Patio's projects

[Bill Shields]

bee there, done that (with trigger lock, not leg).

one of the first things I do on all trigger locks is remove and trash.

My father in law had (I now have) a very old, slow speed 5\8" chuck electric drill with a D handle on the back - he locked the trigger, the bit grabbed and it proceeded to break his wrist....

then there was the British guy that worked with me 40+ years ago who locked the circular saw 'on' and proceeded to set it down on his leg with the guard partially retracted....

[JackF]

Nice work Pat and a good idea. I will have to make one for my Delta Unisaw. Not haveing a 3D printer thou, I will have to fabricate mine the old fachioned way.

[NP317]

If you don't wish to fabricate that knee switch, there are many commercially available:
https://www.amazon.com/s?k=table+saw+kn ... nb_sb_noss

RussN

[Patio]

Russ, those are the switches I used to design the one I made. Those all require power to operate, as they are "magnetic". They are designed to not restart the saw, after a power failure. I only need some thing that will connect two wires together that are low voltage and the restart problem is handled within the VFD software. I have a 3 phase saw and those are also for single phase, I believe.

Jack, look at the link that Russ has provided above. Unless you are using a VFD to run your motor, like I am, those may be a good option for you.

Curtis, glad your need worked out and be good to yourself.

Liveaboard, I feel ya about the shop being full of fun things, just waiting to be gotten to.

Thanks for all the replies.

[earlgo]

I installed a switch from Woodcraft that is nearly identical to the Rockwell switch shown. It works very well and is easy to turn off with my knee instead of reaching under the table groping for the little original switch. I don't have a VFD on the motor so it is just on and off.
--earlgo

[Bill Shields]

Make sure you size the VFD so that it can DECELERATE the motor quickly if you do hit the panic button and loot for a fast stop.

Stopping a spinning motor quickly can take more current than a moderate start, and a modesty sized VFD may overload if you call for a FAST STOP from anything more than dead slow forward.

It may also require an external 'dump resistor'.

Plan ahead

[liveaboard]

The VFD I bought for my lathe has that limitation; it has no provision to add a stop resistor (I only learned what that was after I bought the VFD).
I tried various programmed stop times until I found the shortest one that wouldn't trip the overload (when that happens the motor is released to spin down freely).
If I have some heavy work in the chuck it still happens, but as it is it will brake in around 4 seconds. That's a long time if something bad is happening.

In the case of a tablesaw, it's even longer. I doubt a VFD electronic brake would make much difference.
Machines in commercial shops the EU are required to have instantaneous automatic brakes. Supposedly, if you put your hand on a spinning blade it will stop before it cuts you.
Great big excellent slide table machines without brakes are available cheap because of that law.

Planners can take minutes to spin down unless they have a brake. Some have (had) a reverse position on the power lever that acts as a brake.
Nice...

[Charles T. McCullough]

Those EU mandated instantaneous brakes are not an electronic "motor stop". They come in two forms. One slams a metal bar into the teeth of the blade, which stops the blade (and RUINS it and the metal bar, which is an expensive emergency stop). The other sets off an explosive charge (shotgun shell blanks) to move the whole blade mechanism below the table to get the spinning blade out of exposure above the table. Not nearly as expensive because shotgun blank shells are much cheaper, (though there may be some damage to the blade axle and gearing from the shock). There are often TWO shotgun shells in the machine so you can reset things, continue to do work and still be "safe" for one more time.
.
And they still can do damage to a hand in the path of the teeth of the blade. If you are pushing a wood stick through the saw, you are doing so rather slowly and if your thumb is accidentally in the cutting path, you will probably get a small gash in your skin, but if you slam your hand into the blade, you could sever an appendage before the blade could stop or get out of the way. Most of us have seen the "hot dog test" where someone slowly pushes a wiener/sausage into the blade to see the blade stop or drop out of the way. Inspection of the hot dog shows a small scar where a tooth or two swiped the skin of it before the safety mech came into play. I saw a test where they dropped the hot dog on the blade from above and it was neatly sliced in two before the blade disappeared below the table!

[liveaboard]

My older brother went to the hospital with his severed finger in a bag; they put it back on, but since he was using a carbide blade it's now 3mm shorter than before.

Somehow, miraculously, I still have all my fingers and toes.
I sure hope my luck holds!

One time around 25 years ago, I got my thumb caught under my friend's big old 8HP wood planner. There was a steel rod and the workpiece (a 2' wide teak block kitchen counter top) would pass over it, and I was pinched between with the machine running and the power feed wheels intent on success.

It was a Sunday in summer. no one was in the building and no one was expected. The doors were closed and that machine was so loud that if you shouted at the top of your lungs no one would hear you even if they were in the room.

I tried to get the stop lever with my foot but could not; I had no phone on me (this was before most people had cell phones).
I did have a leatherman on my belt, and I sued it to force the work backwards so I could get free.
I bent the leatherman pliers sideways; I'm not sure I'm normally strong enough to do that.

So Patio's stop switch; that would have been a good thing.

My friend still has that machine, I visited him recently and the great beast was lurking there in the dark of the workshop, as if waiting for another chance.

[JackF]

Pat, mine is 3 PH also, running off a rpc. I will be making just the base plate and flapper.

[Patio]

Jack if you would like, I could print you a set and mail them out to you. The cost of printed parts are really small, once one has it all worked out. To give you an idea of cost and time to print: The paddle cost $.44/2.02hrs. the plate is $.63/1.31hrs, and the bumper is $.01/4 minutes. Once a print has started, I can walk away and monitor it via a camera, so the time involved is small too. Pm me if you are interested.

In regards to VFD and braking.
I have seen the "Saw Stop" videos, and for good reason they are selling well. If the device is trip, one needs to replace the blade and cartridge at a cost of about $125 less the blade. Cheaper than a finger, all day long.
From every thing that I have read, in the USA it is mandated that if a machine's emergency stop is hit the machine must coast to a stop if powered by a VFD. The way I understand the theory is, when VFD stops under power, it will use the entire deceleration ramp time to complete the stop and if an outside force is trying to slow it down faster than the ramp time the VFD will add power to force the use of the entire ramp time.
This is not to say that the ramp time of the VFD won't be shorter, or longer than the ramp time created by an appendage stuck in the machine. As an electrician I was required to go by the rules. JS
The other thought that crossed my mind is, if the VFD stopped fast enough, would it unwind the blade's nut off the spindle. I don't know.
My lathe is powered by a VFD and will stop real fast, and I have comfort in that. The mill is a slow ramp, unless the E stop is hit, then it will coast to a stop. One day I hope to play with the ramp time of the mill, to see how short I can get it to stop. Once the saw is up and running I will play with the ramp time and then decide how I would like it to behave.