Reference Straight Edge for Scraping
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    Question Reference Straight Edge for Scraping

    I would like to try my hand a hand scraping. I have purchased a scraper, bluing dye, and the typical references on the subject. I was planning on starting with two pairs of larger shop made parallels I purchased inexpensively on Ebay. I think they can be self referencing (4 surfaces per pair) using the rotating 3 surface technique.

    However, if I wanted to progress to actual machine tool work I know I would need one or more reference straignt edges. The only thing I have found doing searches is Busch Precision products, and a price list from Newman Tools Inc. The 48" Scrapping Master (6848M) is listed for $10,175 (Ground Finish). The 48" camelback Dovetail Straight Edge (6648S) is listed for $6,222 (B Scraped).

    This level of investment for hobby work is difficult to justify. Have I only found the Rolls-Royce of straigh edges, or is this what is required to do this type of work properly? I know there are probably used straight edges available (although I haven't seen them on ebay), but I would then have to spend the money to have them checked for accuracy, and resurfaced if required.

    Are there other sources I should be looking at?

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    First off, a 48" camelback straight edge is a BIG one. Not sure what you are trying to scrape (besides your parallels there), but there are other ways. With care, parts longer than the reference can be sucessfully scraped in.

    You kind of have the cart before the horse here. This is kind of like buying a buch of tooling and then looking for a lathe. First thing you are going to need is a reference to know what flat is.

    Buy a used granite surface plate to use as a reference and scrape your parallels in. There's a few good sized ones on Ebay for a few hundred bucks. You can do a lot of other stuff with the surface plate, as well as printing those parallels. Generally, the larger the plate, the cheaper it is (as compared to new or to a smaller one in terms of sq ins of area). Only catch is that it will have to be close enough to pick up. You don't want to ship a big plate and stand. Even if you buy a new Busch straight edge, you'll need a surface plate to keep it straight and flat.

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    As Mike says, a granite surface plate is the normal reference.

    Those Busch things are nuts. Straight edges come up on eBay about once a month or so. I've got half a dozen camelbacks on ebay for between $75 and $300. Paid $250 for my 48" Brown and Sharpe. It took only a couple hours to restore to like-new condition using my 48" granite plate as reference.

    Search scraping (terms like scraper, scraping, etc) on PM. It's been discussed a zillions times.

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    There are people selling castings for camelbacks.

    The ones that I know of are Stephen Thomas, a regular PM contributor, He has a 30 inchy one- with the angled portion for dovetails. He has an older version and a newer lighter one, though do not know if he is selling these yet.

    Craig Donges has 36 in casting which does not have the dovetail portion. He used to have a 18 inch casting which has a dovetail angle. Searching posts will reveal contact information
    I had originally written "Craig has been "banned" from PM apparenlty because it was though he had too many items for sale vs typical posts. I personally believe he should be reinstated- but it is Don's site and that is up to him to decide." I am happy to report this is incorrect as per posts 13 and 14 below by Stephen Thomas and John Odor. Sorry about the misinformation originally posted. JRT


    Michael Morgan in the past has sold a 24 inch camelback with the dovetail angle. He has them on his web site- and it indicates he had 7 castings 12-1-09. Years ago Mr Morgan had some problems with not getting orders shipped out. I do not know what the current situation is- but I have not heard anything about problems on PM in recent years.

    As others have indicated- use a surface plate for your reference. You will get plenty of practice scraping in what you have. If your value your time I would drop the 3 surface approach. It can be done- but makes no sense given the cost of granite surface plates.
    Last edited by J_R_Thiele; 01-03-2011 at 04:24 AM. Reason: Correcting information on Craig Donges

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    When I had to scrape my first machine in 1979, a 1929 B&S surface grinder, I bought a new Starrett 30" black granite straight edge. I forgot what I paid, but think it was under $200 at the time. I mention that so that you will know that not all straight edges are cast iron. I don't know what all is available today, but here is the first item that turned up in a search. A new granite 24" for $189 is a lot better than thousands of dollars for a new scraped iron piece.

    http://www.shars.com/product_categor...230304/Granite

    Larry

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    Question Further Question on Surface Plate

    Thanks for the advise. I have an 18 x 24 surface plate from Enco Toolroom Grade B. , quoted as .0003" overall accuracy, Not NIST traceable (unfortunately I didn't know about there frequent no shipping offers at the time). I haven't even unpacked it yet. I purchaced it as a hobbyist's layout surface, never expecting a chinese import to have the overall accuracy across the plate that they quote.

    Are these really sufficient to act as a reference plane for scraping? Is there a relatively in-expensive way to test the flatness? Is it worth getting one of these certified to a known flatness? I have been reading about optical flats, are they any use to assess a surface plate?

    Not sure what I want to do long term, but if I wanted to tune up my bridgeport, or the ways on a surface grinder, what reference tools should I have? I started watching a DVD I purchased on scraping, using a Bridgeport Mill as the subject. Everything I watched so far was referenced/blued with a Camelback dovetail straight edge.

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    Your granite plate should be fine. You are using it for machine tool repair, not inspecting parts for the space station.

    Many smaller parts can be printed on the surface plate, and you may want a good sized camelback for parts left on the machine, or pieces too heavy to lift and handle while printing. As I said before, your surface plate is the reference for your straight edge.

    A 4ft camelback will be in your way more than it helps on a machine the size of a Bridgeport. The only place I can see needing something that big is the table ways, and they can be done in smaller sections with a shorter and lighter edge. A 4ft edge is going to be HEAVY.

    You need to round up a good machinists level and a couple of dial indicators and stands, in addition to the surface plate and a straight edge.

