Thread: WAY SCRAPING

Please tell us about WAY SCRAPING...I got on the Bridgeport/Hardinge web site and I see that they still Scrape the ways of new machines by hand. Why? With all of the high tech stuff around why must they still be scraped my hand??? I noticed that you can buy a brand new series one belt driven Bridgeport Mill. Made in Elmira NY....anyone know how much a new machine would cost? Thanks in advance.

Why? Check all the posts on scraping on this site. It's been asked a few times.

As far as BP prices, don't know about the J heads, but the 2J with 48" table is often on sale at MSC for around $12,295.00. Supposedly $12,600 their regular price.

smt

Who in his right mind except a radical American Iron chauvinist would spend the money to hire a full machine hand scraped reconditioning when for about 2/3 the price he can buy an adequate import posessing comparable function, accuracy, and longevity.

If hand labor is your own to expend then the labor component for hand scraping a turret mill to like new condition is almost free. I caution you the learning curve is steep and about one year long - and the tools and equipment can be expensive and time consuming to accumulate. I know. I teach precision scraping.

If you think you might want to dig deeper into the potential for hand scraping to solve your problems, I suggest you take a liesurely look through Connelley's "Reconditioning Machine Tools" and Moore's "Foundations of Mechanical Accuracy". You'll find them through any competent public libary.

You will also find many old threads and archive entries on "scraping," some delving deep into the intracacies of the technology.

Connelley's "Reconditioning Machine Tools" and Moore's "Foundations of Mechanical Accuracy"

I understand those are good books, covering many important things.

I've not seen a book mentioned as the gospel on scraping alone.

...someone...should consider writing one.


My tailstock is a little low, but seems to run true across it's extension; same amount below perfect touching of two centers either in or all the way out. Would that be covered by the chapter on magic anti-scraping, or dropping the headstock the thing to do?

(for me, it's shims. Wish I knew better)

Use shims. It aint perfection or politically correct but it restores function and productivity to droopy tailstocks. Be sure the bottom of the tailstock bears properly on the tailstock ways. They are often rocking chaired to some degree between slight and comical.

As for a someone writing a precision hand scraping text, scraping is a physical skill like riding a bicycle, not an intellectual pursuit. The most careful and inspired expository writing cannot transfer a physical skill with the effectiveness of a qualified hands-on mentor. It takes a project and a teacher to transfer the skill.

Steven Thomas, several others, and myself have the wherewithal to write a book on precision hand scraping but there's two problems: too small a market and lack of interest from a publisher having the resources to promote such a book. Others have tried. There are several videos, scraper texts, tooling available on a small scale but nothing comprehensive such as what can be mounted by a commitment from a deep pockets entrepreneur. Grizzly and Enco come to mind.

It's odd. The woods are full of people eager to restore their junky old treasures to like new performance but they can't for lack of low cost resources and training.

Several machine tool importers offer hand scrapers, granite surface plates, and other items needed for the well equipped hand scraper yet they don't offer a complete, one stop product line for the home shop machine tool rebuilder with straight edges, a low cost powered scraper, contrast media, etc not to mention fund a book publishing project.

I might sound like I have a horse in the race. I don't. I have seen people intent on acquiring the skills take vast unproductive detours in the wrong direction (flaking is a prime example) for lack of mentoring.

Scraped surfaces can be held to arbitrary degrees of precision, and local errors that develop can be removed. A ground way is limited to the grinder's inherent precision. Ironically, the way grinder's ways will be scraped to provide whatever original degree of accuracy is desired.

Additionally, scraped ways are an ideal plain bearing surface, giving the machine greatly enhanced life expectancy.

Forrest, maybe (well, probably) I've deluded myself into thinking I know more than I do, but in actual time scraping, I've been at it less than a year, with minimal in person direction. And yet I'm still confident that given the time and tools, I could get the average home-shop lathe or mill back to manufacturer specs. Machine tools are entirely based on simple geometric relationships, which really aren't that difficult to wrap one's mind around.

