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I'm looking for what are apparently called flexible locknuts but I'm not having much luck. That is, I can find them in abundance but so far every one I've located is turned down to round on the slotted end rather than having the hex. Does anyone know of a source for new ones? These are Packard part number G451006 and are for my 1951 Henney-Packard but are also used in many other Packard applications.

This isn't a very good photo but it shows, just barely, the fine slots that are cut across it.

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Can't tell how deep the notches are but if they are deep for a cotter pin to lock, check out McMaster-Carr and their selection of castellated nuts. If the notches are shallow or very thin check out AMK products. Look in their bulk catalog on page 47.amkproducts.com/wp-content/uploads/Catalog_BulkFastener/BULK_39-54.pdf

These are not castellated nuts designed for cotter keys. The slots are very narrow allowing the nut to be pre-squeezed (hence the flex in their name) at the outer side which makes it vibration resistant.

Those on AMK Products are very similar but extremely expensive! I could probably have them made for less than that but it's place start so thank you! Those never came up in any of my searches.

These have many Packard applications including inside the Ultramatic but in my case they attach the driveshaft supports which is included in the last two entries in the capture below from the parts book:

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From what I can gather based on the link that Howard so kindly provided, these are called Marsden Nuts, a term I've never heard before now and should be commonly available if I can find someone who doesn't have huge minimum orders,

Marsden nuts were supposedly invented by a Packard employee and they gripped the bolt so tight that they wouldn't loosen. It has been a long time since I read about them.

Randy, perhaps you're thinking of Marsden Ware, a fairly prolific engineer for Packard with several patents to his credit. Here's a page from an article I published many moons ago about Packard's inventors and inventions, on this page Ware's has to do with valve rotation.

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Thanks for the clarification Dave. That is exactly the name I remember - (or didn't).

Fascinating! I had no idea that they'd been invented by a Packard engineer which makes me all the more keen to find them rather than using a plain nut and lockwasher.

Knowing what they're called, I've found quite a few but finding some actually in stock and for sale has been another problem. On the link that Howard provided, they were an outrageous 3 for $6.00 for a Pontiac water pump application and another fastener site that lists them for 44 cents but has none in stock said that they can get them for $3.45 each!

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I finally found some Marsden nuts and bought some in bulk. Still expensive buy as they're used in many places in Packards including in the Ultramatic I thought they might come in handy eventually!

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