Dykem Hi-spot

[Charles Lamont]

As noted the high spots should be bright with the low points filled In with blue. It is when you have a tiny difference between high and lows that contrast becomes a problem.

I beg to differ. Well actually, not to put too fine a point on it, that is utter rubbish.
1) You take a tiny amount of blue on the tip of your index finger and spread it, with the finger, evenly over the whole area of the surface plate.
2) The high spots on the workpiece touch and are marked with blue. The low areas don't touch and are left bare. 3) Scrape where the blue is.
4) Wipe off the work and redistribute the remaining blue on the plate, and repeat from 2
5) When the high spots are too faint, repeat from 1

 

[goldstar31]

Sorry to feel like stepping in but if the work to be scraped against a reference- be it a surface plate or other reference ( see Connolly) is blued, one scrapes the shiny excrescences and eventually one splits the single humps to achieve the 25 spots per square inch.
Connolly suggests a contrasting base of a brown oil paint to see better.

Of course this new diamond affair described for levelling worn oil stones should be fine for taking the fine burrs or arris raised when knocking the tops into a number of smaller crests.

So let's be constructive rather than destructive on other people's methods

Norman

 

[Hopper]

Not sure if I am misunderstanding what is being said, but it can depend too on the weight of the workpiece being moved back and forth on the blued surface plate, or how hard it is pushed down against the blued up surface plate. Under light pressure, blue will transfer from the surface plate to the high areas on the workpiece.

But under a bit more pressure or weight the very tips of those high areas will appear as a shiny metallic spot surrounded by blue. This is where the blue has been completely squeezed out and the high spot has made metal-to-metal contact with the surface plate.

I spent some years bedding-in press tooling for stamping out car body panels, roofs, bonnets, doors etc. One half was blued lightly by rubbing with clean fingers dipped in blue. The two halves were brought together and then apart, then the blue was "read" on the other half. Blue meant high areas. Shiny metal in the middle of the blue area meant the highest point and received the most grinding or in later stages rub stoning and polishing.

More recently I've seen the same phenomenon when scraping in lathe ways and other jobs in the home workshop. Lots of blue areas, with tiny shiny metallic highest of high points. And before that, on large whitemetal bearings on power station turbines and the like that we scraped in.

There is a real art to reading that stuff. You have to learn to tell the difference from a bare metal low spot and a bare metal highest-of-high spot. Usually the latter will have a tell-tale ring of darker blue around it that was squeezed outwards from the metal-to-metal contact. But it can be very slight and easy to miss.

 

[pkastagehand]

I didn't intend to start a fight. As someone long ago said, there are many ways to skin a cat. Whatever works for you is the right way; for you.

My question was not about the techniques really (I own a copy of the Connolly book that many of you have referenced). My point was simply that I can't see the blue and wondered if it was the medium (Hi-Spot) or just normal for a thin layer of transferred blue which seems to be the case. I couldn't ask Connolly that question! But I could ask here.

I've moved on to other projects and will be leaving investigations into scraping for a future time.

Thanks all,

P.

 

[trlvn]

I was going to stay out of this as I have no practical experience. However, one technique that I've seen on Youtube is to use some yellow pigment before checking for high spots. The yellow is to add more contrast. For example, Keith Rucker shows this around the 5:00 mark in this video:



As you'll see, the video is part 30 in a series. Somewhere earlier in the series, I think he said specifically what he was using both for bluing and contrast. Sorry, I don't know which part exactly.

Craig

 

[JimDobson]

I've only ever used a dark blue 1/2" thick Sharpie.

 

[willray]

...one technique that I've seen on Youtube is to use some yellow pigment before checking for high spots. The yellow is to add more contrast. For example, Keith Rucker shows this around the 5:00 mark in this video:... Somewhere earlier in the series, I think he said specifically what he was using both for bluing and contrast.

Being part of the Richard King scraping tradition, Keith is almost certainly using Canode blue and yellow die spotting ink, or possibly Charbonnel Aqua Wash Prussian Blue etching ink with yellow Canode. Canode washes up much more easily than Dykem. (Artco tools, which is frequently the only google hit for Canode in non-bulk quantities, looks like a fly-by-night operation, but I've bought from them several times over the past 10 years and never had a problem. I like the better contrast that the Aqua Wash has over Canode, but in my only mildly-experienced hands, I've had a hard time keeping it consistent on the surface plate over time compared to Canode).

And Hopper up there has it exactly right. There are a lot of differences in how bluing will read, depending on how thick it's put on the surface plate and how the workpiece being tested is treated, but it is absolutely true that a sufficiently low spot will get no blue, because the blue simply can't reach it, and a sufficiently high spot will get the bluing rubbed/squeezed off by contact with the surface plate. The result is that the actual low-to-high scale runs from "no blue" to "blue" and then back to "no blue".

Depending on the bluing used, how "wet" it is on the surface plate, how much the workpiece is rubbed, the phase of the moon, and probably a dozen other factors, you'll get a variety of additional visual indicators of where you are on that scale. In my hands, using Canode blues (and I'm far from an expert!) my scale (low to high) looks something like "no blue" < "thin blue that's 'sticky' looking" < "thin blue that's smooth" < (a typically thin/sharp ring of) "thick/dark/black blue" < "thin silvery-polished blue" < "bare metal".

Anyone who is arguing "the low spots are blue", or "the high spots are blue", is arguing about only part of the whole picture.

 

[ALEX1952]

Hi again
I was always taught to "blue" the work piece and then pressure does not enter the equation also you are not trying to push blue into low spots to get contrast, however as said earlier each to their own as long as the desired result is achieved.

 

[willray]

Hi again
I was always taught to "blue" the work piece and then pressure does not enter the equation also you are not trying to push blue into low spots to get contrast...

