Thursday, April 29, 2010

Types of Bor Gauges

Let's look more into the various types of Bor Gauges. As I mentioned before there are basically Bor Gauges measured for external dimensions and internal dimensions. Bor Gauges is Gauges with a Bor scale to enhance the ability of a Gauges to measure precise dimensions. In today's market Bor Gauges with digital read out are commonly available. Based on this let's list out the various types of Bor Gauges.
  • Digimatic Bor Gauges
  • Zero Checker Bor Gauges
  • Bor Gauges for Blind Holes
  • Bor Gauges for Small Holes
  • Bor Gauges for Short Leg
  • Dial Bor Gauges for Rugged

Tuesday, April 27, 2010

Picture of Bor Gauges

Bor Gauges comes in different shapes and sizes from different manufacturers. Here is a picture of a simple Bor Gauges with fine adjustment which is most widely used in metal working industry.

Picture of Bor Gauges

Accuracy of bor gauges

Accuracy in bor gauges is determined solely on the basis of the indicator's performance. For gauge sizes 0 and 1, the accuracy is ±1/2 graduation over the entire range. For gauge sizes 2 through 6, the accuracy is ±1/5 graduation. In all cases, repeatability is 1/5 graduation.

Monday, April 19, 2010

How to Use a Dial Bore Gauge

Dial-bore gauges (DB) or dial indicators, when used in conjunction with a micrometer, can give very accurate and precise inside measurements. Used for holes of at least two inches in diameter, they consist of a base that houses an interchangeable anvil that sets the range of the measurement and a small sliding stud that when compressed will give a reading on the gauge or dial portion of the tool. The dial will have a rotating bezel that is rotated to "zero' the gauge at the target measurement, which is set by a separate micrometer. Dial bore gauges are useful in checking for taper or out-of-round conditions in a cylinder bore as well as many other inside machinists measurements.

1. Determine the rough opening with a machinist's rule. Lay the rule across the top of the bore and dress the zero end of the rule to one edge of the hole. Orient the rule so that the point measured is 180 degrees away from the zero end. Slide the clip down the rule to mark the edge of the hole and record the measurement.

Select and install the appropriate anvil. The anvil should be long enough to contact the side of the bore and slightly compress the stud when inserted into the hole. Do not use an oversized anvil and try to force the indicator, as this will likely destroy the accuracy of the tool.

Select a micrometer in the appropriate range. Most cylinder bores will be in the two-to-three-inch or three-to-four-inch range. Set the micrometer for the target measurement or for an arbitrary measurement. The arbitrary measurement should be close to the target measurement and be an even number that will be easy to do quick math on to arrive at the actual measurement. Record this number on paper with room to do simple addition problems.

Insert the anvil and stud between the micrometers machined surfaces. Rotate the bezel until the "zero" is in line with the needle position. The DB indicator is now ready to read a measurement relative to the setting.
Using the Dial Indicator

Insert the base of the indicator into the hole. Ensure that the two contact points are 180 degrees from each other and that neither the anvil nor the stud are hanging on scoring or the cross-hatch pattern of the bore wall.

Hold the indicator as near to vertical as possible and gently and slightly rock the DB indicator along the anvil/stud axis. The needle will swing clockwise as the tool comes to vertical and the anvil/stud come to their proper position. Read the number on the dial at the point where the needle stops rotating clockwise and attempts to start backing down in a counter-clockwise direction. This is the "relative" measurement. The number may be a positive or a negative . Record this number and remove the DB indicator from the hole.

Add or subtract the positive or negative number, respectively, from your target or arbitrary number. This final adjusted number is the actual measurement of the hole.

Thursday, April 15, 2010

Bore Gauge Maintenance

Standard maintenance of the gauge should be performed every 3 months or 1,000 bore measurements. Please do not attempt to disassemble your bore gauge.

The Following routine maintenance is suggested every 3 months :
  • Check the extent of flats on shoe contacts

  • Clean, polish or turn the balls, whichever is applicable, or replace

  • Examine abnormal angular play between shoe and bottom section, replace the shoe

  • Examine bell crank for wear or damage on edge of ground face and replace if necessary

  • Examine the top plunger for wear and/or damage

  • Clean and oil all parts carefully

Bore Gauge Work

All models work on the proven principle of two diametrically opposed measuring points, one fixed and one moving, plus a spring-loaded centralizing shoe. Don’t waste your time and money on other inferior brands that do not use this proven method.

Dial Bore Gauges

A Bore Gauge is a term that is used to describe measuring or transfer tools that are used to accurately measure holes.
Telescopic Gauges: These are a set of gauges which are employed to measure a bore’s size. This is accomplished by transferring the internal dimension to a stand –alone measuring tool. Since this type of Gauge is similar to inside calipers and require the user to develop the proper feel in order to get accurate results. These types of gauges are locked by turning the knurled end of the handles in order to exert a small amount of friction on the telescopic portions of the gauge.
Once locked, the gauge is inserted in to the bore at an angle, and then slowly brought to align across the hole. After the bore gauge has been withdrawn from the hold, the anvils remain locked to the bore’s dimension and allow the operator to read the measurement of the bore. We will discuss more about Bore Gauges in the coming posts.