The Vertical Mill Head - 2: Quill Feeding

If the quill feed process requires a close tolerance for depth then be aware that the auto feed mechanism is not ideal for this because the feed mechanism uses contact pressure to disengage the clutch and halt feeding. Therefore repeatability can not be held to much less than .010. For this reason, the machinist often uses the quill handle to pull down and hold the depth after the feed has been disengaged. This "cleans up" the last bit of depth cut and .002 depth tolerance can be held. R.S.


		The Vertical Mill Head - 2: Quill Feeding
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				WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.

	The quill feed selector controls the quill's feed rate in inches per revolution (IPM). The typical settings available on many machines are .001, .003, and .005 inches per revolution. It is sometimes necessary to relate the inches per revolution to inches per minute. The manual milling machine, like the engine lathe, does not list feeds in inches per minute. The formula necessary to convert inches per revolution (IPR) to inches per minute (IPM) is: IPM = IPR x RPM where RPM is the rotation per minute of you cutting tool. For example, if you are rotating your tool at 1000 RPM and you select the .003 IPR setting, you will get: IPM = 1000 x .003 = 3. So your tool will advance at a rate of 3 inches every minute. The quill feed mechanism is driven by the spindle so the speed of the quill feed varies with the speed of the spindle. However the rate of feed is fixed. Note that there is a quill feed engage - disengage lever on the machine also. It should not be engaged if you are not using the quill feed. To change feed settings locate the quill feed selector, pull the detent knob out and rotate to one of the three settings. Release the pin and it will stay in the selected position. Next, locate the quill feed transmission engagement crank and engage the transmission. You may have to turn the spindle a few degrees by hand until the lever finds the right location. Now set a stop depth. The stop depth serves two purposes. First it serves as the physical limiter for machining (it controls the depth of the hole or slot in the part you are going to machine). Second, the quill feed clutch is disengaged when it reaches this depth, thus halting the feed process To begin the feed process turn on the milling machine and note the rotation of the feed selector knob. If the knob is rotating clockwise the quill feed will be downward. If rotating counterclockwise the quill feed will be upward. If not rotating the selector is in neutral. Select the correct rotation of the feed knob and then engage the feed control lever. Quill feeding has begun. Notice that when the quill stop reaches the micrometer nut the feed lever is "kicked out" and feed stops.

If the quill feed process requires a close tolerance for depth then be aware that the auto feed mechanism is not ideal for this because the feed mechanism uses contact pressure to disengage the clutch and halt feeding. Therefore repeatability can not be held to much less than .010. For this reason, the machinist often uses the quill handle to pull down and hold the depth after the feed has been disengaged. This "cleans up" the last bit of depth cut and .002 depth tolerance can be held. R.S.

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