I'm curious how this is read. I assume you need to move the workpiece around on the reference surface to "wipe off" blue from the high spots. Without having tried it, I'm imagining this leaves you with "dark rings" from where the wiped-off blue accumulates around the bare high spots, and uniform blue everywhere else? Kind of like half of the scale of "blue on the reference" methods?

How well does it work as your surface becomes more uniform? At least in my hands, it seems that with the "blue on reference" method, the closer the workpiece matches the reference, the fewer and fewer high spots show up as polished-bare-metal, rather than "smooth blue", and I'm having a hard time imagining what the workpiece progression looks like if you "blue the workpiece". Do you have to rub the workpiece on the reference harder and harder/longer and longer, as the surface become closer?

The lack of a background that helps identify the low spots seems like it would make things challenging. The bare background of the "blue the reference" is really helpful, and the ability to use a contrasting background agent like yellow or red makes it exceptionally easy to read. Is there a way to get useful high/medium/low contrast with blue the workpiece?

Not at all intending to challenge the validity of the method - just curious because I can't quite see how it would work, and so I have to assume that there are differences in how you have to think about the process, or in the variety of workpieces/state of their surfaces for which it's most useful.

 

[ALEX1952]

Yes you rub against a reference surface therefore removing blue from high spots, no matter what your prefered method you are never going to get a uniform overall colour just lots of "rubbed" of spots the more spots the better as previously mentioned by me and one other contributor.
With the blue applied to the work piece the high spots will have no blue and will be the same height, you scrape the same amount of all of these hopefully bringing them down so more high spots are achieved aim for 25 spots per sq. in.
In a previous post someone was looking for blue high spots if the reference was blued, depending on the thickness of blue applied you are going to get lots of blued high spots of different tones these will all be of different heights.
For a truly flat surface you must compare to a known flat surface preferably two, if you are checking against another part of an assembly you are matching the components. Please be aware that if you are aiming for dead flat surfaces and are comparing them to each other it is very easy to think you have a true flat surface with plenty of witness marks, but have in fact produced a surface which is not flat (probably curved) that happens to match the other part of the assembly with probable disastrous consequence, for the sake of argument the ways of machine cross slide, it is entirely possible to have the tool post describe a very different path to the one you want and a hell of a job to isolate the cause.
I'm puzzled as to why we are trying to achieve a level of accuracy that is not required for the tolerances most of us are working to unless of course it is of genuine interest, my question would be where do you stop? yes you have one good part which at the start of the thread was a vice but! do you now go onto something else? the ways, how the carriage tracks etc. Yes get your equipment in good order but please enjoy your hobby don't get fixated on engineering nirvana as it doesn't exist, believe me you are just chasing ghosts.

 

[willray]

Yes you rub against a reference surface therefore removing blue from high spots, no matter what your prefered method you are never going to get a uniform overall colour just lots of "rubbed" of spots the more spots the better as previously mentioned by me and one other contributor.
With the blue applied to the work piece the high spots will have no blue and will be the same height, you scrape the same amount of all of these hopefully bringing them down so more high spots are achieved aim for 25 spots per sq. in.
In a previous post someone was looking for blue high spots if the reference was blued, depending on the thickness of blue applied you are going to get lots of blued high spots of different tones these will all be of different heights.

Thanks - that's kind of what I was imagining, but wasn't sure. With "blue on the reference", and especially with a contrasting background color, as I learned to read it you get a sense of "how far out" a region is, and this is really helpful when you've got a surface where you need to scrub off a half mile of material in various areas to get it close. As the workpiece surface gets closer to matching the reference however, it gets harder and harder to find the few pinprick "really high" spots amongst the mottled sea of medium-height blued areas.

It seems like the blue-on-workpiece approach may help solve that problem, so it seemed like there might be different advantages to each of the approaches in different phases of the work.

 

[ShopShoe]

Alex1952 asked: "where do you stop?"

If we are hobbyists, then we each form our own goals and the standard is what each one of us personally wants. I don't get too excited about trying to compete with an industrial standard or someone else's dictate. I enjoy reading these discussions and following the best of those who post here and elsewhere, but I can't see trying to duplicate their work exactly.

My own standards are always changing and improving, along with my skills, my machines, and my tooling, but I am not going to wait until the world is perfect before making anything. I have made improvements to my cheap Chinese lathe, but I can't make it into a Hardinge or a Monarch. On the other hand, I keep making it better and making my skills better and the parts I make are getting better, and that's the fun of a hobby.

I have done fitting and scraping and cleaning and who knows what all and each time things improve, and that's all learning too. I don't like to read "Mine is better" and "That's not the best way." I like to read "Here's what I did and why it worked and didn't work entirely," as that kind of information really helps me learn and to make my own decisions as to what to do next.

If you want some standards, they are in the Connelly book. I consult them, but don't try to get to them in one try.

--ShopShoe

 

[Wizard69]

I must admit that it has been a long time since I scraped anything for a living but my memory is still pretty clear. When you have a finely scrapped surface and a decent reference surface your spotting action will show up the highest spots as a shinny surface generally surrounded by a border of Blue.

If you thing about it it makes sense the parts in intimate contact will spread the bluing out into an extremely thin coating. the slightly shallower surfaces will take a denser layer of blue. This isn't going to happen on a roughly scraped surface. Maybe I'm not explaining myself well which is very possible. The thought here is that an extremely thing layer of bluing looks shinny.

 

[goldstar31]

I agree with Wizard69 but obviously, an uneven surface will initially take a whole area of blue and with each successive scrape ALL the blue is scraped off. Then it is blued again- scraped until the surface is down to a point where the future surface has bright points as many have mentioned. These are broken into a number of newer points and so on until the magic 25 points per square inch is achieved.

That's the way that I see it

Regards

Norm