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 make cylindrical, conical, or flat surfaces. In a lathe, flat surfaces are made by moving the cutting tool across the work-piece toward, or away from, the spindle axis line by using the lathe's cross slide, this operation is called facing. Cylindrical shapes are made by moving the tool along the length of the lathe, which is called turning.

Conical shapes are made by a compound motion of facing and turning. In a manual lathe a compound rest on its cross slide with an extra travel that can be rotated is used to move the tool along a line at an angle to the spindle axis. In an automated machine lathe operated by my CAM program DANCAM.EXE (tm) the compound motion along a diagonal path can be produced without having to have a compound rest on the cross slide holding the tool, the CAM software just moves the tool along the length of the lathe bed while also moving the tool in and out, by sending signals to the stepper or servo motor control circuits for both axis at the same time.

This photo shows a carbide lathe tool set an an angle to do both turning and facing of the disk in the lathe chucks jaws. In other instances you might want to set the tool to a different or special angle to get a better finish, e.g. for the facing cuts, then change the angle for the turning cuts.

Tool bits can be made of High Speed steel, Cobalt steel, or Carbide tipped steel. High Speed steel can get dull after several cuts and needs to be re-sharpening on a grinding wheel. Cobalt Steel does not get dull as quickly as High Speed steel but is harder to sharpen on the grinding wheel. Carbide stays sharp quite a long time, but sometimes chips at the edges and those chips near the edge are difficult to remedy by sharpening.

You can see the Carbide tip that has been attached to a softer steel body. Carbide is expensive, so the tool makers just put a small piece on the end of a bar of cheep metal that acts as a holder. Carbide comes in different varieties that are supposed to relate to the kind of metal that will be machined, if you use the wrong type you may get more chipping or the Carbide may fracture since it is more like a brittle ceramic than a flexible metal.

I mostly use Carbide tipped tools, except in the lathe boring bar, and the vertical mill's fly cutter. Or in instances where the tool needs to be ground to special angles that the stock Carbide tipped cutters do not come in.

Before you start facing cuts you should bring the cutter up to the work-piece with the spindle off, and check that only the tip of the cutter is touching the material. You also need to check that the tool is the right height. After the first facing roughing cut that goes all the way to the center of the work-piece you can see if the tool is high or low. If the tool is high you may be using a tool bit that is larger than your machine is designed for, which might be the case if you are using a 3/8 or 1/2 inch shank tool in a lathe designed for metric 8mm or 1cm shank tools. If the tool is too low you can put some thin brass strips under the tool to bring the tip up to about 0.0005 inch above the lathe spindle axis center line, and in that way not end up with a "pimple" at the center of the piece you are facing. I keep a set of brass strips for shimming the lathe tool up with, since it is better to use small tools brought up to the center line, than to try to grind large tools down to the center line. Some lathes have a rocking tool holder that lets you tilt the tool up and down to adjust the height of the tip, but that only works for small angle changes since you would also be changing the clearance angles of the tool bit relative to the work-piece, and so you would probably still need to use shims for the gross tool height adjustments.

If you look at the lower right of the exposed portion of the tool you can see the edge of the brass strips that adjust the tool height.

Before you begin turning it is a good idea to check the distance the tip of the tool is from the top of the lathe chuck jaws, since if the carriage moves the tool too far along the lathe bed you will run into the chuck's jaws and dull the tool, damage the chuck, and possibly do more serious damage. After the facing cuts you can turn off the spindle and move the tip of the tool down to the chuck's jaw's face to find out what the maximum turning distance travel, from the faced end, can be, then subtract a safety distance from that value. Not all the chuck jaws may be the same height in their beveled parts, so check all the jaws for interference with the tool to avoid unpleasant surprises, it is not a good thing for the tool to grab the chuck, jab into the work-piece, and stall the spindle motor. Also if the tool hits the chuck's jaws the work- piece may pop out of the chuck and go flying.

If you need to make a large rectangular plate flat you might not think of doing it in a lathe, you might try to use a fly cutter in a vertical milling machine. But, if you have a four jaw chuck that is large enough, facing rectangular pieces in the lathe may give you a better surface flatness than trying to make many cuts using an end mill or fly cutter in a vertical milling machine.

It this situation the cross slide on the mutli-purpose machine did not move far enough to mill the whole plate in one setup, but it did move just about one half the diagonal of the plate. In a lathe since the part is twirling around the tool cuts twice the distance that it moves, so if you are making a plate with a twelve inch diagonal measure the tool only needs to move a little over six inches.

Because the corner of the plate was so far out, the tool was mounted on the back of the tool post rather than the front in order to have enough reach. You can only see the back end of the tool bit in the photo.

When turning long thin pieces in a lathe you need to support the end with a live center or a dead center. A live center rotates with the part by being driven through friction from the motion of the chuck. A dead center does not rotate, it is just a pointed piece of hard metal, so there is friction between the stationary dead center and the rotating work-piece. Live centers have a small amount of play in their bearings, so a dead center may give more accurate parts, but any difference would probably not be very noticeable.

To adjust the pressure against the part the crank or hand wheel on the end of the tail stock is used to move the live center or dead center against or away from the work-piece. If too much pressure is applied the work-piece may "bow" and its center portion might come out too thick of thin. If too little pressure is applied the work-piece might rattle on the tip of the live center or dead center, and the tailstock end of the part might come out undersize or oversize.

In the photo the live center has a Morse taper #2 and the tail stock has a Morse taper #3 so a Morse taper #3 to #2 adapter was used. That extended to center too far out for ideal conditions since the extra length amplifies the deflection of the center on the tail stock when the tool is pressed against the work-piece.