Rewiring chain grinder for CW and CCW rotation

[JHctRednek]

So I have had a Northern Tool chain grinder for 5 or 6 yrs and I decided that I needed to rewire it to give me CW rotation for the LH cutters and CCW rotation for the RH cutters. I searched on here and couldn't find a write up for how to rewire one of these grinders so I wanted to share with you guys how I went about it.
For starters I am working with a Northern Tool model 193020 chain sharpener with normally a CCW rotating grinding wheel. After looking at the guts of the electrical I thought I had a standard capacitor start AC motor.....well I was wrong. It turns out that these grinders are equipped with a permanent split, capacitor-run motor. It has a wiring circuit like so.

After a little research in my old text books I found that to reverse the motor you just need to swap the capacitor to run in series with the main winding vice the aux winding. To make it switch directions I needed a DPDT switch, and rewire the motor like so.

I now know what I need for a switch and how to wire it but I wanted to keep everything in this tiny little area


I have to find the switch I need to make this happen, off to the hardware store I go and find a few different DPDT switches but they are all huge. Also I wanted to keep the original start switch because it seemed to have a thermal protection or overload built into it. (I could have removed it and screwed a plate over the square opening and used a DPDT center off switch but I chose not too).
I ended up at RadioShack and found this little guy for about $4, DPDT and pretty small about 1” long by 1/2" wide…. perfect!

Its rated for 6 amps at 125 volts which is 750watts well above the 230 watts I needed.

I next cut an opening for the switch to fit in and drilled and tapped for a couple #6 machine screws to hold it down.

 

[JHctRednek]

After that was done I started wiring, the switch has solder only connections so I finished most of them prior to installing the switch and then installed it in the case.



With everything wired I test ran it and everything worked right. Now I was on to stuffing 10 lbs of crap in a 5 lb bag…

If you look at the cover you’ll notice that I had to cut the stiffener bar off the bottom where it is molded into the cover to gain the extra room to fit everything.

All in all it worked out well here’s the final product.

 

[lfnh]

Nice write up JH, especially the wiring and pictures.
Myself a filer, but a lot of members use grinders and will appreciate your reversing motor work.
Thanks foir sharing!

 

[z71mike]

Dude! I'm loving this thread. Right up my alley. Nice reverse engineering. And your ladder logic is spot on, down to the symbols. Were you using friggin MatLab?! PSpice?

Real nice work.

 

[firefighterwolf]

This is weird! I wanted to figure out how to do this EXACT modification! Thank you!

 

[ky044]

So having both directions of wheel spin make a difference one for left cutters one for right cutter what does it do to help keep's it from blurring up ??? My ears are open and I'm ready to learn

 

[Philbert]

Your illustrations and photos are very clear.

This has come up a few times:

http://www.arboristsite.com/community/threads/reversing-a-hf-grinder-3-wire-ac-motor.181620/

http://www.arboristsite.com/community/threads/511a-grinder-improvements-tweaks.197073/page-3 (Posts 41 - 47)

Reversing the grinding wheel creates some safety hazards (see sparks in YouTube video below - wheel explosions are also directed to the user) so UL and OSHA don't allow it on current grinders. Anyone doing this should be aware of those hazards.




Philbert

 

[JHctRednek]

Glad you guys are finding it useful !! Thanks for the positive feedback!

So having both directions of wheel spin make a difference one for left cutters one for right cutter what does it do to help keep's it from blurring up ??? My ears are open and I'm ready to learn

I am no pro at using chain grinders and usually get a burr or rolled metal on the top of the LH cutter or side of the LH cutter, where my RH cutters are always nice and clean and sharp. By reversing the grinder I now get both cutters that look nice and clean.

Nice write up JH, especially the wiring and pictures.
Myself a filer, but a lot of members use grinders and will appreciate your reversing motor work.
Thanks foir sharing!

I agree I am usually a filer but I like to touch the chain up every few filings to make sure I am not messing my angles up. I also use it for fixing rocked or metal hit chains, I just managed to hit a section of barbed wire twice (someone years ago wrapped the barbed wire around the tree, the tree grew over it and I didnt see it) while milling an oak log which wiped out three ripping chains which got me going on modding the grinder.

Your illustrations and photos are very clear.

This has come up a few times:

http://www.arboristsite.com/community/threads/reversing-a-hf-grinder-3-wire-ac-motor.181620/

http://www.arboristsite.com/community/threads/511a-grinder-improvements-tweaks.197073/page-3 (Posts 41 - 47)

Reversing the grinding wheel creates some safety hazards (see sparks in YouTube video below - wheel explosions are also directed to the user) so UL and OSHA don't allow it on current grinders. Anyone doing this should be aware of those hazards.




Philbert

I agree with the hazards, good point, I just wore my welding apron while grinding to keep the sparks at bay. I didn't see the other posts when I started this.... I guess I still have to work on my searching ability with this site.

 

[MCW]

Having a reversing grinder is a nice touch. I had a MAXX grinder that did this.
Unfortunately it is more for looks than functionality because in practice you'll find that having the ability to reverse your grinder actually makes very little difference (if any) when cutting.
It definitely does make your cutters look prettier though straight off the grinder
If you have decent wheels you shouldn't get too many cutter burrs either.

 

[anlrolfe]

As a permanent capacitor style motor, this will reverse instantly with a flip of the switch..... even if it is running.

Inertia may unscrew the arbor at high speed.

If this accidentally happens you will be in for some excitement. Be careful.

 

[JHctRednek]

Having a reversing grinder is a nice touch. I had a MAXX grinder that did this.
Unfortunately it is more for looks than functionality because in practice you'll find that having the ability to reverse your grinder actually makes very little difference (if any) when cutting.
It definitely does make your cutters look prettier though straight off the grinder
If you have decent wheels you shouldn't get too many cutter burrs either.

I agree the better wheels help and I found that cleaning the chain a little helps as well. I don't go to the extent that some on here do cleaning chains, I just run them over a wire wheel mounted on a bench grinder to knock off the major stuff.

As a permanent capacitor style motor, this will reverse instantly with a flip of the switch..... even if it is running.

Inertia may unscrew the arbor at high speed.

If this accidentally happens you will be in for some excitement. Be careful.

I agree about the motor, which is why I didn't use a DPDT center off switch. I agree with inertia trying to unscrew the arbor screw but I haven't read anywhere that there have been issues with this. I figured if I started having problems with it I would just nylock the screw with a peice of Zytel rod (makes is self locking).

 

[olyman]

JHctRedneck..that's the most wonderful mod ever..as some that had originally wanted to purchase one,,said it was useless without the reversing feature..now,,theres zero reason!!! thanks a bunch!! dont know that ill ever do it..as im happy with it as it is now..but I copied it,,jic.....