# Tool post grinder



## Clock work (May 19, 2018)

Unsure if this is a lathe or grinder topic... guessing lathe.

I've decided to un-bell-mouth the 3-jaw on my 10k which has caused me to dig out and start to de-crap I believe the last thing that came with the lathe, the tool-post grinder. Since the original owner purchased every single option SB made at the time, I assumed it would itself be SB but no joy. Once the years had been cleaned off the thing, I have this. Anyone recognize it? I haven't determined runout yet due to project overload but in looking at it closely I'm not setting my expectations very high. If it's known junk, I'll just put it back in the box and either get one of the cheapie direct drive units off eBay or one of the Dumore's. Either way, I need more in that it doesn't have the reach to get into the jaws. No plans to make tool post grinding a common thing. Just want my chuck back. Thanks for any input on this thing.

CW


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## Bob Korves (May 19, 2018)

For dressing chuck jaws I would prefer a larger Dremel type tool or an air die grinder mounted in a custom toolholder.  More rigid setup.  Also easier and faster to set up.  What you have should work, though, if it is not clapped out.  The current configuration will probably not have enough RPMs for good I.D. grinding of chuck jaws.  Still, it should work.


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## FLguy (May 19, 2018)

A good, sound TPG with ID spindle will easliy do a fine job. Just remember to block the jaws in a gripping fashion so after grinding and you chuck up a part you have the same clamping as when ground.


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## 4ssss (May 19, 2018)

If you decide to junk it, please throw it in my pile.


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## Clock work (May 19, 2018)

You officially have dibs on it


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## Clock work (May 19, 2018)

FLguy said:


> A good, sound TPG with ID spindle will easliy do a fine job. Just remember to block the jaws in a gripping fashion so after grinding and you chuck up a part you have the same clamping as when ground.



Thank you, Sir. As I'm certain I'll get a different answer at any given point on the scroll, I intended to plot out what the error vs scroll position looks like and select my position from that. See.. like.. I used to be "technical" and I'm struggling to remain boring

CW


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## Clock work (May 19, 2018)

Bob Korves said:


> For dressing chuck jaws I would prefer a larger Dremel type tool or an air die grinder mounted in a custom toolholder.  More rigid setup.  Also easier and faster to set up.  What you have should work, though, if it is not clapped out.  The current configuration will probably not have enough RPMs for good I.D. grinding of chuck jaws.  Still, it should work.



Bob... do you think something direct-drive will hold as nice a finish as something where drive vibration is dampened out by a belt of some kind? I know there are CNC routers and surplus spindles from semiconductor fabs that I was going to look in to if I had to go a different route to mine. 

Clapped out... always loved that phrase

CW


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## Bob Korves (May 19, 2018)

Clock work said:


> Bob... do you think something direct-drive will hold as nice a finish as something where drive vibration is dampened out by a belt of some kind?


I don't think that with or without a belt makes much difference to the finish, as long as the belt and the bearings are good.  Typical surface speeds for internal grinding are around 4000-12000 SFPM (I was going to say 5000-6000 SFPM, but looked it up...)
http://www.abrasiveengineering.com/speeds.htmhttp://www.abrasiveengineering.com/speeds.htm
Unless your TPG motor has a much higher RPM than I guess it does, you will not likely be very close to the numbers above.  It will still remove material, but not with as nice of a surface finish.


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## FLguy (May 19, 2018)

We typically get 25 -34 RMS on ID's with our TPG'S. Belt vs. flexable shaft drive....belt will always win out.


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## Bob Korves (May 19, 2018)

FLguy said:


> We typically get 25 -34 RMS on ID's with our TPG'S. Belt vs. flexable shaft drive....belt will always win out.


What about direct drive?


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## Silverbullet (May 19, 2018)

If you need one you own it . That grinder is well made so use it , get a smaller wheel mount it and dress it on the lathe mounted . Cover your ways and machine surfaces with drop cloths or towels if old give a spray of light oil or wd40  it'll help the grindings stick to them and not the machine. And if you don't like the grinder put my name in the hat too. With the machine you have another spindle with collets can be built easily . Er 11 collet chuck with straight shaft will be the spindle it's easy .


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## Clock work (Jun 7, 2018)

I decided to move forward on the home-made (with an axe? TPG instead of buying new given the encouragement here (thank you again). I took the old motor apart and it was junk... loose.. sloppy... wouldn't put it in a desk fan. That homemade spindle though feels pretty tight so moving forward. Found me a nice sealed Dayton 1/2hp 3450 rpm grinder motor on eBay at a killer price ($40 new). Again... fully disclosing my daunting lack of experience on these particular matters, it just feels too heavy to subject my 10K's cross slide t-slot to and the resulting torques. I'm curious if the more knowledgeable here agree or disagree? I'm guessing there might be a smaller motor on eBay if I go look again and I can always put this on something else... I don't seem to be running low on projects. 

