Cast Iron Straight Edge

Hi, does anyone know where you can buy cast straight edges, for the purpose of printing dye on to ways for scraping?

I found some companies selling them in India and China, but no retailers in the UK whatsoever.

Don't know of any new finished ones in the UK. There's a guy in the South West sells the odd casting for 12" dovetail straight edges and they are nice to scrape in but you'll have to machine all the working faces first.

Kblast straight edge

Other than that you can buy King castings off eBay but they also need machining, perhaps stress-relieving and then scraping to finish before you can call them good to use. You're looking at 400 quid for an un-machined casting, plus import and vat most likely.

Used ones are very thin on the ground.

I don't know how accurate these would be ??
**LINK**

PMed

Try Ian at Rotagrip.

Ketan at ARC

Better to get an old English made straight ,where the castings were allowed to "weather" to relieve the internal stress and were often rough machined and then left to stand for some time before final finishing,Using new "green" castings is not a good idea,Try the second hand tool dealers.

If you have deep pockets and long arms this guy has them

Edited By Pete Cordell on 21/01/2019 11:41:54

The need to weather cast-iron castings means the maker is using the wrong type of cast-iron! Cast-irons that don't need to be allowed to de-stress were developed in the USA during the 1920s and were widely used in Europe before WW2. (Meehanite etc).

Craftsmen often see weathering as a sign of care and quality; on the other hand it gives accountants and shareholders apoplexy! A hundred years ago it was costly to store items for months before they could be finished and sold. These days it's disproportionally even more expensive. I think a Production Manager would look carefully before agreeing to any process that made untoward weathering essential.

Of course, a big advantage of buying an old tool in good condition is that you know it isn't going to warp! Quite a lot of cast-iron is carp and for things like weights and street furniture it doesn't matter. With new cast-iron there's always the possibility of buying from a cowboy. A small foundry making small tools as a sideline might not bother with using the right alloy or weathering.

Dave

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Hi Barrie,

That's interesting. Do you happen to know why they did that? It seems an extreme way of eliminating warping. Presumably the advantage was that old crankcases have been put through a huge number of heat cycles between ambient and hot over a long time. Racing being extreme perhaps the idea was to select crankcases with absolutely no tendency to warp in an extra hot engine run flat out.

However, I stand by my comments about Production Managers - what's done to a Formula 1 engine isn't typical value engineering!

By the by, I'm not familiar with the reasoning behind Formula 1 engine design especially as it's changed over the years. Mostly I expect them to be using exotic materials for triple-extra go-faster performance and then discover the rules don't allow it! Can anyone explain what the state of the art for high-performance engines is, and what's allowed on the track?

Dave

They were using a very old design of engine!

I recall being told that good blocks from high mileage van engines were much sought after for building Top Fuel and Funny Car drag racing engines.

A reasonably lucid account of the BMW story, here: **LINK**

https://f30.bimmerpost.com/forums/showthread.php?t=1350137

MichaelG.

Edited By Michael Gilligan on 21/01/2019 18:08:50

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There are a couple of scraping straight edges on ebay at the moment.

Martin C

Maybe BMW engine castings are of poor quality

Neil

Raw straight edge castings need stress relieving. The HKA-x ones you see on ebay are King design and the finished ones they used to sell were stress relieved, rough-machined, stress relieved, machined then scraped, sometimes with a third round of stress relief thrown in. The ebay ones have one round of stress relief and are said to require no more but it's still possible they would move during machining.

Even old, previously-finished straight edges can develop a twist over time. I bought a 36" one which looked pretty good but had about half a thou of twist in it.

Edited By Brian Oldford on 21/01/2019 21:44:06

Thanks, the one in that link looks like what I'm after, do you know this seller?

So what is the process of 'stress relieving'? I was under the impression it was the casting being left for a period of time? you mention several rounds of stress relieving? what is involved in this?

Cheers.