Download Ampco Machining Recommendations PDF

TitleAmpco Machining Recommendations
TagsMachining Grinding (Abrasive Cutting) Manmade Materials
File Size474.4 KB
Total Pages9
Table of Contents
Document Text Contents
Page 1

Machining recommendations for
AMPCO® and AMPCOLOY®-alloys

General guidelines

The recommendations for the machining of AMPCO® and AMPCOLOY® materials
are based on extensive tests made at the AMPCO METAL factories, which also
match the values of a great number of customers.
AMPCO® and AMPCOLOY® materials are basically easy to machine. For the
machining of AMPCO® 21, AMPCO® 22, AMPCO® 25 and AMPCO® 26 special
care is required, due to the fact that these alloys compared to tool steel of same
hardness present a lower elongation and ductility. An inappropriate treatment of the
parts can lead to fractures.

Since the cutting speeds so much depend on the type of cutting tools used, on the
stiffness and stability of the machine-tools used and on the type of cooling and
lubricating liquids used, the recommended machining speeds for AMPCO® and
AMPCOLOY® alloys are indicated as a relative value compared to the machining
speeds used for tool steel 1.7225 (DIN 42 Cr Mo 4), see correspondence table


U.S.A. Italy Japan France Spain


Page 2

Influencing values such as machine-tool rigidity, optimal heat extraction, specific
cutting tool configuration and so on play independently from this a big role, which is
even more marked with the harder AMPCO® grades.

Please take notice that the lifetime of the cutting tools for the harder grades will be
considerably shorter.

In general all AMPCO® harder grades, from AMPCO® 21 upwards should be
machined from the edge into the material or alternatively the edge can be generously
chamfered at an angle of 45°. Non conformance to this rule will lead to breaking of
the edge.

Machining tools

The clearance angle α for all AMPCO® and AMPCOLOY® alloys must be set at 6°.
Cooling is more important than lubricating when machining AMPCO® material,
specially for the harder grades M4, 21, 22, 25, 26. Water mixable lubricating coolant
are recommended, where the emulsion generally contain 5 to 10% cooling lubricant.
For parts where a high precision is requested, it is recommended to pre-machine
first, then wait 48 hours before finish machining is performed. In special cases where
the parts require very tight tolerances or for thin wall parts a stress-relieving heat
treatment before or even better after the pre-machining can be done. Please ask your
local AMPCO®-office for the necessary temperatures and holding time.


The softer AMPCO® alloys up to AMPCO® 18 can be sawn with bimetal saw blades.
The harder grades AMPCO® 21 up to AMPCO® 26 and M4 are best sawn with
hardmetal saw blades. Depending on the section of the pieces to be cut, the number
of sawing teeth will vary between 2 ½ and 3 teeth / inch.

Manufacturer recommendation: hard metal saw blades from WIKUS-Sägenfabrik,
Wilhelm H. Kullmann GmbH & Co. KG


The cutting tool has to be set up in the centre of the part or up to 0,4 mm below this

For roughing or finishing it is best to use hard
metal cutting tool tips in the quality K10 / K20. For
real fine machining (hole-shaft fits) a very good
surface condition (N3) can be achieved with
diamond tooling (PKD).

To avoid breaking of the edge when turning rings,
you should always turn rings from outside of the
material to inside of the material when machining

the harder grades from AMPCO® 21 upwards. Alternatively a generous 45 degree
chamfer can be machined before on the edge where the cutting tool will be finishing
its turning operation coming out of the material.

Page 6

Drilling, sinking and reaming

For the AMPCO® – grades 18 up to 26, hard metal plates drillers or fully hard metal
drillers must be used. Since AMPCO® – alloys do not produce flowing chips, it is
important to pay attention to a good chip removal. For deep holes it is recommended
to withdraw the drilling tool and to remove the chip. For through holes (AMPCO® 21
up to 26) it is necessary to place a steel plate under the part or to drill the hole from
both sides in order to avoid a breakage of the part around the exit end of the hole. A
very good cooling of the drilling tool is absolutely necessary for AMPCO® and

Material Brinell – hardness
HB 30/10

Cutting speed

(DIN 42 Cr Mo 4)

Max. 250 100 %

AMPCO® 8 109 - 124 125 %
AMPCO® 18 159 - 183 130 %
AMPCO® M4 270 - 305 120 %
AMPCO® 21 285 - 311 115 %
AMPCO® 22 321 - 352 110 %
AMPCO® 25 356 - 394 100 %
AMPCO® 26 395 - 450 75 %

AMPCOLOY® 940, 95, 97 180 – 255 125 %
AMPCOLOY® 83 340-390 100 %
AMPCOLOY® 88 260-280 120 %

Manufacturer recommendation:
Fa. Gühring
For AMPCO®-alloys: RT 100 U art. nr. 2471, 1243, 730, 732 and 305
For AMPCOLOY®: RT 100 F art. nr.1660, 1662 and 620

Important recommendations:

For through holes in AMPCO® 21, 22, 25 and 26 drill from both sides
Good chips removal has to be guaranteed
Cooling with cooling lubricant
If the depth of the chip is too small, the reaming tool will jam
Hard metal plates reaming tools with unequal division
When drilling with inner cooling tools observe the recommended cutting datas

of the tool manufacturer

Machining of threads

For the middle hard and hard grades AMPCO® 18 up to 26 it is recommended to use
thread cutting tools which are relief grinded. Hard metal thread cutting tools are an
advantage compared to HSS thread cutting tools, they allow higher cutting speeds
and last longer.

Page 7

Manufacturer recommendation:
Fa. Gühring
Art. nr. 969, 2506, 809 and 821

Important recommendations:

- For AMPCO® 25 and 26 the diameter for drilling of the hole before tapping
must be 0,15 - 0,25mm bigger than the value of the diameter of the hole given
by the norms.

- The hole must be chamfered on both sides before tapping when the threaded
hole is a through hole.


When honing a part made out of AMPCO® alloy, a geometry precision of the
machined part between 0.0005 and 0.015 mm with a surface roughness between 0,5
µm and 1,5 µm can be reached depending on the size and type of the part to be
machined. For parts with a diameter between 25 and 130 mm, an undersize of 0.01
up to 0.038 mm must be foreseen for honing, for parts with a diameter greater than
130 mm up to 280 mm an undersize of 0.038 mm up to 0.063 mm must be foreseen.


AMPCO® alloys can be lapped with especially high excellence. A precision of 0,1 µm
up to 2 µm can be reached. The lapping powder used is corundum.

Grinding and polishing

One of the advantages of the AMPCO® alloys is that an excellent surface quality can
be reached when fine machining. All AMPCO® grades can be grinded with feed rates
as they are usual for steel. The grinding speed when deburring varies between 30
and 45 m/s, when flat or round grinding between 24 and 25 m/s. For flat or round
grinding, silicon carbide grinding wheels will be used. Optimal results are achieved
with rotating speeds of 5000 and 6000 RPM for the ginding wheels and when round
grinding with a rotating speed of the part itself between 25 and 150 RPM. It is
recommended to grind in wet condition.

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