Scraping Blue?

[mechman48Participant @mechman48]

Still have a tin of Stuarts marking blue from many, many, moons ago… did some practice back in Jan. to see if I still have the knack… blue dabbed lightly on plate glass, with a balled up piece of cloth so the layer was translucent…

I reckon I have…

George.

Edited By mechman48 on 16/05/2017 15:04:55

[SteveIParticipant @stevei]

Hi,

 

I am not good at photography and don't often take pictures but please see the photo below which is the best I have to show the benefits of high lighter and blue in use together.

 

This is a zoomed in section of a 36" dovetailed straight edge that I have scraped in from a casting, from memory it is about 1.5" wide. For scale there are about 40 PPI on average some times less and some areas more. I have also got a few scrapes where I slipped and I spoiled the finish and also more seriously I "rolled" the edges of the straight edge. This was not planned and is undesirable. You can see that there is no blue contact on the edges. This means spotting tight in to an edge  is impossible. I unfortunately need to redo the work from scratch as the rolling is about 1 thou low compared to the blue high spots.

 

However what I hope you can see clearly is how easy it is to spot the high spots with the yellow high lighter. The print is clear and does not look like a smudge.

 

 

Steve

 

Edit: for typos

Edited By SteveI on 16/05/2017 15:37:48

[Andrew TinsleyParticipant @andrewtinsley63637]

Steve,

A very impressive photograph! I have never seen such contrast on a rubbed surface. I didn't get my wires twisted and do appreciate that it is the US water based system we are talking of. I got my fingers twisted instead and didn't type what I intended!

I am one of those unfortunate people that get engineering blue just EVERYWHERE, except for what I am trying to coat! I assume the water based products are not nearly so messy?

I never expected this thread to reveal such a wealth of detail about scraping and systems used for highlighting high spots. It has been a real education and there may be more to come. I shall mull over all the helpful advice and see where to go. It is hardly expensive to try most suggestions (including the water based system). I can then see which one suits my needs best.

Thanks for such a response!

Andrew.

[Brian HParticipant @brianh50089]

Posted by roy entwistle on 16/05/2017 10:37:18:

Jewellers rouge is an abrasive and I doubt whether you could get Red Lead today. At one time any paint manufacturer sold it

Roy

Yes, jewellers rouge is an abrasive. I remember now! It was used to finally lap in the diesel injector pistons on large diesel engines. We were warned NEVER to stop moving the piston. I did once and the piston welded itself in, ruining the entire block of 6!

The foreman was not pleased and let me know in no uncertain terms; it never happened again!

Brian

[SteveIParticipant @stevei]

Andrew,

My photo is using the 2 colours of the volkcorp canode i linked to previously. I have limited personal experience and am a hobby scraper, but like I have said people that have tried the water based products seem to prefer them to the stuart's, no massive sample set though… Note that many people do wonderful work getting on just fine with the stuart's. I personally found switching to the water based helped me get better at efficient use of time when scraping.

In that photo the yellow was rubbed on via a cotton rag (old t-shirt) and the excess rubbed off with the side of my hand. The hand also smooths out the variation in thickness. The blue was rolled on to a granite plate and the excess wiped off. At this stage in the job I had very very little blue on the plate. Note also that as an experiment/learning process I tried to scrape that straight edge very deeply the variation between the high and low spots is ~0.0006". Much deeper than I would a machine bearing. The idea was to create a straight edge that was more robust to wear. I wanted the tool to last longer before it needed a rescrape. The experiment was only partially successful, I got the depth I was looking for but with pushing harder I lost control and had a few slips when bump scraping and consistently rolled the edges.

I have since learned that rolling the edges is a problem on a machine bearing because it creates an unnecessary gap for swarf/dirt etc to get in to the ways and leads to excessive wear. So it is a very bad habit to get in to.

Also to correct an error in my post this picture is not from the dovetail straight edge. (Not that it matters much but the dovetail straight edges is about 3" wide on its flat bottom.)

Steve

[Mark RandParticipant @markrand96270]

I have water based Canode in red, blue and yellow and Stuarts oil based compound in blue and red.

