# TPG



## Tony Wells (May 10, 2012)

Anyone build a tool post grinder? I've yearned for one about like the Dumore series 57 OD/ID, but they are kind of pricey. I have a couple of prototype parts that sure would be simpler with a grinder, so I was considering building one. I haven't looked on the Bay yet, but may have a look. I know there are plans on the Net, but I would rather have first hand experience if someone here had built one.

All suggestions appreciated.


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## 8ntsane (May 10, 2012)

Ive never built one either Carl
But if you decide to build your own, be sure to start a thread on it. It would be nice to build a TPG from scratch,in that size.


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## Tom Griffin (May 10, 2012)

Building one is definitely high on my to do list. I've been collecting info on various models for some time and pretty much have the design roughed out in my head. Just need to take the time model it up. Spindle or angular contact bearings are the most expensive component of a TPG by far and I haven't found a good source for them yet other than directly from Dumore for $200+. They occasionally pop up on ebay but if I'm going to go to the trouble of designing a grinder, it would be nice if the bearings were an off the shelf part. I've also been keeping my eye on ebay for a Bodine motor. There are  several suitable motors available from the surplus houses but they  aren't near as cool as a Bodine. :worship:

Tom


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## mhooper (May 10, 2012)

I am current working out the bugs on a toolpost grinder that I am building (my first).  I used bronze bushings for spindle bearing (got the idea from utube video jimathanexup) they work pretty good right now.  Some items that I found to be a problem on design and part selection are: 
1. If you use manufactured pulleys, check the run out. I found some off the shelf pulleys have more than 0.010" run out.  I made my pulleys and trued them up on a arbor turned between centers.
2. Check the run out on the motor that you use.  Tolerances for electric motors can vary a lot.
3. Balance everything (pulleys, grinding wheel, electric motor rotor, electric motor fan, etc.)
4. Make the grinding wheel guard heavy duty. Grinding wheels do fail.
5. Use a fine filter on the electric motor fan (cut from a vaccum cleaner bag or a "cut to fit" HVAC filter). The abrasive dust get sucked up by the fan and blown around, especially when you are true up the grinding wheel.
6. I found that the inexpensive grinding wheels have hard and soft spots. The softs wear away quickly and you have to redress the wheel several times during one use. 
7. Watch out on the amount that the end of the spindle sticks out past the grinding wheel. The shorter the better.
8. I have not had any luck using adapter bushings on the grinding wheels. I use JB Weld to fill the space.
9. I used steel for everything on mine and it is very heavy. (consider Aluminum for most of the parts)
10. Large tool post grinders a great but may be tough to use on small items.

Hope this helps
mhooper


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## DMS (May 11, 2012)

There was a series of articles in Home Shop Machinist running from July/August of 2010. I didn't focus too much on them, at the time as I was not planning on building a TPG. I also recall an article in Digital Machinist (don't recall the month) which involved making a tool post mount for one of those pencil grinders you can get at Harbor Freight. 

The gist of the HSM article is that it's just a spindle (just), a mount, some guards, and a motor to power the thing. Seems the author had more problems finding a suitable motor than anything else. For the spindle, you might check out the Quorn users group over on Yahoo. In the files section are plans for the Broadley spindle. It's intended for a small grinder, and I would guess that it would work well for a TPG. If anything, it might give you some ideas.

DMS


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## Tony Wells (May 11, 2012)

Thanks all for the suggestions. I was considering using a router for the motor. I have several, so wouldn't miss it for wood work. A spindle should be no problem. As Tom stated, it's all about the bearings. My primary objective is to focus on ID grinding. I am quoting a couple of parts where it sure would be handy. The part has a two lobed ID of 1.450 diameter with a 0.080 offset. Desired finish is 16 Ra. Since they are offset, honing is out, for at least the second one. So, I am thinking that grinding is the best way to go. 

Bodine does make a nice motor that would be good to base a grinder on.


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## 8ntsane (May 11, 2012)

Carl
Have you had a look over Bob Warfields site?
He has a bunch of TPG others have built. Some are using router motors in the mix. Could give you some idea,s


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## Tom Griffin (May 11, 2012)

8ntsane said:


> Carl
> Have you had a look over Bob Warfields site?
> He has a bunch of TPG others have built. Some are using router motors in the mix. Could give you some idea,s



Paul,

I assume you mean the CNC cookbook site? I checked it out, but didn't see any TPG's. Do you have a link to the ones you saw?

Tom


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## DMS (May 11, 2012)

Looks like there are a few that use a router as a power source. 

http://www.cnccookbook.com/CCLatheTPGrinder.htm

I really love that site


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## 8ntsane (May 11, 2012)

DMS said:


> Looks like there are a few that use a router as a power source.
> 
> http://www.cnccookbook.com/CCLatheTPGrinder.htm
> 
> I really love that site




Yup, this is the one I was talking about.


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## bcall2043 (May 11, 2012)

42 said:


> Thanks all for the suggestions. I was considering using a router for the motor. I have several, so wouldn't miss it for wood work. A spindle should be no problem. As Tom stated, it's all about the bearings. My primary objective is to focus on ID grinding. I am quoting a couple of parts where it sure would be handy. The part has a two lobed ID of 1.450 diameter with a 0.080 offset. Desired finish is 16 Ra. Since they are offset, honing is out, for at least the second one. So, I am thinking that grinding is the best way to go.
> 
> Bodine does make a nice motor that would be good to base a grinder on.



If your primary use is for finishing small ID bores then a quick and easy solution might be the use of a die grinder mounted on the tool rest. I have attached a copy of a Sears catalog that shows one they use to offer. Die grinders and plentiful and not that costly. I think HF even offers one similar to the Sears one. 


Benny


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## Tony Wells (May 11, 2012)

I have a need to do ID's primarily, and I'll either build a spindle with an extension similar to the style Dumore uses, or possibly purchase one of their accessory spindles and build the rest. I have used a Dumore extensively, and like the way they run. If I build my own spindle, I'll be going with ceramic bearings if I can get the sizes I want. 

I don't believe a die grinder will be stable enough. I have a +/- 0.0005 16 Ra finish bore about 3.500 long to do, and it will be interrupted. That would be asking a lot of a die grinder, seems to me.

If I build instead of buying a used one, I'll do a build thread.


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