade with a clutch would allow it to be stopped safely. I don't think it's necessary though, and no need to ruin the blade or any other part of the mechanism by trying to get the blade to stop instantly when it can be dropped below the table just as fast. But if it could be stopped quickly just be disengaging the clutch without dropping the blade then that's an even simpler mechanism to employ. The majority of the momentum in the system is in the very heavy motor, not the blade, so it requires much less torque to stop the blade once the clutch disconnects and the motor is allowed to spin.

But again, the problem here is the contact detection method that SawStop has so far managed to keep locked up with patents.

[RFGuy]

Ed,

Sounds like an urban myth to me!!! Perhaps Scott can chime in, if this were the case. In any event, what I had in mind was creating a reverse pattern in the DVR windings that would negate/slow down the sawblade as quickly as possible to a stop. Since it is a switched reluctance motor design for the PowerPro, it should be fairly easy to create this in concept, but a bit more involved from a system/circuit point of view of course.