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Making a straight edge, need some advice

marino1310

Plastic
Joined
Aug 16, 2017
So I cant afford a normal straight edge from the usual suspects so I decided to try and make my own. I can get a 2 1/8"x5"x24" piece of grey cast iron from Mcmaster for $160 and in was thinking of using that and a thinner piece of iron to make a "bride" over the top and weld it in place before machining and scraping it. Any idea if this would cause problems? Also, any suggestions on different ways to make a straight edge?

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A straight edge needs to be stress free to be stable in use. Welding introduces stress. Would avoid. You also would want a straight edge to handle well in use. To be able to feel hinge points etc. For a 24” long straight edge I think the best casting currently on the market is Richard King’s HKA 24. For an 18” I prefer Denis Foster’s prism design. Denis’ prism is also designed to hold a bubble level.

I’d suggest spending some money up front for a stress relieved proven design casting. They are cheap compared with the amount of time you’ll spend rescraping, time and time again an unstable chunk of iron.

L7
 
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Not to mention that welding cast iron isn't trivial and if by "iron" you mean something like steel for you bridge you'll have more challenges. Brazing would work, but you still face heat induced stresses that can't be eliminated with the usual cast iron stress relief without melting the braze. And you may have some differential coefficient of expansion issues.
 
Not to mention that welding cast iron isn't trivial and if by "iron" you mean something like steel for you bridge you'll have more challenges. Brazing would work, but you still face heat induced stresses that can't be eliminated with the usual cast iron stress relief without melting the braze. And you may have some differential coefficient of expansion issues.
I have a friend that works at a welding shop who's welded cast iron cracks for me in the past so I have faith in his skills, but stress releaving is a different issue. How would I go about it?

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Well aware cast iron can be welded. No expert here, but I’ve done it. Wouldn’t dare try to weld/heat treat/stress relieve a straight edge. They take plenty enough time to scrape and maintain if properly made from a casting. Why reinvent the wheel? Again, I’m no expert, I’ve only scraped six SE’s and used 10, maybe 12 others. And use mine weekly.

I’m sounding more and more like my Dad...

L7
 
If you are cash strapped I would suggest skipping the buying from mcmaster part. Hit the scrap yards and find a table off of an old bridgeport or a bed section from a lathe as your straight edge material. Not only will it be cheaper than $140, you will get plenty of material to practice on.
 
People have made their own straight edges before, but from what I've seen, the most success has been with using one solid piece and getting it stress relieved after all the major cutting is done. Sometimes it even takes a couple rounds of stress relief, more cutting, and more stress relief, to get it normalized.

If you use the 2 1/8" x 24" piece, I wouldn't add anything to it. Use the 2 1/8" side as your working face, then the 5" height will give it some stability. You can still print a wider surface with it and if you know how to map the separate printings together, you'll be better off than taking one questionable print.

As far as welding one together. I've never worked with one, but typically breaks and cracks are big red flags when shopping for straight edges, even if they've been repaired. If I broke one of mine(:vomit::ill:), I might try welding it back together, but I'm afraid I would always doubt it's readings.

For $160, I'd be patient and look for a good used SE, but for that much you're not far off from getting a small un-machined casting. You'll still have a lot of work to finish it, but it'll be without all the unknowns that potentially come with a DIY straight edge's geometry.

Also remember, if you intend to rebuild a machine(s), you'll probably need more than just one straight edge, and you'll for sure need to know that they are reliable. Sometimes It's better to save up and get the right stuff the first time, rather than go cheaper and end up loosing twice as much in the long run. You'd be better to invest in a 12" or 18" SE now, use it to hone your skills, and save up for bigger ones as needed.
 
Well aware cast iron can be welded. No expert here, but I’ve done it. Wouldn’t dare try to weld/heat treat/stress relieve a straight edge. They take plenty enough time to scrape and maintain if properly made from a casting. Why reinvent the wheel? Again, I’m no expert, I’ve only scraped six SE’s and used 10, maybe 12 others. And use mine weekly.

I’m sounding more and more like my Dad...

L7
Any good sources on where to buy them? I cant afford the king way stuff, I dont know if theres other suppliers though but google doesnt show much

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Mc Master adds quite a bit of markup on their cast barstock. Check out Versa bar, they have a warehouse in Wisconsin. They are happy to sell you one piece.

Or buy a Kingway casting.
 
So I cant afford a normal straight edge from the usual suspects so I decided to try and make my own. I can get a 2 1/8"x5"x24" piece of grey cast iron from Mcmaster for $160 and in was thinking of using that and a thinner piece of iron to make a "bride" over the top and weld it in place before machining and scraping it. Any idea if this would cause problems? Also, any suggestions on different ways to make a straight edge?

Surely: "Not at all!"

Need of deep section, then azures for lightening is HIGHLY proportional to o/a length.

At 24" and below? Yah do not necessarily NEED the tall, windowed "camelback" styles. Unless... the SE is going to be transported, knocked around a great deal, etc, in a highly active service.