What I'm getting at is that fundamentally a lathe or mill is a very, very simple tool. i rebuilt my lathe with six important tools: a straightedge, a dial indicator a large square (24" in my case), a planer, a Starrett 199 level, and a scraper. I could've gotten by without the planer. A rebuild is hard work, no doubt about that, but understanding the concepts behind the measurement and alignment of the surfaces is really pretty simple, and not really worthy of a book. Then again, if most people out there think they can figure out something meaningful about a machine's alignments with just an indicator and a mag base, then maybe I'm wrong and there should be a book.

I won't argue Halco. Machine tool re-building is not rocket science. The hand skills are quickly built and some extended practice will drive the lessons home and lead to proficiency, stock removal, and judgement of indications.

However, time can be saved if the scraping is organized in definite ways and is preceded by a survey of the machine's condition. From the survey a scraping plan can be developed and those existing surfaces suited for future reference identified and used to develop the machine's accuacy, alignments, linearities etc.

This survey/planning phase is where the neophyte tends to skimp - often to great sorrow as the work stretches on and on. Too many attack the table and saddle of a mill or the bedways of a lathe without even determining the amount, location, and extent of wear present. One who starts a horizontal knee mill without first establishing the column ways as being parallel to a radial plane to the spindle is asking for trouble.

Here Connely and Moore offer considerable guidance to the home scraper. It's the developing scraping skills in the hands and mind of the would-be scraper hand that require the steadying hand and guidence from a mentor. Books and videos may be helpful but few offer the negative (corrective) feedback needed for skill development. Scraping is a physical skill. There's the scraper's anatomy, innate eye-hand coordination, and other personal variables possessed by the student tha thas to be cranked into the instruction somehow and no book or video can apply these except as an endless series of confusing caveats.

[ 08-01-2007, 08:54 AM: Message edited by: Forrest Addy ]

If not a book, how about a "primer" or pamphlet type with intro info. Basic measuring techniques, or even just how to hold and shape a scraper. I've got no intention of rebuilding my Bridgeport, but I would love to improve the feel of the compound on my lathe. And if that went well, the cross slide.

If more than that was required I would sell and upgrade before putting in that much time for the class of machine I have. Then again, those basic "survey" techniques would be useful in determining if an "upgrade" was called for, or even actually an upgrade at all...

well you have to check about hand scraping allot of people/manufacturers hand scape oil marks in ground ways and try to pass them off as hand scraped.I do agree for a home shop a new bridge port is a waste.you would have to work hard and long to pay it off.

By the way, Bridgeport ways are not hand-scraped. I don't know why they claim that.
They're ground or milled, with power flaking applied with a Biax.

Take a look at any newish Bridgeport, and you can see the Biax flaking is applied over a smooth (not scraped) surface.

With all of the high tech stuff around why must they still be scraped my hand???

Convergence through iteration.

If not a book, how about a "primer" or pamphlet type with intro info. Basic measuring techniques, or even just how to hold and shape a scraper.

Mike Morgan's "Basic Scraping" book is excellent, and very comprehensive on everything you need to get starting with scraping.

Mike's book covers how to pick a scraper, how to size it (according to your height), blade shape, how to sharpen it, the various parts of the scraping stroke, how to get the elusive Moore "Curl", the difference between files and stone when deburring and break-up bearing, how to use a power scraper,...

There's also a really good chapter on machine alignment.

http://www.machinerepair.com/scrapingbook.html

If you don't want to deal with ordering through Mike Morgan's web page, most of the Dapra dealers carry the book (and video).
I ordered mine from E. S. Dyjak in Michigan: (248) 684-4260

Hey Forrest--there is a possibility, perhaps. I agree, that a master mentor is critical. I wish I had one just for my turning.

Anyway, the possibility: xlibris is an on-demand publisher. But along with the text--videos on DVD to accompany the text. And we would invest in the production--some could make the DVD's from digital recordings...some could review the material--you could serve as master editor.

Market limited--yes, but a niche market. Taunton Press is a niche publisher for woodworking venues--perhaps American Machinist might be willing to help in some way, perhaps a grant to get the project started.

Just a possibility--and I like learning possibilities.

H*ll of an undertaking, but it could be done.

Joe

Milacron--whatcha think???

That "Basic Scraping" book sounded promising until I saw the "subjects covered" including...
"Accounting for the curve of the Earth"

um..what?


