bench grinder speed

[tim]

Is it possible to slow a standard bench grinder down to tormek t4 speed?

[Ken S]

Good question, Tim.

With US electric power, the standard "low speed" is 1725 RPM. (High speed is 3450 RPM.) The T4 speed is 120 RPM. Tormek gets its speed reduction from the small diameter motor shaft against the much larger rubber drive wheel. This works like the low gear in a vehicle transmission, higher RPM drive side, lower speed, high torque driven side.

You could put together a very slow speed grinder using a variable speed DC motor combined with a reducing pulley belt. However, in my opinion, a T4 would be more practical.

Ken

[tim]

Thanks Ken
Found a 6 inch leather wheel and picked up 1 micron diamond paste. No bess tester but customers are loving the results. Mounted on t4 next to stock leather wheel. Wanting to do this off to the side. Maybe a servo motor might be better.

[RickKrung]

Although it is "out of stock" at the moment, Penn State Industries sells a variable speed motor for retrofitting to wood lathes, it could be made to serve the purpose you desire.  It comes with the variable speed control box.  I believe you wouldn't need to get the speed down to as low as a Tormek.  The smaller diameter leather wheel and diamond paste ought to work for you.  Afterall, Knife Grinders uses diamond pastes (or at least they did at one time) for deburring on high speed (grinders) paper wheels. 

PSI's current motor is 3/4 hp.  I have the earlier one, at 1/2 hp on my Viel 1x42 belt grinder and have tweaked it down to much slower than stop.  This voids the warranty, but I didn't care. 

Fitting such a motor with a support stand and mounting the wheel to the motor would take some doing, but no different than if you use a servo motor.  Surplus servo motors can be had very cheaply and low voltage DC controllers as well, so going the servo motor could be much cheaper, if you have the wherewithal to do this yourself.  I have these items that I plan to retrofit to a currently AC operated wrapping machine for bamboo fly rod making. 

Rick

[tim]

Thanks Rick
Awesome clue for cheap servos. Although retired I still have access to milling machines etc.. Also can pick the brains of 3 engineers who deal with servo controlled machines for a living. Wife having surgery next week so all is on the shelf for now.

[RickKrung]

Thanks Rick
Awesome clue for cheap servos. Although retired I still have access to milling machines etc.. Also can pick the brains of 3 engineers who deal with servo controlled machines for a living. Wife having surgery next week so all is on the shelf for now.

Sounds like you are better situated on the servo controllers than me.  I'm more seat-of-the-pants, never got into electronics much.  I just ordered a variable speed controller for the servo motor I have that I hope will be better than the one I have.

Access to those machines is valuable.  Sure has served me well.  On the servo motor I have, it is geared, which I need to remove and machine a new bearing end cap, but they are available new and sell for over $300.  I paid $20. 

Rick

[Ken S]

Tim,

Thinking about your question, we have been focused on the "how". We have ignored the "why".
What is it you want to achieve by having another grinder running at 120 RPM? (that could not be achieved with a or another T4).

If you are essentially wanting a second grinder which will share wheels with an existing T4, you should know that some dealers (like Advanced Machinery) sell stripped down T4s.

Ken

[tim]

Ken
Guess it is the toolmaker in me coming out. During my career I was able to learn new ways of doing thing and gain some satisfaction creating fixturing and other tooling. Saved employers a lot of money doing so.

[tim]

Thanks Rick
Awesome clue for cheap servos. Although retired I still have access to milling machines etc.. Also can pick the brains of 3 engineers who deal with servo controlled machines for a living. Wife having surgery next week so all is on the shelf for now.

Sounds like you are better situated on the servo controllers than me.  I'm more seat-of-the-pants, never got into electronics much.  I just ordered a variable speed controller for the servo motor I have that I hope will be better than the one I have.

Access to those machines is valuable.  Sure has served me well.  On the servo motor I have, it is geared, which I need to remove and machine a new bearing end cap, but they are available new and sell for over $300.  I paid $20. 

Rick

Rick
Love making my own stuff. Some servos can have spindle speed changed through the controller by computer. Huge speed range.

[RickKrung]

...snip...
Rick
Love making my own stuff. Some servos can have spindle speed changed through the controller by computer. Huge speed range.

Sounds like we are birds of a feather.  Jigging and fixturing is huge part of the fun.  I was once asked by my pattern maker friend to help him teach one of his classes for the jigging and fixturing portion.  I wasn't able to do it, but it would have been fun.

Rick

[tim]

I think so too. Have a lot of ideas but keep them to myself out of respect to Tormek. Pattern maker? Awesome skill set. My background is metal stamping along with robotic weld fixturing and cnc work holding. Finished up
my career in machine building there is where I learned about servos.

[RickKrung]

Tim,
Very interesting background.  I took pattern making classes and made patterns for several things as part of that.  I also made patterns for two parts as part of restoring a very cool, unique lathe for which no replacement parts were available.  A photo of it is my avatar.

I hope you become more comfortable about developing your ideas and sharing her on the forum.  If you read the historical topics, you will find that many great innovations have come out of member's and collaborative efforts.  I believe these are largely supportive of Tormek and I hope that Tormek is also.  After all, Tormek sponsors and supports this forum and, as far as I know, has not discouraged or squelched the sharing of advancements and innovations.  Unfortunately, due, at least in part, to patenting issues, Tormek has not taken up any that have come out of the forum for production. 

So, please feel free to share with us as many ideas as you become comfortable with. 

Rick