View Full Version : Need electrical switching advice please???

02-24-2008, 10:22 AM
Hey guys! I'm just finishing up the plumbing on the new downfeed cylinder for my bandsaw. Decided to build a nice panel that's easy to use...going to mount the flow controls and switches right where the operator stands.
Ok.. I thought this had a magnetic switch. It looks like one but doesn't work properley if you unplug it. Plug it back in and away it goes. Maybe they wired it so the switch doesn't work.. I don't know yet.
Anyway.. I need to put a limit switch on this saw so it'll shut off automatically when the cut is done.
I have to fix this mag switch or replace it for Workers Comp rules.
So would I just run the hot wire through the limit switch... then on to the mag switch?
Saw hits limit switch... kills hot...then kills mag switch...correct?
Lift saw...closes limit switch...reset mag switch and start next cut. Correct?
Thanks to all the "Sparkies" out there.
Russ (the electrical dummass.)

Bob Ford
02-24-2008, 10:50 AM

Your description is not real clear. If you have a manual starter. No coil to pull in the contacts. Running the L1 wire through the limit switch will burn the micro switch. They are normally rated for less than 2 amps.

If you have a magnetic starter. You should have a stop start switch with three wires. The wire from L1 goes to number 1 on the start stop switch. You can have any number of stop switches in series. From L1 to first switch than from switch to switch than ending on number 1 on start stop switch


02-24-2008, 11:14 AM
OH CRAP! I knew it wouldn't be as easy as I figured. Ok...I better take the cover off the box on the machine to find out if it's a mag switch or what it is.
I wasn't thinking of a micro switch but I guess that's what I'd need alright.
I also never thought about running full power through a micro switch. I believe that's a no no :D

02-24-2008, 11:21 AM
torker, if the current draw of the mag switch is within the current limits of the travel limit switch then your ok. Limit switches come in several current ratings so look at it.

The way you describe the operation is the right way. The limit switch is wired in as an electrical latch for the coil on the mag sw. and when the limit switch is opened at the end of the travel it breaks the circuit and drops the contacts out stoping the machine. You wouldn't want to run the motor through the limit switch. It should be run with a magnetic switch controled with the start button and the limit switch.

02-24-2008, 11:25 AM
Thanks Carl! Ok..I won't be getting this done today then. No hardware store limit switches then. Have to go to the electrical supply house on Monday and buy the "real" stuff.

02-24-2008, 11:26 AM
If you have a magnetic starter, then the only current carried through the limit switch will be the holding current for the coils.

If its not a magnetic starter, I would get one. They are not all that pricey and I know that surpluscenter.com has some without switches (you make your own panel with one NO and one NC switch for start and stop). This makes it easy to use a limit switch as it is normally closed and just goes in series with the NC stop switch. Hitting either one just opens the circuit for the holding coils.

BTW-- you can use most three phase starters with single phase (220v)equipment...you just have one unused contact.

I hope that helps!

02-24-2008, 11:26 AM
Do you need a wiring diagram? I may have a diagram you could use in an industrial book I have.

02-24-2008, 11:30 AM
Ooops! I forgot to mention..don't know if it matters but this is a 110V motor, single phase.
I wouldn't mind having a boo at a diagram. I'm thinking I got this right but you never know with me :D
Thanks for your help guys!

02-24-2008, 12:53 PM
Don't know if you need these or not,but here are some good diagrams-


You might also add in a normally closed solinoid valve to the feed system.Plumb it in after the needle valve and wire it so it draws power off the motor when it's switched on.

The way it works is the needle valve and check valve allow the saw to work normally,but with the additon of the solinoid valve the feedrate can be set once and left alone through the whole job.When you raise the saw head to advance more stock the head will hold at whatever level you set it at until the motor is switched on and the valve opens.

It's a convience thing,but makes like easier not having to reset the feed for every cut or having the head constantly driting down while you pull steel through.

I did it on the Wells at work and like the saw even more now.The next mod will be a length stop setup with an air solinoid valve and a spring return air cylinder to actuate the stop.Stop will hold at full extension until the motor starts when it will retract and allow for drop a cut through.

02-24-2008, 01:39 PM
Darin...Crap...that solenoid idea is genius. I do have a seperate ball valve to use as a holding feature. It is plumbed in after the air speed valve. The speed valve will control the downfeed speed. The ball valve will just block or open the flow as needed.
Arrrghh.. I was looking at those solenoids when I ordered my cylinder stuff and never clued in. They are pretty cheap also.
Now I'm trying to think of a way to incorporate yet another cylinder. I'd love to have a power lift for this.
We had a new Hydmech at my last job. It had power up. After a few hours on the saw you really appreciated that. Hit a button and up it goes.
The gurl would like that. It's always a fight around here...who has to saw 4 million pieces. I usually win as I'm sometimes still the boss :D I really need another employee to do all this brainless stuff and let us make the money part. But I'm not quite there yet.
I'm now thinking an air cylinder would work pretty darn good.
This is turning into a "Million Ways To Improve An Old Saw" deal.

