Grinding how to..

[JerryFlyGuy]

Anyone have some good 'How to Grind' websites? [no not just your run of the mill 4 1/2" grinder either.. ] I'm looking at a future project here where we need some parts ground to size [they are produced oversize w/ normal shop fab practices then ground to size.] I'm looking for some very very loose tolerances [when talking grinding anyway] but am hoping to make an arbour for my mill, chuck up a grinding stone and go to it..

Looking for just general info on the in's and out's of machine tool grinding practices and what not.

I know its an odd way of going about the job but hey.. I like to do things the hardway..[ and I have my reason's ]

Jerry [seem to be in perpetual question mode lately. ]

[NC Cams]

Radiac and Carborundum both have/had some grinding manuals/catalogs that some real good information in them on grinding. The manuals are not that easy to come by anymore and we guard ours closely.

When it comes to grinding tool steels, the Timken website has some PDF's that provide very good info on what grit and stone hardness to use when grinding the various tool steels that they make. You'd be hard pressed to do better for getting started info.

Grinding is a skill that is learned and developed over time. Trust me, it took months to learn how to grind even basic cast iron cams and I won't even admit how long and hard it was to learn how to grind hard face welded (stellite) and/or tool steel cams. We're still learning.

Find a good source of wheels!!! See if they'll provide you wheels "on approval". Not all wheels cut as planned or as promised. You will end up with some boat anchors over time so be forewarned. Then there will be others that you'll paint over the codes on so nobody will see what you're using - it gets that critical.

Finally, don't use cheap coolant. Find one from a name supplier and stick with it. Don't skimp over a few bucks in cost. My business partner tried that and it simply doesn't pay. We ended up using Valenite "Valcool" after some fits and starts with generaic crap and Valcool works very well for our application (OD and camshaft grinding and turning).

[JerryFlyGuy]

Thanks Nc! I was going to ask you directly, but figured I might as well post a thread, I knew you'd get here sooner or later

I'll do some more searching, maybe some of the wheel providers can help w/ their sites.

Thankfully, my application isn't anywhere near as critical as what your doing. These parts are fine at +/- 0.010, however they are +/-48" in dia. They do have several different tapers running on the outside/vertical face. My current options are to get someone w/ a very large boring mill, or lathe, or do them myself w/ my machine [ which isn't done yet, but its getting very close] I wouldn't be comfortable doing the job w/ some type of end mill as I don't think my machine would be strong enough [it's heavy enough however] so I figured some type of grinding might be the best route. I've got some old books on CD coming w/ grinding info on them as well, we'll see if its helpful or not [doesn't matter really as they were soo cheap]

Grinding isn't something that I planned to get into, however this job is one we've fought w/ at work [my real job] several times. This time, however, things have changed a bit as there is a huge hunk of metal in my garage .
Very soon that huge hunk of metal will be called a machine, but not until it moves under its own power..

Thanks again!

Jerry

[JerryFlyGuy]

Ok so I've got some more grinding questions.

I'm planning to just go buy some 8" bench grinder [Silcon Carbide] wheels as this is project is not very technical [not worthy of expensive grinding wheels]. I plan to chuck this up in my mill and operate it as if it's a huge, non center cutting end mill w/ a 1" DOC. The part I'm grinding to size is 48" in o/a dia. It has two tapers on the outter face [cylindrical face] Should a person grind a taper on the grinding stone to match this taper before starting, or is it proper to just use a sqr'd face on the wheel and just let it grind on the corner of the wheel as it moves down the taper. I post some sketch's of the part if need be to help clarify. Also I'd assume that taking 1/8" off the dia is going to be a long grinding job, as far as grinding job's go?

Lastly, I'd planned to use a tool dia compensated code, which mean's I could just adjust the dia spec in the control [Mach 3] and let it compensate for the decreasing dia of the tool as it works [adjusted between pass's]. Not sure if this is the proper way to control grinding process's like this.

Grinding isn't something I want to get into, however for this particular part, there isn't really any other way to do it [other than a large boring mill, but time and money prohibit this]


Thanks!!
Jerry

[Newby2]

I work in a grinding shop where we hold tight tolerances. +/- .00005. As for the grinding of a taper on a mill, if you can't tilt the head of the mill, ( as in a bridgeport), then I strongly suggest you dress the wheel to the taper you want. You will ruin the piece you are working on if you try to allow the wheel to "run itself in" so to speak, and use plenty of coolant. If the part is 48" in dia., then you will want to dress the wheel after each full rotation of the part.
You'll only need to to take about a thou at a each dress to maintain the greatest cutting action of the wheel. Dressing the wheel refreshes the grit and renews the cutting action. A clogged wheel will burn the part you are grinding and may even cause chatter on the surface of the part.
Good luck!
Steve

[miljnor]

I am going to be looking into acquiring a centerless (thru-feed) grinder and will be looking for information on running/setup on these as well.

So if anyone want to throw any information on that up as well, that would be cool!

thanks

[JerryFlyGuy]

Thanks Steve, seem's that getting info on grinding is kinda tuff, almost a black art. I don't think I'd have trouble dressing the stone to the taper. I might be able to make some type of sub program/macro which would do a dressing pass once per rev.

The final tolerance on this part is ~ +/- 1/64" so it's no where's near as tight as what your doing. I just need to take this pc which is made from rolled and welded parts and clean it up so its pretty round and has smooth transitions between the tapers. Pretty simple, just hard to find a machine which can do it..

Anything else you can point out would be greatly appreciated. I can see that I'm going to do going at if for a while if I have to remove ~ 1/16" of metal all the way around.. thats 30-60 passes yikes!

Jerry