Close-tolerance elliptical cones are fabricated by cutting-tool guide assembly used with conventional tracer cartridge on turret lathe accurately produced in two machine operations

Allen, J. H., Sr.

Wobig, O. A.

English

NASA Technical Reports Server

June 1965	 Brief 65-10168 
NASA TECH BRIEF 
_& 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Lathe Attachment Used to Machine Elliptical Cones 
Tracer Guide Bar 
Tracer Follower (To Tracer 
Cartridgeand Cutting Tool 
Pin and
Pivot Point 
Slider Bar
Reference rence Line 
Cutting Tool 
Elliptical Cone 
To Lathe Chu 
Elliptical Plate /	 I_i	 I--- X2 
The problem: To eliminate expensive and time-con-
suming hand operations in fabricating close-tolerance 
elliptical cones required in limited quantities for ex-
perimental purposes. Two methods are commonly 
used for such fabrication. The first method requires a 
handmade pattern that is then used to provide a cast-
ing which must be tediously ground and machined to 
the desired dimensions. The second method requires 
several machine operations and handwork to produce 
the elliptical cone from bar stock.
The solution: A simple cutting-tool guide assembly 
used in conjunction with a conventional tracer cart-
ridge on a turret lathe. With this arrangement, only 
two machine operations are required to produce the 
finished cone. An oversized right circular cone is first 
cut from bar stock in the normal manner on the lathe, 
and then the guide assembly is used with the tracer 
cartridge to machine the cone to the desired elliptical 
shape.
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000166 2020-03-11T17:23:25+00:00Z
How it's done: The guide assembly consists of an 
elliptical plate, which is an accurate scale (2 to 1, 1 to 
1, etc.) of the base of the cone, a sliding bar, and a 
pivoted tracer guide bar. These members are all 
mounted on a standard turret lathe. The lathe cutting 
tool is positioned by a tracer cartridge (not shown), 
which is controlled by the guide assembly. The cross-
sectional contour of the finished cone is determined 
by the curvature of the elliptical plate which is used as 
a pattern. The elliptical plate is mounted in the lathe 
chuck behind the oversized right circular cone (which 
has been previously cut on the lathe). A roller 
mounted on the end of the slider bar engages the edge 
of the elliptical plate, so that as the plate rotates (with 
the cone), the slider bar moves in and out following 
the elliptical contour of the plate. Since the pin on the 
slider bar engages the slot in the tracer guide bar, the 
latter oscillates about its pivot' in conformance with 
the movement of the slider bar. The motion of the 
tracer follower, which rides against a guiding surface 
of the tracer guide bar, is sensed by the tracer cart-
ridge. The linear distance (Xi) of the follower from 
the pivot point of the guide bar is proportional to the 
distance (X2) of the cutting-tool edge from the vertex 
of the cone. The angular position (01) of the tracer 
guide bar from a fixed reference is equal to the semi-
vertex angle (02) of the cone at each position of con-
tact with the cutting tool. Thus, the distance (Y1) of
the tracer follower from the fixed reference is propor-
tional to the distance (Y2) of the cutting-tool edge 
from the center line of the cone. 
Notes: 
1. With this device, elliptical cones can be made in 
two machine operations to an accuracy of ±0.0005 
inch. 
2. Guide assemblies based on the principle described 
can be used to make accurate, inexpensive dies for 
mass-producing metallic or plastic-molded parts. 
3. Inquiries concerning this invention may 'be di-
rected to: 
Technology Utilization Officer 
Manned Spacecraft Center 
P.O. Box 1537 
Houston, Texas, 77001 
Reference: B65-10168 
Patent status: NASA encourages the immediate. 
commercial use of this invention. It is owned by 
NASA and inquiries about obtaining royalty-free 
rights for its commercial use may be made to NASA, 
Code AGP, Washington, D.C., 20546. 
Source: Orrin A. Wobig and John H. Allen, Sr. 
(MSC-l00) 
Brief 65-10168	 Category No. 05


Lathe attachment used to machine elliptical cones

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