Каталог Iscar высокоточные развертки и метчики 2022 - страница 22

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Cutting SpeedCoolant/Lubrication
The cutting speed has the highest influence on theThe high degree of friction between the tool and the
surface quality of the reamed hole and on the life of thewall being reamed demands the use of a fluid for
tool. Increasing the cutting speed beyond the optimumlubrication and cooling. Using lubrication is more
speed will cause increased tool wear due to the increasedcritical for maintaining tolerances than using a coolant.
cutting temperature. The increased speed also causesGeneral cutting oils and emulsions may be used. It
an increase in the built-up edge (material that is weldedshould be noted that in some cases emulsions will yield
to the cutting edge). The built-up edge damages thea better surface finish than cutting oils. Emulsions are
surface finish and shortens the life of the tool. In orderthinner fluids that are able to reach and more uniformly
to achieve high surface quality and longer tool life, thelubricate 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 Ratefor a particular application, tests should be run on
The feed rate directly influences the wear on the cuttingthe 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 qualityIn order to achieve high tolerances for
and tool wear than the cutting speed (i.e. the feedreaming applications, there are certain
can be varied in a relatively wide range without havingrequirements that must be considered.

material influence the quality of the machined hole and 1 Condition of the tool - If the tool is reground, both an exact the respective tool life). It is therefore recommended concentricity and high quality grinding are indispensable. to select the highest possible feed in order to shorten 2 Workpiece material - Axis shifting and warping (i.e. reaming times without significantly reducing the tool life. incorrect hole positioning) can only be corrected to a

certain degree when reaming. A critical factor is the Reaming Allowance initial opening in the workpiece. This opening must be The reaming allowance (the amount of material to be even, or if the prepared hole is countersunk, a cone reamed) also influences the tool life. In order to achieve countersink must be used. Failure to properly prepare high tool life, the reaming allowance should be kept the initial opening can result in irregular countersinking at a reasonable minimum considering the process to that leads to the reamer being pushed out of its be performed. If the reaming allowance is too small, it proper alignment. Ideally, pre-machining should be may result in a high dimensional variation (inability to performed in a chuck to avoid alignment defects. maintain the required tolerances) and a decrease in the 3 Through holes - For best results, the holes to be reamed machined surface quality. When reaming materials that should extend completely through the workpiece have surface defects or have been welded or flame material. This allows for easy exit of both the cutting cut, the reaming allowance should be increased so fluid and the reamed material. Negative flute reamers these factors do not appear on the reamed surface. are advantageous in through hole reaming. 4 Blind holes - Use straight flute reamers for blind holes.