US 3819343 A
A medium is disclosed useful in abrading or deburring metal parts by extruding the medium through openings which otherwise are quite often inaccessible. The medium comprises essentially guar gum, boric acid and borax, and one of the features of the invention is that the medium may be easily tailored to suit the size of the opening being abraded since optimum results are obtained using a less viscous medium in smaller openings and using a heavier viscosity of the medium when treating larger openings.
Description (OCR text may contain errors)
United States Patent [191 Rhoades MEDIUM FOR PROCESS OF HONING BY EXTRUDING  Inventor: Lawrence J. Rhoades, Pittsburgh,
 'Assignee: Extrude Hone Corporation, Irwin,
 Filed: Nov. 1, 1971  Appl. No.: 194,567
 US. Cl. ..l 51/302, 51/306  Int. Cl C08h 1712  Field of Search "106/383; 51/302, 308, 293, 51/298, 306
 References Cited UNITED STATES PATENTS I 3,l67,440 1/1965 McVicker 106/385 3,384,498
5/1968 Ahrabi 106/385 [111 3,819,343 [451 time 25, 1974 3,387,957 6/1968 Howard ..5l/298 3,521,412 7/1970 McCarthy ..5l/293 Primary Examiner-Donald J. Arnold Attorney, Agent, or FirmBaldwin, Egan, Walling &
F etzer  ABSTRACT openings and using a heavier viscosity of the medium when treating larger openings.
7 7 Claims, No Drawings An object of the present invention is to provide an improved medium for use in carrying out the method disclosed and claimed in U.S. Pat. No. 3,521,412, granted July 21, 1970 to Ralph W. McCarty for Method of Honing by Extruding. Advantages of the medium disclosed hereinwith respect to other gels or water base materials are that when honing or abrading repetitive jobs in large numbers of production parts, successive batches of the medium disclosed herein may be prepared with the same exact characteristics with respect to components and viscosity so that, using the same time control, the abrading action on each processed part may be exactly reproduced.
The improved medium of this invention is capable of abrading'through small holes having a dimension of a few thousandths'of an inch, as well as through larger holes, the cost ofthe medium is low and it is easy to clean the parts after they have been processed.
One ofthe ingredients of the medium of this invention is a dry pulverulent composition, hereinafter called precursor in the specification and claims, comprising manogalactan gum, alkali metal borate and boric acid as described and claimed in U.S. Pat. No. 3,384,498, granted May 21, 1968 to Robert B. Ahrabi. The specific composition utilized in the present invention has the following'essential components, percentages being by weight: Guar gum, 50 to 75 percent; boric acid, 30 to 40percent', and borax, 1.0 to 2.5 percent. Preferably also, the above composition includes 0.25 to 0.60 percent of a high molecular weight polysaccharide comprising the alkali deacetylated derivative of the acetylester form of a polymer comprising mannose, glucose and potassium glucuronate,.as indicated by the trade designation B-l459 in the above-mentioned Ahrabi patent. The purpose of the polysaccharide is to immediately establish a gel system so as to maintain a reasonably homogeneous suspension of the gumhydrophobing agent-neutralizing substance system so as to materially assist in dispersing the gum and maintaining such dispersion until such time as the gum becomes fully hydrated and polymerization or quasi-polymerization thereof continues to the degree desired.
, The above precursor composition is generally utilized in a dry powder form and mixed with various percentages of water, depending upon the size opening through which the medium must pass during the abrading operation, together with certain percentages of finely divided grit to produce the abrading action. Preferably, but not necessarily, a certain amount of oil is added to the composition to delay the formation of a crust upon themedium if it is not-to be used immediately. Suitable formulations by volume for different hole sizes are listed below.
There are a number of different oils which are satisfactory for use in the above set forth compositions. One is a dimethyl polysiloxane which is non-volatile, chemically inert and non-toxic and sold as silicone fluid by the General Electric Company under the trade designation SF-96 (500) and by Dow Corning Corporation under the trade designation No. 200. This silicone fluid has a viscosity at 25 C. of 500 centistokes, a flash point above 600 F., a pour point of -58 F. and a specific gravity at 25 C. of 0.973. Another suitable oil is a silicone-polyether copolymer having a viscosity between 1,200 and 1,500 centistokes and sold by General Electric Company under the trade designation SFl066. Two other suitable oils are straight-cut petroleum oils sold by Humble Oil and Refining Company under the trademark F lexon and under the trade designations 790 and 791'. These are rubber processing and extender oils. These oils have a specific gravity at 60 F. just under 0.920, a viscosity, SSU at 210 F. between 200 and 220, a flash point between 555 and 610 F., and a pour point between 10 and F. On a carbon type analysis, they have between nine and 1 l aromatic carbon atoms, between 32 and 28 naphthenic carbon atoms and'between 59 and 61 percent paraffinic carbon atoms. Another suitable oil is sold by Union Carbide Corporation under the trademark Flexol with the designation DOP which is a di-2-ethylhexylphthalate having a specific gravity of 0.9861, a flash point of 425 F. and a viscosity of 81.4 centipoises at 20 C. Other useful oils are petroleum based oils as used in the motor industry and automotive type greases.
