Inverto 18
"Staking Tools and How To Use Them", 1910, provides a clear explanation of how the Inverto 18 is different from the Inverto/Inverto 17. It's all about the punch frictioning assembly.
The picture of the Inverto 18 on page 17 is clearly a modified version of the picture of the Inverto 17 on page 14. The reflections/highlights on the frames are nearly identical.
The picture of the Inverto 18 on page 17 is clearly a modified version of the picture of the Inverto 17 on page 14. The reflections/highlights on the frames are nearly identical.
After K&D introduced the "On or Off Punch Frictioning Device", covered by the second Inverto patent, new frames with this mechanism as a standard feature were designated Inverto 18.
Customers owning the older model Inverto/Inverto 17 could return it to the factory for an upgrade.
The availability of factory upgrades makes it difficult to make definitive identifications of these tools. An early serial number frame could have originally been sold as an Inverto or an Inverto 17 but be found today in a configuration that looks like an Inverto 18.
In addition, K&D may have opted to use up their remaining inventory of "Inverto 17" branded components even after the new model was introduced. The model number appears on some frames on the knurled steel disks for the die-binding mechanism as well as on some of the box handles.
Customers owning the older model Inverto/Inverto 17 could return it to the factory for an upgrade.
The availability of factory upgrades makes it difficult to make definitive identifications of these tools. An early serial number frame could have originally been sold as an Inverto or an Inverto 17 but be found today in a configuration that looks like an Inverto 18.
In addition, K&D may have opted to use up their remaining inventory of "Inverto 17" branded components even after the new model was introduced. The model number appears on some frames on the knurled steel disks for the die-binding mechanism as well as on some of the box handles.
Now for the confusing part...
As I mentioned on the Inverto 17 page, the above is consistent with the primary sources and documentation to which I have access, but it is not consistent with the Inverto products I've seen in the wild.
I've never seen an Inverto with the old style frictioning assembly. There are older, Hall design (non-Inverto) sets from K&D out there on which the heads look much like the Inverto design shown on page 14 of "Staking Tools and How To Use Them". But no Invertos.
Also, frames regularly appear on eBay that have both a knurled die binding disk marked "Inverto 17" and what appears to be the newer punch frictioning assembly. At least some of these have only the 1902 and 1908 patent markings on the underside of the frame, indicating that they are earlier production.
These Inverto 17s could be explained by the factory upgrade service mentioned in "Staking Tools and How To Use Them". But it's hard to believe that all the older Inverto 17s were converted to the new punch frictioning mechanism. So where are the unconverted ones?
Maybe K&D never actually manufactured an Inverto with the older punch frictioning assembly. But why, then, go to such lengths in "Staking Tools and How To Use Them" to differentiate the Inverto 17 and Inverto 18 based punch frictioning mechanism?
Or, perhaps the two different types of punch frictioning assemblies look similar to each other, and neither look like the illustrations of the earlier design in the patents (see the references page) or on page 14 of "Staking Tools and How To Use Them".
I hope to get to the bottom of this some day.
On to the accessories.
As I mentioned on the Inverto 17 page, the above is consistent with the primary sources and documentation to which I have access, but it is not consistent with the Inverto products I've seen in the wild.
I've never seen an Inverto with the old style frictioning assembly. There are older, Hall design (non-Inverto) sets from K&D out there on which the heads look much like the Inverto design shown on page 14 of "Staking Tools and How To Use Them". But no Invertos.
Also, frames regularly appear on eBay that have both a knurled die binding disk marked "Inverto 17" and what appears to be the newer punch frictioning assembly. At least some of these have only the 1902 and 1908 patent markings on the underside of the frame, indicating that they are earlier production.
These Inverto 17s could be explained by the factory upgrade service mentioned in "Staking Tools and How To Use Them". But it's hard to believe that all the older Inverto 17s were converted to the new punch frictioning mechanism. So where are the unconverted ones?
Maybe K&D never actually manufactured an Inverto with the older punch frictioning assembly. But why, then, go to such lengths in "Staking Tools and How To Use Them" to differentiate the Inverto 17 and Inverto 18 based punch frictioning mechanism?
Or, perhaps the two different types of punch frictioning assemblies look similar to each other, and neither look like the illustrations of the earlier design in the patents (see the references page) or on page 14 of "Staking Tools and How To Use Them".
I hope to get to the bottom of this some day.
On to the accessories.
The stakes and stumps originally included in the early Inverto 18 staking tools are described in detail in "Staking Tools and How To Use Them" on pages 32-33.
"Originally included" is the operative term here. Because many staking sets are most of a century old, few found today are complete and in their original configuration. |
The information in the 1910 K&D book is explicit for the stakes because the stakes are numbered in addition to being described. Figuring out the stumps is a bit more difficult as they have no markings. After a bunch of searching, I turned up a Google book called "The Jeweler's Circular" for 1919. It's a bound copy of a trade magazine. In the Sept 3, 1919 issue, page 232 is a full page ad for the Inverto.
