Thread: Scraping Projects

Thanks for the right up Bryan
I haven't done any scraping, but I am sure you wouldn't be the only one that has been caught out with this, and you won't be the last, but at least with you putting it up others can be warned.
Look forward to your pictures.

Ray
I like how you take on the little jobs first after the scraping class.
Your doing a good job restoring the angle plate, something like that new these days would be worth a fortune scraped true and square.
I am also looking forward to your pictures of it finished, so stop reading this and get back to it, LOL

Dave

Hi Bryan,
Gotcha. Thanks for clearing that up.
See pictures would have helped

Are you trying to keep it level front to back?

Stuart

Originally Posted by Bryan

Too small to see, but just detectable with a fingernail.

Thanks for the tip, I am finding out just how sensitive the markup process is, and learning how to read the patterns to adjust the scraping accordingly.

By combining the spin test on the surface plate, and looking for "shiny" spots in a blue area, you can pick the higher spots, and knock them down. Also it's amazing how quickly the patterns change as you get flatter.. I think it's a long learning curve, but very satisfying when you start to realize just how accurate the technique can be.

Now, what about those pictures...

Regards
Ray

Today I learned that assumption and denial will conspire to waste your time and energy if you're not careful.

The streaky problem came back. Couldn't be the wear ridges because I fixed that. So I wasted a lot of time scratching around, in denial. Finally took some more off my chamfers and the problem was gone again. For a while. As I removed material, the slides sat lower and kept finding the ridges on the ways. Enough was enough. I sharpened up the scraper and attempted to scrape the ridges off the ways. It wasn't real pretty but I gradually refined my technique and met with some success. Enough to get the ridges out of the way. For now. And I don't think I did any damage.

Now it was finally spotting properly, I did something I should have done right at the start. I blued up the entire TS ways, and spotted the slide at 4 positions, which together covered the whole of the ways. (My TS ways are short.) The different patterns revealed the error of my earlier idea that the TS ways were not significantly worn. I don't even remember why I thought that, but it now looks like a very stupid assumtion.

What it means is that I will not waste a lot more time fussing over this, since it can't be perfect in every position. I will scrape it to the flatter part of the ways, near the TS end. This should make it stable everywhere except possibly nearest the HS. It's the best compromise I think. Then I can work my way up. There will be more compromises ahead no doubt. I've already spent more time on this than I want to admit. It's not fun any more. I just want to be able to use the stupid tailstock.

The photos show the spotting at each position, starting at the HS end. They are big blobs because I haven't been scraping for bearing yet. (Actually I was, then I stopped.)

PS: I learned another thing: Don't leave water based medium on your ways, it stains.

Hi Bryan.. Canode will rub off with oil.... So what I do when I finish scraping for the day/night is just put any old oil on the surface and rub it off... The canode will come off with the oil...

Hi .RC, Bryan,

Canode washes out with soap and water for cleaning hands, but for the thing being scraped, I'm not keen on using water, and have found Metho works fine, dries in a few seconds as well.

I think Bryan, you've discovered the secret of scraping,... knowing when to stop..

Regards
Ray

Say you've got a surface that's getting close. Nice even sprinkling of spots, except one or two small areas are a bit sparse. What's the correct technique? Do you only scrape some of your high points? If so, how do you select? Or do you sacrifice all of your high points and trade them for lower ones? If this was covered in class I must have been goofing off or something. I haven't been able to find guidance in MTR either.

I push down harder when I'm spotting (that was a joke!)

I think, in your case if the sparse areas are towards the middle I wouldn't worry about them.
If you are going to worry about them. I think it depends on how many spots you have and how many you want to end up with. If you want more spots than you currently have cut the bigger ones you have in half, If you want to keep the number of spots about the same, they all have to go.

I think.... so there is about a 75% chance I'm wrong

How many is enough? how many is to many?

Pictures! BTW I just thought I would mention an idea I came up with. You know how MTR goes on about drawing the spot patterns(or words to that effect). Being lazy, I take pictures, if you keep the camera set up about the same you can flick though them and see what's going on. I found it the most help when I was tried spotting the same part 10 times in a row to be sure I was getting consistency.

