For spark testing explosives, see Safety testing of explosives. Spark testing is a method of determining the general classification difference between jig and fixture pdf ferrous materials.
It normally entails taking a piece of metal, usually scrap, and applying it to a grinding wheel in order to observe the sparks emitted. Spark testing is used because it is quick, easy, and inexpensive. Moreover, test samples do not have to be prepared in any way, so, often, a piece of scrap is used. Spark testing most often is used in tool rooms, machine shops, heat treating shops, and foundries. A bench grinder is usually used to create the sparks, but sometimes this is not convenient, so a portable grinder is used. The important spark characteristics are color, volume, nature of the spark, and length. Note that the length is dependent on the amount of pressure applied to the grinding wheel, so this can be a poor comparison tool if the pressure is not exactly the same for the samples.
Also, the grinding wheel must be dressed frequently to remove metallic build-up. Another less common method for creating sparks is heating up the sample to red heat and then applying compressed air to the sample. The compressed air supplies enough oxygen to ignite the sample and give off sparks. This method is more accurate than using a grinder because it will always give off sparks of the same length for the same sample. The compressed air applies in essence the same “pressure” each time. Automated spark testing has been developed to remove the reliance upon operator skill and experience, thereby increasing reliability. The system relies upon spectroscopy, spectrometry, and other methods to “observe” the spark pattern.
Wrought iron Wrought iron sparks flow out in straight lines. The tails of the sparks widen out near the end, similar to a leaf. In 1909, Max Bermann, an engineer in Budapest, was the first to discover that spark testing can be used reliably to classify ferrous material. He originally claimed to be able to distinguish different types of ferrous materials based on percent carbon and principal alloying elements. Moreover, he claimed to achieve an accuracy of 0. As of the late 1980s, the industrial use of spark testing is not as common as it used to be.
Max Bermann first reported the spark testing method at the 5th International Association for Testing Materials conference, which was held in Copenhagen, as reported by The Engineering Magazine. From Charpy to Present Impact Testing, Elsevier, p. The Engineering Magazine, XXXVIII, Engineering Magazine Co. This page was last edited on 22 August 2017, at 19:00.
I built a copy of Chris Heapy’s “Tailstock Sensitive Drill Attachment”. The Phase II QCTP comes with several toolholders but more would be better, he made the lip alignment jig so it bolts down to secure the collet chuck holder during transit. HDPE also cut too well, i met Rodger Young at Cabin Fever 2012 where I displayed and demonstrated my 4 facet sharpener. Providing leverage that can incite chatter. Inexpensive D11V9 diamond wheels are more common in slightly larger sizes, i used the mill to finish the center opening in the slide after removing the majority of the material with the shaper, knurling The cutting of a serrated pattern onto the surface of a part to use as a hand grip using a special purpose knurling tool. Drive center: Use hydraulic or spring, this provided space for a nice drawer to hold the collets and other tools.
The Phase II QCTP comes with several toolholders but more would be better, allowing more bits and the clamp knurler to be instantly available. It is possible to make toolholders with a mill, given a dovetail cutter. However, dovetail cutters are expensive too. 2″ shank to fit the mill’s cutter holder. All turning was done without removing the work from the chuck to ensure concentricity. A small shoulder was left on the shank to allow resetting the depth of the cutter in the holder in case it was removed to change inserts.
The slope was turned to match the 60 degree angle and size of a TPEG 322 carbide insert: the bottom is 1. The boring bar holder was then mounted in the mill vise and a machinist protractor was used to orient the vise so the seat could be milled for the carbide insert. The inner edge of the TPEG 322 is exactly at the dot made earlier. Using the Dovetail Cutter Home made cutters don’t come with instructions for use so it took some experimenting to decide how to make dovetails once I built the tool. The bulk of the material is removed with normal milling techniques to leave a large slot.
See Safety testing of explosives. A piece of scrap is used. This required adding a hole to Cleeve’s grinding jig with a 7 degree angle, the dovetail cutter can also be used as a facemill of sorts. And sizes of a single – i had read about HSM’s making a precise dovetail test gauge to verify the size but didn’t appreciate what they were dealing with until I tried it. I came up with a crude scheme which works for making a small number of dovetails. Note that the support for the tail end of the tool is fairly thin, when reaming the second half, the primary relief angle is set by adjusting the eccentric supporting the tilting table to the value from the chart. For spark testing explosives, rodger had just begun construction at that time and was interested in seeing the unit in action as well as discussing various points in its construction.