Cast Iron Straight Edge

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 23/01/2019 13:28:15:

But then again they can probably click a button and much like FEA get a computer simulation of how a part may move.

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… and any informed engineering decision then gets over-ridden by the bean counters

MichaelG.

[Karl ManssonParticipant @karlmansson91253]

Hello!

A friend and I are looking to get smaller (30cm or so), knife edge cast iron straight edge castings. My friend has managed to locate a seller in the US but for many reasons I would prefer to get them from within the EU.

Does anyone know of a seller of either raw castings, semi finished or finished straight edges as per my description above?

Best regards

Karl

 

 

Edited By Neil Wyatt on 23/01/2019 16:44:44

[Karl ManssonParticipant @karlmansson91253]

I should add that my above post was posted as it’s own thread before it was kindly moved by Neil Wyatt. I have since read this thread.

[Anonymous]

Posted by Karl Mansson on 23/01/2019 15:32:31:

A friend and I are looking to get smaller (30cm or so), knife edge cast iron straight edge castings.

Just buy a length of standard rectangular cast iron and machine it from that.

Andrew

[David George 1Participant @davidgeorge1]

I used to machine parts for Bridgeport in my apprenticeship, the castings came in from the foundry across town Mansfield, then we checked fettling and roughed out on a planner or shaper. They were then taken outside and a date stamped on. We just left them outside in the rain, sun and snow to weather. They were left for up to 18 months but usually only a year. They came in to re-machining and although they were rusty it was only skin deep perhaps 15 to 20 thou. They were 're planed drilled and final ground for despatch to Leicester.

David

[Pete RimmerParticipant @peterimmer30576]

I did that, it bent like a banana though I did try to mill it from round, not square. I then got hold of some dovetail pieces which were slideways off an old machine and scraped one of those as a prism for doing cross-slide dovetails. That worked well but 6 months later it had developed a 2 tenths bend. Didn't take much scraping to fix it but I remind myself to check it on my plate each time I get it out to use it.

Edited By Pete Rimmer on 23/01/2019 19:17:28

[Karl ManssonParticipant @karlmansson91253]

Both are good suggestions but I wouldn’t know where to get either. I don’t know of any larger machine being scrapped and none of the Swedish metal vendors I’ve come in contact with carries cast iron in bar stock. Any suggestions for the UK market? Germany?

[Nigel McBurney 1Participant @nigelmcburney1]

Natural "weathering ' iron castings was a very good way of stress relieving iron castings there was the daily temperature cycle and then the annual cycle from winter to summer temperature cycle,this produced very stable casting in good quality iron and was quite common practice 50 years ago, the very best makers of precision tools would leave them out longer,iwas informed jig borer makers would leave them up to 3 years, its no good telling the buyer of a very expensive tool expected to be accurate to within 2 tenths of a thou over the capacity of the machine that its not as accurate as specified because the accountants did not like the slow procees,I once was in technical contact with a swiss jig boring company,their machines had a normal life of 40 years before reconditioning was reqired ,when a borer table was machined and scaped in a minimum of 3 millimeters was machined from the table as it was found that a stress was built up in the surface of the table dues to years of clamping work to the table and they found that it was essential to remove a least 3mm to remove this local stress.The company where I did my training made a range of optical benches up to 2 metere long and these castings spent a long time in the stores prior to machining and were used in a first in first out arrangement. The problem with car cylinder blocks is that the bores tend to go out of round as the motor industry did very little in in stabilising the castings in the 1960s it was found that if the cylinder head of one popular car was removed for say a decoke ,some of the engines would tend to burn oil,and it was believed at the time that the removal of the head removed a clamping force ,the block relaxed and the internal stresses released tended to cause bore ovality.When of a visit to Massey Fergusson at Coventry I found that there was no stress relieving of the iron castings,but on the other hand ,all steel bar material and steel forgings were stress relieved at red heat and there were massive chain bed furnaces which must have cost a fortune to run. Years later I was involved in machining LM25 gravity die castings which had recieved a very precise heat treatment and the metalurgy was strictly controlled,plus machining was under temperature control, I found that even with this control about one in a hundred castings distorted slightly when the clamps were released after machining,I would add that the clamps were not causing the distortion,eliminating distortion caused by internal stress be relieved during machining can be a problem,Perhaps with modern very accurate manufacture very few assemblies are dismantled during the life of a product and a bolted up assembly has no chance to distort,Cars for instanceare now rarely decoked or totally stripped.

[Pete RimmerParticipant @peterimmer30576]

Posted by Karl Mansson on 23/01/2019 19:52:22:

Both are good suggestions but I wouldn’t know where to get either. I don’t know of any larger machine being scrapped and none of the Swedish metal vendors I’ve come in contact with carries cast iron in bar stock. Any suggestions for the UK market? Germany?

Last weekend I had a visit from a Norwegian friend who was over for the Ally Pally show and we were discussing this very thing (the difficulty in finding used straight edges). He told me that by far the easiest place he knew of to find cast iron straight edges was Sweden.

If you're in Sweden and struggling to find them I don't know what I would suggest.

Edited By Pete Rimmer on 23/01/2019 20:57:58

[Pete.Participant @pete-2]

Posted by Karl Mansson on 23/01/2019 19:52:22:

Both are good suggestions but I wouldn’t know where to get either. I don’t know of any larger machine being scrapped and none of the Swedish metal vendors I’ve come in contact with carries cast iron in bar stock. Any suggestions for the UK market? Germany?

One of the guys who has already commented on here messaged me regarding making castings as someone else asked him about this a month ago, Personally I'm after a bevel edged straight edge for the purpose of scraping ways, maybe 50cm/24inches something that sort of size, I'm waiting to hear from him to see if what I want is similar to the other request he had, if this is something that would interest you, I'm sure he could put your name down for one.

[Anonymous]

Cast iron rounds, squares and flats are readily available in the UK. I use M-Machine Metals in Darlington, but there are other suppliers. The material is often listed as GR17, or grade 250, about 17 tons per square inch tensile strength.

Going to get spendy if you want 24" (60cm) rather than the originally mentioned 30cm.

Andrew

[Pete RimmerParticipant @peterimmer30576]

Another supplier is United Cast Bar they also do GD250. Call them up and talk to one of the sales team, they might have a piece on the shelf. They also have a Kendall milling machine so they can pre-finish any part you order. I bought 3 metres of iron bar from them for the scraping class and they did give a good service.

United Cast Bar (UK) Ltd
Spital Lane
Chesterfield
S41 0EX.
Telephone: 01246 201194
Fax: 01246 540434

[Pete.Participant @pete-2]

Posted by Pete Rimmer on 23/01/2019 23:22:42:

Another supplier is United Cast Bar they also do GD250. Call them up and talk to one of the sales team, they might have a piece on the shelf. They also have a Kendall milling machine so they can pre-finish any part you order. I bought 3 metres of iron bar from them for the scraping class and they did give a good service.

United Cast Bar (UK) Ltd
Spital Lane
Chesterfield
S41 0EX.
Telephone: 01246 201194
Fax: 01246 540434

I found a place 'west york steel' https://www.westyorkssteel.com/cast-iron-bar/ who have a variety of different grades of Iron Bar, if you're more enlightened on this subject than I, which grade would be most suitable for making into a straight edge? and why?

Anyone else feel free to enlighten me on this subject if you can

[Mike PooleParticipant @mikepoole82104]

So now we have sown doubt on the stability of anything made of cast iron what do you use as a dead cert reference? From anecdotes on this forum of granite distorting if not cared for correctly you will need to prove the truth of anything regarded as a standard.

Mike

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mike Poole on 23/01/2019 23:44:24:

So now we have sown doubt on the stability of anything made of cast iron what do you use as a dead cert reference?

.

An autocollimator may be the best we've got.

MichaelG.

[Pete RimmerParticipant @peterimmer30576]

Posted by Mike Poole on 23/01/2019 23:44:24:

So now we have sown doubt on the stability of anything made of cast iron what do you use as a dead cert reference? From anecdotes on this forum of granite distorting if not cared for correctly you will need to prove the truth of anything regarded as a standard.

Mike

The sensible person would always check their straight edges before use especially if there's been a long interval since last use. I have an as-new 48" cast iron straight edge that I don't use but check the others against. The only thing that tells me that this 48" is not moving is that the other straight edges all check against it. If one day one of them didn't, I would check another. Two straight edges are not going to move the same so the second check would identify which part has moved.

Really though if they are correctly stored a commercial straight edge should stay straight fairly indefinitely. It's tools you make from cast iron that you should be careful with checking before use. As for granite moving over time, I never experienced that nor met nor talked with anyone who did. worn, yes but warped no.

[Mike PooleParticipant @mikepoole82104]

Someone has posted a story on here of a granite slab surface table being leaned against a wall that distorted as it was not properly installed on its base. It was quite a big one if I remember correctly. I doubt that a normal workshop sized surface plate would be inclined to move whatever it’s orientation. When a CMM became redundant at work the part that had any interest from the machinery buyers was the cast iron bed slabs. They were rather large at about 5mx4m but I think the concrete to fill the hole in the floor cost more than they got for the bed slabs. Meanwhile back in the real world of my workshop I think I will just accept that my surface plate is flat and if my mics zero that will do and my slip gauges are the size marked. As I don’t have equipment to calibrate my tools or make anything where it matters if I’m out by a few 10ths I will muddle along in blissful ignorance. Calibration of the large CMMs at work involved a few days work and a mountain of flight cases with all sorts of clever laser stuff etc.

Mike

Edited By Mike Poole on 24/01/2019 09:21:08

[Swarf, Mostly!Participant @swarfmostly]

At the risk of going from the sublime to the ridiculous, here's a suggestion for anyone who has the time but not the money:

Find a neighbour who's disposing of an upright piano, the older the better. The one I dismantled (back in the 1970s ) had a cast iron frame on a wooden frame. The cast iron had a bell-shaped cross section, fairly suitable, I thought, for an engineer's level. Not out of the question for a straightedge either? The material I acquired from this source machined beautifully. The piano could easily have been fifty years old when it fell into my hands so aging was probably not a problem. I still have a piece about 24" long under my bench.

I never did make the base for the engineer's level – a complete level turned up in an estate disposal.

The material of the wooden frame was rather special too, softwood by definition but age hardened in condition, 4" x 5" in pieces four feet long and not a knot to be seen!!!

(Before I get accused of vandalism, the neighbours concerned had made long and valiant but unsuccessful efforts to find the piano a good musical home.)

Best regards,

Swarf, Mostly!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mike Poole on 24/01/2019 08:59:50:

… As I don’t have equipment to calibrate my tools or make anything where it matters if I’m out by a few 10ths I will muddle along in blissful ignorance. Calibration of the large CMMs at work involved a few days work and a mountain of flight cases with all sorts of clever laser stuff etc.

.

… Reality Check [Complete]

[Pete RimmerParticipant @peterimmer30576]

Posted by Mike Poole on 24/01/2019 08:59:

As I don’t have equipment to calibrate my tools or make anything where it matters if I’m out by a few 10ths I will muddle along in blissful ignorance. Calibration of the large CMMs at work involved a few days work and a mountain of flight cases with all sorts of clever laser stuff etc.

Mike

Can't argue with that philosophy Mike. You work with what you got and there's often an enormous gap between perfect and adequate. You wouldn't strip and scrape a machine for 2 or 3 tenths wear so if that's the best your tools can get it you're no worse off than if it was that much worn.

[Anthony KnightsParticipant @anthonyknights16741]

On the subject of accuracy, I use HSS tool blanks as parallels when required. I just wonder how accurate these are compared to purpose made parallels?

[Pete RimmerParticipant @peterimmer30576]

Posted by Anthony Knights on 24/01/2019 11:15:19:

On the subject of accuracy, I use HSS tool blanks as parallels when required. I just wonder how accurate these are compared to purpose made parallels?

VERY variable Anthony. Rarely a perfect square and often not even square-sided. Ok for rough stuff but I'd put a mic across each end of each pair to check they are actually parallel.

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