Stuart

Stuart, I'm not referring to the TS slides pictured above. I'm working on the opposite side - the top of the base - so it's just a flat rectangular shape. Being a static bearing I'm not too fussed about it, but wanted to use the opportunity to learn.

I think it depends on how many spots you have and how many you want to end up with. If you want more spots than you currently have cut the bigger ones you have in half, If you want to keep the number of spots about the same, they all have to go.

Ok thanks. I'm still thinking about that.

Bad guess hehe. Like you say being static you can aim as high as you want to go and its not going to hurt.

Have you checked how you are going with center height and parallel in both planes?
I guess in a perfect world you would like that face to the level front to back as well(though really it wouldnt matter much)

Stuart

Stuart, stop complicating my life, I've got enough to worry about. No I haven't bothered about keeping it level. As you say, it doesn't matter. The top of the base just has to be flat. The bottom of the top is where most of the adjusting will happen. With one exception: I may try to tweak the transverse way alignment as I scrape the bottom of the base. Because I can't think of another simple way to adjust that.

But to return to my earlier point. What does my head in, in the example above, is that you have to swap your set of known high points for a set of unknown ones. You don't know where the new ones will pop up. You know they won't be where the old ones were because you just scraped those. But they may or may not be evenly distributed. It's a lottery. I don't like lotteries. I think they're foolish. And I would like to feel more in control of the scraping process.

I'm off to the shed for some more experience. I hope others will do some posting in this thread at some point too. It's getting a bit lonely.

Originally Posted by Bryan

Say you've got a surface that's getting close. Nice even sprinkling of spots, except one or two small areas are a bit sparse. What's the correct technique? Do you only scrape some of your high points? If so, how do you select? Or do you sacrifice all of your high points and trade them for lower ones? If this was covered in class I must have been goofing off or something. I haven't been able to find guidance in MTR either.

Hi Bryan,

I must have been goofing off at the same time... I'd like to know that answer as well.

My only answer is keep scraping.. and hope it goes away in subsequent passes...

Regards
Ray

Originally Posted by Bryan

I may try to tweak the transverse way alignment as I scrape the bottom of the base. Because I can't think of another simple way to adjust that.

Me! needlessly complicate things? never!
I wonder if you would be better off "roughing it in" then measuring it so you know which way you need to go(if any). No use finishing the vee slide(is that the right name?) then finding you have to scrape it for alignment, Both at the same time it says in the book.

Originally Posted by Bryan

But to return to my earlier point. What does my head in, in the example above, is that you have to swap your set of known high points for a set of unknown ones. You don't know where the new ones will pop up. You know they won't be where the old ones were because you just scraped those. But they may or may not be evenly distributed. It's a lottery. I don't like lotteries. I think they're foolish. And I would like to feel more in control of the scraping process.

I see what you are saying but as I see it, once you get to a certain flatness, depending how you scrap the spots you effect the way things go. Deep scrap of all the blue will give you less points, shallow scrap of cutting the spots in half will give you more points. You don't know where the new points will be(but you dont really care), what you do know if there will be more or less of them and that the sparse areas will now be closer than they where last time. That on a basic level is what I think scraping is about, being closer than you were last time. Sure with different techniques and more experience you might get there faster, but as long as you are closer than last time that's all that matters. I hate that you have to scrap the good parts down to the bad parts, but "what can you do?"

As always I could be very wrong about all that.

Stuart

I think this will be quite sufficient, 'for government work'. It was a long journey - Melbourne via Mt Isa - but I think I understand the process a bit better as a result. I think splitting the spots is important because then you hit the centre which would be the highest point. That way you bring up the next layer of points, and only lose a small area. I think this is pretty much what you said Stuart. You have to think of it as a landscape, not just a binary high or low. A contour map would be handy. How could you generate that? Connelly goes on about the different coloured spots showing the heights, but I'm not seeing that with this medium. Maybe my eye isn't trained enough.

Stuart, the slides are already roughed in. I will check the transverse alignment and let that guide me.

Edit: Here is a more complete answer to my earlier question: I think it depends on how low the low areas are. If they're only a teensy bit low, you split your points. If they're lower than that, you need to scrape all blue and kind of start again. It's the difference between roughing and finishing.