Motorized TT-50 Truing Tool

[RichColvin]

Misalignment of the shafts can be fixed by a flexible coupling (simple as a piece of tubing, or custom made things) or you could have a wheel on the motor and then drive the shaft or knob with it. Kind of like how the grindstone is driven by a wheel.

If you can remove vibration you can determine if it's the vibration or something else causing it.

Yes, I have a flexible coupling coming from McMaster-Carr.  I'll give it another try once it arrives.  I also have some SS M10x1.5 threaded rod coming that I'll use to make a replacement TT screw to get away from having to attache the motor/coupling on the existing M6 threads.  It would also help if I got my knee mill back together and running so I could be a little more accurate when drilling holes, etc. 

Rick

Rick,

Will you post a parts list with costs & where you got them ?

Kind regards,
Rich

[RickKrung]

Rick,

Will you post a parts list with costs & where you got them ?

Kind regards,
Rich

Rich,

Stand by, please. 

I have made substantial improvements to the Motorized Truing Tool since I last posted what you are referencing/asking about.  I've been distracted by multiple other projects, several Tormek related and have not made the effort to update here. 

Improvements include:
1) Ball bearings on both ends of the drive screw,
2) Replaced the stock drive screw with a 10mm threaded rod for turning precision bearing races on the ends for the ball bearings,
3) Drilled out and reamed screw carrier hole on one side of the Truing Tool frame to mm receive ball bearings (there was already a 10mm hole on the other end, but it was oversized, so I pulled a machinist trick to bring it back to a more precision usable condition),
3) Flexible drive coupling between motor and drive screw, and
4) Delrin insert into the diamond cutter carrier to stabilize movement to eliminated vibration causing it to travel in a more true and consistent path (replaces and improves upon the zip-ties). 

I will attempt to get this posted soon.  I'll have to go back through my records to get parts and sources, but can do that. 

After making these improvements, I am re-thinking the hard-coupling drive in favor of timing belts.  Much simpler and easier for folks with less machining capabilities.  I have it in mind to try to make the re-designed timing belt version using very simple parts and tools to make it more universally accessible. 

More later,

Rick

[RickKrung]

Okay, here goes.  We'll see how far I get tonight.

When I last left this project, the motor was misaligned and could not be secured.  There was vibration in the tool as it traversed, resulting in diagonal grooves toward the outer edge.  I had installed the two zip-ties through the diamond tool carrier previously and that helped with keeping the diamond tip from dancing around, at least to an extend (read more on this later).  I had given up on it in that condition and had gone back to hand truing.

I ordered and received ball bearings, 10mm stainless steel threaded rod, a 10mm reamer and a mis-alignment tolerant coupling.  I also got my vertical mill set up and running, including the three-axis DRO, which I cannot live without now. 

I started with machining the 10mm threaded rod to form journals for mounting the bearings and 6mm dia. stubs for mounting the drive components and bushings. 


Once the journals were turned, I reamed out one side of the Truing Tool frame to receive the 10mm OD ball bearings.  One side already had a 10mm hole, through which the stock 10mm threaded shaft passed as part of assembly.  It was oversized, however, and the bearing would wobble.  Could not go to all this trouble and have that.  So, I took a sharp carbide scribe and dimpled the inside diameter where the bearing would mount.  Fit snugly after that. 


Here are all the shaft, bearings and other parts for mounting the shaft in the TT frame. One half of the mis-alignment tolerant coupler is visible on the far right. 


The stock steel box tube that carries the diamond truing tip, that is driven across the TT by the 10mm threaded shaft is quite sloppy on the threads.  The only threads in the two sides of the box are very minimal width and a fairly loose fit to the threads.  To correct for this, I machined a piece of black delrin to fit snugly width-wise within the steel box tube, but with room to move vertically to allow for imprecision in placing the hole in the delrin, relative to the threaded hole in the steel box tube.   I then drilled a hole through it where the drive screw crosses, using Letter Drill "W", which is 0.386" (9.80mm) but as with all drills, drills larger.  The final hole is a snug but slip fit to a 0.388" (9.86mm) plug gage.  The threaded rod I used measures 0.389" (9.88mm) for which a 0.389" plug gage is a very tight fit.  This is exactly what I wanted, so that it reduces play as much as possible.  It might be better if the delrin was also threaded, but I'm not sure.  This procedure could be replicated fairly closely with metric drills, as there are sets in 0.1mm increments, from 6 to 10mm. 
This delrin part fits quite snugly over the threads and virtually eliminates all wobble and play. 