John Stevenson
02-24-2008, 03:40 PM
Your wish etec etc and all that rubharb.

Now bear in mind I have no pic's of this and had to rush out into that haunted workshop at 8:00 pm at night just to get some.

Standard power saw MKII


Stop and start swithes with coolant on the frame at top, another stop switch wired as a limit out of sight but in pic two.
These go to the no volt switch at the back of the machine.


Power lift cylinder disguised as a normal air cylinder along side the standard hydraulic feed cylinder.

Points to note:-
Lift hight adjustable by a bowden cable that can be trapped by the bolt on the ram arm so it can be set to lift just high enough for the job in hand.
No need to lift 8" every time when cutting 1" bar.

Ram arm is fastened to a curved surface on the lift frame. Two lower bolts clamp the arm to the casting, two upper bolts with lock nuts act as jacking screws, saves having to machine a flat surface for the arm.

Principle of operation:-

When it's parked air is in the cylinder holding the frame up. When you press Go it latches the no volt switch and the same supply operates a solenoid / solenoid 3/2 air valve.
Releases the air and the frame drops, hydraulic cylinder takes over and it cuts thru.
On completion of the cut limit switch above the feed cylinder hits adjustable bolt to right of feed cylinder.
This trips the no volt and stops the motor. Second terminal block engerises other side of the sol / sol 3/2 valve and the frame lifts to the extent of the cable and stay there whist you feed new piece in / make coffee / trim toe nails [ delete as required ]

Note also jacking screw fitted to vise so you can hold short pieces without the vise tilting.


02-24-2008, 11:42 PM
Use weirdscience's diagram for a 3 ph starter with 1 ph motor and put a N.C. limit switch in series in the stop circuit. When the limit sw. trips the motor will stop.

02-25-2008, 07:01 AM

If you are still looking for a heavy duty limit switch I can send you this one today. Not all microswitches are created equal. This one is good to 2 hp at 250 volts AC. It's double throw so you have your choice of NO or NC. I'll send it to work with Janet.


02-25-2008, 07:11 AM
Evan, that'd be cool! Thanks! You still got my address?
John, Thanks for taking the time for the pics! That's just the setup I was thinking of. The cable adjust is a bonus...hadn't thought of that. Funny..I think my old boss paid $14,000 for that Hydmech saw. It didn't have lift limiter....you had to do it by eye. I like your way a lot better.

02-25-2008, 07:15 AM
Of course Janet still has your address. :D She is the most organized person I know, especially in her office. If you need anything else let her know.

hey, wait. Brain fade. You moved. PM me with your current address.

02-25-2008, 07:18 AM
Geez... You're right...lol! Guess I forgot I moved also!

02-25-2008, 07:22 AM
Evan.... don't me and you ever sleep? It's 5:15AM here... been up since 4.
You beat me! :D

02-25-2008, 07:24 AM
Got your address. Sleep? I've been up since 3:00.

02-25-2008, 07:35 AM
OK...you really beat me :D
Speaking of...I better get busy...got to light the shop stove and get the saw panel ready to roll.

John Stevenson
02-25-2008, 08:19 AM
I converted it to power lift as it's one of those machines you either need three hands or to be both sides of it at once :D

Now it just let the frame go up, undo the cam lever that holds the vise screw nut, one hand, slide the bar thru to the stop, keep it held flat and to the stop, other hand, and pull the cam lever.

This is one of those saws where you tighten the vise screw onto the work, back off a 1/4 of a turn so the material can slide thru and final tighten with the lever at the botton of the lift cylinder.

If I have a load of small parts that cut quickly I have an overide switch at the back that doesn't shut the motor off so its one hand on the lever and one on the work. Push thru, lock, cut, unlock and push thru again, blade running all the while.

As there is only me works here and I;m aware of how it works it's safe, but with employee's it would be a different matter.

Under UK H&S regs as I'm self employed and in my own shop I don't come under any of their rules and regs.

It gives one a great feeling when I get a visit by the factory inspector and refuse to let them enter. I'm on the radar with being VAT registered and when they come round I refuse to let them enter as they don't have safety boots, hard hat and glasses.
When they point out I don't I just tell them I work here.

Sh!t hot feeling.


Lew Hartswick
02-25-2008, 08:55 AM
Evan, That switch dosen't look like any of the Microswitch (rtm) I've
seen. Is it by any chance a Cherry (tm) ?
...lew... who has used a zillion Microswitch ones.

02-25-2008, 10:02 AM
That is a Unimax switch. I was using the Microswitch name in the generic sense. That switch is used as a main power interlock on a machine.