OldTools Archive
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251392 | JAMES THOMPSON <oldmillrat@m...> | 2014‑10‑26 | Bearing scraper |
Went to an estate sale this morning, and found a Goodell-Pratt bearing scraper in salvageable condition. Don’t need any more bering scrapers, but just couldn’t leave it behind for a dollar. Decided to prep it correctly so y’all can see what such a beast looks like. Few people have ever seen a correctly prepared bearing scraper. I included 2 pictures of the Hirsch tool I found last week, which several people insisted is a bearing scraper. A quick comparison should dispel any notion that the Hirsch tool is a bearing scraper. If you lay a nicely prepared scraper on your arm and drag it sideways you will shave hair. That’s how you know it’s right. https://picasaweb.google.com/102358420595488787966/October252014?authus er=0&feat=directlink------------------------------------------------------------ ------------">https://picasaweb.google.com/102358420595488787966/October252014?a uthuser=0&feat=directlink------------------------------------------------------- ----------------- |
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251394 | Don Schwartz <dks@t...> | 2014‑10‑26 | Re: Bearing scraper |
On 10/25/2014 7:41 PM, JAMES THOMPSON wrote: > Decided to prep it correctly so y’all can see what such a beast looks like. Few people have ever seen a correctly prepared bearing scraper. I included 2 pictures of the Hirsch tool I found last week, which several people insisted is a bearing scraper. A quick comparison should dispel any notion that the Hirsch tool is a bearing scraper. > > If you lay a nicely prepared scraper on your arm and drag it sideways you will shave hair. That’s how you know it’s right. Jim: When you prep a bearing scraper, are the flats on the two sides in the same plane? If not, what is the angle between them - or does it matter? I have one of those, but have only ever used it to scrape flat surfaces. Don |
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251399 | Michael Blair <branson2@s...> | 2014‑10‑26 | Re: Bearing scraper |
> I included 2 pictures of the Hirsch tool I found last week, which > several people insisted is a bearing scraper. A quick comparison > should dispel any notion that the Hirsch tool is a bearing scraper. That certainly is a classic bearing scraper, but it isn't the only form. Mine is a simple triangular piece, hollow ground on all three sides to keep the edges very sharp. There are, I believe other shapes as well. The Hirsch tool still bother's me as a burnisher. The surface, not being polished, will abrade the surface on which it is used, and abrasion is not what I want from a burnisher. Still, the Hirsch doesn't look like a bearing scraper either. Mike in Sacto |
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251400 | Tony Blanks <dynnyrne@i...> | 2014‑10‑26 | Re: Bearing scraper |
On 26/10/2014 12:41 PM, JAMES THOMPSON wrote (in part): > Went to an estate sale this morning, and found a Goodell-Pratt bearing scraper in salvageable condition. Don’t need any more bering scrapers, but just couldn’t leave it behind for a dollar. > > Decided to prep it correctly so y’all can see what such a beast looks like. Few people have ever seen a correctly prepared bearing scraper. G'day Jim, I don't dispute that your GP scraper is one form of bearing scraper: there is one of that form in my father's toolbox from his days at sea. > I included 2 pictures of the Hirsch tool I found last week, which several people insisted is a bearing scraper. A quick comparison should dispel any notion that the Hirsch tool is a bearing scraper. But see http://store.apextoolgroup.com/nicholson- 21667n-3-1-4-machinist-s-scraper.html">http://store.apextoolgroup.com/nicholson- 21667n-3-1-4-machinist-s-scraper.html for a Nicholson bearing scraper of the same form as your Hirsch tool. The answer may come down to whether your find has a convex, flat or hollow grind on the faces. I checked my Dads' and they both have flat faces. As far as I know he never used a cabinet-makers' scraper, (I never saw him with one and and there is no cabinet-makers' scraper amongst his gear) so he didn't use them as scraper burnishers, but rather I believe, as he told me, as bearing scrapers. But then I have never worked as a fitter nor a machinist, nor engineer, so I can only go on what Dad told me. Or maybe it was a case of making do do with what was to hand during WWII when a bearing failed at sea. I suspect that when the pressure is on there are more ways of skinning a cat than twirling it around your head by the tail........... Regards, Tony B Hobart, Tasmania |
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251401 | Don Schwartz <dks@t...> | 2014‑10‑26 | Re: Bearing scraper |
On 10/26/2014 6:35 AM, Tony Blanks wrote: > for a Nicholson bearing scraper of the same form as your Hirsch tool. That one is hollow-ground. the Hirsch sems to be flat. So are the Blu-Dans. Don |
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251411 | John Ruth <johnrruth@h...> | 2014‑10‑27 | RE: Bearing scraper |
