Ta k a m a z R Y U - G I

Here, we introduce the knowledge and various knowledge
about the product TAKAMAZ a variety of machine tools.
I hope you will help the daily work of customers.

The 15th About Reaming
Reaming is commonly used
for small-diameter hole
work (around ~φ20) wherethe inner diameter dimension
and circularity, surface
roughness, etc., demand
accuracy. However, problems
such as unstable hole diameters,poor surface roughness, andshort tool life are common,
and a lot of people avoid it,seeing it as"difficult machining". We would like to introduce
you to reaming with improved surface roughness
accuracy.

The Principles of “Reaming”"Reaming", refers to the widening of an innerdiameter machined by drilling, etc., to a holedimension set by the cutting lip section, andfurther performing a burnishing (polishing)action while grinding the margin of the worksurface.
The Principles of “Reaming”
Machining
direction

tool

workpiece

Cutting Edge (Cutting)Margin (Burnish)

Back Taper (Retract)

It performs cutting
exclusion of an allowance.
The allowance is generally
0.05~0.2mm

The work surface machinedby the cutting edge
is pulverized, improving
surface roughness

The tool bending iscorrected using the cutting
surface as a guide.
This prevents chips fromjamming and ejects them.

The reason of a problematic surface
roughness is because of the reaming① In reaming, the burnishing width is small,and when the hole diameter expands and the surface
roughness concavities reach the μm level,
proper burnishing is not possible (the burnishingvolume is about 5μm)
② Although "Superoll" burnishing performs polishing
while rotating a roller, in reamer burnishing,it is performed by rubbing the work piece with amargin part. These are the two main reasons given.

Countermeasure ①
Improvement of Tool Mounting Accuracy
In cases where center deviations and runout islarge when mounting a reamer tool, burnishingwill not be performed once the hole diameter
becomes large, and will result in a finishedproduct with feed marks machined by the cuttingedge. In addition, each of the reamer blades
will generate an uneven machining force.
circularity and cylindricality will be poor,and waviness will be observed. Moreover when
the reamer performs reaming in a warped state,
the occurrence of seal marks is also seen during
reamer retraction. Although the general benchmark
is for center deviation/runout to be less than
5μm, it needs to be as close to 0 as possible.
Even if reliable accuracy is produced by mounting
a master to the holder, one should be aware that
center deviation is still seen when the original

reamer tool is mounted. In addition, in rotary
type machines for parts in horizontal machining,
tool mounting accuracy is a critical point, andcentering holders for reamers are being appropriatedin machining centers. Measures will need to be
put in place such as countermeasures for mechanicalaging, and the like.
NormalEnlargementof the Hole
Diameter

tool

Abnormaltool

Workpiece

workpiece

The feed marks are uniform,
with organized thread heights,
and the pre-machining hole diameteris suitable.

The effect of reamer runoute,etc., is to make the row heights
uneven, and the pre-machining
hole diameter will be larger.

Surface roughness is improvedby burnishing.

No Burnishing Effect Without
Crushing the Rows

Countermeasure ②"Proper Lubrication with Cutting Oil"
Because the cut material is directly rubbed by
the margin part during reaming, insufficientlubrication will result in deposition due tofriction heat in addition to poor surface
roughness due to the friction, and both accuracy
and tool life will degrade. It is of course mandatorythat a lubrication oil be interposed in those parts
where there is high-speed metal-to-metal rubbing.
Therefore, in reaming running out of cutting oil
will cause poor accuracy, and is particularly fatal
to surface roughness. Non-water soluble (oleic)cutting oils are recommended, but also using awater-soluble cutting oil but use an emulsion typeof 20% or higher concentration. In the case of deepholes and blind holes, use an internal oil feed(coolant-through) type (especially for deep holes
and blind holes), and be careful to supply oil tothe machining parts without interruption.
In addition, because machining with depositions
attached as is shall degrade surface roughness,remove these before machining.

Countermeasure ③"Reliable Chip Ejection"
When the chips generated by the cutting edge are
not ejected well, they get jammed between the tooland the cut material, damaging the work surface,and degrading surface roughness. Particularly
when the prepared hole diameter is small but
the allowance is too big, and the feed rate duringmachining is too fast, the chip thickness becomes
too large, making them difficult to eject. Be sure
to match the prepared hole setting and machining
conditions to the tools used and the material cut.
Properly adjust the cutting oil delivery method,
supply amount, and delivery pressure. For throughholes, a back-side ejection type tool is recommended
so that chips do not enter the work surface.

Summary
In recent years, there have been demands forincreased accuracy even in drilling due tothe demand for increased component performance.
Please take these points we have introduced
here into consideration and use them forhigher-precision reaming.