Limits Fits and Tolerances Questions and Answers

Answer: D

The BIS system has 18 grades of tolerance.

Indian workshop and metrology textbooks give the BIS system of limits and fits (IS 919) 18 fundamental tolerance grades: IT01, IT0 and IT1 to IT16. The fine grades IT01 to IT4 are used for gauges, IT5 to IT11 for fits between machined parts, and the coarser grades for rough work.

16 counts only IT1 to IT16, leaving out IT01 and IT0, and 17 leaves out one of those two. The current ISO 286 lists 20 grades, adding IT17 and IT18 for very coarse work; the key follows the textbook count of 18.

Answer: B

A plug gauge with its Go and No Go sizes on the same end is a progressive plug gauge.

On a progressive gauge the Go diameter comes first and the No Go diameter is a short step behind it on the same end. A single push checks the hole: the Go part enters and the gauge stops at the No Go step. That is quicker than turning the gauge round, so it suits through holes in production inspection.

A double ended plug gauge has the Go member at one end of the handle and the No Go member at the other, so it is the opposite arrangement. 'Single ended' describes a gauge with one gauging end, which on its own does not say it carries both sizes, and 'continuous' is not a standard gauge type.

Answer: A

A taper ring gauge checks an external taper.

A ring gauge is a hollow gauge that fits over the work, so it is used on outside surfaces. A taper ring gauge has a tapered bore; the tapered shank is pushed in, and the fit, often checked with a light coat of Prussian blue, shows whether the angle and size of the taper are right.

An internal taper is checked with a taper plug gauge, which goes into the hole. Threads are checked with thread ring and thread plug gauges, which have threaded forms rather than a plain taper.

Answer: C

The Go side of a plug gauge equals the minimum size of the job, the smallest acceptable hole.

The Go member must enter every acceptable hole, including the smallest one, so it is made to the lower limit of the hole. The No Go member is made to the upper limit, so it enters only an oversize hole. A hole is good if Go enters and No Go does not.

A Go plug at the maximum size would reject every hole but the very largest. The actual size of a particular job is what the gauge tests, not a size the gauge is made to, so 'actual size' and 'all of the above' are wrong.

Answer: B

The keyed answer is on the same side.

A fixed snap gauge is built for one size. The progressive type has the Go gap and the No Go gap in one frame, one behind the other on the same side, so the part passes through the Go gap and stops at the No Go gap in a single movement. The Go and No Go ends in the other type are placed on opposite ends of a double-ended gauge.

Both sides and either side describe no standard arrangement.

Doubt: a double-ended fixed gauge has the ends on opposite sides, so option A is also defensible for that type. The official key gave B, and it is kept.