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the feature industry this month is....
Glass Bottle Making
Last month's page discussed Float Glass factories, making sheet glass such as for automobile windshields. A completely different type of glass factory is the places where bottles and jars are made. Construction millwrights are familiar with both industries, as we are used to working on the machinery for either process.
Electric drills are probably the number one power tool that anyone cannot be without. This is true on a job site as well. Drill bit sharpening is one of the first things a millwright apprentice is taught on the job. Here are a few miscellaneous "rules of thumb" about drill bits.
Quiz Question:
You are going to drill six holes, 3/4" diameter, 3" deep, in a plate of mild steel which has already been center punched for you. Assuming you keep a constant feed rate of 0.01" per revolution and use the correct spindle speed on your drill press, and not including the time it takes you to stop and reposition the plate for each hole, how much actual drilling time will you require to complete the plate?
In Float Glass factories discussed last month (well, ok, it was more than a month ago. I'm a construction millwright; I've been working 7 days a week on the contract I'm on now, and I didn't have time to update my web site. Better luck next month!), the melted raw materials for glass were poured onto a bath of molten tin to float into a flat sheet. However, if the desired product is a shape, rather than a sheet, things go a little differently.
One ancient way to create a glass container was to "blow" it. This was done by blowing air into a ball of molten glass at the end of a hollow rod, thus creating basically a "bubble" of glass which cools and hardens in that shape. In a modern factory, instead of blowing the air by hand, compressed air is injected into a mold. It usually begins with the molten glass being pre-shaped into a preliminary mold for general shape, and then passing into a finishing mold to give it the final shape. Once shaped, the bottles will be passed through another machine to smooth the surface (eliminate the mold marks, for example), and most likely heat treated for additional strength. The conveyer line will then often take the bottles through a washer, rinser, and dryer, to make them ready for filling with food or drink. They then are gathered into cases or onto pallets to be shipped to the companies which make the food that they are to hold.
Here are a few links to sites related to glass bottle making:
The NZ Glass Company has a page with diagrams explaining more details of how they make their bottles, as well as articles on the history of bottle making in New Zealand (this manufacturer has been making bottles since 1921): http://www.glass.co.nz/NZglassbottles.htm
the BSN Glasspack company's site includes a general history of glass, and explains the advantages of the use of glass in food packing. There are also overview diagrams for the manufacturing process: http://www.bsnglasspack.com/html_gb/le_verre_gb.htm
This page has a collector's corner and descriptions of various types of antique glass: http://www.antiquebottles.com
The Old South Jersey Glass page has blown glass for sale, with historical notes on some of their unique products: http://www.oldsouthjerseyglass.com/
Here's the web site of the Glass Line newsletter for Hot Glass artists, where you can read a sample issue and learn about people who are carrying on the glass blowing craft: http://www.hotglass.com/
It's mild steel, so you can use the rule of thumb cutting speed of 80" per minute.
4 x 80
RPM = 0.75
= 427 RPM
penetration speed = feed rate x RPM
= 0.1 x 427
= 4.27 inches per minute
Total inches to be drilled = 3" x 6 holes
= 18"
Time to drill 18" = 18 / 4.27
= 4.2 minutes
See you on the next update of the Construction Millwright Feature Page!
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