The cut on the left side of the ad shows a frame apparently identical to the Inverto/Inverto 17 shown nine years earlier in "Staking Tools and How To Use Them". The cut for the complete tool on the right is titled "Inverto 18 with Improved Box". The improvement includes the auto-tilting tool block like my Inverto 18 has. It also clearly shows a frame with the later punch frictioning assembly design. The Google scan is reasonably high resolution, so it was possible to zoom in on the cut and see the actual layout of the stumps in the box...and it appears to match the list on page 33 of "Staking Tools and How To Use Them" exactly (see annotated image at right). It seems safe to conclude that these are the stumps that were included in at least the early Inverto 18 tools. |
One interesting detail about the picture in the Jeweler's Circular ad show above. The Inverto 18 shown in the cut on the right contains a small knurled pin spanner for removing the retaining screw in the center of the die plate. Its not visible in the ad, but the screw in the center of the plate has two small holes to match the studs in a pin spanner.
My Inverto 18 set doesn't have the same screw and didn't come with the spanner. There isn't even a hole in the box for one.
Presumably the Inverto/Inverto 17 models had this type of die binding mechanism and at some point after the Inverto 18 was introduced, the frame design changed. This was probably after 1919, based on the date of this ad. The change may have been associated with the K&D patent of 1925, which describes an improved die binding mechanism. My Inverto 18 has a 1925 patent date stamped on the bottom of the frame.
My Inverto 18 set doesn't have the same screw and didn't come with the spanner. There isn't even a hole in the box for one.
Presumably the Inverto/Inverto 17 models had this type of die binding mechanism and at some point after the Inverto 18 was introduced, the frame design changed. This was probably after 1919, based on the date of this ad. The change may have been associated with the K&D patent of 1925, which describes an improved die binding mechanism. My Inverto 18 has a 1925 patent date stamped on the bottom of the frame.
One of the unique aspects of the earliest Inverto models, including the early Inverto 18s, was the inclusion of a set of ten screw knocking sub-punches that look like short stakes. These are hardened steel punches designed to force a broken steel screw out of a brass watch plate/part.
The sub-punches fit in to the top row of the box, where the holes are drilled less deeply than the others to accommodate the shorter sub-punches.
The sub-punches in my Inverto 18 set are all broken, and it's hard to know exactly how they worked from just looking at the wreckage. One end of each broken punch has a XXXmm diameter center hole about XXXmm deep. The other end has the remains of a smaller diameter shaft which was integral to the punch.
The sub-punches fit in to the top row of the box, where the holes are drilled less deeply than the others to accommodate the shorter sub-punches.
The sub-punches in my Inverto 18 set are all broken, and it's hard to know exactly how they worked from just looking at the wreckage. One end of each broken punch has a XXXmm diameter center hole about XXXmm deep. The other end has the remains of a smaller diameter shaft which was integral to the punch.
Based on pictures of other Inverto 17 and Inverto 18 sets from eBay auctions, it appears that one end of each sub-punch has a hole in it, into which a hardened punch tip of the required diameter was pressed. The other end has a stubby shaft meant to fit into a holder that extended the length of the sub-punch to the typical length of a stake so it would fit in the staking tool frame.
The description of the Inverto from a 1923 advertisement supports this interpretation of the design: "...it also includes something entirely new in the punches for knocking out broken screws, etc. These punches are most frequently broken, for the strain put on them is often very severe. The new punch is so made that the part which gets broken is interchangeable. These pieces (sub-punches) may be instantly changed without tools. There is furnished with each holder 10 sub-punches, graduated sizes. These sub-punches are comparatively small, easily made, and of small cost if one wishes to buy them. This punch alone is a great addition to any staking tool equipment." |
Simply replacing a hardened tip when it was broken in use seems like a convenient way to maintain a set of screw knocking punches, but including all of the sub-punch "holders" must have been an expensive feature for the staking set.
The high cost of the original design likely explains why this type of sub-punch was later replaced with the No. 316 set of 10 screw knocking punches and No. 120 holder. The ten punches range from 0.005" - 0.050" by 0.005" increments. Presumably, the individual punches were available separately if broken. These sets appear from time to time on eBay. Image at left courtesy of eBay seller christies_watches. |
I've never been able to find pictures or a definitive description of the holder for the old style screw knocking punches. On page 33 of "Staking Tools and How To Use Them" (see above), the holder is referred to as No. 120, which is the same number as the modern version of the screw knocking punch holder included in the No. 316 set. Might the exact same holder design have been used for such different punch designs? Or perhaps the design of the No. 120 changed when the punch design changed.
Standard Accessories - 1937 Sets With New Frame Design
By 1937, the design of the staking frame for the Inverto 18 as well as the set contents had evolved. The changes are documented in the 1937 Inverto 18 brochure.
The new frame design featured a "floating die and cut away front". All future configurations of the Inverto tools (18B, 18R, 18L, 600 series, etc) employed a frame of this type. Presumably this floating die design is an implementation of the invention patented in the 1925 Inverto patent. The cut away front is touted as simplifying the mechanism for removing inverted punches and, in combination with the floating die, making it more convenient to use the "Inverto" feature of the tool. Other changes include an increase in the number of stakes to 130 and the elimination of the rising block to organize the stakes and stumps in the box. Tables containing detailed stake and stump lists are available at screen resolution at left. High resolution pdfs for download are available at right. |
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Inverto 17A & 18A
K&D offered their various staking tool sets in practical wooden boxes for the bench, or showy round bases with glass domes, presumably for display in areas where customers might see them.
The 17A and 18A are standard Inverto 17 and 18 sets on the showy bases. Page 18 from "Staking Tools and How to Use Them" does send a mixed message to K&D's customers. "We'll sell you this if you want it but we don't recommend it" isn't much of a promotional message for a product. |