Precision Small Hole Gauges

As any machinist knows, when you drill precision holes, you should always measure at least the first one or two to determine if the tool you are using is cutting the correct size.  Normal measuring tools, say a dial or digital caliper, may work just fine when the hole is over 1/2 inch, but what do you do when the hole is smaller?


Today's tool is one that my father used in his machine shop when I was a teenager. In fact, the tool pictured here is the actual one that he used years ago:  a set of expanding small hole gages made by Mitutoyo.  Each gage has a fixed hole size range that it can expand into and provide accurate measurements.  The small hole gage does not directly show the measurement; a micrometer or other measuring tool must be used in conjunction with the small hole gage to get an actual measurement.


In operation, the user selects the correct gage for the hole size that is being measured.  The upper knurled part of the handle is grasped with one hand and the expanding split spherical end is placed into the hole.  With the other hand, the knurled knob on the end of the tool is turned clockwise or counterclockwise to expand or contract the spherical end until it contacts the hole sides.  When the tool is extracted from the hole, a measuring caliper or micrometer is placed over the spherical end and the measurement of the hole is determined from the caliper or micrometer.  


There are several U.S. patents describing this measuring tool, number 1,806,893 issued to H.G. Cunningham of Los Angeles and number 4,136,456 issued to Mineo Yamauchi and Masao Nakahara of Kawasaki, Japan (this patent was assigned to Mitutoyo).  


Surprisingly, this very precise tool set is still available under the same part number from a number of sources.  One of those is from Grainger for around $100.  Other stores on the internet also sell this set for slightly more or less.  If you drill small holes and need to precisely measure them, get a set of these gages to make your job easier.

Offset Duct Crimper

Klenk's Offset Duct Crimper

Sheet metal heat ducting is one of those parts of any home that is not often seen or appreciated, especially since it is buried in the attic or below the floor.  The heating and ventilation contractor that installed the ducting had to use some special tools to make all the piping fit together and the subject of this article is one of those tools.

Normal machine crimped duct end

In some places where the ducting has to fit together, the last two ends are the same diameter and will not push together.   Normally, there is a crimped end that reduces the diameter and the mating pipe has a smooth, un-formed end.  The crimped end of the first pipe is then pushed inside of the smooth end of the second pipe.  I also ran into this problem in several places when installing dust collector piping in my wood shop.  I purchased lots of fittings, connectors and different size pipes.  When I started to put the pieces together, more than a few places ended up with an un-crimped end of one pipe needing to be installed into another pipe or fitting with another un-crimped end of the same diameter.  

Five crimping fingers on tool make two creases at once

As anyone that has tried to install ducting knows, it is virtually impossible to push two ducts of the same size into each other.  Usually, one end is machine crimped to make it smaller so it will fit inside of another duct of the same size. 
The tool I used is made by Klenk Tools of Canton, OH, model number MA71260.  The working end of the crimper has three steel fingers on one half of the jaw and two fingers on the other half.  When squeezed together with the handles, the fingers pass each other. 

Crimping a piece of snap lock ducting with offset crimper

When a piece of sheet metal ducting is placed between the fingers, the sheet metal is creased in two places as the fingers pass each other.  To make a complete crimped end of the duct, the tool is squeezed repeatedly around the perimeter of the pipe until it is all crimped.  The handle is offset from from the same line as the jaws to provide more clearance for the user's hands when using in tight places. 
  
It appears this tool has been around for almost a century in various forms.  In fact, U.S. patent number 1,284,993 describes this tool very closely and was issued in 1918 to Frank Bellman of Los Angeles.  So, if you need to install some ducting and want to make the job easier this tool can be purchased online from Klenk Tools for less than $30. 

Internal Pipe Wrench

If you have ever done any plumbing in your home, and had to tighten a close coupled pipe nipple, you probably wondered how to grip it with a standard pipe wrench without damaging the threads.  So, you screw it into the mating fittings by hand and tighten them, assuming that the nipple will seal when you are finished.  Maybe it will, maybe it won't.  There is an easier way, but usually only the professional plumber has the correct tool to do the job.  


Today's tool was created to tighten or loosen a pipe nipple that has no external smooth surfaces except for pipe threads.  Of course, if you grip on the pipe threads with a standard pipe wrench or vise grips, the threads will be damaged and the nipple will become unusable.  So, an internal pipe wrench was designed to grip the inside of the pipe.  Turning the tool is accomplished by using a standard six point socket wrench or even a standard open end wrench.  As the tool is turned with the wrench, there are a number of small spline teeth on an eccentric ring designed to dig into the pipe interior as the tool is turned, either to tighten or loosen the pipe.  

The task of loosening and tightening small pipe nipples must have been a problem for many years, since there are a number of patents for internal pipe wrenches.  This particular wrench, made by Brasscraft and available at home centers or hardware stores, is most closely described by patent number 2455005, issued to Lee R. Hall of Tonasket, WA in 1948.   There have been several other designs patented since that time, but since this design is still in use over a half century later, it has definitely stood the test of time.


So, if you have a plumbing task in the future that involves short pipe nipples, save yourself some time and get a set of these internal pipe wrenches at your favorite tool store for $10-$12.


  

Telescoping Wire Retriever

The cool tool of the day is one I found at the local Lowe's home center- a telescoping wire retriever.  This retriever is found in the electrical tools area of the store and looks like it would be great to use to hook onto wires in a wall and inside of cabinets where a person can't see the wire and the power is of course turned off.  In use, the retriever can be stored in the user's pocket with a handy clip.  Extending the telescoping sections makes the tool 3 feet long.  It almost looks like a public speaker's pointer that was accidentally damaged on the end when someone sat on it.  That is probably not the case, but U.S. patent number 6,499,778, issued December 31, 2002 indicates that this retriever is unique.  The particular tool I saw at the local store is manufactured by Greenlee, an electrical tool manufacturer.  If you need to make an electrical job easier, you can find the telescoping wire retriever at various local and online retailers for $15-$20.