Magnetic Indicator Stands

Ya know, I have a bunch of those. I'd had a bunch more too, but all of the cheap import ones (not counting Yuasa) didn't work very well so I let those go. I point mine sort of straight up and down when I'm done with them and they do stand up just fine, would probably fall down in an earthquake though.

GWE

Stability has nothing to do with weight (or, more precisely, mass). It has to do with the center of mass (center of gravity) of an object, and the forces acting upon it. So a very wide and short, lightweight indicator stand base will be less prone to tipping over (i.e., more stable) than a very heavy base that is tall and narrow.

However most mag bases have fairly similar, proportional dimensions (roughly a square cube). So what you want for max stability is a base that is dimensionally larger, thus concentrating more mass in the base than in the arms. Lighter weight arms (e.g., aluminum) will also help to keep the center of mass low.

Of course, if the arms are extended outward, they will increase the tipping moment acting on the base, and if they are extended upward, they will raise the center of mass (thus reducing stability). This negative effect will increase with increasing mass of the item (e.g., indicator) being held by the arm.

I'm curious though: why *can't* you keep the "darned magnet turned on all the time" (except when moving/repositioning the base, of course)? It's not as if the magnet will wear out or lose strength. You suggested turning the magnet half-on, so it appears as if you are still placing it on a magnetic surface. Perhaps you'll find the answer you're seeking if you were to explain the actual problem that you're having.

- Michael

True by the strict definition, but if "stability" is being used in a more generic sense, then stiffness will be a factor, and the amount of material involved will make a difference.

In fact, I doubt stability is a design criterion, otherwise, they wouldn't need the magnet to hold it in place.

That and one that is well made with good materials so that parts tighten well, hold position, etc. To do a good job, a magnetic base and arm needs to be a relatively rigid structure.

Ultimately, we probably are in agreement. I suspect the problem is not that there is not enough metal, but that the offending item is poorly made.

Bill

Ok, I'm sliding it around on my table and it stands up because it is pressing on the workpiece, then I set it aside and forget that the contact pressure was keeping it upright, and it falls over. Maybe if I could turn the magnet "half on" a metal surface would keep it upright and still allow you to slide it. But not on a wooden bench or surface plate. The larger dials make balance even worse and can be annoying to use on a surface plate. Are lead bases perhaps used on surface plates?

Bill, please go back and re-read the original post. He was asking specifically about stability (in the strictest definition). His problem wasn't lack of rigidity or positional accuracy in the holder, but rather that the base would tip over when not in use.

- Michael

I suspect part of your problem is that you are using the wrong tool(s) for the job. Again, it would help to know what it is you're trying to accomplish, rather than simply what you are doing. Are you trying to set up a part in a machine (e.g., centering a round part in a lathe chuck)? Or are you trying to take dimensional measurements?

In any case, if you are using the pressure from the indicator on the part to help support and stabilize your magnetic base, then that is one of your problems.

- Michael

Are you suggesting there are several types of magnetic bases an I am using the wrong one? When I am measuring the part I don't notice that the indicator pressure is keeping it upright because it is in place and also I have my hand on it. As far as what I am attempting to accomplish I am obviously verifying the part is flat on the table or checking differential heights on the workpiece.

The correct device to use on a surface plate is the surface gage. Trying to use a magnetically mounted device on a surface plate is asking for trouble. Magnetic dial indicator holders aren't designed to be stable in the non-magnetic condition. Without magnetic attaction they are unstable and apt to be just plain wobbly. Personally, I am glad that mine is able to be laid down so's I can put it away in a drawer.

Bob Sw>> [...]

No, I am suggesting that a magnetic base is not intended to be used as a surface gage (which, apparently, is what you are trying to do).

Wrong tool and wrong technique.

Perhaps obvious to you. But there was absolutely no hint of what you were trying to accomplish in your first post, and your second post was ambiguous: there were several possibilities based on the meager information you provided. For example, you could have been trying to ensure that a part is parallel to a milling table. In any case, you'll find that people are more willing to take the time to assist you if you are willing to take the time to provide more information (and are not snotty in your responses).

- Michael

You want one of the large indicator stands that were made by Brown and Sharpe. They were supplied with the 744 dial test indicator.

Kevin Gallimore

"Dave" wrote in news: snipped-for-privacy@g44g2000cwa.googlegroups.com:

What you need is a height gauge, not a magnetic base.

Dave:

As others have pointed out, a mag base holder isn't the "proper" tool for the job. But if it's all you've got, you could magnetically mount it on a small flat plate of steel (something dimensionally like 4" X 4" X 1"), or anything reasonable.

"Robert Swinney" wrote in news: snipped-for-privacy@comcast.com:

Brown & Sharpe, among others, makes a magnetic surface gage. It is way more stable than an ordinary mag base.

So if you were checking that something was flat on your milling table you wouldn't use a mag base?

I have several that I store by keeping them stuck to a steel plate above the lathe. This is a beam that supports the floor above my basement, and I just turn the magnet on. Keeps the indicator out of the way and safe. I use three other cheap Chinese ones (base only) as "feather boards" on my table saw in my woodshop. These I keep stuck to the side of a steel cabinet near the saw.

You might want to consider screwing a steel plate to the wall near your machine tools just for sticking magnetic bases, if you don't already have something suitable.

The problem with a height gauge is that it doesn't have any reach. I'll consider one of the larger mag bases that some have mentioned. Maybe make a heavy steel base I can lock the mag base onto? Thanks.

The fluorescent light over my lathe has enough magnets on the steel reflector that it is tipped 1" off level. Gerry :-)} London, Canada