Milwaukee 4004 Manuel De L'utilisateur page 11

3. After removing the core, reinsert the bit or use a
bit extension and continue coring (see "Acces-
sories"). Removing cores with diameters greater
than twice their length can be difficult. One
method to remove such cores is to fi rst break
the core into smaller pieces and then remove
the pieces. Electric hammers and chisels are
ideal for breaking cores.
WARNING
cores generally drop from the bit. To reduce
the risk of injury, provide proper protection
for people and property below the coring area.
Diamond Coring
Factors that infl uence diamond core performance:
• Amount of coolant
• Dymorig rigidity
• Dymorig condition
• RPM of drill motor
• Feed pressure applied to bit by operator
• Amount of steel
• Size of embedded steel
• Age of concrete
• Aggregate (size, type, hardness, abrasiveness)
• Type of sand–manufactured vs. river (natural)
• Operator technique
• Operator care
• Bit runout
Operator Technique
Core with consistent, fi rm feed pressure. Do not
subject the bits to sudden impacts. Uneven feed
rate cracks diamonds. Low feed pressure polishes
diamonds, slows penetration and contributes to bit
glazing. High feed pressure can overload the drill
motor or can cause diamonds to pull out prema-
turely, particularly when coring embedded steel.
Make the bit work, but do not try to jam the bit
through the material.
If vibration occurs:
1. Stop drilling.
2. Turn motor off.
3. Check for loose bolts, nuts and gib screws.
Tighten if required.
4. Check for bit runout. Replace if required.
If vibration continues to occur, remove the core and
loose material.
If vibration continues to occur after attempting these
measures, return the rig to the nearest MILWAU-
KEE service facility.
Water
Water provides two main benefi ts during coring:
1. Water acts as a coolant, eliminating the heat
caused by the friction of the coring action. This
preserves the integrity of the diamonds, the
bond matrix, the segment solder, and core tube.
Without a coolant, the heat buildup during coring
can cause all of these components to fail.
2. Water fl ushes loose, abrasive particles created
during coring. These particles consist of ag-
gregate, sand, diamond particles and various
metals from embedded steel and the core bit
matrix. The hole must be free of debris to allow
the core bit to work. If loose particles are not
properly fl ushed from the hole, an unnecessary
When coring through fl oors,
drag will occur along the side of the core barrel.
This can contribute to bit glazing through lack of
power as well as motor damage through amper-
age increases due to bit resistance. In addition,
loose particles tend to wear the bit tube, which
can eventually result in the loss of segments.
Monitor water fl ow. Water volume should be ad-
justed until water return is a muddy, solid color.
Clear water or clear streaks indicate too much
water volume. Excess water is a leading cause of
bit glazing and failure. Other factors contribute to
glazing, but water adjustment is one of the most
easily controlled by the operator. Excessive water
prevents adequate segment/material contact.
When the bit segments do not properly contact the
work surface, the desired "controlled erosion" effect
which maintains bit sharpness does not occur and
the bit begins to glaze. This happens especially with
smaller diameter bits. Adequate water volume var-
ies according to the bit diameter. Use only enough
water during coring to fl ush the cuttings from the
work surface.
Equipment
• Make sure machinery is in good operating condi-
tion. The column, carriage, motor connection and
base should all be fi rmly connected and should
not vibrate during coring.
• Motors should be of proper size (amperage and
RPM) for the diameter of the core bit used. Consult
motor guide in catalog.
• Always make sure the Dymorig is rigidly mounted
with an anchor or vacuum; any movement or vibra-
tion will shorten the life of the core bit. Standing on
the rig's base as a form of anchoring is dangerous
and does not provide the necessary rigidity.
Diamond Core Bits
• For the fi rst 2 or 3 holes, use light feed pressure,
so the new diamond gradually breaks in.
• Lower the bit very slowly onto the work surface.
Use light feed pressure until the bit crown has
penetrated or "seated" into the material.
• If the core bit encounters embedded steel, slow
down the feed pressure and let the bit core at its
own pace. Don't force the bit. Typically the water
around the bit will clear when embedded steel is
encountered. Do not allow any vibration whatso-
ever or severe diamond breakage or pullout will
occur.
• Keep bits sharp.
Bit Glazing & Diamond Core Motor Shear Pins
Bit binding is caused by one of two things: a dull
(glazed) bit or a poorly stabilized rig.
Causes of bit glazing:
• Wrong RPM for bit diameter
• High feed pressure
• Low feed pressure
• High steel content in work surface
• Large, hard aggregate
• Too much water
• Low motor power
A sharp bit typically has good diamond exposure
and will cut/grind almost anything in its path, includ-
ing embedded steel.
11