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Pratt & Whitney R6/R8 grinder help

deerefanatic

Aluminum
Joined
May 17, 2011
Location
Colon, MI
I picked up a P&W Radius Grinder, either an R6 or R8.. Not sure which. I got it cheap at an auction a while back, and now have some time to give it attention. It didn't come with a vise or tool holder, although I have a 5C collet ficture I can put on the table. My main thought is to use it for accurate grinding of HSS lathe bits, and more specifically, form tools.

That being said, it appears that I'd want a diamond wheel for sharpening brazed carbide, but what type of wheel for sharpening HSS? I'm new to grinding, so it's all very foreign to me. I'm guessing from the look of the wheel guard this grinder is supposed to take around a 4" diameter stone, with a fairly small arbor.. Is there any reason I can't put a stone with a larger arbor hole if I machine a steel arbor spacer to fit? It seems most of the T&C stones have large (1" plus) arbor holes in them.

Thanks for any advice.

-Matt
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
For HSS either a plain white aluminum oxide wheel or CBN. You can put whatever you want on there as long as you have an adapter to align it and keep it aligned and the wheel can still be clamped tight by the flanges.
 

donie

Diamond
Joined
May 17, 2003
Location
Walla Walla Wine and Wild Turkey
With HSS grinding you must be very careful. Cup wheels are delicate and can blow off the spindle with not much of a bump, and cause injury and damage.
Dish wheels are more robust, but always stay out of the scatter path. Non reinforced cut off wheels, can do smaller features with a great finish, but be careful.
Often, its nearly impossible to keep a guard on the wheel head, but a piece of steel can be attached to the table or machine to help protect you.
I mention these things, because its easy to crash the work into the wheel on these machines.
 

michael.kitko

Cast Iron
Joined
Oct 30, 2012
Location
Gales Ferry, CT USA
Sorry to revive an old thread, but I was wondering if any of you experienced guys could answer me a quick question.

Here goes:

I have an R6 here at my home. I work for a company now that has these multikutter things in their disposal system for cutting trimmings off of sheet goods. It essentially is a spinning cage with two blades on it and they move past a stationary blade, causing little squares to be made with every rotation of the blades. Well, this company spends 6000 a month on repairing these things, vice 200 for just new blades. Now, where I come in. So, I asked why we can't do it ourselves or locally, instead of shipping them back to the original manufacturer Apparently, they have sent them to a local grinder and they couldn't grind them correctly. This was before my time. I just don't believe they are that hard to grind properly. I found the instructions for grinding them and it seems pretty straighten forward. I kinda want to prove them wrong and there is an old guy at work that said he wouldn't mind trying to pitch for an old grinding machine if he could be shown how to operate it.

So, can I do cylindrical grinding on this machine for the bed in procedure and shave off .0005", given the length of the blade is roughly 5" and the diameter is probably 3".

If more information is needed, I can provide it.
 

MCritchley

Hot Rolled
Joined
Mar 22, 2007
Location
Milwaukee
Sorry to revive an old thread, but I was wondering if any of you experienced guys could answer me a quick question.

Here goes:

I have an R6 here at my home. I work for a company now that has these multikutter things in their disposal system for cutting trimmings off of sheet goods. It essentially is a spinning cage with two blades on it and they move past a stationary blade, causing little squares to be made with every rotation of the blades. Well, this company spends 6000 a month on repairing these things, vice 200 for just new blades. Now, where I come in. So, I asked why we can't do it ourselves or locally, instead of shipping them back to the original manufacturer Apparently, they have sent them to a local grinder and they couldn't grind them correctly. This was before my time. I just don't believe they are that hard to grind properly. I found the instructions for grinding them and it seems pretty straighten forward. I kinda want to prove them wrong and there is an old guy at work that said he wouldn't mind trying to pitch for an old grinding machine if he could be shown how to operate it.

So, can I do cylindrical grinding on this machine for the bed in procedure and shave off .0005", given the length of the blade is roughly 5" and the diameter is probably 3".

If more information is needed, I can provide it.
6 k a month? Buy a cylindrical grinder for 6k if that’s all that’s required. It my be a better tool than a the grinder you have.
If the blades are like planer blades a regular T & C grinder like a KO Lee may also work if you wish to grind longitudinally along the blade.
 
Last edited:

michael.kitko

Cast Iron
Joined
Oct 30, 2012
Location
Gales Ferry, CT USA
Thank you everyone, just to confirm, the company that I work for doesn't want to buy the machine till they prove it can be done. They have said, if it can be proven, then they are all for purchasing a used grinder. During our morning meeting, several of the engineers have told me that it can't be done and it has to go back to the manufacturer. I countered with, how do you think they do it? They gave me a lecture about how they used a local grinding shop that could never grind them to the same dimension, so it must be difficult. I again responded, I have a precision grinder in my shed here and wouldn't mind trying this. One of the engineers, laughed, and said you can't do this on a bench grinder. I laughed and said, my "bench" grinder is 1300lbs with lead screws and ways, not a Screwfix Special. There was silence.

The blades are set at a 10 degree-ish angle in the cutter (I haven't measured), so the manual I've seen for regrinding them says to take the blades out of the cutter, mount them in a fixture, flat grind them, then put them back in the blade holder for final cylindrical grinding.

I was only asking about this machine, because this is the one I have to prove that it would be a good investment. I think I'm gonna try and coerce the Engineering Lead to let me give it a try.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Thank you everyone, just to confirm, the company that I work for doesn't want to buy the machine till they prove it can be done. They have said, if it can be proven, then they are all for purchasing a used grinder. During our morning meeting, several of the engineers have told me that it can't be done and it has to go back to the manufacturer. I countered with, how do you think they do it? They gave me a lecture about how they used a local grinding shop that could never grind them to the same dimension, so it must be difficult. I again responded, I have a precision grinder in my shed here and wouldn't mind trying this. One of the engineers, laughed, and said you can't do this on a bench grinder. I laughed and said, my "bench" grinder is 1300lbs with lead screws and ways, not a Screwfix Special. There was silence.

The blades are set at a 10 degree-ish angle in the cutter (I haven't measured), so the manual I've seen for regrinding them says to take the blades out of the cutter, mount them in a fixture, flat grind them, then put them back in the blade holder for final cylindrical grinding.

I was only asking about this machine, because this is the one I have to prove that it would be a good investment. I think I'm gonna try and coerce the Engineering Lead to let me give it a try.

Go for it. It can be a lot quicker and easier to do multiple parts to the same diameter with a close tolerance with digital readouts, but not impossible to do without. Maybe save that battle for when you have done a successful part.
 








 
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