Should be able to find a used 24" to 30" ready-made for what you cite for raw iron, or now and then a good deal LESS. Parallel-sided with azures - or even solid, and not all that thick - is OK in that short a length.

Doesn't need to be a tall camelback.

THEN yah re-scrape it.

If even it NEEDS that.

And yah know in advance it is worth the effort and will hold what you put into it for long years.

I'm pleased to own Denis Foster's lovely goods. But I'm old. Didn't have anything that nice when younger.

Start cheap. Struggle with lesser goods. Learn what matters and what yah can and cannot do with them.

Grow into a higher level of skill and understanding. But don't bust the budget, Day ONE. You need a decent surface plate, too. And more.

THEN chase "the good stuff" as opportunity for a good deal crosses your radar. PM, even, as other members finish their projects, clear out duplicates, change direction, wind-down a shop and such. Not long ago sold a 30" I had bought FROM a PM member TO another PM member.. when my latest Denis Foster arrived..

Here's "cheap" - surely NOT "legendary" - but sumthin' yah can "bootstrap" yerself up off of for a saner start than "welding":

Precision 4-Sided Machinist Straight Edge 200mm / 7.87". 741685158135 | eBay

Longer ones in triangular and parallel are "out there". Former East Bloc, India as well as China. I have a vintage East German and a Ukrainian-made, via Moldova, that are value for money. Poles made nice goods, too. My long B&S may be older even than I am. Mighty light in weight after as many times as it has been refinished!


2CW ....and a whole dam' TRIBE of various straight edges!

Which ones see the most use?

The LIGHTEST ones, of course. A brand-new I-Gaging ignorant steel rule!

I don't really kid myself I can split tenths. Nor have any pressing NEED to do.

Best SE in the world ain't gonna push the scraper blade for yah.

Good blade, handle, and grind, second-rate SE might git 'er done faster than a bitchin' good SE and a shit-lousy scraper, yah?

Master the scraping part first, and wuddn' yah know it? Greasy eyeball lands on that second-rate SE, "SE" becomes the grin on yer face as yah IMPROVE the truant sumbich by yer own hand!

:)
 
Surely: "Not at all!"

Need of deep section, then azures for lightening is HIGHLY proportional to o/a length.

At 24" and below? Yah do not necessarily NEED the tall, windowed "camelback" styles. Unless... the SE is going to be transported, knocked around a great deal, etc, in a highly active service.

Should be able to find a used 24" to 30" ready-made for what you cite for raw iron, or now and then a good deal LESS. Parallel-sided with azures - or even solid, and not all that thick - is OK in that short a length.

Doesn't need to be a tall camelback.

THEN yah re-scrape it.

If even it NEEDS that.

And yah know in advance it is worth the effort and will hold what you put into it for long years.

I'm pleased to own Denis Foster's lovely goods. But I'm old. Didn't have anything that nice when younger.

Start cheap. Struggle with lesser goods. Learn what matters and what yah can and cannot do with them.

Grow into a higher level of skill and understanding. But don't bust the budget, Day ONE. You need a decent surface plate, too. And more.

THEN chase "the good stuff" as opportunity for a good deal crosses your radar. PM, even, as other members finish their projects, clear out duplicates, change direction, wind-down a shop and such.

Here's "cheap" - surely NOT "legendary" - but sumthin' yah can "bootstrap" yerself up off of for a saner start than "welding":

Precision 4-Sided Machinist Straight Edge 200mm / 7.87". 741685158135 | eBay

2CW ....and a whole dam' TRIBE of various straight edges!

Which ones see the most use?

The LIGHTEST ones, of course. An ignorant Igaging steel rule!

I don't really kid myself I can split tenths. Nor have any pressing NEED to do.

:)
I have no issue scraping my own. Any recommendations on where I can find some blank castings? Almost every one I find is scraped already so price shoots up

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I have no issue scraping my own. Any recommendations on where I can find some blank castings? Almost every one I find is scraped already so price shoots up

I think you are putting too much emphasis on initial outlay and not enough on what you GET from what is actually a quite reasonable spend for the long years of service a(ny) SE can deliver.

Think of a(ny) used, but recognized / name-brand SE as something you "rent"- initial cost amortized over several years. Then yah can sell it for a decent price, seldom any loss to it, now and then a modest profit.

Unless you plan to have it buried with you as "grave goods"?

As to "finding" blank castings?

Denis Foster "finds" his own castings, but it is clearly a "labour of love" for the TIME he has put into "getting there" vs his sell price!

I buy 'em as much as an investment in "legend" as anything else.

Cheaper, more durable - and take up less space than a Bentley Arnage "Red Label".

:)
 
The OP asked about castings: Richard King and Denis Foster are on PM and would likely respond to private messages. I’ve purchased from both and found their prices very reasonable. How much do you think it would cost you in time and/or money to make your own pattern, get it cast, and heat treat it? Or chop a much less user friendly chunk of Fe out of an old lathe bed or mill?