CW


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## Bob Korves (Jun 7, 2018)

Clock work said:


> I decided to move forward on the home-made (with an axe? TPG instead of buying new given the encouragement here (thank you again). I took the old motor apart and it was junk... loose.. sloppy... wouldn't put it in a desk fan. That homemade spindle though feels pretty tight so moving forward. Found me a nice sealed Dayton 1/2hp 3450 rpm grinder motor on eBay at a killer price ($40 new). Again... fully disclosing my daunting lack of experience on these particular matters, it just feels too heavy to subject my 10K's cross slide t-slot to and the resulting torques. I'm curious if the more knowledgeable here agree or disagree? I'm guessing there might be a smaller motor on eBay if I go look again and I can always put this on something else... I don't seem to be running low on projects.
> 
> CW


Take a look at the Dumore site and see what they are using on their tool post grinders.  I have a 44-011 Dumore, their second largest one, recommended for lathes with 8-14" swings, and it has a 1/4 HP motor that is quite small and light, though high speed.  It works fine for the light jobs I use it on.  Pay attention to motor RPM and pulley and wheel sizes, for both internal and external work.  Grinding typically works best at around 5,000 SFPM.  Do the math for the wheel sizes, motor speeds, and pulley combinations you might expect to use on the grinder.
https://www.dumoretools.com/tool-post-grinders


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## Bob Korves (Jun 7, 2018)

You might also want to look at a manual as well to learn a bit more before getting started on it:
https://www.dumoretools.com/documents/Tool-Post-Grinders-Dumore-Series-44-Operating-Instructions.pdf


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## f350ca (Jun 7, 2018)

I wouldn't be concerned about the weight, think about the forces the cross slide sees when machining. But that motor probably won't be fast enough. As Bob pointed out you need to get the grinding wheels and points spinning at their recommended speeds. To get a mounted wheel running 20,000 + rpm you'd need a pretty big drive pulley. The motor on my Dunmore, (forget the model) is a universal type motor, guessing in the 10-20,000 rpm range. Maybe a small wood router would be a good donour.

Greg


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## bill70j (Jun 7, 2018)

f350ca said:


> Maybe a small wood router would be a good donour.



Agree on the router motor. Either a trim router or a full-sized router motor will work.  I have both.  They can get you 24K RPM for internal grinding, and with a potentiometer and pulley change, you can get down to 5K RPM for external grinding with a 3" wheel. 

The cheap HFT routers both have good donor motors.


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## Clock work (Jun 8, 2018)

Guys... thanks. I wasn't paying close enough attention to the mission. I do love the suggestion of HF as an organ donor as I have several I don't ever seem to even touch anymore... probably the trim router sitting under a quarter inch of dust, as Bill suggested. After I fix the chuck, I don't see me using it again and hope to move to a surface grinder asap for all other grinding... 

Appreciated!

CW


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## bill70j (Jun 8, 2018)

CW: 

If you're going to build your own TPG, and haven't built a spindle before, there is a book that has some very good information on building your own spindle - including drawings in metric and imperial.  It is a trifle difficult to follow the author's writing, but all the info is there.  You can pick up a used copy for less than $10 off Amazon.

Bill


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## Clock work (Jun 8, 2018)

bill70j said:


> CW:
> 
> If you're going to build your own TPG, and haven't built a spindle before, there is a book that has some very good information on building your own spindle - including drawings in metric and imperial.  It is a trifle difficult to follow the author's writing, but all the info is there.  You can pick up a used copy for less than $10 off Amazon.
> 
> Bill



Bill... thank you for taking the time. It's already in my cart. I enjoy several other books from that series. I think for my one-off need, I think I can make the one on the original TPG that started this work but it'll be modular.. I can swing another in if I need to, but the original spindle feels like the only rock-solid part of it. Still going to enjoy the book (when I finish reading the heat treat book from that series actually)... I'm amazed at the extraordinary precision our species has built up. 

CW


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## pontiac428 (Jun 8, 2018)

bill70j said:


> CW:
> 
> If you're going to build your own TPG, and haven't built a spindle before, there is a book that has some very good information on building your own spindle - including drawings in metric and imperial.  It is a trifle difficult to follow the author's writing, but all the info is there.  You can pick up a used copy for less than $10 off Amazon.
> 
> Bill



Or you can download that book (and most of the series) in the downloads section of this site...


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## Clock work (Jun 8, 2018)

pontiac428 said:


> Or you can download that book (and most of the series) in the downloads section of this site...



That is appreciated. Thank you!


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