convention lathe machine job - machining time calculation or its formaula

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For each feature on the part that you will generate by machining on the lathe you need to calculate the following:

(((length of tool infeed /feed per rev)*60)/Spindle speed in rpm's)+ time to index in seconds= machining time for that operation

I'm a multi spindle guy, and by length of tool infeed I mean what is called "length of Cam" or "throw"

Example 5/8" tool infeed;.0064inch per rev ; spindle speed 466rpm; Index time 2.43 seconds

((.625/.0064)*60)/466= 12.57 plus 2.43 seconds index time = 15 seconds to make that feature.

Now calculate this for each and every feature, add them up to make a total, and that will give you your machining time calculation. Keep it in seconds! multiply that by .75 for an efficency factor (You may be better efficiency, you'll likely be lower) and then take that result (in seconds ) and divide it into 3600 seconds (the number of seconds in an hour) to get the number of parts that you can expect to produce (in reality, not theoretically) in an hour.

Important technical footnote: Yes Gentle Reader, milo knows that 2.43 seconds is a long darn time to index a simple lathe, but it gets us to 15 seconds, a very tidy number for our example.

On a multiple spindle machine, you just need to do the calculation for the tool with the longest "cam throw," as that becomes the controller of the cycle time; all other operations are done simultaneously in less time while that long operation is in cut.

Don't forget to lock out the power when you change gears, and wear your safety glasses!

milo