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View Full Version : THE CONTINUING SAGA OF MY tool POST GRINDER



loose nut
01-08-2009, 05:00 PM
This week as I stated in a post a few days ago I have been making a mounting fixture for the TPG. Today I did my first trial "grind" running the lathe in its lowest speed (130 rpm's).

At first I was greatly under impressed, their where wavy lines all over the work and after a couple of very light finish cuts it still looked like beaver teeth gnaw marks. Next I increased the speed of the lathe to 300 rpm's and the finish looked some what better, so logic dictated that I try more speed. I cranked up the lathe to 600 rpm's and the finish looked quite acceptable considering the stone was the fairly coarse one that came with the LMS grinder.

I had noticed a vibration in the lathe itself that wasn't normally there and determined that because I had the work mounted between centers using a dog to drive the work it was out of balance and this seemed to show up more at the lower speeds. My next task is to make up a balanced drive dog of some kind and see if the problem goes away.

What would the normal lathe rpms be for grinding, light cuts .001" for example, the lathe is running in reverse to get the right rotation of the work.

There doesn't seem to be much info available for this.

lane
01-08-2009, 06:26 PM
I usually run 70- 100 rpm. But run the lathe in reverse. You want the work to meet the grinding wheel .Not travel with it.

loose nut
01-08-2009, 07:09 PM
Next question, what feed rate should I use

IE: a fine feed or a more course feed.

DR
01-08-2009, 09:38 PM
Do you have the correct wheel for the material you're grinding? And, are you dressing the wheel frequently?

lazlo
01-08-2009, 09:43 PM
Next question, what feed rate should I use .

Optimal grinding feeds and speeds are described in Machinery's Handbook. I don't have mine within reach right now, but you can find old copies on Google Books.

Teenage_Machinist
01-08-2009, 09:43 PM
Very good questions. Make a holder to hold a diamond dresser in the lathe, and machine-dress the wheel.

oldtiffie
01-08-2009, 09:54 PM
I think that I have the same TPG from LMS that the OP has.

Some of the wheels I had/have were not of even thickness. The "cure" was to dress the sides of the wheels as well as the periphery - made quite difference.

Dress the periphery to just have a "land" about 1/8>1/4" wide and use a "fast" feed (hand-wheel is best) and don't hesitate at the ends. It is better if the feed directions are stopped and reversed off the work being ground. That is often why there are large/wide recesses/reliefs on grinding jobs.

Use as coarse a wheel grit as you can.

Don't let the wheel "glaze" or "burn" the work.

loose nut
01-09-2009, 11:17 AM
OK, more questions and answers.

-Are the speeds and feeds for cylindrical and surface grinding the same for using a TPG

-I have a diamond dresser mounted in a holder for dressing the wheel, I dressed it across the full periphery of the wheel then turned the TPG on an angle so it would clear the tail stock and dressed it again.

-The wheel is the one that came with it I don't know the grade, it looks like it's about a 40 grit. at a guess I think it's for general purpose steel use.

-Tiffie the one I bought is the smaller single speed model, How did you get a dressing tool into the base/support side to dress that side of the wheel, I suppose that every time the wheel is remounted on the TPG the sides would have to be dressed again.

These machines aren't Dumores so certain allowances on the finish have to be made

lazlo
01-09-2009, 11:50 AM
Are the speeds and feeds for cylindrical and surface grinding the same for using a TPG

Yes. You just need to match the correct size/PRM of the TPG grinding wheel.

IIRC, Machinery's Handbook has grinding speeds/feeds for maximum metal removal, and a different table for best finish.

oldtiffie
01-09-2009, 06:52 PM
OK, more questions and answers.

-Are the speeds and feeds for cylindrical and surface grinding the same for using a TPG

.......................................
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-Tiffie the one I bought is the smaller single speed model, How did you get a dressing tool into the base/support side to dress that side of the wheel, I suppose that every time the wheel is remounted on the TPG the sides would have to be dressed again.

These machines aren't Dumores so certain allowances on the finish have to be made

Go flat out. Feed it quickly and smoothly.

I dressed that side in one of two ways:
- use an old piece of TC tip; and
- swap the wheel over so that the required face is accessible - but dress the outer face first.

I think I recall posting how I made a replacement mounting set for the wheel and how I would modify/enlarge/remove the curved wheel guard and to replace the 70?/90?mm wheels supplied and to use a common 100mm (~4") aluminium oxide cup or saucer wheel for T&C and surface grinders - with a standard Tool-room grinder 1 1/4" bore as they are very well balanced out of the box.

I didn't proceed with a lot of the modifications as my Universal Grinder made a lot of those TPG mods redundant.

That TPG is a good machine.

loose nut
01-10-2009, 09:33 AM
I tried it again yesterday and I'm getting a finish that looks faceted. Running the lathe at a higher RPM makes the facets almost to small to see but they are there. I'm going to dress out the sides of the wheels, there is about .015" run out on them, and try again.

I'm not sure that the problem isn't the lathe it self, there seems to be a vibration in it now?? The vibration seems to be worse when running the lathe in reverse, to get the work to meet the grinding wheel properly. If I run the lathe in the forward direction the vibration is a lot less and the faceting is less. There might be a problem with the motor bearings etc.

It's never easy. :confused: :( :mad: