11 replies to this topic

[datsun100a]

Does anyone know what the thread is on the end of the crank? I was pretty sure it was a unf thread but minipares quote it as a uns thread. I find it hard to believe that bl used an american thread form on a mini crankshaft.

[Dan]

Mate, UNF and UNC are American threadforms! We started using them when Britain and America had to start producing interchangeable parts during World War 2, that was called 'Unification', hence Unified thread. Before that the thread was called NF or NC and was American, the only change on unification was to round over the peaks as per British preference. British threads are called things like Whitworth, British Association and British Standard.

UNS is just a Unified threadform with a non standard pitch, each pitch being designed for each specific application for material or loading reasons. It's part of the UNF, UNEF, UNC family. As such, if the crank bolt is UNS you will have to work hard to find one outside of a Mini specialist. Which end of the crank are you talking about and what are you after? If you are lookiong a flywheel bolt tap they are available but because of the special pitch they cost a fortune.

[datsun100a]

Mate, UNF and UNC are American threadforms! We started using them when Britain and America had to start producing interchangeable parts during World War 2, that was called 'Unification', hence Unified thread. Before that the thread was called NF or NC and was American, the only change on unification was to round over the peaks as per British preference. British threads are called things like Whitworth, British Association and British Standard.

UNS is just a Unified threadform with a non standard pitch, each pitch being designed for each specific application for material or loading reasons. It's part of the UNF, UNEF, UNC family. As such, if the crank bolt is UNS you will have to work hard to find one outside of a Mini specialist. Which end of the crank are you talking about and what are you after? If you are lookiong a flywheel bolt tap they are available but because of the special pitch they cost a fortune.

Should have worded things a little better, I know about the unified thing ok(bs1580), it was just the fact that ns is not something I have come accross in all my years of working at british cars and it seems to have been a mainly american used thread format.

Flywheel side, the one that always gets chewed a bit

ta

[Dan]

Well if it is a tap you're looking for, as I said I know people who have bought them and they cost loads. I don't think they're hard to find, just expensive. Since it's UNS you'll have to quote the diameter and pitch to the supplier along with stating UNS because UNS threads are all different.

Edited by Dan, 17 September 2008 - 11:16 AM.

[datsun100a]

Well if it is a tap you're looking for, as I said I know people who have bought them and they cost loads. I don't think they're hard to find, just expensive. Since it's UNS you'll have to quote the diameter and pitch to the supplier along with stating UNS because UNS threads are all different.

Really trying to find out if someone can confirm that it is a ns thread and what tpi.

[Dan]

If you have a bolt there, measure the diameter and count the treads. If the pitch isn't standard for that diameter at UNF, UNEF or UNC then it's UN Special. Mini Spares are usually right though and I know this tap is a specific and expensive one to buy so I don't think it's a standard type at all.

[Ethel]

I'd ring round a few machine shops that deal with Minis it would be cheaper just to take your crank in if you can. Failing that they can tell you who they got there's off.

[Dan]

I've just checked and Mini Spares list the size right there on the page. It's 5/8 x 16 UNS. That's definitely a UNS pitch because at 5/8" UNC is 11, UNF is 18 and UNEF is 24. It'll probably be a UNS because the material the cranks are made from couldn't hold UNF and still develop enough load. Remember there's only room for quite a short drilling in order to avoid weakening the crank nose at the critical point where the taper sits.

Found one on this page. 5/8" x 16 UNS. £67.50 + Vat special order only. I said they weren't cheap.

Edited by Dan, 17 September 2008 - 11:59 AM.

[Rosslin Racing]

yes sir you have found a good one , when I built my own crank I had the same problem old swifty in kent has a cutter but was worried he might break it so he would not thread it for me, before hand I had looked high and low for a tap and die but no luck. good old Minispeed can and will cut it for you.

[dklawson]

I hate modern text speak, but... OMG!!! 68 GBP + VAT???

Normally I would NOT recommend a supplier in the U.S., but please consider contacting McMaster-Carr (www.mcmaster.com) .

I've already done the search there and these are their three 5/8-16 taps:
Profile Part No. Price
Taper 2595A303 $35.23
Plug 2595A304 $35.23
Bottoming 2595A305 $35.23

They do make international sales. It is up to you to contact them and find out what shipping would be to the U.K. However, their price for the taps works out to 20 GBP based on the current exchange rate. For that difference in price you could buy all three tapers and still be less expensive than the U.K. price... until you add shipping charges.

[datsun100a]

I hate modern text speak, but... OMG!!! 68 GBP + VAT???

Normally I would NOT recommend a supplier in the U.S., but please consider contacting McMaster-Carr (www.mcmaster.com) .

I've already done the search there and these are their three 5/8-16 taps:
Profile Part No. Price
Taper 2595A303 $35.23
Plug 2595A304 $35.23
Bottoming 2595A305 $35.23

They do make international sales. It is up to you to contact them and find out what shipping would be to the U.K. However, their price for the taps works out to 20 GBP based on the current exchange rate. For that difference in price you could buy all three tapers and still be less expensive than the U.K. price... until you add shipping charges.

Thanks for the help, think I will check out the american connection as it is much cheaper.

[Guess-Works.com]

When I get mine back, it's out on loan/rent at the mo, I'll happily let you borrow it for a small fee £10+p&p