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Large scrape marks on older machines.

JST

Diamond
Joined
Jun 16, 2001
Location
St Louis
I have a Rivett 608 which I am gradually restoring. When I removed the headstock (the bed needs to be scraped-in), I noticed that the scraping marks there were VERY wide, on the order of an inch or so. But the marks were rather "elegant" if I can use that term, about scraping marks. The machine was made just after WW2, if that helps identify the time and likely scraping technique.

I will try to get pictures, but it is very difficult to take a good picture of scraping marks.

What sort of grind on the scraper gives that wide a mark? Straight across?

What is the purpose of that width? It is a bearing only area, and not a way, so the ppi is not so important, but that is very wide.

I can see such a tool might be very useful for roughing, to cut down the small islands that often exist after a heavy pass or two, do you suppose it was actually ground straight across (presumably with corners rounded)?
 
I have an old Sloan & Chase milling machine. It has the same 1" wide scrape marks on parts also. I always wondered how they were made.

Vince
 
I think those were just cut under there for practice before scraping the bed. I tell students to practice their first few passing scraping strokes where no one will see it. The Japanese method was taught to them the Germans before the world wars. They use to copy everything way back when, like the Chinese do now. South Bend also had a wider mark on the ways after they were ground or planed. To break up the gage block ring affect. Rich
Jerry you know how to take a picture. Use auto flash on your cell samrt phone camera or new digital camera.
 
I think those were just cut under there for practice before scraping the bed. I tell students to practice their first few passing scraping strokes where no one will see it. The Japanese method was taught to them the Germans before the world wars. They use to copy everything way back when, like the Chinese do now. South Bend also had a wider mark on the ways after they were ground or planed. To break up the gage block ring affect. Rich
Jerry you know how to take a picture. Use auto flash on your cell samrt phone camera or new digital camera.

I tried to take pics but they just do not show the marks well enough to bother posting. Flash just washes them out totally. If I can get the right lighting to let the camera "see it", I'll post a pic, but I have tried before without good success. Plus, there is some "patina" that partly obscures them when taking a pic.

I doubt they are practice, the Rivett folks guaranteed alignment to produce no more than 0.0001" variation in several inches when turning similar to the collars test, so when they scraped the bed in that area they meant it to be aligned....
 
I have a Rivett 608 which I am gradually restoring. When I removed the headstock (the bed needs to be scraped-in), I noticed that the scraping marks there were VERY wide, on the order of an inch or so. But the marks were rather "elegant" if I can use that term, about scraping marks. The machine was made just after WW2, if that helps identify the time and likely scraping technique.

I will try to get pictures, but it is very difficult to take a good picture of scraping marks.

What sort of grind on the scraper gives that wide a mark? Straight across?

What is the purpose of that width? It is a bearing only area, and not a way, so the ppi is not so important, but that is very wide.

I can see such a tool might be very useful for roughing, to cut down the small islands that often exist after a heavy pass or two, do you suppose it was actually ground straight across (presumably with corners rounded)?

.
i often machine surfaces that need no scraping if linear bearing bolted on but they still put scraping marks on for oil retention if it is used as a flat bearing slide surface. literally a milled or ground surface is too smooth and the scraping marks are to hold oil or for oil retention
.
i have seen also on printing press cylinders that had a mirror finish wouldnt print properly. i often had to hand sand a cross hatch pattern with 220 grit sandpaper otherwise it would not print properly. it needed the rough surface so surface was never totally dry thus friction was more consistent. 220 grit surface would only last a month or 2. scraper marks last a lot longer. cannot make deep marks on printing press cylinder depth of scratches had to be not too shallow or too deep. but on a machine tool slide for oil retention it dont matter if scraper marks are close to .001" deep
.
properly milled surface the waves are usually .0003" tir or less thus the need to make scraping marks for oil retention. in theory a milled surface can be made more wavy but normal practice is to make it look like it was ground or very smooth
 
Well the Rivett was scraped for alignment, and this was a contact surface, not a way, so oil is not an issue. As mentioned, the tolerances they spec'd were very tight, so this was obviously scraped for alignment.

I am just wanting to know what sort of a scraper grind (or type) would have been used for the purpose.
 
Just to add, I helped with the purchase and install of an old HBM,
IIRC an "Defiance", and the oil scraping (not up on all of the terminology)
Looked like very deep, machine made Plus signs.

I always wondered what that was all about.
 
The flatter the grind the wider the cut. Plus more likelihood to get a corner scratch. The may have blued the head and rubbed the bed where it hit but more for percentage of contact then PPI.
 
Wondered what radius would be used that produced that wide a mark. Even rather large radius grids still produce a fairly narrow mark, even at low angles.

And, since that was on a scraped for precision surface, what advantage, if any , there was in that sort of scraper grind and usage.
 
Wondered what radius would be used that produced that wide a mark. Even rather large radius grids still produce a fairly narrow mark, even at low angles.

And, since that was on a scraped for precision surface, what advantage, if any , there was in that sort of scraper grind and usage.

Could it pull scraping with a flat blade? A pull scraper will leave a lot more flat surface than a push scraper with a radius. For a non-sliding surface, you want more contact surface, most likely over 50% bearing, even if you scraped it in a more traditional push scraping method. You would stone the hell out of it to increase the size of the flats.

dee
;-D
 
I suppose that is perfectly possible, I have no idea what type of scraping they did.

And I do not know if there is a visible difference in the mark. These are long marks, as long as 3 inches or more.
 
Gradually or Glacier? Its only been a little past 6 years.

Question for the expert scraping folks..... long

Tell us again what a guru you are fraud.

I'm not a guru on this one, if I am on any.. Don't claim to be. Bed has 10 large surfaces to align. I need to make some fixtures to do it, because of the shape.. Do not NEED the machine, and do not have room for it at present, so it waits. Base is out in the shed. Crosslide assembly is done, has been for a while. Bed is gonna be a big job, due to wear, and I do not have Biax..

Right now , I have paying jobs of scraping in my own shop. No time to mess with the Rivett bed.
 
That's hardly procrastination. My folks started a renovation of their kitchen the year I left for college. I was just there yesterday. I think we could call it 75% complete.

13 years and counting.
 
Phil you have a hell of a memory...I like reading Jerry's posts as I like reading yours.

I was in Surfers Paradise (Australia for you blokes who haven't had the pleasure) back in 1971....I remember the beer and women were amazing.... I can remember way back then, but forgot who I lent a scraper to 2 weeks ago. Sucks getting old...lets all have fun on here and be kind to each other. Rich
 
Certainly. Exactly why you just started a thread about it.:ack2:

Because I moved the Rivett bed recently, (closer to where it would be worked on) and remembered the marks.... Wondering if there was any special reason for the size, and what sort of grind radius on the scraper would make that mark.

I'll get around to the thing once I figure out what approach to take. And I need a longer SE... the other stuff I work on is small, mostly under 2 feet long... This bed is longer, and I want to do as good a job on it as I possibly can, the machine is worth it. I freely admit I am no expert, I am self-taught, I understand the wrong ways to do things, probably tried most of them.... So I DO understand newbie questions.

The rest I am still learning....and asking questions, just like this one. If you know the answer, please go ahead and explain it.
 








 
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