I find that the Canode product is significantly more coarse than the stuarts product and does not transfer as well with a thin layer. It also needs re-wetting when left for a while or it won't transfer at all well.

Having said that, I get very good results by applying the yellow Canode as a background and thinning it using glass cleaner (detergent type, not Windolene!), then using the Stuart's blue for spotting.

Canode will give good marking if you are scraping half a thou, but not if you are scraping half a tenth.

[SteveIParticipant @stevei]

Mark,

Very interesting points about canode vs stuarts. You are correct it does dry out. I also use window glass cleaner to thin the yellow as needed and for general clean up.

I will do some experiments with using the stuarts for finer work. Thanks for the advise.

Where did you source the canode?

Steve

[Mark RandParticipant @markrand96270]

I had to order it direct from Volk Corporation in the States. They were quite helpful with shipping to far foreign lands, even though it was unsusual for them. I couldn't find any UK or European resellers, although they could well exist.

[Pete RimmerParticipant @peterimmer30576]

Hi gents,

My first post here and I know this thread is a few months old but some members will recognise me from other forums so I thought I'd just chime in. You can buy canode in the UK now you can get it from aetools in Bolton. It's not advertised on their site yet but they are the UK importer so if you need some give them a call or send an email. I have no association with them I only mention this because I'm placing an order myself and this thread came up in a search. I thought it would be handy for the scrapers here to know that you can get it locally now.

Cheers.

Pete

[Martin DowingParticipant @martindowing58466]

Regarding Stuarts Micrometer blue.

Are you diluting it with some oil or use it as it is?

I have found diluting useful but I am still new to scraping, so I wonder if it is legitimate approach?

Martin

[Pete RimmerParticipant @peterimmer30576]

I do dilute it with a light oil. Often you'll find when you open a tube that some oil has separated out. I put down a small bead of blue ready for rolling out and apply one single drop of oil, it's a bushing oil similar to 3-in-1 oil. I find that this makes it less likely to suck the part to the plate and it does print much better. I have a small 6" plate which I roll out the blue on to load the roller then roll it out on the plate I'm using for spotting.

Pete.

Edited By Pete Rimmer on 09/11/2017 20:36:27

[John ReeseParticipant @johnreese12848]

The brands I am familiar with are Dykem Hi-Spot Blue and Canode. Dykem was often put on the underside of machine handles as a prank.

[Mike PooleParticipant @mikepoole82104]

I have used Prussian Blue oil paint, works very well in my opinion. The finger does seem to be most effective for application but it is very messy.

Mike

[David Standing 1Participant @davidstanding1]

Posted by duncan webster on 15/05/2017 23:57:13:

If all else fails use lipstick, it's not as good as the proper blue stuff, but it works. I nick it from SWMBO

Yeah, that's what you tell us now .

[Russ BParticipant @russb]

I've enjoyed following this thread.

I think the lack of availability of scraping tools and consumables is perhaps a contributing factor to the decline of the skill??

Could someone give Ketan a nudge at Arc, it would be good to get some red/blue Volkcorp Canode in stock, and perhaps a small section dedicated to hand scraping bits and pieces!

[Pete RimmerParticipant @peterimmer30576]

Posted by Russ B on 10/11/2017 05:26:33:

I've enjoyed following this thread.

I think the lack of availability of scraping tools and consumables is perhaps a contributing factor to the decline of the skill??

Could someone give Ketan a nudge at Arc, it would be good to get some red/blue Volkcorp Canode in stock, and perhaps a small section dedicated to hand scraping bits and pieces!

They aren't so plentiful, I've had to make most of what I have.

Scraping is now almost relegated to home enthusiasts and whatever handful of rebuilders of old equipment there are still going. Not much of a market for the equipment you'd need but it wouldn't take much for someone to at least stock a couple of boxes of the small bottles of spotting dye.

The most difficult stuff I've had to find is the cast iron straight edges. Very thin on the ground nowadays and a lot of what you see isn't fit for use until it's been scraped in itself.

Pete.

