Straight Edge Scraping Questions

Check out Standridge for good prices on granite, they are on the same coastline as you at least. https://standridgegranite.com/forms/catalog-price-list

Splurge for a AA, once you've scrapped a few things and really understand hinge you will be glad you spent the money. I messed around with a bad Mitutoyo plate for too long, it was convex by a half a thou, parts would not hinge the same anywhere on the plate. Once i bought a nice plate thing were more repeatable and i didn't waste time. The plate you have is a Busch bench plate, their tolerances were listed to be something like+/-.0005 flatness, that's not bad but it's enough to confuse a scraper hand.

I first started off with small prism style straight edges like you have as that's what was easy to make. They are difficult to spot repeatably as they are flimsy and are very temperature sensitive. If you're scraping a compound, make a short prism that's like an inch longer than the way. It will be less flimsy and less surface to spot and scrape. The longer length prism's sag quite a bit, so you must be careful as others have mentioned.

Rich's comment about .0005 off being better than .005" off is spot on. We are all after tenths when sometimes a half thou is fine.

One thing to add when shopping for a surface plate: IMO the real value in a "good" granite surface plate has less to do with it's composition or country of origin and more to do with how flat it was made. Buying a new plate you should receive a certification with it that tells you what was done to it. I have my doubts about how good cheap import plates are, but if it was certified, it's better than a name-brand plate with questionable certs. That said, it may be good for you to find where your nearest accredited metrology lab is as someday (depending on your usage), you may need or want to get your plate recertified. It all goes back to the pitfalls of making assumtions. Like so many other machining operations, the more you can nail down as fact, the better your results will be.

Now your iron plate may still make for a good plate. IMO the construction underneath doesn't lend itself to supporting a precision surface, but iron plates can be resurfaced same as any other piece of iron you scrape with simpler tools than granite.

A good cast iron plate with 3 points and a lot of ribbing was designed to be flipped over to scrape smaller plates, colums on Mills or table tops. The Bench plate he has is not good for flipping. I suggested he add some jack screws and stand cross members to help support the plate. He won't be ale to use the Airy points but he said he has a Starrett 199 level that he can use to map the plate and set something on the plate and watch the level bubble to see if it moves. Be sure not to walk around the plate as it looks like your working in your garage, so the floor is probably thin and the floor will sag. In the classes I have the lightest student watch the bubble and then have the class walk around the plate and the student watching can see the bubble move. Do you have heat in your garage? I think under your circumstance your doing a bang up job.

You're experiencing a learning and cash curve. We had a member who had a lot of scraping tools in BC just north of Vancouver named Shane Carr and his PM name was Collector. He took 2 of my classes too. I don't know if he still comes to the forum. Email me and I'll forward it to him as I have his email and phone number. [email protected]

Shane retired and is on the island now. Great guy.

I took a suggestion from someone here and scraped in a worn 10”x30“ cast iron plate and use it as my daily driver for smaller work.

Peter. said:

A Grade AA plate used for scraping won't be AA for long. You could content yourself with a grade A or even a B at your stage of learning.
I true my own plates and I was amazed at the change in one plate after I had used it to scrape in a single cast iron straight edge from planed to finished. It had a pronounced dip in it, easily spotted with just a run-over of the lapping plate.

Click to expand...

Interesting comment, I never realized that this was an issue. Is this a well known problem?

The iron alone wouldn’t abrade granite, it must be leftover abrasive from stoning between cycles. What are you stoning with and how are you cleaning after stoning? Just curious and wondering if I need to change my own process.

Richard King said:

A good cast iron plate with 3 points and a lot of ribbing was designed to be flipped over to scrape smaller plates, colums on Mills or table tops. The Bench plate he has is not good for flipping. I suggested he add some jack screws and stand cross members to help support the plate. He won't be ale to use the Airy points but he said he has a Starrett 199 level that he can use to map the plate and set something on the plate and watch the level bubble to see if it moves. Be sure not to walk around the plate as it looks like your working in your garage, so the floor is probably thin and the floor will sag. In the classes I have the lightest student watch the bubble and then have the class walk around the plate and the student watching can see the bubble move. Do you have heat in your garage? I think under your circumstance your doing a bang up job.

You're experiencing a learning and cash curve. We had a member who had a lot of scraping tools in BC just north of Vancouver named Shane Carr and his PM name was Collector. He took 2 of my classes too. I don't know if he still comes to the forum. Email me and I'll forward it to him as I have his email and phone number. [email protected]

Click to expand...

