Motorized TT-50 Truing Tool

[Ken S]

Justme,

One statistic I have not seen (it would vary quite a bit) is the cost of a replacement grinding wheel compared with the revenue produced by the consumed grinding wheel. We could compare the cost of ink and toner compared with the number of documents and photos consumed. We could compare the cost of a brake job with the number of trips to work, the kids or grandkids to school and family vacations.

I would expect the loss efficiency to improve with experience.

I have never thought that using a Starrett Satin Chrome scale as overkill; it is just pleasant.

Ken

[Herman Trivilino]

I would hold my square on the side of the stone and look at the surface of the stone.

Do this immediately after truing. If the surface is not square to the side then the horizontal portion of the US is not parallel to the axis of rotation of the grindstone. This might be okay if they are indeed not parallel, as long as they lie in a plane. But if they don't, that is, if they are askew, then you are definitely in trouble. Tormek won't comment on this issue, as far as I know. There was a chap here a couple years ago unable to get his chisel ends square and I believe this must have been his problem. Tormek replaced his machine.

The mounts that hold the two upright legs of the US have undergone a redesign when the T7 was replaced with the T8 (and likewise when the T3 was replaced with the T4 before that). They are now cast into the housing.

And then I wonder... What difference does it make... ?  I've read about how the stone not being true has caused problems.  I don't get it.

When the grindstone is out of round, you will definitely notice it. And unless you true right away the problem gets a lot worse a lot faster. Waiting too long means you'll have to remove a lot of material to get it round again. That's the real waste.

[Ken S]

Herman states, quite correctly, that the mounts that hold the two upright legs of the universal support (commonly called the sleeves) are now cast into the top. This is only part of the story. All four sleeves are part of the single top casting, and they are also machined. They are aligned to a very high degree of accuracy, and that accuracy will not change. They are also machined slightly out of round for easier insertion of the support bar. This advance first appeared with the T4. Not only did it increase accuracy, the zinc top acts as a radiator to solve the overheating problem which had plagued the all plastic T3 housing. For practical purposes, the overheating problem was the housing, not the motor. The T4 corrected that. In my experience, the operator needs a rest long before the T4.

With the T8, over the long run, the single piece cast and machined zinc top may prove a more significant advance than the new water trough. (In my opinion, the redesigned feet which do not fall off are a welcome advance as well.) I do not believe many of these improvements were available when Tormek began in the 1970s.

Concerning the machine which was replaced a couple years ago, I believe that Tormek replaced that machine more for customer relation reasons than product problems. The problem occurred during the extended Scandanavian vacation period, and apparently there was also a shortage of trained troubleshooters in the UK who could be dispatched to work with the customer. I believe a proper training session with the customer would have prevented the problem.

Ken

[Herman Trivilino]

Concerning the machine which was replaced a couple years ago, I believe that Tormek replaced that machine more for customer relation reasons than product problems. The problem occurred during the extended Scandanavian vacation period, and apparently there was also a shortage of trained troubleshooters in the UK who could be dispatched to work with the customer. I believe a proper training session with the customer would have prevented the problem.

IIRC his problems disappeared when the machine was replaced.

I wonder what would have happened if they weren't on vacation? I wasn't aware that trained troubleshooters are dispatched when there's no shortage.

[RickKrung]

I've had some time to work on the design of a motorized Truing Tool.  CAD drawings are attached below.  I spent a lot of time trying to work with a piece of U shaped box channel but the space on the side of the TT around the knob is just too confined.  When I went to just an "L" shaped bracket for the motor mount, the design got real simple and even easier to make. 


Also, when I got home, I could not find the 1/8" wall thickness box channel that I know I had before my move a year and a half ago, so I had to use what I had, which is 0.202" wall thickness.  I like it better too.  More rigid.  I have not figured out exactly how I'm going to attach the knob chuck to the knob.  I'm thinking with some drive pins, maybe.  I'd like to come up with something that will break free when (not "if") the screw reached the end of its travel and I haven't switched off the motor.  Limit switched would be good, so maybe I'll give that a go after getting this thing built.

Rick

[RickKrung]

Here are some photos of the first stage of fabrication on the motorization of the truing tool.  My layout skills are a bit rusty, so I had to enlarge the holes to get the motor mounted and the bracket square on the TT.  I believe it will require further enlarging of the motor mount holes and the bracket holes so the motor/mount can float and find its own center on the knob.






I'm still thrashing about trying to figure out how to connect the motor shaft to the knob.  I'd like to drill a hole in the center and thread it to insert a screw of some sort and lock it with a nut.  My concern is being able to adequately find the center of the knob. 

I have figured out how to hold the TT for drilling.


Rick

[RickKrung]

I'm still thrashing about trying to figure out how to connect the motor shaft to the knob.  I'd like to drill a hole in the center and thread it to insert a screw of some sort and lock it with a nut.  My concern is being able to adequately find the center of the knob. 

