US Patent: 2,936,679
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| Method for Cutting Metal
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Patentee:
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| Walter C. Thuerwachter (exact or similar names) - Fond Du Lac, Fond Du Lac County, WI |
| Manufacturer: |
| Not known to have been produced |
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Patent Dates:
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| Applied: |
Jul. 02, 1956 |
| Granted: |
May 17, 1960 |
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Joel Havens
"Vintage Machinery" entry for Giddings & Lewis Manufacturing Co.
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Description: |
| This application is a continuation-in-part of my co-pending application files, filed 08 April, 1955, now abandoned.
Claim:
The present invention has as a general object the provision of an improved method of machining using carbide cutting tools having tool angles selected to promote more efficient cutting. This result is obtained in one aspect, by causing a new type of negative rake cutting to take place in metal. It has been standard practice, heretofore, to use cutting tools in both positive and negative rake positions. Furthermore, it is popularly believed and commonly explained, that the contrast between the cutting action produced in these different positions is essentially the difference between "shearing" off material, the action which it is conceived occurs in the positive rake position, as compared with "crushing" or "pushing" the material off, the action which it is generally conceded occurs with the tool in the negative rake position. Thus, in the negative rake position, a much thicker chip may be removed, although considerably greater power is required from the machine itself as well as ability of it to withstand greatly added loads. With carbide cutting materials, the generic name for the various sintered carbide materials which have been developed for cutting tools, it has been found particularly desirable to use negative rake angles. The reason ordinarily given for this is that the carbides while called "miracle" cutting materials for being second only to diamonds in hardness, and temperature and abrasive resistant, suffer somewhat in a comparison with previously known tool materials by reason of being brittle and having low tensile strength. By using a negative rake angle more material may be caused to lie behind the cutting edge, obtaining superior support for the cutting edge by way of a reinforcing of it and as a consequence, the result that the tool bit itself is more resistant to failure by cracking. The negative rake angles which have been recommended for carbide cutting tools heretofore, have been selected to provide this improved support or reinforcing of the cutting edge, but the angles are such that the cutting action of the tool bit may be described as aforesaid, as a "crushing" action, or as a "scraping" or "pushing" action. Such negative rake cutting is accompanied by increased tool loads and as a corollary to that, considerably greater power is required from the machine to produce the high surface speeds used in machining with carbide tools. |
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