The grit used in the above listed compositions may be boron carbide, silicon carbide, aluminum oxide, tin oxide, diamond dust, rouge, corrundum, garnet, alundum and glass. In general, any finely divided grit having the capability of abrading the metal upon which it is used is suitable for use in this invention. In any one of the formulas listed herein, the grit usually has a substantially uniform particle size in any given formulation. The particle size preferably runs from about six to 10 microns up to about 16 mesh size.
In the Examples 1 through6 given above, viscosities were run on special examples chosen from approximately the median range of water and oil in each case. The viscosity was tested without grit mixed in the medium so as not to damage the measuring device. The results on these special examples were as follows:
According to ASTM D4824 using Brookficld Model RVT. Examples 1 and 2 at 5 r.p.m. Example 3 at 0.5 r.p.m. '"Accnrding In ASTM D-2 I 7 using a penctromcter with u weight of g.
The .oil component in the above defined compositions not only delays the formation of an oxide crust on the medium but also controls the tackiness of the material. With little or no oil, the medium is tacky and adherent to metal as well as to the hands of the operator. The oil is, therefore, an important additive in tenns of actual practical use.
Sometimes the shelf life of the medium disclosed herein is limited due to attack by bacteria or fungus. The addition of a very small amount of a biocide such as methyl-or para hydroxy-benzoates is therefore helpful.
It is possible, under some circumstances, that very fine metallic parts collected in the medium during a deburring or abrading process may contribute to the breaking of the gel structure of the medium. In such cases, it may be desirable to add to the above formulations one-tenth part'of a common sequestering agent, such as sodium phosphate. However, the heat and pressure of the extruding operation contributes primarily to the breaking of the gel, so that it is not particularly necessary to add this sequestering agent.
In the use of this invention, the medium for abrading by extruding is prepared by mixing one part of the guar gum-alkali metal borate-boric acid pulverulent gel precursor with about two to fifty parts of water, stirring thoroughly and allowing the gel to form at room temperature before adding the grit. This usually takes about to minutes. Then from about one to about fifty parts of metal abrasive grit is thoroughly mixed into the gel and, if desired, from aout 0.5 to ten parts of oil as taught herein is thoroughly mixed with the previous mixture. If the gel is allowed to form after adding the water to the precursor, and then thereafter adding the grit, oil, etc., one provides a much stronger and longer lasting medium.
The medium is then passed back and forth through a workpiece as taught in McCarty U.S. Pat. No. 3,521,412, and thereafter the medium is flushed off of the workpiece with water, or a better job is done by adding about ten percent glycerine to the water cleaning bath. This greatly improves the cleaning process.
What is claimed is:
l. A medium for abrading by extruding consisting essentially of by volume one part of a guar gum-alkali metal borate-boric acid pulverulent gel precursor, from about two to about 50 parts water, from about one to about 50 parts metal abrasive grit, from about 0.5 to about 10.0 parts of oil to retard formation of a crust on said mixture and to increase lubricity of the material said oil selected from the group consisting of dimethyl polysiloxane, silicone-polyether copolymer of viscosity between 1200-1500 centistokes (25C) and specific gravity 1.04 (25C.), low-volatility naphthenic oil having nine to 11 aromatic carbon atoms and 32 to 28 naphthenic carbon atoms and 59 to 61 paraffinic carbon atoms, di-2-ethylhexylphthalate of specific gravity 0.9861 and automotive hydrocarbon oils.
2. A medium as defined in claim 1, wherein said grit is chosen from the group consisting of boron carbide, silicon carbide, aluminum oxide, tin oxide, diamond dust, rouge, corundum, garnet, alundum and glass.
3. A medium as defined in claim 1, wherein said grit has a substantially uniform particle size from about 6 to 10 microns to about 16 mesh size.
4. A medium as defined in claim 1, wherein said water is from about 20 to about 50 parts.
5. A medium as defined in claim 1, wherein there is added to the pulverulent gel precursor about 0.5 percent by weight of high molecular weight polysaccharide.
6. A medium as defined in claim 1, including less than one percent by volume of a biocide.
7. A medium as defined in claim 1, wherein said precursor and said water are mixed before said grit is added and mixed.