The box tube rides smoothly across the TT frame, on the ball bearing raced drive screw (this is only a temporary fix, as the delrin will wear as the screw turns in it.  More on this later). 

Also required was drilling an access hole for the diamond tip part and the 12mm set screw that holds it in place, as well as a clearance hole towards the rear for the USB.  Note that this latter hole is oval in the steel box tube, but may not need nearly so much ovaling with the delrin insert, but I matched the oval hole in the steel tube.  Parts shown, including one half of the coupling.


Here is the assembly, with the diamond tip dampening delrin insert, drive coupling and the retainer bushing on the other end.  This assembly is tight, no wobble, just smooth travel. 


I have visions of replacing the steel box tube and delrin insert with a fully machined, solid brass block, with all the appropriate features, but that is for the next phase.  The fully threaded brass block would be a snug but smooth fit over the threads, and a slot would be cut across the threads and an adjusting screw placed so the block threads could be tightened over the shaft threads as the block wears.  This is how it is done on machine tool linear motion screws. 

At this point, you'd think I'd have a photo showing this improved version mounted on the T8, but somehow that got missed.  Best I can do is to show a short (5 sec.) video of it in action, during what turned out to be a four minute traverse time on the final pass.  First time or two, the wheel was not in full contact with the stone. 

https://vimeo.com/258565704

I was truly impressed with the result.  This SB stone had not looked this good since it was new.  First shot shows the entire surface, second a closer up shot of the part of the wheel that was in the best focus.




As this stands now, I consider it a success and I will use it for truing all three of my grindstones.  Modification I may make to this design are the solid brass diamond tip block, as discussed above and limit switches. 

As mentioned earlier, I do have thoughts about how to simplify the design by converting it to timing belts, largely in part to get away from the hard drive line connection requiring the mis-alignment coupling.  Timing belts might even aid in preventing damage if the motor were left on too long and jammed the diamond block against the end of the travel. 

I envision mounting the drive motor lower, between the two USB uprights with timing pulleys on and extended TT shaft and drive motor shaft.  I also hope to be able to design it using angle aluminum that anyone can buy at hardware stores, hacksawing parts to size and drilling holes using a hand drill.  There will need to be some way of securing the drive motor to the USB to maintain position to keep adequate tension on the timing belt.  It doesn't take much, and the two applications where I've used them before, they seem too loose, but they work great. 

Rick

P.S. Forgot to mention, this design definitely needs limit switches.  If left to drive all the way to the end of the the travel, it binds up really badly and something is going break.  It would be nice to find reversing limit switches, but I'm not sure what to look for.  It would need to turn off the DC current for the one direction (at the very least) and hopefully, switch the + & - leads to run the motor in the opposite direction.  Would that be SPDT (single pole, double throw) variety of limit switch?

[cbwx34]

Your work never fails to impress!!! 👍 👍

[RobinW]

I'm very impressed. Well Done.

[RickKrung]

...snip...

At this point, you'd think I'd have a photo showing this improved version mounted on the T8, but somehow that got missed.  Best I can do is to show a short (5 sec.) video of it in action, during what turned out to be a four minute traverse time on the final pass.  First time or two, the wheel was not in full contact with the stone. 

https://vimeo.com/258565704

I was truly impressed with the result. 
...snip...

Nothing new to report, just and updated video, showing a full cycle of truing (over and back) using the motorized mod.  Travel time is about 60 seconds each way, which is faster than previously shown and used, but it provides a sense of how it works without belaboring the viewing. 

https://vimeo.com/270241192

Rick

[cbwx34]

Nothing new to report, just and updated video, showing a full cycle of truing (over and back) using the motorized mod.  Travel time is about 60 seconds each way, which is faster than previously shown and used, but it provides a sense of how it works without belaboring the viewing. 

https://vimeo.com/270241192

Rick

That's pretty cool.  👍 👍