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 tap a hole made in a work-piece in a lathe. Holding on to round parts for tapping can be difficult without using a three or four jaw chuck, so it may be easier to just tap the hole while the part is still in the chuck after drilling. Since it may be hazardous to be putting the tap into the work-piece while it still is in the lathe's chuck you should unplug and otherwise disconnect and lock the spindle motor so that the spindle cannot rotate while you are tapping.

Larger threaded holes can be produced by using a boring bar in the lathe. Larger threaded holes can be made by using a helical tool path in a CAM machine such as a CNC vertical milling machine. But for small holes taps seem to be the most practical way of making threads.

Be sure you unplug the spindle motor in your lathe before using a hand tap on a part in the lathe chuck.

Small holes can be tapped using the type of tap wrench shown. Here a small tap is being used to make a tapped hole that will be used to mount a another part over this part. The tap should be removed frequently and the chips removed to avoid having the tap seize and snap off in the work-piece. Putting oil on the tap can help withdraw the chips, but should not substitute for removing the tap and brushing the tap off every few rotations. When tapping the tap is rotated a little into the work-piece, then back a full turn, then forward a little more, then back a full turn, although the tap may seem to screw into the hole just fine without going back and forth, it may seize and snap off when you try to back it out if you do not work the tap into the work-piece carefully. If you are going all the way through the back end of the work-piece, be careful when the tap is coming through the other side since it may catch and snap off just when you are almost done.

To remove the chips from the work-piece after tapping I have found that forcing liquid dish soap through the holes picks up the chips and caries them out. In a blind hole, e.g. a hole that does not go all the way through, you can put the liquid soap in a syringe and force the soap into the bottom of the hole so that the chips are carried upward and out of the tapped hole.

Regular taps are tapered on their tip and only make useful threads on the outer part of the hole, so you need to drill about twice as deep as the length of the screw you will be using. When you cannot drill deep into the part for blind holes, you can start the tapping with a regular tap and finish with perhaps a plug tap and then a bottoming tap. The bottoming tap is not tapered and cuts useful threads closer to the bottom of the hole, but it cannot be used to start the tapping operation, and so more than one type of tap of each size is needed. If your local hardware store does not have bottoming taps you can probably get some through mail order or on the internet.

Be sure you unplug the spindle motor in your lathe before using a hand tap on a part in the lathe chuck.

When you are drilling the hole to be tapped it is a good idea after the hole is drilled to use a larger drill or counter sink to make a beveled edge on the top of the hole that is larger than the diameter of the tap, since when tapping a bur is raised that might interfere with the flatness of the fit of the parts when they are later attached.

Large taps require quite a bit of force in order to cut into the work-piece, even when working with "soft" materials like aluminum. Here a long tap wrench is being used to tap a 3/8-16 thread into the end of a aluminum post. As with the small taps you need to turn a little into the work-piece, then rotate the tap backward, then forward a little more, then backward, then every so often back the tap out and brush off the chips, oil the tap and then continue.

Tapping holes takes quite a bit of time, and is risky because if the tap breaks off in the part you may lose a week or more of work on the part. Tap extractors are made to back the broken part of the tap out, but extractors do not seem to come in sizes for 2-56 and smaller which is a problem since the small taps are usually the ones that break off the most often. Broken taps can be vaporized, i.e. removed through destruction, by Electronic Discharge Machining a.k.a. EDM but unless you have your own EDM setup you might have to pay several times the cost of the tap to have a broken tap burned out of your part. Some alternatives to tapping are pressing threaded inserts into parts, riveting, welding, glue, and using taper pins. Taper pins might be driven in at opposing angles like "toe nailing".