Harold,
Didn’t you put a treatise on surface grinding settings somewhere on the board? I know you outlined depth and step over etc. can you point me to it or possibly post it again here?
Thanks,
Steve in Indianapolis
Ping Harold Vordos
Re: Ping Harold Vordos
Steve,
Nice to hear from you.
I don't recall putting that information on the board, but I have always used the deep depth of cut and slow step-over method of grinding. It is just as fast as the other method, and yields a much better surface finish, with the benefit of greater control of size.
If you have a reasonable surface grinder, say a 6 x 12 or 6 x 18, at least a horse on the grinding head, you should be able to rough by taking a five thou depth, about a .030" step-over. If you take all cuts in the same direction of saddle feed (or head feed, which ever your machine has), you'll generate a worn step in the wheel, same depth as the cut, but the balance of the wheel constantly sparks as you progress, which accounts for the nicer finish, as well as a more precise cut, as the breakdown of the wheel is pretty much limited to the roughing corner. You likely understand that the five thou is, more or less, a maximum. Shallower depths are very much acceptable, and may be required, depending on what you're doing.
There's more to grinding that just removing stock. If you hope to keep pieces flat, you must grind each side equally, and take smaller cuts. That keeps internal stresses balanced.
It's always a good idea to dress the wheel for a final cut, which can be as little as a tenth or two, or as much as a half thou. All depends on the tolerance you have at your disposal, and the finish you'd like to achieve.
The other method of grinding dictates shallow depths of cut, accompanied by rapid movement of the saddle/head. That causes the majority of the wheel face to grind material, so it tends to break down slightly, and will yield an inferior surface finish. The only time I even think of using that process is when I am trying to establish a relatively flat surface on a part, grinding both faces. It's faster to pick up the highs and flip the part, then repeat. However, once I have a respectable surface (more than 75%), I then resort to the process I outlined, above.
I'm not suggesting that what I do is right, and the other process is wrong. What I am suggesting is that if you hope to achieve a good finish with greater accuracy, my method will prevail.
H
edit:
It's relatively important that you match the wheel to the work at hand. Use a hard wheel for soft materials (aluminum oxide for ferrous, but not cast iron, for which a silicon carbide wheel is preferred). Diamond dress the wheel, traversing the final pass slowly, as that will influence the finish you achieve on the part. You can get a surprisingly nice finish with a 46 grit wheel, but for a finer finish, you might entertain the use of a 60 grit. It won't be as aggressive, but it does yield a nicer finish. An even finer wheel (80, or even 100) for ultra nice finishes, of course, but they will be less than good at stock removal.
If I didn't address a particular issue, please ask.
Nice to hear from you.
I don't recall putting that information on the board, but I have always used the deep depth of cut and slow step-over method of grinding. It is just as fast as the other method, and yields a much better surface finish, with the benefit of greater control of size.
If you have a reasonable surface grinder, say a 6 x 12 or 6 x 18, at least a horse on the grinding head, you should be able to rough by taking a five thou depth, about a .030" step-over. If you take all cuts in the same direction of saddle feed (or head feed, which ever your machine has), you'll generate a worn step in the wheel, same depth as the cut, but the balance of the wheel constantly sparks as you progress, which accounts for the nicer finish, as well as a more precise cut, as the breakdown of the wheel is pretty much limited to the roughing corner. You likely understand that the five thou is, more or less, a maximum. Shallower depths are very much acceptable, and may be required, depending on what you're doing.
There's more to grinding that just removing stock. If you hope to keep pieces flat, you must grind each side equally, and take smaller cuts. That keeps internal stresses balanced.
It's always a good idea to dress the wheel for a final cut, which can be as little as a tenth or two, or as much as a half thou. All depends on the tolerance you have at your disposal, and the finish you'd like to achieve.
The other method of grinding dictates shallow depths of cut, accompanied by rapid movement of the saddle/head. That causes the majority of the wheel face to grind material, so it tends to break down slightly, and will yield an inferior surface finish. The only time I even think of using that process is when I am trying to establish a relatively flat surface on a part, grinding both faces. It's faster to pick up the highs and flip the part, then repeat. However, once I have a respectable surface (more than 75%), I then resort to the process I outlined, above.
I'm not suggesting that what I do is right, and the other process is wrong. What I am suggesting is that if you hope to achieve a good finish with greater accuracy, my method will prevail.
H
edit:
It's relatively important that you match the wheel to the work at hand. Use a hard wheel for soft materials (aluminum oxide for ferrous, but not cast iron, for which a silicon carbide wheel is preferred). Diamond dress the wheel, traversing the final pass slowly, as that will influence the finish you achieve on the part. You can get a surprisingly nice finish with a 46 grit wheel, but for a finer finish, you might entertain the use of a 60 grit. It won't be as aggressive, but it does yield a nicer finish. An even finer wheel (80, or even 100) for ultra nice finishes, of course, but they will be less than good at stock removal.
If I didn't address a particular issue, please ask.
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Ping Harold Vordos
If I may, using a finer wheel increases the heat in the part.
For some reason the coarser grits have less heating effects. I am going to guess that more coolant, either air or liquid, is carried along the surface of the wheel.
I cannot disagree with anything Harold said, but then my grinding experience has been in sharpening Pipe Thread chasers and not precision flat parts. I was able to hold a set of 4 chasers within .001 which is plenty good enough for pipe chasers.
--earlgo
For some reason the coarser grits have less heating effects. I am going to guess that more coolant, either air or liquid, is carried along the surface of the wheel.
I cannot disagree with anything Harold said, but then my grinding experience has been in sharpening Pipe Thread chasers and not precision flat parts. I was able to hold a set of 4 chasers within .001 which is plenty good enough for pipe chasers.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
-
sierevello
- Posts: 92
- Joined: Sat Feb 01, 2003 3:24 am
Re: Ping Harold Vordos
Thank you so much Harold!
-Steve
-Steve
Re: Ping Harold Vordos
I am going to have to go out and throw a piece of scrap on the grinder .
I won't say it's nice to learn your doing things wrong .... but it is nice to learn how to do things right from someone you can trust .
I won't say it's nice to learn your doing things wrong .... but it is nice to learn how to do things right from someone you can trust .
Re: Ping Harold Vordos
Something to consider.stephenc wrote:I am going to have to go out and throw a piece of scrap on the grinder .
I made mention of wheel selection, based on part hardness. You'll come to understand (if you don't, already) that hardened pieces grind much nicer than soft pieces. The scrap you select, if soft, may not yield a great finish.
I didn't address grinding wet or dry, but I'm a bit of a mule in that regard, just as I am with grinding manually, or with power feeds. Even for fine tool grinding, I use coolant. Yeah, it's messy, but it also lends a degree of precision that may be hard to master if you grind dry. And I wouldn't own a manual surface grinder---but that's just me. Others often strongly disagree.
Power feeds.
I can imagine that rapid stepover grinding is the result of learning to grind on a manual machine, where one's arm gets tired of the endless traversing of the table. That, of course, with an auto feed machine is a non-issue.
Stepping over in greater increments limits the number of times the table must be traversed, but the end result will, almost without fail, be less desirable than the fine stepover method. Each individual will make the choice of which to apply based on their abilities and needs.
H
Wise people talk because they have something to say. Fools talk because they have to say something.