I’m not sure there’s anyone else making SE castings right now. There was a guy in Washington state who made 18”, 36” and a 54” Straight edges but not sure if he’s still making them. There’s also Stephen Thomas who made a very nice 30” SE, but you can do a search on PM for the history of those patterns..

I trust the OP realizes one straight edge casting is just the start down this rabbit hole. Then come right angles, cylindrical squares, levels, different length SE’s etc... And all are fun to make/modify and use!

Lucky7
 
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So I cant afford a normal straight edge from the usual suspects so I decided to try and make my own. I can get a 2 1/8"x5"x24" piece of grey cast iron from Mcmaster for $160 and in was thinking of using that and a thinner piece of iron to make a "bride" over the top and weld it in place before machining and scraping it. Any idea if this would cause problems? Also, any suggestions on different ways to make a straight edge?

Sent from my SM-N950U using Tapatalk

Here is what I use to stress relieve edges... It is not cheap but it is easy to use and controls the temps very well. I use the method recommended by the US Navy Study and bring the edge up to 1050 degrees for one hour per inch of thickness and then slowly bring it back to room temp.


I now stress relieve when I receive a edge, plane it to size, stress relieve it again and then back to the planer for final planing.

I have been told that stress relieving is a one shot deal and I just don't understand the concept. What I do understand is at the tolerances we are shooting for cast iron moves just by looking at it!
 
As for welding the handle to the bar you want to use... Here is a video of the way I found to weld cast iron with no pre or post heating... It works very well.

I have repaired a side wall defect in an edge and found it to blend in very well. It is a little brighter than the cast iron in appearance. It is also harder that the cast iron and is similar to the hardness of the edge surface after casting and stress relieving treatments. Once you plane through the hard layer cast iron is much softer. The weld material is NOT and stays hard.

The planer cutting tool does not like the sudden change in material hardness and jumps a bit when it passes through the area. IF you are careful and just weld the strap to the back of your improvised edge you should not be bothered by this.

I did stress relieve the edge after the welding repair and found that the weld material was a bit softer.

You will need to stress relieve the materials both before and after the welding procedure. If the material is cast you will probably need to stress relieve after the first machining operation.

 
What are you going to use to machine and test the edge after you put it together? A bridgeport will machine a 24" but it's going to be hard if the machine is not tight. You will probably have to machine a little and then test and maybe even step machine the part to get it close enough to test.

I use another edge to test the edges I'm planing mainly because I have them and it is easy. Another benefit is I don't have to remove the edge from the planer for testing. If you can't borrow an edge a surface plate will be needed.

Here is a video that shows how to test the surface of your edge using a cigarette paper. You would do the same method on a surface plate.

 
Frankly if I were going to try to make a straight edge I would look into buying a piece of Dura Bar 2" thick 24" long and 5" wide... Then take away anything that does not look like a straight edge on a mill.....

Then I would make some type of insulated box and use three or four electric milkhouse heaters to see if I could get the temp up to 1050 degrees. Enough heaters would do it, if they did not turn off from over temp... It would be a fun project, if a project is what you are after...

Good luck :)
 
Looks good Steve. I am offering a 10% discount on all my Straight-edges during the shut in....I can send a skid of SE's down to Steve's Or UPS them. Shoot me a note if your interested. Stay Safe everyone. Rich
 
The OP asked about castings: Richard King and Denis Foster are on PM and would likely respond to private messages. I’ve purchased from both and found their prices very reasonable. How much do you think it would cost you in time and/or money to make your own pattern, get it cast, and heat treat it? Or chop a much less user friendly chunk of Fe out of an old lathe bed or mill?

I’m not sure there’s anyone else making SE castings right now. There was a guy in Washington state who made 18”, 36” and a 54” Straight edges but not sure if he’s still making them. There’s also Stephen Thomas who made a very nice 30” SE, but you can do a search on PM for the history of those patterns..

I trust the OP realizes one straight edge casting is just the start down this rabbit hole. Then come right angles, cylindrical squares, levels, different length SE’s etc... And all are fun to make/modify and use!

Lucky7
I'm hoping I can make do with just a 24" lol. I do have a really nice 6x18 CHALLENGE angle block and a brown&Sharpe cylinder square. No idea where I got either but I do have them. I plan on scraping in the angle block however. My original plan was to cut a dovetail into one end of that and use that as an SE.

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Frankly if I were going to try to make a straight edge I would look into buying a piece of Dura Bar 2" thick 24" long and 5" wide... Then take away anything that does not look like a straight edge on a mill.....

Then I would make some type of insulated box and use three or four electric milkhouse heaters to see if I could get the temp up to 1050 degrees. Enough heaters would do it, if they did not turn off from over temp... It would be a fun project, if a project is what you are after...

Good luck :)
I have a 5 gallon bucket forge, dont think it can fit that but the forge at the makerspace does have a through passage, maybe I could heat it piece by piece?

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