I bought a set of inexpensive gauge blocks, mostly to be able to check the accuracy of my motley collection of calipers and mikes.
I spent about 2 hours cleaning the rust preventive goop from them and then I went over them with a rag wet with LPS. If I keep them in the living area of my house, is that sufficient protection to keep them from rusting?
I noticed that in order to get them to wring together, the surfaces had to be close to perfectly clean. I assume they have to be re-oiled after use.
Does anyone know what the accepted procedure is for testing mikes and calipers? Some sort of progression of blocks that serves as a worst-case test?
I wipe my gauge blocks down with Sewing Machine Oil after every use to clean them and to prevent oxidation. It is a highly refined "stainless" oil that tends to dry out over time but, since I use the blocks regularly, this is not a problem for me. The oil is sold in sewing machine shops.
To wring together properly, they do have to be clean and dry. Cheaper sets sometimes benefit from a tiny bit of the grease made for that purpose, good ones shouldn't need it.
Pick the intervals that you want to check them at, but avoid anything that would come to an even interval for a caliper, use odd and random intervals. For micrometers, maybe zero, 1/4, 1/2 /34, etc but always include at least one that will come out a half turn of the thimble from the zero to check for drunken threads, it does happen.
Just an extract from a sales brochure note that they say the gauges are cylindrical!! Hope this helps, by the way this is how I check my Micrometres
"The set consists of eight cylinders 3.1, 6.5, 9.7, 12.5, 15.8, 19.0, 21.9,
25.0mm diameter manufactured to ±0.001mm tolerance on diameter. The sizes, taken from AS 2102-1978, are carefully selected to check a range of sizes at different positions around the micrometer barrel.
In technical parlance the set enables tests for both systematic and progressive errors. For example if the micrometer anvils were not square to the axis of the spindle correct readings could be indicated at zero, 6.5,
12.5, 19.0 and 25.0mm with significant errors indicated at 3.1, 9.7, 15.8 and 21.9mm."
I usually wipe the working surfaces on a clean sheet of paper. I've found the wring the best using this simple cleaning process. Laying the paper on a clean surface plate does an excellent job.
While I've heard paper is abrasive, I'd be surprised if you could actually do any damage to the blocks (just in case anyone wants to object). The gauge blocks at work are subject to an environment rife with abrasive dust, as well as what some would call abusive use, and they still wring.
Those gauges that Peter mentioned are pretty neat. I have to ask though, are you doing work that will hinge on the last .0001" or so of your mic's accuracy? Seems excessive unless the mic you're checking is very old or well used.
I can speak somewhat authoritatively on the subject of paper, having served as project manager designing high speed ballot counters.
As trees grow, silica matter is picked up from the soil and gets tightly embedded into the cellular structure of the tree. The silica stays there even through normal paper production.
A piece of mild steel or AL, pressed against quickly moving paper, can have thousandths sanded off in a surprisingly short time. Likewise, a glass window will get scored quickly.
Whether one or two swipes with a gauge block would do any damage over the life of the blocks, I don't know. I'd probably not do it if I were using the blocks frequently.
No, not at all. What I'm more interested in is whether or not my import calipers are reading right over their full length of travel. The calipers only have to be accurate to a couple thousandths for my work. Lenny's advice of staying away from even intervals is probably all I need to do.
I'd be interested in seeing the results of this practice. I do a lot of abrasive finishing of hardened and unhardened steels and I can't fathom anything as fine as paper having any functional affect on hardened steel gauge blocks.
I suppose the reason I'm so interested is that I frequently read posts from people who are too concerned with issues that are of virtually zero consequence to their overall objective. At work, I am (aggressively) encouraged not to worry about such issues as there is no time for it. The master toolmakers are the ones who focus all their energy on fixing problems which are of import, while doing as little about trivial issues as possible.
There are over 100 certified Tool and Die Makers where I work and none of them work to .0001. We do precision grinding with 1/4" die grinders, disc grinders, polishing stones and sand paper.
You're right, of course. Sometimes the last .0001" *does* matter. As far as function is concerned, I'd be surprised if five people reading this group were actually capable, or had access to facilities capable, of doing that type of work.
Ah Ha! IF you're checking the import calipers, make sure you check several places along the length of the jaws. I have four from HF, checking back where the jaws aren't thinned, beautiful. Checking where they beveled them, off by a full thou. A couple of swipes with a very fine stone, deburring the edges took care of it.
Jim Stewart wrote in news:192dndLul4OAXozZnZ2dnUVZ snipped-for-privacy@omsoft.com:
In addition to what the others have said...... remember that your gauge blocks will pick up body heat by holding/wringing, etc. Let the blocks sit undisturbed and unhandled for a minimum of 15 minutes before you record any readings.
Increments that represent uneven turns around the spindle so that you can check for errors at places other than the same increments each time. I think Fundamentals of Dimensional Metrology covers it (worth a library trip)
Blocks should be cleaned prior to use and lightly oiled when put away. There are spray cans of gauge block cleaner and preservative available.
I accepted work with .0001" tolerance in my humble shop when I was actively machining, and had success. The few times I had a tool returned was not attributed to having missed a tight tolerance, but to having made a stupid mistake elsewhere. In part, I was engaged in building tooling for the manufacture of guidance systems, such as used in military aircraft. Tight tolerance was the norm, and quickly sorts those that can from those that can't.
I was called upon on several occasions to quote work with .000050" tolerance, which I declined. I was (and may still be) capable of working in such a manner, but without a proper facility, it becomes almost impossible. My shop left a great deal to be desired in that regard, but in my youth, I worked where there was a certified secondary standards lab. One of the jobs I ran with complete success was a set of ring gages with .000020" tolerance. Someone, somewhere, must be able to produce the work with tight tolerance demanded of gauging. These people work in a different manner from others (of necessity), and are often misunderstood.
I knew you were one of the five. Then there's Steve. I wonder how close I am.
Anyway, about the only thing I know about that area of machining is that the more you're able to see, the greater the aggravation. Things like spotting blue, comparators, tenths indicators, and other "gauges" can be very humbling after dealing only with very-nears and micrometers.
That's the part where machinists gets sorted that I spoke of. You may discover you are very talented in a given arena, but struggle in others. I've rarely met anyone that is skilled across the board. The best lathe man I ever met, hands down, was heads and shoulders above anyone else, but was at a loss on a mill, for example.
I've always been gifted with the ability to do small, precise work. I can tolerate doing it endlessly, and am very patient (very unlike my normal demeaner) where it drives most guys crazy. By sharp contrast, I'm not good at large work----and don't particularly enjoy doing it. The size of the items you've discussed in pursuing your apprenticeship would drive me mad.
While it wasn't tool related, one job I ran in my shop, many years ago, took two months to complete. It consisted of a minute hook made of aluminum and Armco iron, with two stainless steel pins, .022" diameter. It was titled an antenna latch, and was a defense part. The pins were provided, but I made the balance of the parts from stock. The purchase order required 200 pieces, one first article, and 199 from production. I sold 209 pieces when the job was completed, having started with something like 240 pieces. Lots of close tolerance dimensions, although none under a thou except for hole diameters. The entire lot fit easily in the palm of one hand. I still have a few of the scrap parts, along with one completed item, assembled. If you're interested, send me an email on the side with your address and I'll send you a picture (77 kb in size) of some of the parts in various stages of development, along with the finished part. Included in the picture is a common straight pin, to give you perspective.
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