Costing Example
Lets compare Twist Drill Bits and Insert Drill bits in the real life
fabrication situation. We will just look at one example 13/16
(the most commonly drilled hole diameter)
Lets first look at the cost of using twist drill bits that
need to be resharpened
A. Twist Drill bits
-
13/16 (18mm) Twist drill bit is
typically $165.00
-
Need to have a minimum of two
drill bits of each size so we can change out and re-sharpen one
drill bit while the other one is drilling
-
Operator gets 300-500 holes per
sharpening lets use 300 to be conservative
-
Operator gets approximately
100-150 sharpenings per drill bit lets use 100 to be
conservative
-
Therefore 300 x 100 = 30,000
holes per drill bit
-
Two drill bits = 2 x $165 = $330
provides 60,000 holes
A. Cost to drill 60,000 holes is $280
consumable cost (plus
the $10,000 capital of the sharpener which gets amortized over the
life of the machine - There are many Rush 250 grinders in
fabrication shops that are in excess of 10 years old).
Now lets look at the
cost of using Insert Drill Bits
B. Insert Drill Bits
-
13/16 holder is typically
$187.00
-
13/16 T/A drill insert is typically $33.85
-
Need to have a minimum of two
holders of each size so we can change out the inserts while we
are drilling with the other holder
-
Operator gets 800 - 1,000 holes
per insert lets use 800 to be conservative
-
Therefore we require 2 holders
($374) and 75 inserts ($2,539) to drill 60,000 holes
B. Cost to drill 60,000 holes is $374
+ $2,539 = $2,913 (consumable cost)
Observation
The consumable cost is 9 TIMES more
expensive using insert drill bits
The above example is true for all drill sizes, but the cost differential
increases with the size of the drill bit.
This also does not take into account any replacement holders that
need to be ordered when
-
The holder is damaged when an
insert breaks while drilling
-
The holder is no longer usable
when the insert screws strip off or seize
-
And it does not take into account
the cost of grinding the exit of the hole.
All of the above situations do occur in real life. Also note that as
the drill diameter increases the cost of the holders can go up to as
much as $800 each.
It doesnt take too much math to realize that in significantly less
than one year you will have completely paid off the drill grinder from
your savings in consumable costs and you will be well on your way to
becoming a low cost producer.
So what drill bit does Ocean Machinery
recommend for beam lines?
We believe that for now, based on current pricing from the various
suppliers, the customer is better off with good quality twist drill
bits and a good quality sharpener. Any one of the brands above will
do a great job (Ocean Penetrator, Nachi or Cleveland).
Of course, training an operator to sharpen drill bits properly is important,
and we do a thorough job during the installation of the Avenger. We
have trained hundreds of operators who totally get it and are able
to resharpen bits in less than a couple of minutes.
To assist our
operators with their drill sharpening techniques we host online
drill sharpening video tutorials on our Web Site.
* Pricing comparison during Summer of 2004,
drill and inserts prices are subject to change without notice.
Consult Ocean Machinery for current pricing information. *
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