The A and the B SPT Mounting Adapters are a fairly rare item but are sought after ones. The Jointer, Bandsaw and Sprayer (air pump) use the A Adapter while the Jig Saw and Belt Sander use the B Adapter. The Jig Saw can also use the A Adapter as it did when the first Power Mount Adapter Kit 11-800 came out only having the A Adapter. In the picture below are the parts of the later Power Mount Adapter Kit 11-920. The Mounting Posts shown in the kit are for the Jointer.
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Below as a PDF of the Power Mount Adapter Kit 11-920 instructions for anyone needing it.
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Power-Mount Adapter Kit 11-920 02-56.pdf
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Something I noticed in the drawing of the A Adapter is the depiction of the finished Adapter in the upper right corner that doesn't resemble the other drawings.
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I don't know how much interest there may be in getting an aftermarket adapter over an original one. There has been an aftermarket adapter made by MKC Tools in the past, but I don't know how many have been sold. Judging by the response so far, unfortunately there doesn't seem to be much interest. Sorry since it is a good idea for anyone wanting to use SPT's on their Model 10E or 10ER. The Model 10E and 10ER, even after over 70 years, are still popular Tools. Waiting to get an original adapter can take some time and they tend to bring a premium price. Depending on the cost of these adapters they can be a good alternative. As much as I do like the idea of these as an option, I have the complete Power Mount Adapter Kits 11-920 and 11-800 plus another A Adapter so I wouldn't be looking to buy your adapters.
Another item needed to use the SPT Adapters is the "special" Pulley with the cast on hub as seen in the first picture above on the right in the Power Mount Adapter Kit 11-920.