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    Yes, Grade B is adequate for most things.

    No, you cannot test it for flatness at home (to do so requires specialized tools)

    No, an optical flat will not help (it only tests for flatness under the area of the optical flat. An optical flat is for determining very high degree of flatness in a small area. For example, you can measure flatness to within a couple millionths of an inch across the area of the flat, but that's not important here. You want the surface to be flat within a few tenths over several feet, but you don't care if that surface is wavy at the level of plus or minus 20 or 30 millionths)

    To do a machine, you needs lots of things, but you should start with learning to scrape and buying Machine Tool Reconditioning by Ed Connelly.

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    "you should start with learning to scrape and buying Machine Tool Reconditioning by Ed Connelly."

    Totally agree, but don't just buy it, READ it, lol.

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    Smile Thanks Again

    Thanks. I do have a copy of Connelly's book. Hope I didn't bother you all with questions I could have found the answers too in the book

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    Quote Originally Posted by mark thomas View Post
    To do a machine, you needs lots of things, but you should start with learning to scrape and buying Machine Tool Reconditioning by Ed Connelly.
    The actual mechanical technique of scraping is fairly easy to get "decent" at. That gets you capable of making flat surfaces, assuming you have a reference.

    The harder part is to do that while satisfying other alignment requirements. You have to visualize results in advance, and see what results certain actions will have. You must understand the goal, be able to measure to see when you have arrived there, understand what "arrival" looks like, etc.

    the best way to get good at the mechanical technique is to make some of your own reference tools, using other purchased tools to check them. It is a sort of self-imposed apprentice graduation project. And you will want to do the job to the very best standards, since those tools will determine later results.....

    While theoretically, you can generate every needed reference tool from lumps of iron, it is hardly worth while to do that. It takes a long time, and you have to make more than you will need.

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    "the best way to get good at the mechanical technique is to make some of your own reference tools"

    Totally agree with this, too. Many small straight edges and guages can be made. Connelly shows how to do a lot of this. Read the book and then go for it.

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    J-R -

    Thanks for mentioning my products. I am selling both styles, almost out of lightweights.

    Craig Donges also sells a good product as you mention, and he is a straight shooter. I would not hesitate to buy from him.

    I have to take issue with your description about him being banned, though. I believe it is one of those things where a mod told him to up his ratio of help posts to sales posts and everyone got uncomfortable with it. I consider Craig a friend (although many of you know him better) and he is a good resource on a lot of things and a wealth of information on "old time" stuff. This past Fall I stood in Craig's shop in Ohio and asked him the same question, why we didn't see him so often; and he mentioned the issue that it was perceived that he made too many sales posts. I said straight up that it had struck me the same way when he first came on that it was all sales oriented, but that I had come to appreciate his broader perspective and knowlege. AFAIK, Craig was never "banned" from PM, (& he did not personally claim to be, at least not to me). Don, who puts this show on for free and does a pretty good job of it, seems to be framed as the "bad guy" by people taking sides where none really need taken. What you have is a good old fashioned difference of opinion, and one person choosing not to participate at the moment under the circumstances.

    I'd like to see him post again but don't hold it against Craig for whitholding his expertise and presence because he was asked to lower the ratio of sales posts, and I don't hold it against Don for maintaining a policy that if you don't buy banner ads, you should keep a high percentage of general participation vs. sales and marketing efforts. But it is unfair to keep saying Don "banned" him.

    (unless there is a lot more information that I have not heard)

    smt

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    Craig's 36 is from my donated B&S (which was busted in top rib) and is a nice light one.

    Naturally a new casting won't have this "feature".

    As can be seen here, Craig is a member in good standing:

    http://www.practicalmachinist.com/vb.../craig-donges/

    J.O.

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    How does Craig sell his wares, now?

    Does he have a website or ebay or ???

    I do miss his contributions!

    Mike

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    If you are going to start, don't start on a machine... Start on something small to practice your skills.. Like this chap has done so here Re-aligning a good vice. - The Home Shop Machinist & Machinist's Workshop BBS

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    Smile Challenge Precision

    I like the idea of practicing on my own precision straight edge, and am trying to find links to the Donges, and Thomas references above.

    I also found this much less expensive (compared to Busch) source, Challenge Precision. 24" Camelback at $532, 36" at $637, and 48" at $752, quoting .0002 overall.

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    Quote Originally Posted by ChuckM View Post
    Thanks. I do have a copy of Connelly's book. Hope I didn't bother you all with questions I could have found the answers too in the book
    The Connelly book isn't a how-to DIY guide, it's a reference book (THE reference book), and as I see it assumes that those using it will either already possess some scraping skill or knowledge, or have a mentor on hand to guide the actual work. So ask away- lots of good scraper hands here who know what's up.

    As mentioned above, scraping flat is one thing, doing alignments is another. Connelly really goes into great detail there, excellent material. If I was you I would get some small pieces of CI and scrape them flat on your current surface plate, while searching for a used straight edge and eventually another better surface plate. You'll have a chance to try out the several options of transfer medium (I'm a fan of Dapra's water based stuff at the moment), get used to prepping scrapers and getting all the moves down. It takes practice... soon you'll be looking for a Biax .

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    Smile Massive Camelback Straight Edge

    In the past I wasn't getting any hits on Ebay because I was searching specifically for a Busch straight edge. Just tried searching for camelback straight edge. Anyone interested in a 12 foot model! Camel Back Straight Edge 12' Cast Iron Camelback level - eBay (item 350426620889 end time Jan-28-11 11:14:42 PST)

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    Wow, that is a huge one!


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