Talk:Jig borer

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Contents 1 Article still needs expansion

[edit] Article still needs expansion

So, what exactly is a jig borer? What does it look like? How does it work?

This is a very uninformative article.

84.9.78.13 18:06, 20 February 2007 (UTC)

There are several kinds of jig borers. Most are classified as a vertical jig borers. The most common kind (plain ol' jig bore) looks like a cross between a milling machine and a large drill press. The head moves up and down to handle movement in Z, and the table handles movement in X and Y. The second vertical kind is the bridge type jig bore, which has an A frame that sits over top of a table. The head, in this case, manages both Z and Y movement, and X is handled by the table. This type is a bit more rigid than the standard jig bore. The third type is somewhat unrelated to the vertical jig borers, and that is a horizontal jig bore. Horizontal jig borers, or boring mills, are a type of horizontal milling machine. The head rises and falls on a pendant to control height. The table is free to move in two axes, and often has a large rotary table built in. The spindle itself will often have a long stroke. Most machines come with a tailstock for line boring (boring holes with the cutter supported on both ends of the hole).

http://www.biklemfg.com/_borders/2A_Jig_Borer.jpg - Jig bore

http://www.horstman.co.uk/images/SIP_Jig_borer.JPG - Bridge jig bore

http://www.toolmachine.com/devlieg1.jpg - Horizontal jig borer

They work in a couple different ways. New ones, of course, use full CNC control for positioning. Older ones used one of three methods. The first, and most common method, was end measuring bars. Bars of a precise length (similar to gage blocks) were placed in a channel parallel to a machine axis. There is a dial indicator at the end of the trough. The machine has moved into position when the dial indicator contacts the stack of measuring bars and reads zero. The dial indicator also allows setting the start point ( X/Y 0,0 is called the start point in the coordinate measuring system, the layout system used for jig boring machines). Using measuring bars, the operator starts with the farthest holes from the origin, as it is easier to remove measuring bars as things progress, rather than than insert one. The second method is the direct reading leadscrew. A leadscrew is made to gage standards, so that it may incorporate a vernier scale directly on the handle. This works only for relatively small (18" or so) distances. The third system was a variant on the direct reading leadscrew, called a compensated leadscrew. After the leadscrew is ground and corrected, it is gone over with a microscope comparator, noting deviations down the length. The deviation is ground into a bar, mounted over the leadscrew. This bar moves the vernier scale itself using a cam follower system, allowing ten-thousandth accuracy anywhere on screw of any length. The last system is the optical scale. A microscopic scale is created and mounted on the machine, and microscopes are placed to take measurements. This system is popular where thermal expansion may be an issue during machining. The scales expand and contract with the machine, removing some sources of error.

Locating the origin and centering the workpiece on the table were achieved by a method called "picking up the edge," which differs substantially from standard edge finding methods. Edge finders and other standard setup tools do not have the accuracy required to zero a part on a jig borer. I would try to explain it here, but imagining it is kind of hard and I can't find any good pictures describing the process. It is, unfortunately, a mostly lost technique. Ironic, since it allows very accurate setups on modern CNC milling equipment compared to the average modern practice. User: Toastydeath

Thanks for adding some good info here, Toastydeath. User:84.9.78.13, the point is not that "this article sucks", to paraphrase the spirit of your verdict. The point is that this article is well begun but needs expansion. So far the only topic that it covers well is the significance of the jig borer's development to the history of technology. Admittedly, the article does not yet discuss how a jig borer works (how it achieves its precision), and how that's different from a typical production-shop-floor (manual) milling machine. Also, the point is well taken that there are not yet any photos here. The Moltrecht and Jones books listed in the bibliography do in fact have some very wonderful photos, but they are of course copyrighted, so I am not going to scan them and slap them up here. Regarding again the topic of duly explaining the machine's development and its significance to the history of technology: that is currently done better in this article than in many other articles in Wikipedia. For example, the article on turret lathes is a perfectly acceptable stub at the moment, but it will not be a developmentally mature, great-quality encyclopedia article (no matter how many pretty photos it may eventually have) until it discusses the evolution of the turret lathe during the 19th century and the fact that the turret is, in abstract terms, a means of providing positioning control. Thus the turret itself fits into the same history-of-technology theme—machine tool control— as jigs, fixtures, PLC, and CNC. Someday we will fully develop that theme in Wikipedia. None of us will be achieving that overnight. In summary, the article needs expansion, especially of the "what it looks like and how it works" variety, but I sure hope that no one scraps the history-of-technology discussion with an attitude of "who cares about this junk?". It is important information. Lumbercutter 16:13, 21 February 2007 (UTC)