Proceedings from the Boston meeting; Ashworth discusses drilling holes in glass, mentions Hemingray

LIST OF MEMBERS.

Honorary Members in Perpetuity,

DECEASED FOUNDERS OF THE SOCIETY,

HENRY ROSSITER WORTHINGTON,

ALEXANDER LYMAN HOLLEY.

Honorary Members.

·

·

Life Members.

·

·

Members.

·

·

Ashworth, Daniel .................... Mech, and Cons. Eng'r, Sheriff & Ashworth,

                                                                            80 Water St., Pittsburgh, Pa.

·

·

TOPICAL DISCUSSIONS AND INTERCHANGE OF

DATA.

XIIth Meeting.

·

·

No. 204. 15.

What is the best method for drilling holes in plate glass? Is there anything better for true holes than a copper tube and emery?

DISCUSSION,

Mr, Durfee — Many years ago I had occasion to drill a number of holes through glass. The holes were 3/16 of an inch in diameter and the plates were perhaps 1/8 of an inch thick. The method adopted was that of using an ordinary bow drill with spirits of turpentine as a lubricant. The hole was drilled from one side until the point of the drill just punctured the opposite side of the glass. Then the glass was turned over and the hole finished by drilling from the opposite side. I do not remember that I cracked a single glass in that work. That drilling operation is a very good one for a hole of moderate size.

Mr. Oberlin Smith. — I used to drill holes in plate glass years ago, and I always had pretty good success with a very hard drill lubricated with turpentine, as Mr. Durfee has mentioned; but I did not turn over and drill through the other side, because the drill would be apt to run sideways somewhat. I used to put a piece of perfectly flat cast iron under the glass, with a little piece of paper between, clamping all firmly together, of course seeing that the iron fitted the glass at that place. By letting the drill puncture the iron a little it went clear through and did not break the bottom side of the glass, except the corner which would crack off a little — perhaps a sixty-fourth to a thirty-second of an inch. It was not more than that, I think, and some of the holes I worked were as large as half an inch in diameter in plates perhaps 1/4 of an inch thick.

Mr. Ashworth — Those who are not familiar with glass can scarcely realize how stubbornly it refuses to yield itself to the hands of the operator. The Hemingray Glass Company with which I was connected did considerable of this drilling. The drills used by that company were built up of lead reduced to a conical form, having no cutting edges whatever, saturated with turpentine and emery. There was no drilling from the other side. This produced a countersunk hole, and it was drilled out afterward with a straight rod and emery. A system of doing it efficiently was desired, and that system was the sand blast steam jet. By that means 100 holes could be drilled for one by the old method not only accurately but rapidly; a clear straight hole and with perfect success, without breaking. The breakage is very small in plate glass. When we enter into colored glass the fractures are very numerous. The subject of glass, I think, is one which will probably occupy our time in the future to a great extent. As mechanical engineers, applying ourselves to the other branches and to work in metals, we are apt to form the idea that we can form, mould and drill glass with impunity; but such is not the case. Even the tubes which to the ordinary eye seem to have been bored and turned and polished have been only blown and drawn out, and though they result marvelously in their diameters so far as accuracy is attainable by that process, yet they are not accurate enough for the operations of a piston.

Mr. Durfee. — Mr. Campbell has just reminded me that in a certain place in Bridgeport glass is drilled in large quantities by means of a black diamond. The plates are perhaps 1/4 of an inch thick, and the drill is lubricated with oil and spirits of turpentine, and when the hole is nearly through the glass is reversed. The plate to be drilled is held in a mechanical holder so that it can be reversed perfectly.

Mr. Kent. — Some time ago I had occasion to want some plate glass drilled and in considerable quantity, and I thought the best place to go to have it done was at the plate-glass maker's. I wrote to one who said he could do anything of the kind, and I got a price from him which was almost prohibitory. I was in somewhat of a quandary, when somebody told me of the sand-blast process. I got a price from a party using it which was low enough to allow of the order being given. I believe the plates are now being drilled by the sand-blast process, but I have not seen them yet and do not know what they will be like. But I am obliged to Mr. Ashworth for what he has told us.

Mr. Towne. — Undoubtedly the sand blast is the best method of cutting glass that we know of where the work is to be done in large quantities and can be sent out to be done.

It happened that in the Yale & Towne works this question came up some time ago, and noting this inquiry on our list I wrote to the gentleman who had the work in charge, and obtained the following data in regard to it, which may be of interest to persons who want to do this work in small quantities and in their own establishments instead of sending it away to be done. The holes which we had to drill are 7/16 of an inch in diameter. The work has been done for more than ten years, and very satisfactorily and economically, The cost is a small fraction of what it was done for originally by some of the plate glass people. The best tool for the work has been found to be a brass tube 5/100 of an inch thick. The cutting agent is emery, number 5 H, and the lubricant simply water, which has been found as efficient as oil or turpentine and much less troublesome. The glass is 1/8 of an inch thick, and the workman is able to drill 30 to 40 holes per hour. The drill is run at 2,000 revolutions per minute, and the drilling of 40 holes through the 1/8-inch glass uses up about one inch of the tube. It is important to keep the emery well washed and cleaned, that is, with the dust removed from it which results from the abrasion of the glass. In our case, as the holes are required to be all in one position, the glass is put into a steel jig, and the drilling tube is run through a steel bushing. The hole produced is exceedingly smooth and true, and is carried straight through without the need of drilling back from the other side. It seems to me that the hollow tube drill must be a better method than the solid drill, because the amount of glass cut is only that covered by the area of the annular edge of the drill, instead of the whole surface of the hole.

Mr. Oberlin Smith — How much larger are the holes than the original diameter of the tube? I suppose some emery must get in alongside of the tube after it is partly through the glass, and there must be an appreciable difference? And are the holes tapering, being larger at the top where that loose emery runs along, than at the bottom?

Mr. Towne. — There is a slight difference between the diameter of the hole and that of the drill, The tapering effect I have not noticed, I doubt if it is apparent. The emery is kept packed around the drill during the process so as to cause as much as possible to work down through the hole.

Mr. Oberlin Smith — Is there any of the emery put inside through the tube?

Mr. Towne. — No; merely packed around it.

Mr. Stetson. — I suggest that the difference in size of the hole would necessitate a difference of method. In corroboration of one of the statements made, I would say that I watched the drilling of a part of a sewing machine with a diamond drill, and it was really comfortable to hear the little "zip" that finished the work. It was so satisfactory that it made the contractor who discovered the process quite comfortably off in this world. The suggestion came to him of a diamond instead of a copper rod and emery. I cannot see what could be better than this diamond drill in small holes.

·

·