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DRILLING COST PER HOLE

Material and processing costs, as well as the resulting total drilling cost, may be determined by using an analysis matrix such as a cost model specifically designed for this purpose and generated with the use of a computer spreadsheet program.The advantage of using a spreadsheet is that it allows changes to be made in, for instance, specific material prices and processing times or parameters, and allows instantaneous viewing of the resulting effects on the total drilling costs, the cost per panel, and the average cost per hole. Knowing the cost per hole is important because it allows comparing different jobs or processing situations. Following is a step-by-step description of how to construct a drilling cost analysis

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1 Machine Time

Table A in the drilling cost analysis matrix is used to calculate the total time that is required to complete the job.

First, the different drill sizes(a)

and their respective total drilled holes per panel(b) as well as the total number of panels (c) to be drilled are determined and entered in the spreadsheet; this allows the spreadsheet to calculate the total number of holes for each size to complete the job (d).Second, using the appropriate drilled stack height (e), the total number of drilled stacks (g)

and the total number of drilled hits per drill size (f) can be calculated. The total number of drilled hits (drill strokes) is the total number of drilled holes per panel (b) divided by thenumber of panels per drilled stack (e).Third, the number of total drilled stacks (g) is divided by the number of stations per machine (stacks per load [h]) to calculate the number of machine loads (i).Fourth, the total drill time per load required per drill size (j) is entered to calculate the total machine time for each drill size (k). Fifth, the total times of each of the drill sizes are simply added up to arrive at the total time

required to finish the job.An option is to enter the total drill time per load instead of entering the time for each of

the drill sizes and multiplying the total drill time per load by the number of machine loads to determine total machine time.

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2 Drill Bits

The cost of the drill bits needed to complete the job may be determined after the average cost per drill bit use has been calculated.To find the average cost per drill bit use, the typical number of repoints for the particular size (o) is multiplied by the cost of each repointing (n).The resulting cost, added to the new drill bit price (m), is the cost per drill bit life (p). By dividing the cost per life by the number of uses (q) per life (the number of times the bit is repointed +1), you arrive at the average cost per drill bit use (r). Next, by dividing the total number of hits per drill size (s) by the number of maximum hits per drill bit use (t), the number of required drill bit uses (u) for each size may be determined.Then calculate the total cost per drill bit size (v) by multiplying the number of uses (u) by the average cost per use (r).The sum of the total costs of each of the drill bit sizes (v) brings you to the total cost of drill bits needed for the job.This cost, of course, is true only with the assumption of no drill bit breakage.

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3 Entry and Backup Materials

Entry and backup material cost per stack (y) is determined by multiplying the stack size(square foot per panel [x]) by the cost per square foot. Remember to divide the backup cost by 2 since each backup panel may be used twice.Total material cost (aa) is calculated by multiplying cost per stack (y) by total number of drilled stacks (z).

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.4 Burden and Labor

Using typical burden and labor rates per hour (ab), these values are multiplied by the number

of hours to complete the job (determined in Table A) in order to calculate the total burden

and labor costs (ac).

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5 Total Drilling Cost and Cost per Hole

After entering the required data in Tables A through D of Fig. 24.11, the total drilling cost and

the cost distribution (see Table E) as well as the drilling cost per panel and the cost per hole

(see Table F) can be calculated. Because the cost per hole typically ranges around 1⁄10 of a cent,

a more accurate and easier way to comprehend this value is by showing the average cost per

1000 holes, as is done in the cost model.

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