Why should a reamer never be rotated backwards during removal from a hole?
It damages the cutting edges and accuracy
A reamer is a finishing tool that cuts on the leading edges of its flutes as it rotates forward, lightly shaving a drilled hole to an accurate size and a fine finish.
Each flute has cutting relief provided only behind its forward-cutting edge, so the teeth are keen in the forward direction only.
When the reamer is turned backward to remove it, the chips lodged in the flutes and the unrelieved backs of the teeth are dragged against the freshly cut hole wall.
This rubbing chips and dulls the delicate cutting edges and scores the finished surface, destroying the very accuracy and finish the reamer was used to create.
Reversing does not aid chip removal, lower temperature or improve finish; on the contrary it traps chips and damages the tool, so those options are false.
For this reason a reamer must always be withdrawn while still rotating in the forward, cutting direction.
Hence, the answer is It damages the cutting edges and accuracy.
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Important Questions from Drilling and Reaming
What is the point angle of the drill used to drill copper?
The clearance angle of a drill is between ______.
What is range of drills provided on a Morse taper?
Which of the following formulas is used to calculate rpm where cutting speed and diameter are known?
The Morse standard taper is available in _______ numbers.