I ordered an AA plate today. 6 week lead time but it will be here around about the time I get back from visiting my family in Australia (way more expensive than a surface plate lol)

I'm working out of a 20x60ft commercial bay. I keep it around 10*c. The floor doesn't seem too bad, I have jack bolts under the stand legs too. My monarch lathe hasn't moved noticeably in a month since getting it leveled.

Id like to get some more machining work now I have a bit more capacity in my shop, but the other part of me doesn't want to. Currently I run a service truck, doing heavy equipment and industrial mechanic type work, along with the odd line-boring job. It's a lot less bullshit business wise than what I remember from working in general machine shops. None of my work is quoted, just charged by the hour. The trade off having to lay in the mud/snow/side of the highway!

Machine rebuilding would be a great trade, and something I always wanted to do once I read Connelly's book. When I was an apprentice in Australia I looked pretty hard for places to work to learn handscraping etc, but for memory there was only a couple of machine tool rebuilders in the country and none in Melbourne where I was living, plus none hired me obviously (smart move on there part; I was an 18 year-old shit head).

It only took 11 years but hey better late than never.

I got the flat side to where I'm going to call finished. I'm going to get some castings from Denis, so I will save the time and energy to use on them.




Started on finishing the bevel side to find out it still had a big bow in the front face (thanks previous me) . The excess weight on one side made it pretty hard to spot this accurately and I regret not taking some weight out of it.



I circled the section where I have scratches in the middle of roughing strokes running with the stroke. This only happens in durabar. What is the likely cause? I sorted out most of the blade magnetism by rapping it on the bench


Still got a little bit left to finish bevel side but I think I'm going to take a break for a day or 2 as I might have little bit of scrape-brain. I don't need this edge to spot with for the cross slide ways but I'm sort of committed to it now.



Also Richard I am using Norton fine India knife stones for deburring, a little smaller physical size than the part number you recommend. Is it an acceptable method to stone excessively/use a burr file in initial scraping passes or a bad idea?

One of these makes quick work of magnetic build up on tools. Also, I mentioned before that it seemed like the 'parallel to stroke' scratches seemed to be caused by edge dullness in my testing, and a better lap should be tried (the disks are cheap!) The inserts you are using do not look like they are micro-polished on the large top and bottom faces that make one side of your cutting edge, you may want to lap those surfaces as well.

This fellow used to teach scraping classes in his shop north of Melbourne. He used to write here as Machtool until the troll drove him away.. The scraping looks better. Unless Dennis has updated his SE it will sag too. The one Lucky brought to the Bourn & Koch class sagged when we tested it. That was years ago, so he may have changed the design. I would suggest you buy a Gary Martin Camelback casting as they don't sag like non camelback prisms. I have never had issues with Dura-Bar, but I buy Grey Iron. Ductile is a pain to scrape and isn't as stable. I used to buy a square piece and had them cut the casting diagonal corner to corner. It would sag, but only a few tenths. If your down near Thomastown give Phil a call. He's a good Mate and I consider him a friend.

Phillip Fehring
P & L Machine Tools Pty. Lt
24 Bostock Court
Thomastown Victoria 3074
Australia
Tel: +613 9466 3655
Mob: 0412 555 326
[[email protected]][email protected]

One has to be careful with long stones. Set the stones on a flat surface (ground, granite or scraped and hinge the stone. 1 in 10 (I would think) are bent and not flat. When I have a long one like that I grind a grove around it and snap it in 1/2. Only stone lightly to remove the burr. I used to use a smooth cut file when I was a kid that we dulled on a wire wheel on a grinder. Have to grind down the tang on files as if they are bent, they scratch. I only file the sharp edges on parts now and use a tapered stone now. Norton MS-24. I also only use a wet stone every 5 or 6 times as they are to sharp when wet. Just want to remove the burr left from scraping. I also am not a fan of diamond ground stones as they are to dull. I have 2 sets, one made by Spencer Webb and one by Lance Baltzley who both are students too. I have used them when I'm scraping 30 + points, but never did until I tested them 5 years ago.

I use one of these to demagnetize blades and parts. https://www.mscdirect.com/product/details/09180019

Years ago I made them out of motor starter coils.

To be clear, I use Denis’s 36” camel back straight edge more than any of my other straight edges. I like it. It does NOT sag. What Richard saw, was me seeing how much it flexed under roughly 30 pounds of pressure. ALL materials will flex under pressure (including granite), I was only trying to quantify how much Denis’s new (at the time) lightweight flexes. From memory, it was about 1 tenth, with more pressure on it in one location than it that it ever sees in use. One tenth is far less than I expected, and his 36” camel back straight edge has turned out to be an excellent tool.

I would recommend, from my experience in using them, Denis’s 18” prism (which can also be a level) and his 36” camelback for your first two tools. The fact he will heat treat stress relieve and machine them at a very reasonable price is a bonus. I’m a happy customer of his and get nothing from recommendation. As a third (when you are able), Keith Rucker’s 9” or 12” for small work, if Richard still makes it, his 48” HKA (with dovetail) as your fourth. If Richard still uses the same foundry, make sure to high temp stress relieve well at least once after machining. These are the tools that I use and like. A pro could probably use crappy tools and make them work, but I’m just an amateur scraper, so I need tools that work well. Have fun!

Bakafish said:

View attachment 380224
One of these makes quick work of magnetic build up on tools. Also, I mentioned before that it seemed like the 'parallel to stroke' scratches seemed to be caused by edge dullness in my testing, and a better lap should be tried (the disks are cheap!) The inserts you are using do not look like they are micro-polished on the large top and bottom faces that make one side of your cutting edge, you may want to lap those surfaces as well.

Click to expand...

I am going to make a demagnetizer out of an ac motor windings. I need to demag my tailstock quill also. I tried wrapping a long extension cord around it but I think the magnetic flux is cancelled out not having the electrical phases separate.
I also ordered a bunch more lapping compound down to 1 micron -2000 grit so that should keep you happy lol

Lucky; I was going to get his 36" and 18 prism along with 2x 12" box parallels. He does good work and he is thorough. I don't think I will have any qualms.

lucky7 said:

To be clear, I use Denis’s 36” camel back straight edge more than any of my other straight edges. I like it. It does NOT sag. What Richard saw, was me seeing how much it flexed under roughly 30 pounds of pressure. ALL materials will flex under pressure (including granite), I was only trying to quantify how much Denis’s new (at the time) lightweight flexes. From memory, it was about 1 tenth, with more pressure on it in one location than it that it ever sees in use. One tenth is far less than I expected, and his 36” camel back straight edge has turned out to be an excellent tool.

I would recommend, from my experience in using them, Denis’s 18” prism (which can also be a level) and his 36” camelback for your first two tools. The fact he will heat treat stress relieve and machine them at a very reasonable price is a bonus. I’m a happy customer of his and get nothing from recommendation. As a third (when you are able), Keith Rucker’s 9” or 12” for small work, if Richard still makes it, his 48” HKA (with dovetail) as your fourth. If Richard still uses the same foundry, make sure to high temp stress relieve well at least once after machining. These are the tools that I use and like. A pro could probably use crappy tools and make them work, but I’m just an amateur scraper, so I need tools that work well. Have fun!

Click to expand...

“Unless Dennis has updated his SE it will sag too. The one Lucky brought to the Bourn & Koch class sagged when we tested it. That was years ago, so he may have changed the design. I would suggest you buy a Gary Martin Camelback casting as they don't sag like non camelback prisms.”

Lucky is right about the rigidity of my straight edge designs. I have tested every one of them and written up the results here. Everyone deflects less than .0001 when supported on 1-2-3 blocks placed at the extremes of their sole and the loaded in the center with an additional weight equal to or greater that of the straight edge in question. In actual use one would never subject It to such extreme loading.

This has all been thoroughly discussed here before. It is a mystery to me why such straw-man objections (there have been others) continue to be fabricated.

The stiffness issue is not hard to think through based on common experience. Most people know that a tube of a given diameter willl sag under its own weight less than a solid bar of the same material and diameter. So, the more a design cores out the center of its mass and preserves it in its “shell” the less self-induced sag it will produce. So, the more blocky a design is the more it sags under its own weight.

In actual use, self induced sag will rarely actually be a significant factor regardless further raising the question of why this objection continues to be ginned up.

I cast each and every straight edge myself in my one-man foundry using certified feedstock and careful attention to every step of the melting, pouring, and cooling process. Not a single casting ships without proper thermal stress relief in my furnaces that are digitally-controled, dedicated, monitored, and personally fabricated I have never had any purchaser report voids, hard spots, or any other concern regarding the quality or usability of my raw casting or machined castings.

Denis

jwearing said:

Interesting comment, I never realized that this was an issue. Is this a well known problem?

The iron alone wouldn’t abrade granite, it must be leftover abrasive from stoning between cycles. What are you stoning with and how are you cleaning after stoning? Just curious and wondering if I need to change my own process.

Click to expand...

I stone with the same type of stone most people use and I clean thoroughly. I have a pressure pot of brake cleaner and an endless supply of blue shop towel.

Have to say I was surprised at the amount of wear but it was there for sure. It was a Black Gabro stone I don't know how well they are regarded usually. I did do a LOT of scraping cycles though.

Richard gets tiresome with his vague and unsupported claims about sag. I notice he offers no data to support his claims. Bullshit is bullshit no matter how often its repeated. No more gaslighting, Richard. We in the metalworking trades depend on standards, objective data, known materials, and precision equipment and procedures to manufacture our products in conformance to plan dimensions and tolerances, on time, within budget. Nothing is left to chance.

I propose next scraping class where a King straightedge and a Foster straightedge are available that a side by side instrumented comparison be performed. The conditions are:

- both straightedges are cleaned and inspected and allowed several hours to reach thermal equalibrium.

- a thick granite surface plate or machine table is available sufficient in length to end support the straightedge under test.

- a Federal, Ames, Brown and Sharpe, Mirutoyo, etc electronic indicator capable of resolving 0.5 microns or 20 millionths of an inch and display is availabe for the test.

- the straight edge under test shall be end supported on 1-2-3 block and the electronic indicator set to "zero."

- a weight equal to the weight of the straightedge under test shall be placed on the center for its upper surface and any diflection registered by tbe electronic indicator noted.

- the weight shall be removed and the repeat zero verified.

- this test shall be performed on both the King and the Foster straighteges plus any other comparable straightedge on hand.

- acceptance criteria shall be 0.0001" or less indicated loaded deflection at center.

Dennis do you have a Paper showing what you claim? Forrest longtime no read. Again does the forum know you hired me to teach your emoloyee's to scrape 3 different times? Why did you hire me if your such an expert? I am helping the OP and made some points. I was standing behind Stan (Lucky) when he made the tests to the Foster SE in 2017 I saw the test. I was pointing out the error. I am sure the Foster SE is better then the Dura-a-bar.

lucky7 said:

To be clear, I use Denis’s 36” camel back straight edge more than any of my other straight edges. I like it. It does NOT sag. What Richard saw, was me seeing how much it flexed under roughly 30 pounds of pressure. ALL materials will flex under pressure (including granite), I was only trying to quantify how much Denis’s new (at the time) lightweight flexes. From memory, it was about 1 tenth, with more pressure on it in one location than it that it ever sees in use. One tenth is far less than I expected, and his 36” camel back straight edge has turned out to be an excellent tool.

I would recommend, from my experience in using them, Denis’s 18” prism (which can also be a level) and his 36” camelback for your first two tools. The fact he will heat treat stress relieve and machine them at a very reasonable price is a bonus. I’m a happy customer of his and get nothing from recommendation. As a third (when you are able), Keith Rucker’s 9” or 12” for small work, if Richard still makes it, his 48” HKA (with dovetail) as your fourth. If Richard still uses the same foundry, make sure to high temp stress relieve well at least once after machining. These are the tools that I use and like. A pro could probably use crappy tools and make them work, but I’m just an amateur scraper, so I need tools that work well. Have fun!

Click to expand...

I no longer make Straight-edges as it's hard to find foundries that make 1 at a time pours plus it's not worth all the effort. A small amount of money for the effort. I will be donating my wood patterns to Vintage Machinery (Keith Rucker) as he has a friend make his SE's . I have been telling people to buy Gary Martin straight edges as he is a professional pattern maker and works at a foundry. I never said Denis Foster Straight edges are bad. I have seen them change tenths and change after vibration stress relieving them. All SE's change when they are new, that's why you should always check ant type or brand before use.

Richard King said:

Dennis do you have a Paper showing what you claim? Forrest longtime no read. Again does the forum know you hired me to teach your emoloyee's to scrape 3 different times? Why did you hire me if your such an expert? I am helping the OP and made some points. I was standing behind Stan (Lucky) when he made the tests to the Foster SE in 2017 I saw the test. I was pointing out the error. I am sure the Foster SE is better then the Dura-a-bar. I don't see Forrest or Dennis teaching anything in this forum, just a lot of hot air.

Click to expand...

Richard,

I will try to stay on topic here and not go off on tangents.

Your memory must be short. Over the years, I have posted deflection test results here on this forum of every one of my designs (except the short little 8”) with clear reports of my setup and results. I have invited you on multiple occasions to do the same. You have not shown ANY test results of any of your SE's or any other designs.

Here is a link to the testing I posted here of my first design—the 36”


I have done similar testing and posted the results here on every subsequent design including my 30" box square (excepting the 8” prism—-it is so short and stubby that common sense indicated testing it just was not necessary.) But if you would think testing the 8 a key point, I could do it. ;-)

But in reality, the discussion is pointless as practically any SE I am aware of is quite stiff except for the long skinny prisms. Even so, as actually used, the stiffness of the prism is not likely to be a determinant of its suitability to the task. You know that and that was discussed ad nauseum in 2014 if you care to look back at the linked thread and threads contemporaneous to that one. Which brings me back to the mystery of why you keep taking swipes at my straight edges as "moving" or "deflecting" or "bending" with the implication that some other straight edges might therefore be a better choice.

I take great pride in the work that goes into the design and casting of my straight edges and take exception to unfounded criticism. I will continue to pipe up if groundless criticism is leveled at them. Your criticisms are totally unfounded. Show us your data,Richard. Where is the beef? as they say. Or is what you are saying just, in fact, a foul-smelling byproduct of beef production?

And with respect to the difficulties of getting competent work from foundries for small production work, I could not agree more. That is precisely why I decided to start pouring them myself. And that is how I have been able to maintain unmatched quality control. I know of no other supplier who actually does his own casting or provides a better product.

I regret muddying up this thread with this defense of my work. But I am not likely to idly stand by while my work is falsely called into question. The forum would be better off without that "stuff."

Denis

wildo said:

I also ordered a bunch more lapping compound down to 1 micron -2000 grit so that should keep you happy lol

Click to expand...

I'd be happier if you used a cheap electroplated lapping plate or resurfaced your lap because the picture of your lapping plate had massive circumferential grooves, and I'm worried its surface is creating ridges in the edge not visible to the naked eye. Those scratches are only fractions of a micron deep, and it's really easy to imagine how edge irregularities from the lapping surface or latent grits might cause the cutting edge to have teeth. I think it is more of an aesthetic issue, I don't think those scratches will really have an impact (and your scraping looks good even with them) but I like to understand the root cause of things before deciding they can be ignored or not

Although active demagnetizers are really simple and I'm sure there are a lot of DIY hacks out there, they should be approached with caution as most of the cost of the things is in designing them to not overheat or electrocute you. The one I pictured was a mess when I bought it used for a few bucks, but it cleaned up very nicely and with the new cord and switch I installed will last beyond my days... Get a good one and focus on the hard stuff.

Bakafish said:

I'd be happier if you used a cheap electroplated lapping plate or resurfaced your lap because the picture of your lapping plate had massive circumferential grooves, and I'm worried its surface is creating ridges in the edge not visible to the naked eye. Those scratches are only fractions of a micron deep, and it's really easy to imagine how edge irregularities from the lapping surface or latent grits might cause the cutting edge to have teeth. I think it is more of an aesthetic issue, I don't think those scratches will really have an impact (and your scraping looks good even with them) but I like to understand the root cause of things before deciding they can be ignored or not

Although active demagnetizers are really simple and I'm sure there are a lot of DIY hacks out there, they should be approached with caution as most of the cost of the things is in designing them to not overheat or electrocute you. The one I pictured was a mess when I bought it used for a few bucks, but it cleaned up very nicely and with the new cord and switch I installed will last beyond my days... Get a good one and focus on the hard stuff.

Click to expand...

its a groove in the lapping compound nothing to worry about. There shouldn't be contact between the lapping plate and the blade as there should film of lapping compound. You should try it out. It works pretty slick, just wipe compound off plate with wd40 and re-apply if you're changing grits. I have 15 and 10 micron right now thats why the finish isn't super fine. I expect I will get mirror finishes with the finer grits . I can take a skim cut lapping plate if it ever gets significant scratches or if you were really excited you could lap it



I wouldn't let anyone else use it, but it's quite safe aside from the coil winding insulation maybe not meeting spec for human handling. It's out of a 1200 watt angle grinder. The iron core is bonded to ground. Hot leg ran through coil. I plugged a 5 amp load into the other end.

Another one for my collection of naughty cords.

I could buy one, like I could buy a lapping plate, but I like messing around and finding new ways to re-use stuff. Half my shop is from the scrap yard, and the other half probably belongs in the scrap yard lol.