Copyright (C) 1986-2008 by Daniel H. Hudgins, All Rights Reserved.

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This Web site is dedicated to the thousands of "users" of my programs, those who have helped test my programs over the last 22 or so years, and especially those who shared their experiences with me.

You must read this notice: This is a licensed Web site (HTML document and associated files). You must read and agree to be legally bound in contract by the Terms of Use and conditions given in the End User License Agreement ("EULA"), Legal Notices, Instructions, Warnings, Disclaimers, and all other text in "SECTION: 0" of "This Web Site" (HTML document and associated files) before reading or using any of the information, software programs, and or files, contained in, linked to, and or associated with, "This Web Site" (HTML document and associated files). Any use or "Beta Testing" of "This Web Site" constitutes your acknowledgment of your full agreement with the current End User License Agreement ("EULA") and your decision to have this current license supersede all prior and contemporaneous agreements and understandings. Information and files in "This Web Site" (HTML document and associated files) have been placed here so that long time users of "The Author's" programs DANCAD3D.COM (tm) , DANCAM.EXE (tm) , or DANPLOT.EXE (tm) could help proofread the text of the documentation files or screens displayed, and also help test data files, example files, and or any software programs that might be made available from time to time, to aid "The Author" in finding mistakes, bugs, and other errors, omissions, defects, mistakes, and faults. Everything in "This Web Site" (HTML document and associated files) is "Beta Test", "Beta Code", Experimental, Preliminary, requires proofreading, or is being evaluated for possible revision, and is NOT warranted to be free of defect. To help "The Author" report any bugs, foul-ups, defects, or mistakes that you find, see "SECTION: 8" for instructions. "This Web Site" (HTML document and associated files) and all other files and programs by Daniel H. Hudgins are made available "AS IS" without warranty of any kind express, expressed, or implied. All offers and specifications are subject to change or discontinuation without notice of any kind. Please read "SECTION: 8" of "This Web Site" (HTML document and associated files) before trying to contact "The Author."

SECTION: 7.20 is for some "general" discussion about Metalworking, see also the program files in the current distribution of my programs, the other parts of this HTML documentation, and the current On-Line version of this Web site for information more specifically about my programs. Any comparisons of my programs or methods to some others is only given as a vague generality of my opinion and is not intended as a recommendation or reference to any particular products, or methods, always make your own evaluations and comparisons before taking any action.

The illustrations in the sections and sub-sections of SECTION: 7.20 are not intended to be examples of recommended or proper practice, and in some cases may illustrate methods that you yourself would not apply as shown. The variety of illustrations, showing both practical and discouraged practices, has been included to provide illumination of the general metalworking principles discussed in these sections, and other parts of the documentation, in order to help the reader understand some of the many issues relating to the practical matter of producing parts of usable quality by manual, semi-manual, semi-automated, or fully automated machine operation, and how CAD and CAM software, such as my programs that are described in this Web site, might be of assistance to that end.

A couple of the photos in subsections of SECTION: 7.20 where taken using a Sears (tm) Craftsman (tm) Atlas (tm) type lathe, the others were taken while using a ShopTask (tm) model 17-20 type 3-in-1 multi-purpose combination mill, drill, and lathe. When a manual machine tool is retrofit for computer control you need to consider how safety shields should be added, and where the emergency power cutoff switches should be placed.

Be sure to watch all of the video clips linked to in SECTION: 4, in order to see my CAM program DANCAM.EXE (tm) being used to automatically make a part under a form of Computer Numerical Control a.k.a. CNC, and to also see other narrated lessons on how to use my CAD program DANCAD3D.COM (tm) for related tasks.

When making parts, whether by manual or automated means it is frequently necessary to remove the part from the lathe chuck and turn it around to machine the part on the other side. Whenever you remove the part from the lathe chuck and put it back in it will probably never be exactly "true", rather it will be a little off center or wobble somewhat. You can generally reduce the degree the part is out of true by loosening the chuck and pushing on the part and tightening the chuck, but to know if you then have the part running true a dial gauge on an adjustable magnetic base can be a big help.

In theory a three jaw lathe chuck lets you remove the part and put it back in with the machined surface against the jaws and have the part run reasonably true. A new three jaw chuck will probably let you flip the part around and after pushing on it a little get the part within +/- 0.002 of running true.

If the three jaw chuck is old or dirty it may hold the work-piece off center more than you can tolerate. You may be able to put a piece of brass shim stock between one of the three jaws and the part to help have the work-piece run true.

When you use the dial gauge to check the part to see if it is running true you should check several points between the face of the chuck's jaws and the "free" end of the part since tightening the jaws can distort or crush the part somewhat. You should only rotate the spindle and chuck slowly by "hand" in one direction to read the centering on the dial gauge, never turn the spindle motor on while the dial gauge is in contact with the part. Unplug or otherwise disconnect the spindle motor while you are making measurements with the dial gauge.

Long pieces should be supported by a dead center or live center at the tail stock end. You can use the dial gauge to check if you drilled the dimple by use of the center drill on center by rotating the part while measuring with the dial gauge while the dead center or live center is in the dimple.

If you do not have a dial gauge you can make a very light trial cut in some portion of the part to be removed, and when the part is out of true the cutting will be intermittent. The portion being checked would need to have been machined true before the part was flipped around, since the "factory" surface of round bar may be quite uneven.

Although a three jaw chuck is a convenience since the three jaws draw together or apart with one adjustment, four jaw chucks let you adjust each jaw independently, so you can get the part as true as you like by adjusting each jaw.

Four jaw chucks also let you hold square or rectangular parts for facing cuts. You can make a cube or box in a lathe by using a four jaw chuck.

Because the jaws in a four jaw chuck can be adjusted independently, you need to check all of the jaws to see that they are applying equal pressure onto the work-piece. If you tighten one jaw you may need to loosen the opposite jaw a little to get the part to move in that direction. Because the part will dent or crush when you tighten the four jaw chuck's jaws you need to check several points along the part by rotating the part and reading on the dial gauge to see if the part is running true along its full length.

Putting a little oil on the part helps the dial gauge's probe tip slip along the part. If you do not want to mar the surface of the part you may be able to put some thin transparent adhesive tape around the part, in a single layer, so that the probe will run on the tape and not the part's surface.

I had to hold a part I was working on from the inside, but the jaws in the four jaw chuck were too large, so I held the smaller three jaw chuck in a larger four jaw chuck. This also allowed me to true up the three jaw chuck by adjusting the jaws of the four jaw chuck.