Rick

Issue solved.  I got the knob off of the TT screw. The knob mounts on the shaft via a threaded insert.  M6x1.


There is about one turn of thread exposed, which is enough to get an M6x1 screw locked in place as a drive shaft for the motor.  Now all I have to do is make a sleeve to fit over the motor shaft and thread the other end. 


I have an M6x1 tap, so I should be truing via motor control very soon.   

Rick

[RickKrung]

Issue solved.  I got the knob off of the TT screw. The knob mounts on the shaft via a threaded insert.  M6x1.

Issue NOT solved.  I cut down an M6 screw and machined a sleeve to mount it all up.  Used a couple nuts to lock the screw in place. 


There is huge wobble in the assembly.  I tried taking a video of it, but it was massively large and I won't post it.  I think the wobble is due to too few threads engaged between the screw and TT shaft.  If I can get the brass threaded/press on fitting off of the TT shaft, I might have a chance at getting things lined up.  Otherwise, I'll see if I can press on a length of delrin to serve as the connection between the motor and TT shaft.

If you look at the photo, you may notice I've added the zip-ties, ala Wootz, to steady the cross travel.  Those  ties are impinging on the added motor mount bracket, so I'll have to shorten the bracket.  I'll also have to shorten the screws that mount the motor mount as the do-hickie that holds the diamond tip will impinge on the screws sticking out underneath. 

This is all part of the design/implement/discover issues/redesign/reimplement/repeat...  process that I enjoy so much about making things. 

With this motor, I get a traverse time of 24 sec. at 100% power on the train controller.  60 sec. traverse time at 25% setting and 100 sec. traverse time at 20% setting. 

Rick

[RickKrung]

I think the wobble is due to too few threads engaged between the screw and TT shaft.  If I can get the brass threaded/press on fitting off of the TT shaft, I might have a chance at getting things lined up. 

Yup, that is the issue.  I tried getting the threaded fitting off the motor end of the shaft, but the other end came off first. 


After getting the intended fitting off and putting the threaded sleeve on it and checking runout with it in the lathe, there was less than 0.010" runout. 


I will modify the design/assembly to rely on this method of connecting the TT shaft to the motor shaft.  I'm hoping this will work satisfactorily. 

Rick

[RickKrung]

After getting the intended fitting off and putting the threaded sleeve on it and checking runout with it in the lathe, there was less than 0.010" runout. 

Apparently not good enough.  Still too much wobble to bolt it all down snuggly. 


It would work as is, with not all the screws snugged up, but I'll pursue this some more to see if it can be resolved.  I ordered some M10x1.5 SS threaded rod and will turn the motor end to mate with the motor shaft.  I also ordered an M6x1 threading die to be able to put that on the free end to get that knob back on.

If that all doesn't do it, I'll probably just use it not snugged down.  I believe it would work just fine.

Rick 

[RickKrung]

I have gone back to hand turning the Truing Tool. 

After trying motorized version on my black stone, it left those angular wavy lines about a third of the width in from the outer edge.  I think without the dampening effect of the hands on the TT and USB, it is too free to vibrate.  I tried holding it while it was running and going as slow as possible, but I could not prevent the waves from forming until I disassemble the TT from motor, reinstalled the knob and trued the wheel by hand. 

It was fun trying.

Rick

[Hlokk]

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.

[RichColvin]

I LOVE that !!  And thank you for the pictures.   I wasn't following the CAD drawings. 

Rich

[RickKrung]

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

[justme]

That looks absolutely awesome!

RE: "wobble", almost makes one wonder if a bit of re-design shouldn't happen:
- move drive screw to a more "centered" position, enabling:
- use of ball-bearings (logical "front" and "back") to ensure that movement of the truing tip can only be "side to side".
- move to Rick's design (motorized + speed control) and micro switches at each end to enable "auto-reversing" of the motor to true in "multi-pass" mode.

In looking at your zip ties - went ahead, doing same, and attempted to re-true my SJ-250.  The "more bound" (less movement/wobble) made a substantial improvement in the results.  Had a portion that was "wavy" from previous truing attempt(s).  A good portion of that was removed.  Suspect that a couple more passes (removing barely topical amount) will completely clear that issue.

The balance of the stone's surface (majority of width) came out far better than previous.  If you look at the right hand 20%, you'll see the uneven cuts into the stone (see attached image).  Suspect that this may have been a result of the truing tip being able to 'bounce' off the stone due to "wobble" (movement space, albeit small - but present).  The zip tie effect appears to hold the tip at a fixed distance.  Thus, only removing at a specific depth and preventing it from being able to "dip" down into the stone.  On an SG-250, likely not an issue.  However on the much softer SJ-250 - huge difference.

Have to wonder how many people end up inadvertently applying "downward" pressure, because of hand weight or "resting" of the hand (possibly added limb weight) onto the truing tool - also impacting the result(s).