[SteveIParticipant @stevei]

Russ,

I do not know of any supplier to the hobby in the UK offering "good" (I define good as easy to work with) new hand scrapers. Greenwood tools offer the sandvik range which are used by professionals and hobbyists alike but they have no flex and the handle is not comfortable to position in to the stomach. (well not for me in my physical condition!). A bit of flex makes life easier. My ideal hand scraper would have the following attributes:

Mild steel construction. e.g. width 1", thickness 3/16" length to suit but approximately 18" with a tang for a file handle or similar. Clamp on the business end to take the standard BIAX style "carbide tipped mild steel blades".

You can buy the blades or make them from mild steel based on the BIAX type::

Length: 150mm, Width 20mm, thickness 2.5mm.

Short 80mm long, width 20mm, thickness 2.5mm

You then have a bit of carbide brazed in at the business end that you grind a radius profile and rake on.

I use a long blade (which give you more flex over the whole assembly) for scraping for flatness. Scrape to within 0.001" or better flatness. Then I switch to the shorter blade (as I get more positioning control) for scraping for bearing.

I wrap a tennis racket grip over the part of the scraper that I grip with my hands. This stops me getting too tired in the hands too quickly. I have put an angle grinder flap wheel rubber disk in at the file handle end. This spreads the load across my stomach. I've seen others turn a nice stomach support from wood or plastic. The angle grinder plastic wheel is perfectly fine for me. Without it scraping hurts my stomach!

I am pretty sure the average model engineer could knock up such a design in a short while for not much outlay. Perhaps this is why no one stocks them. If e.g. Arc stocked them I am sure they would sell plenty of blades. I have a fair few with different radius and rake ground on them and some with an angled grind to facilitate getting in to a dovetail.

I'll get a couple of pictures taken and post them later.

Thanks,

Steve

[Martin DowingParticipant @martindowing58466]

@Steve,

What radiuses of scrapers are you finding most useful?

[Pete RimmerParticipant @peterimmer30576]

Martin if you're starting out you should go for a 6omm radius scraper or smaller. Anything more and you risk gouging the part with the corner of the blade. If you're scraping small ways use 40mm or even down to 20mm so your scrapes are smaller in width.

If you guys want to make a scraper for yourself you could take my approach. I just made a bunch of them for the scraping class we held last week and knocked up some handles from wooden curtain rail dowel I got at the boot fair. The cost for batches of 10 scraper handles was about £3 a pop. Buy the metal from Tilgear 25x3mm cold rolled steel.

http://www.practicalmachinist.com/vb/machine-reconditioning-scraping-and-inspection/beginner-scraping-question-scraper-design-343434/index3.html#post3089226

These were very popular at the class and most of them were taken away by the students, I managed to keep a handful for myself.

Edited By Pete Rimmer on 17/12/2017 12:44:34

[Brian HParticipant @brianh50089]

When I started my apprenticeship as a fitter too many years ago, one of the first tasks was to make a set of scrapers out of old files. I still have 2 of mine and they are still useful.

I've always found carbide ones to be inferior.

Brian

[Pete RimmerParticipant @peterimmer30576]

Carbide needs a different sharpening technique to high carbon/high speed steel. Can't say that I ever heard anyone else call them inferior, perhaps the file might suit your scraping technique better. My HSS scraper need sharpening a lot more frequently for sure.

[donkeyParticipant @donkey]

I too made scrapers from old files and still have them. I even ground the teeth off on the surface grinder. I also prefer them to the sandvic carbide scrapers.

Brian

[Pete RimmerParticipant @peterimmer30576]

Sandik scrapers are gash. One of the guys at the class brought a brand new one, tried one of mine and put his Sandvik insert in it for the rest of the week.

[mechman48Participant @mechman48]

Posted by Brian Hutchings on 17/12/2017 13:01:13:

When I started my apprenticeship as a fitter too many years ago, one of the first tasks was to make a set of scrapers out of old files. I still have 2 of mine and they are still useful.

I've always found carbide ones to be inferior.

Brian

Snap! Didn't think anyone else would remember making their own scrapers, chisels…

​George.

[VicParticipant @vic]

There must still be a use for Micrometer Blue as you can still buy it in many places?

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