Mk3 - How long are the #8 screws?

[Ty_Bower]

This is in regards to the original Dynaco Mark 3 (and probably the Mark 2 as well):

Does anyone know how long the #8-32 screws (used to mount the transformers and choke) are supposed to be? I know the exact length probably isn't terribly critical, but I'd like to be close.

I don't have one here with me to measure...

[TomMcNally]

I think I used 10/32's on my clones ... In any case, 3/8" or 1/2" are fine.
I like to use flat washers on top of the chassis. The loose stainless
Phillips from Ace Hardware are nice.

[Ty_Bower]

I was thinking 3/8" should be about right. That's what is in the parts list for the DIY ST-35 transformers.

Is stainless really necessary? I think the stock parts were just cheap zinc plated steel, and they were good for forty years. I'll be dead in another forty, so why stainless?

Any favorite places to order hardware online? Mouser doesn't seem to stock small hardware anymore, unless you want to buy stainless at over $5 a box. This place looks pretty easy: http://www.boltdepot.com

[TomMcNally]

The originals were chrome plated steel, and rusted pretty quickly,
to my eye, flat head zinc exudes cheesiness.

Stainless Phillips is just my personal preference, it looks sooooo much
better and adds a quality look. BoltDepot.com is pretty reasonable,
I got about $ 80 worth of stuff last time, # 4 for tube sockets, # 6
for misc stuff, # 8 for transformers.

Ace Hardware is cheap enough ... you only need about $ 10 worth.

[erichayes]

This is who I use for my bulk purchases, but they sell onesy-twosey as well, and they know WTF they're doing.

http://www.olander.com/catalog/index.ht ... index2.htm

[Ty_Bower]

Thanks for the tips. Maybe I'll give Olander a call tomorrow. I'm already up to $21 at Bolt Depot for stainless hardware. I tried the local store - they didn't even have the 4-40 stuff.

I checked the 8-32 screws used to mount the transformers to the chassis. The rusty old ones were indeed 3/8". All the lockwashers seem to be "inside star", except on the transformers' end bells. Those use "outside star". The screws on the transformers' end bells are #8-32, 2 1/2" long.

[TomMcNally]

Ty -

I forget what these nuts are called, but they are great.



They really speed assembly, and you rarely have to
hold them with tool, then grab and tighten easily.

[erichayes]

They're called kep, or keps nuts, depending on who you talk to. I mentioned this in another thread: if you order SS kepnuts, the nut will be SS, but the lockwasher probably won't be. Ask.

[TomMcNally]

The ones I got from Bolt Depot, in the picture, are all
stainless. I have gotten some zinc plated versions
packed up by Philmore before, reasonably priced.

[Ty_Bower]

Looking through the item descriptions at Bolt Depot, it seems that SS machine screws and nuts are typically of the 18-8 alloy, while SS star washers are of the 410 alloy. They describe the 410 alloy as "A stainless alloy harder than the 18-8, but not as resistant to corrosion as 18-8".

There must be some issue with the normal 18-8 alloy not being hard enough to make a good lock washer. Maybe that's why most SS kepnuts have a non-SS washer?