Tony called our attention to a type _machinist scraper_ > But see > > http://store.apextoolgroup.com/nicholson- 21667n-3-1-4-machinist-s-scraper.html">http://store.apextoolgroup.com/nicholson- 21667n-3-1-4-machinist-s-scraper.html > > for a Nicholson bearing scraper of the same form as your Hirsch tool. Now, note that ad says "MACHINIST SCRAPER". No where does it say a word about bearings !!! If the bearing was wide, that scraper would not be of much use. On a wide bearing, you'd only be able to scrape with the curved part right near the tip. It could readily scrape narrow bearings such as the poured babbit in early auto engines, but only up a width corresponding to the straight part of the edge. > The answer may come down to whether your find has a convex, flat or > hollow grind on the faces. This, I think is "the rub". The convex creates a "relief" on the back of the blade which I think is vital to scrape Babbitt to a smooth surface. The flat- sided, sharp-arrised scrapers may in indeed be scrapers, but they are not _bearing_ scrapers. They will do general scraping such as deburring, but aren't going to make a fine surface on Babbitt. That's my uninformed opinion and I'm sticking to it! (But, see below, because open-minded John just found a counterexample.) Now, just to muddy the very waters I indended to clarify, I present this for the Porch's perusal: http://www.csosborne.com/brscr ape_1.htm and, the "killer" reference: http://www.csosborne.com/no29B.htm">http://www.csosborne.com/no29B.htm Because, here, BOTH hollow-ground ( concave ) and flat-sided triangular scrapers are referred to as "bearing scrapers". !!! So, now I think we are all, all of us, correct. ------------------------------------------------------------------------ |
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251412 | David Nighswander <wishingstarfarm663@m...> | 2014‑10‑27 | Re: Bearing scraper |
>This, I think is "the rub". The convex creates a "relief" on the back of the blade which I think is >vital to scrape Babbitt to a smooth surface. The flat- sided, sharp-arrised scrapers may in indeed >be scrapers, but they are not _bearing_ scrapers. They will do general scraping such as >deburring, but aren't going to make a fine surface on Babbitt. That's my uninformed opinion >and I'm sticking to it! (But, see below, because open-minded John just found a >counterexample.) Scraping a bearing or a machined surface does not have the goal of making a smooth surface. Gauge blocks are lapped to create a smooth surface but bearings are scraped to create a surface that has a percentage of the area in contact. A completely smooth bearing will wipe clean of lubricant and quickly gall to the point of failure. Scraping leaves small pockets in the surface to allow trapped lubricant to provide a film. The film separates the bearing surfaces so the bearing actually rides on the film. Having scraped many a press gib and managed a shop where hundreds of bearing sections were scraped, assembled, and run in under load, if you make the surface smooth the bearing will fail. Machine tools have the beds and tables ground smooth and then scraped. The cross hatch marking on the surface is the result of scraping. Scraping tools have rounded cutting edges similar to that of a scrub plane blade. The marks left have a radius that lets the edge of the mark blend into the surface without a sharp edge. Babbitt cuts relatively easily. It is softer than the surface it rides on so it is sacrificial. Scrapers for babbitt can be made from old files or various other metals. In many ways Babbitt scrapers could be used for wood and wood scrapers can be used for babbit. The materials are similar in hardness. The purpose of scraping the two materials is entirely different. Scrapers for steel gibs and machine ways and tables are usually made from tools steel and sometimes from tungsten carbide to help maintain the edge longer. Carbide has a tendency to chip so I’ve always favored tools steel. If you are interested you can venture off charter and find out more about metal scraping here: http: //metalscraping.com/w2-Preview.html#01-Metal |
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251413 | JAMES THOMPSON <oldmillrat@m...> | 2014‑10‑27 | Re: Bearing scraper |
Usually, when I want information about something I try to consult someone who has actual experience on the subject. In this case, machinists and millwrights come to mind. Possibly some auto restoration people haver also scraped bearings. When I was serving my apprenticeship (1956 through 1959), the journeymen made a special effort to show me things. The reason for this was that my father had some influence in the union. It was a good idea to be on his good side. Construction unions were strong back then. So when things like bearing scraping came up, they would send for me so I could learn. At the time I kinda thought I was being picked on because the other apprentices were just doing normal work, and I was often being taken from what I was doing and reassigned to a different task, which meant packing up my tools and carrying them to a new location. I was too young then to realize what was being done for me. I thought it was a burden. So anyway, I got to do a lot of different things, and learned a lot in the process. Back to bearing scrapers. There were more than 250 journeyman millwrights working on constructing the steel mill where I served most of my apprenticeship. In my 4 years there I got to know most of them. I showed them my tools, and I looked at theirs. Millwrights are always proud of their tools. I never saw a bearing scraper that looked much different that the one I posted the pictures of recently. Long handle, curved end. 250 sets of professional tools, and not one bearing scraper that looked any different. I truly believe that if there were other types in use for the purpose of scraping large babbitt bearings that I would have at least been told about it, or read about it in my books. So until someone tells me that they have actually scraped a babbitt bearing with the other kind of tool, I remain skeptical. A horse is a horse, is a horse, is a horse of course, but there is only one Mister Ed. > On Oct 27, 2014, at 8:39 AM, John Ruth |
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