Yet, nothing on relativistic effects.


Now very glad my ways seem lightly used and in good shape, since they're hardened anyway. Puzzled why the tailstock center would ride a little high. but maybe it's always been that way. A little blue paint rolled onto the ways should lift it up about the right amount

edit, tail's center is low. better lift and blue-paint the headstock base [img]smile.gif[/img]

Forrest, it appears we are in agreement. A book is a good way to keep someone from jumping the gun. And personal instruction is a great way to keep someone from skimping during the work. It's easy to say "good enough" when such is not really the case.

Lazlo, you are correct in your assessment of bridgeport crossfeed ways, however the reason they say they are scraped is that the saddle is hand scraped to fit those ground ways. You can't see it without disassembly, but every way (except maybe the turret) has at least half of the bearing surfaces scraped. both for fitting it up and for adjusting squareness during final fitup.

Tailstocks are often set slightly high to extend the wearing life of the tailstock. When I rebuilt my lathe, I set the tailstock 0.010" high, IIRC.

That "Basic Scraping" book sounded promising until I saw the "subjects covered" including...
"Accounting for the curve of the Earth"
um..what?
Yet, nothing on relativistic effects.

You need to read the book Joe. Mike is talking about the error induced in a precision machinist level due to the curvature of the Earth.
Mike is a professional machine rebuilder, and a lot of the machines he works on are very large.

I'll quote you that section that you're worried about:

"Because of the curve of the Earth, a level displays an error of approximately .00003" per foot. With this in mind, a surface that is 10' long when scraped or adjusted to indicate dead level along its entire length is actually .00015" low on each end. This is a minor problem with a surface this small, but when setting up up a machine 60' long, this curve begins to be an appreciable problem. With a machine of this length, the error on each end would be .0009" or nearly one thousandth of an inch."

Guys...thanks for your replies...I'm learning more as i use this site. But I still ask...if we can machine to a millionth of an inch for NASA...why must we hand scrape a way? Is it a matter of practical cost?? If one were to program a CNC machine, like the Bridgeport Comapany for example, wouldn't the resulting product not need hand fitting? I don't understand why with this state of the art tech.....a way still has to be hand fitted.

Thanks

It takes a project and a teacher to transfer the skill.

Not really, Forrest. Teachers often think they are indispensible, but anyone with a basic curiosity can teach themselves a new skill, just by knowing what the possibilities are and having an ability to observe and react and apply ideas learned elsewhere. Pictures and books are an excellent resource for learning scraping. There is nothing special about self-teaching that wasn't learned by about the age of 5.

-Dave

Joecr,

On my little Rockwell 10X36 lathe the centerline of the tailstock was low by about 0.006" TIR. I pulled the tailstock off to check the ways on the stock. They were ground slightly concave originally so the wear was all at the front and the back. Only about an inch at each end was showing any wear (or contact).

To remedy it I shimmed it up by 0.003". That got me to within 0.0005" TIR. Only other way to fix this without replacing parts would be to scrape the base of the headstock... which I was not about to do.

I just checked the setup because I had been turning some tapers by offsetting the tailstock a few thou. It is now 0.0005" TIR up-down and sideways. I can change that depending on how hard I tighten things down so I set it so it is as close as I can get it with typical 'tightness'. This is OK.

I also extended the ram all the way with the handwheel and locked it. I then set an indicator in the toolpost against the top of the ram and ran it along the length of the ram. Fortunately the top and sides of the ram appear to be dead parallel to the ways. This is good.

At some point I will try touching up the ram taper (MT 2) with a finish reamer because it is pretty rough. Seems the previous user spun a few centers or chucks in it. My centers don't seem to always 'land' on center. This is bad.

This little lathe has always been a bit of a struggle but with some care and patience I can make good working parts with it. I have loaded it up with heavy 8" diameter parts and turned them to within the specified tolerances. I have turned little 1/16" diameter parts (lead screw shear pins). I can cut useable threads with it. With careful tool preparation and selection of speeds and feeds I can get nice finishes. It works. Though I hope to get a bigger lathe at some point I will not get rid of this Rockwell. As long as I can make good parts, it stays.

-DU-