GB2489731A - Method of making punches - Google Patents
Method of making punches Download PDFInfo
- Publication number
- GB2489731A GB2489731A GB1105874.0A GB201105874A GB2489731A GB 2489731 A GB2489731 A GB 2489731A GB 201105874 A GB201105874 A GB 201105874A GB 2489731 A GB2489731 A GB 2489731A
- Authority
- GB
- United Kingdom
- Prior art keywords
- punch
- electrode
- shaped
- shaped recess
- discharge machining
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000009760 electrical discharge machining Methods 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 11
- 239000007788 liquid Substances 0.000 claims abstract description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 229910000831 Steel Inorganic materials 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000009191 jumping Effects 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K1/00—Making machine elements
- B21K1/44—Making machine elements bolts, studs, or the like
- B21K1/46—Making machine elements bolts, studs, or the like with heads
- B21K1/463—Making machine elements bolts, studs, or the like with heads with recessed heads
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K5/00—Making tools or tool parts, e.g. pliers
- B21K5/20—Making working faces of dies, either recessed or outstanding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
- B23H1/04—Electrodes specially adapted therefor or their manufacture
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
Abstract
The present invention is an improved method of making a punch 26. The punch 26 can be used in the production of fasteners having a shaped recess in the fastener head and which as suitable for use in the aerospace industry, for example. The punch 26 has a shaped protrusion 22 for forming the shaped recess. The shaped protrusion 22 is formed by an electrical discharge machining (or 'spark erosion') process. The electrical discharge machining process may involve immersing an electrode 2 having a shaped recess 4 and a punch blank in a liquid dielectric. An electrical voltage is then passed between the electrode 2 and the punch blank to remove material from the punch blank to form the shaped protrusion 22.
Description
TITLE
Method of making punches
DESCRIPTION
Technical field
The present invention relates to a method of making punches, and in particular punches that are used to produce fasteners such as those for the aerospace industry.
Background art
Fasteners of the type commonly used in the aerospace industry have a shaped recess in the fastener head for receiving a correspondingly shaped driver. The fasteners are typically manufactured from titanium feedstock. After being heated the individual fasteners are forged by striking them with a punch to form the fastener head and the shaped recess. The punch also permanently indents details such as the part number and manufacturer details into the fastener head.
The punches are produced using a master hob. The master hob in turn is produced by pressing a tool with a suitably shaped tip into a steel cylinder to form a shaped recess.
The master hob is then engraved with the part number and manufacturer details, cleaned up to remove any distortion caused by the tool, and hardened by heat treatment. The punches are manufactured from steel in a grade that is suitable for a hobbing process where the punches are struck by the master hob to form a shaped protrusion which is subsequently used to form the shaped recess in the fastener head.
It will be readily appreciated that a new master hob is needed for each version of the indented details. This means that the conventional process for producing punches is time consuming and has high tooling costs. As a consequence, there is normally a minimum viable quantity of between 10 and 20 punches for each version of the indented details even though in many cases this number of punches will not be needed for fastener production.
Summary of the invention
The present invention provides an improved method of making a punch for the production of fasteners having a shaped recess in the fastener head. More particularly, the punch has a shaped protrusion for forming the shaped recess in the fastener head, the shaped protrusion being formed by an electrical discharge machining (or spark erosion') process.
The electrical discharge machining process preferably includes the steps of: immersing an electrode having a shaped recess and a punch blank (or workpiece) in a liquid dielectric, e.g. synthetic oil, and passing an electrical voltage between the electrode and the punch blank to remove material from the punch blank to form the shaped protrusion. The electrode is typically made of copper but other conductive materials may also be used. The electrode and punch blank are connected to a suitable power supply that generates an electrical potential between them. As the electrode is lowered towards the punch blank a dielectric breakdown occurs and sparks jumping between the electrode and the punch blank gradually erode the punch blank to form the shaped protrusion which corresponds generally to the shaped recess of the electrode. The liquid dielectric flushes the eroded material away from the spark gap between the electrode and the punch blank and serves as coolant. The electrode is typically lowered towards the punch blank automatically as the spark gap increases so that the electrical discharge machining process can continue without interruption.
Because of the amount of material that needs to be removed from the punch blank, more than one electrode can be used, e.g. for roughing and finishing purposes.
The punch blank is typically cylindrical with a first planar surface that faces the electrode during the electrical discharge machining process and an opposite planar surface. Material is eroded from the first planar surface of the punch blank to form the shaped protrusion. The punch blank can be of any material that is suitable for an electrical discharge machining process. It will be readily appreciated that the punch blank can therefore be a material that is exceptionally hard wearing, for example, and there is no requirement for it to be made of a grade of steel that is suitable for hobbing. The ability to use different materials can significantly extend the working lifetime of the punch.
The shaped recess in the electrode is preferably formed by pressing a tool with a suitably shaped tip into a surface of the electrode. It is important that the electrode and the tool have the correct alignment when the shaped recess is formed because this will determine the position of the shaped protrusion on the punch blank and hence the position of the shaped recess in the fastener head within the required tolerances. The correct alignment can be achieved by temporarily positioning the electrode in a suitable workpiece holder.
The method preferably further includes the step of engraving details (e.g. the part number and manufacturer details) on the electrode before it is used in the electrical discharge machining process. The details can be engraved inside the shaped recess or on the annular planar surface surrounding the recess and will be transferred to the punch blank during the electrical discharge machining process as a corresponding embossment. It is therefore much easier to produce punches with different details but with the same shaped protrusion for the same fastener type. This significantly reduces lead times and makes it cost effective to produce punches in smaller quantities.
