Tadd's Southbend 9" Scraping Project

It's 10 45 and Im about to go to bed, But that check in no good. Your measuring a clearance surface that was milled and the parrelell (Spelling sucks) could be cock-eyed. I would lay the compound over and rub it...hinge it ..get your 30 % from ends..ap on top with a small dead blow hammer and listen for the solid sound on your granite. when its flat use a surface gauge to indicate he clearance from end to end. or check the top surface of compound. More later...bed time...I'm Rescraping a cyl grinder at MN grinding in Crystal ..maybe I can swing by some evening and help in person...Im driving 694...give me a call..651 338 8141.
 
Okee Dokee,
Just spent a little time with the test indicator trying to figure things out. here is what I found. It looks like the surfaces are fairly flat, but skewed slightly from the original plane. In the last picture, the x's show where it hinged.

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I am glad you figured out what I told you on the phone.I like that test better, on the bottom of the compound even though it's a clearance surface, but if you think about it, the factory machined that at the same set-up when they machined the ways. I did a school at a GE plant in Cincinnati and one of my students had been a machinist at Cincinnati Millicron and he said that is what they did, one set up 2 surfaces cut, accept the ways were a slower feed rate. Plus your using a dial indicator and not a depth mic, it's easier to read. One other thing, for the guys who don't know plus / minus on the indicator please mark it in the pic's.

I'm not real excited with the test bar check, you're introducing multiple error into it. It might look impressive, but it is to confusing. indicate the top not the test bar. Plus your not working on a jig bore your working on lathe. I would rather trust the bottom check where 3 of 4 of the checks are close. I would get the bearing better on the ways and then grind the top of the compound on a surface grinder. If you don't have a grinder, mill it. That's good enough. Per the call, be sure when you stone the scrape marks, only dry stone it with a MS-24 Norton or a small medium grit Indian stone t knock off the burrs and not flatten of the high spots you just created by scraping. The hind on the left side is what you want. Remember to take your soft blow hammer and tap the top and "listen" for the same sound when you hit it. When it is flat you will hear the same sound a thud when its flat. If it has a ring sound it is not flat. If you not sure what I mean slide a .001" feeler gage under one corner and tap it, you will see what I mean about the sound. I know you want to get it perfect, but it's only a lathe and the spec is .0002 per 12". It's a waste of time to get it better then that. 18-20 PPI / 50% POP. It probably was 12 PPI / 40% when new. (PPI = points per 1 ") and POP = percentage of points).
Keep up the good work. Rich
 
I've been a little bit busy at work and home with the holidays so haven't had much time to scrape. I did start working on the bottom of the cross slide, I had scraped the top surface flat during class this summer. I indicated the bottom and found it was .005" higher at one end. I step scraped it until it indicated within .0005", then started to blue it up on the surface plate. I forgot to take pictures of that as I went. Right now I'm at about 1-2 PPI, so still a bit of work to do.
One of the guys had brought a nifty little angle straightedge with him to class, and that was what I had used to spot the dovetail on my compound. In order to scrape the dovetails on my cross slide, I figured I'd need one, so I proceeded to make one out of Durabar.

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I also needed a way to hold the gibs in order to scrape them, so I made a little fixture to hold them. The brass hex pieces clamp the edges by means of an eccentric headed screw.

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I'm hoping to start scraping the straightedge this weekend. Need to come up with a good way to hold it on the table for scraping.

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I got a little time this afternoon to work on the straightedge:
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Here is where I left off with the cross slide:
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I also wanted to share a tip for the scraper handle I discovered - found these rubber sleeves on McMaster, they make scraping much more comfortable. Just have to cut off one end and slide it on the handle. My thumb no longer goes numb.
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Looking good, but you can get the straight-edge to come in a bit faster by only scraping the bottom edge, tip it in. That edge is high because your a little gun shy about the edge. When I scrape those angled straight edges I screw in a hex bolt with a jam nut jammed against the end of the straight-edge and hold those nuts in 2 vises, one on each end. That way you can adjust the nuts so the face it upright and not on an angle. I use those 2 screw Johansen wood clamps that I used in class as a vises if you don't have 2 mill vises to hold the nuts.
 
Wow, I haven't posted anything for quite some time. I've been absolutely slammed at work and pursuing a couple of extra income opportunities after hours...
Things should be settling down a little bit now and I'm looking forward to getting back to scraping. I spent a couple hours on Sunday modifying my surface plate by welding cross-members in so it can be supported on the correct 3-points. It had been supporting the plate at all 4 corners :(
I picked up a couple of things recently, I got a broken Biax power-scraper (the armature is shot), and just purchased a 4' camelback straightedge yesterday.
I was planning on having the armature re-wound, but this one is damaged so bad that the repair company can't rewind it unless they have another "good" one so they can figure out the wiring trace from commutator to windings.
If anybody out there would be willing to borrow me a good armature for a couple of weeks so I can get mine repaired, that would be greatly appreciated!
I'll get back to posting pics an updates before too long here.

Tadd
 
Where did the last year go? I'm gearing up to get scraping again finally. I bought another blue Biax power scraper (this one works), so eventually I can have my other one's armature rewound. Yesterday I picked up my lathe bed from the local machine tool rebuilder that resurfaced all of the bearing surfaces. Here's a couple pictures of machines at the rebuilder and a couple of the bed. Note, there is oil and lint on the ways, I'll get some better pictures. The worst bearing surface had about .006" wear. Stay tuned for hopefully more frequent updates.

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