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Lec. 4 PDF

The document discusses different types of milling fixtures used to securely hold workpieces for milling operations. It describes vertical and horizontal milling machines and some basic fixtures like detachable vise jaws. It then covers facing, straddle, and gang milling fixtures. Finally, it discusses methods to reduce idle time through indexing, rotary, reciprocal, and slotting fixtures as well as string milling fixtures for round parts.

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Awad M. El Araby
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104 views12 pages

Lec. 4 PDF

The document discusses different types of milling fixtures used to securely hold workpieces for milling operations. It describes vertical and horizontal milling machines and some basic fixtures like detachable vise jaws. It then covers facing, straddle, and gang milling fixtures. Finally, it discusses methods to reduce idle time through indexing, rotary, reciprocal, and slotting fixtures as well as string milling fixtures for round parts.

Uploaded by

Awad M. El Araby
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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MNF.

UNIVERSITY
Faculty of engineering – Shebein Elkoam
Production engineering and mechanical design dept.

Jigs and fixtures


PRE 510
2019/2020
4. Milling fixtures

Milling machines are now used for so many different


purposes that the fixtures used for holding parts to
be milled differ considerably in form and size, and
there are several distinct types.
 Vertical milling m/c : tool axis is vertical.
 Horizontal milling m/c : tool axis is horizontal.
The simplest form of milling fixture is represented by
the type which simply holds and locates a single
piece for a milling operation. Then there are multiple
or gang fixtures for holding a row of duplicate
castings or forgings.

2
4. Milling fixtures

3
4. Milling fixtures
Detachable Jaws for Vise:
 The cheapest kind of milling fixture that can be
built is a pair of detachable vise jaws, as shown
in Fig. These jaws are made of cold-rolled steel
and casehardened.
 They can be removed from the vise quickly and
replaced by other jaws.
 It is advisable, however, to use vise jaws only
where great accuracy is not required.
 The jaws here shown are used for cutting off
pieces from a bar of stock, which is pushed up
against the stop and then cut off to the desired
length. 4
4. Milling fixtures

5
4. Milling fixtures

Facing fixtures :
• Milling m/cs are
used for facing
,seating and
mating flat
surfaces.
• Facing is the
first operation
performed on
milling m/c.

6
4. Milling fixtures

Straddle milling :
• Simultaneous facing
of two parallel sides
of w.p.
• Straddle milling
produces precisely
parallel opposite
faces of w.p.

7
4. Milling fixtures

Gang milling :
• Number of faces
are machined at
the same time.
• The w.p. is holded
against vertical
face.
• Angular clamp
exerts downward
pressure.

8
4. Milling fixtures
Idle time reduction:
Time wasted in clamping and unclamping could be reduced by
several methods
Indexing milling
• In indexing milling a multi station fixture table is used.
• When the w.p. is machined at the machining station the previous
w.p. is unclamped and replaced by new one.
• Then the indexing device is rotated .

9
4. Milling fixtures

Rotary milling :
• Number of w.ps are mounted on a rotary fixture which is
rotated to feed them to the milling cutter.
• At the opposite end the machined w.ps are replaced by new
ones.

10
4. Milling fixtures

Reciprocal milling :
• Two fixtures are mounted at two ends of m/c table.
• While w.p is machined , the preceding one is replaced by new
one.
• Then the m/c table is reversed.

11
4. Milling fixtures
slotting fixtures
In slotting must be holded close as possible to the machined portion.
String milling:
• fixtures are used for milling number of round parts at the
same time.
• They are aligned in one line to be milled in one stroke of
cutter.

12

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