The present invention may also provide a punch for the production of fasteners having a shaped recess in the fastener head, the punch having a shaped protrusion for forming the shaped recess, the shaped protrusion being formed by an electrical discharge machining process.
Drawings Figure 1 is a side view showing how a shaped recess is formed in an electrode; Figure 2 is a top view and a side view of part of the finished electrode; and Figures 3A and 3B are a side views showing how the electrode is used to make a punch as part of an electrical discharge machining process.
With reference to Figure 1 a cylindrical copper electrode 2 includes a shaped recess 4 that is formed by pressing a tool 6 with a suitably shaped tip 8 into a planar surface 10 of the electrode. The electrode 2 is maintained in correct alignment with the tool 6 during the pressing process by a workpiece holder 12.
The tip 8 of the tool 6 may have any suitable shape and will determine the shape of the recess that is formed in the fastener heads as discussed in more detail below. For example, the tip 8 may be shaped to form an offset cruciform recess (e.g. as defined by National Aerospace Standard (Metric) NASM 33781) in the fastener heads.
Details such as the part number and manufacturer details 14 are engraved on the electrode as shown in Figure 2. The engraving may be within the shaped recess 4 or alternatively on the planar surface 10 of the electrode so that it will appear on the fastener head.
The base of the electrode 2 (not shown) is adapted to allow the electrode to be inserted into an electrical discharge machining apparatus. With reference to Figure 3A a cylindrical punch blank 16 made of a suitable material (e.g. an exotic steel or alloy) has upper and lower planar surfaces 18, 20. The electrode 2 and the punch blank 16 are immersed in a bath of liquid dielectric and connected to a suitable power supply. During the electrical discharge machining process, material is spark eroded from the upper planar surface 18 of the punch blank to form a shaped protrusion 22 surrounded by an annular planar surface 24 shown in Figure 3B. The shaped protrusion 22 corresponds generally to the shaped recess 4 in the electrode 2 and is embossed with the part number and manufacturer details. During the electrical discharge machining process typically three different electrodes will be used, each having a slightly different shaped recess to allow for different spark gaps and providing a progressively fine surface finish to the punch blank.
After the electrical discharge machining process is complete, the lower planar surface will typically be surface ground to ensure the finished punch 26 has the correct overall form and dimensions, and in particular the correct height.
Aerospace fasteners can be forged by striking them with the punch 26 so that the shaped protrusion 22 forms an offset cruciform recess in the fastener head for receiving a correspondingly shaped driver and permanently indents the part number and manufacturer details into the fastener head.
Claims (4)
- CLAIMS1. A method of making a punch for the production of fasteners having a shaped recess in the fastener head, the punch having a shaped protrusion for forming the shaped recess, the shaped protrusion being formed by an electrical discharge machining process.
- 2. A method according to claim 1, wherein the electrical discharge machining process includes the steps of: immersing an electrode having a shaped recess and a punch blank in a liquid dielectric, and passing an electrical voltage between the electrode and the punch blank to remove material from the punch blank to form the shaped protrusion.
- 3. A method according to claim 2, wherein the shaped recess in the electrode is formed by pressing a tool into a surface of the electrode.
- 4. A method according to any preceding claim, further comprising the step of engraving details on the electrode before it is used in the electrical discharge machining process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1105874.0A GB2489731B (en) | 2011-04-07 | 2011-04-07 | Method of making punches |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1105874.0A GB2489731B (en) | 2011-04-07 | 2011-04-07 | Method of making punches |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB201105874D0 GB201105874D0 (en) | 2011-05-18 |
| GB2489731A true GB2489731A (en) | 2012-10-10 |
| GB2489731B GB2489731B (en) | 2013-04-10 |
Family
ID=44072083
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1105874.0A Active GB2489731B (en) | 2011-04-07 | 2011-04-07 | Method of making punches |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2489731B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN86100570A (en) * | 1986-05-06 | 1987-01-31 | 上海模具技术研究所 | Process for producing printing matrices |
| US5402692A (en) * | 1993-08-10 | 1995-04-04 | Bennett; Edward D. | Method of making blanking dies and punches having rounded edges |
| US5994250A (en) * | 1995-11-07 | 1999-11-30 | Ngk Spark Plug Company Limited | Sintered ceramic bodies and ceramic working tools |
| JP2002045932A (en) * | 2000-08-02 | 2002-02-12 | Amada Co Ltd | Punch die, manufacturing method for the die and punch tip base material |
-
2011
- 2011-04-07 GB GB1105874.0A patent/GB2489731B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN86100570A (en) * | 1986-05-06 | 1987-01-31 | 上海模具技术研究所 | Process for producing printing matrices |
| US5402692A (en) * | 1993-08-10 | 1995-04-04 | Bennett; Edward D. | Method of making blanking dies and punches having rounded edges |
| US5994250A (en) * | 1995-11-07 | 1999-11-30 | Ngk Spark Plug Company Limited | Sintered ceramic bodies and ceramic working tools |
| JP2002045932A (en) * | 2000-08-02 | 2002-02-12 | Amada Co Ltd | Punch die, manufacturing method for the die and punch tip base material |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2489731B (en) | 2013-04-10 |
| GB201105874D0 (en) | 2011-05-18 |
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