Page 22 - HOLE MAKING CATALOG p311-382
P. 22
REAMERS USER GUIDE
Cutting Speed Coolant/Lubrication
The cutting speed has the highest influence on the The high degree of friction between the tool and the
surface quality of the reamed hole and on the life of the wall being reamed demands the use of a fluid for
tool. Increasing the cutting speed beyond the optimum lubrication and cooling. Using lubrication is more
speed will cause increased tool wear due to the increased critical for maintaining tolerances than using a coolant.
cutting temperature. The increased speed also causes General cutting oils and emulsions may be used. It
an increase in the built-up edge (material that is welded should be noted that in some cases emulsions will yield
to the cutting edge). The built-up edge damages the a better surface finish than cutting oils. Emulsions are
surface finish and shortens the life of the tool. In order thinner fluids that are able to reach and more uniformly
to achieve high surface quality and longer tool life, the lubricate the cutting edges better than viscous cutting
cutting speed for reaming should be kept relatively low. oils (especially when performing deep applications).
In order to determine the most suitable lubricant
Feed Rate for a particular application, tests should be run on
The feed rate directly influences the wear on the cutting the material to be cut, on a case-to-case basis.
edge. As the feed rate is increased, the cutting forces
increase almost proportionally. The feed, however, Reaming Prerequisites
has less influence on the machined surface quality In order to achieve high tolerances for
and tool wear than the cutting speed (i.e. the feed reaming applications, there are certain
can be varied in a relatively wide range without having requirements that must be considered.
material influence the quality of the machined hole and
the respective tool life). It is therefore recommended 1 Condition of the tool - If the tool is reground, both an exact
to select the highest possible feed in order to shorten concentricity and high quality grinding are indispensable.
reaming times without significantly reducing the tool life.
2 Workpiece material - Axis shifting and warping (i.e.
Reaming Allowance incorrect hole positioning) can only be corrected to a
The reaming allowance (the amount of material to be certain degree when reaming. A critical factor is the
reamed) also influences the tool life. In order to achieve initial opening in the workpiece. This opening must be
high tool life, the reaming allowance should be kept even, or if the prepared hole is countersunk, a cone
at a reasonable minimum considering the process to countersink must be used. Failure to properly prepare
be performed. If the reaming allowance is too small, it the initial opening can result in irregular countersinking
may result in a high dimensional variation (inability to that leads to the reamer being pushed out of its
maintain the required tolerances) and a decrease in the proper alignment. Ideally, pre-machining should be
machined surface quality. When reaming materials that performed in a chuck to avoid alignment defects.
have surface defects or have been welded or flame
cut, the reaming allowance should be increased so 3 Through holes - For best results, the holes to be reamed
these factors do not appear on the reamed surface. should extend completely through the workpiece
material. This allows for easy exit of both the cutting
fluid and the reamed material. Negative flute reamers
are advantageous in through hole reaming.
4 Blind holes - Use straight flute reamers for blind holes.
332 ISCAR
