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View Full Version : biax power scraper and biax scraping video



lalatheman
10-23-2002, 05:58 PM
Biax claims their handheld power scrapers are 5 times faster and more acurate than strictly manual scraping. Any comments on this and has anyone seen their 3 part scraping video $75)

Lalatheman

lalatheman
10-23-2002, 06:19 PM
Along this line of thought How about the 40$ hand scraping video and the 25" X 3" cast iron machine tool rebuilders straight edge that he offers. Also since in the raest form this edge is $150 . . so what about welding one up from mild steel.
Looking fwd to Conally's book.
lalatheman

lalatheman
10-23-2002, 06:20 PM
Along this line of thought How about the 40$ hand scraping video and the 25" X 3" cast iron machine tool rebuilders straight edge that he offers. Also since in the raest form this edge is $150 . . so what about welding one up from mild steel.
Looking fwd to Conally's book.
lalatheman

Spin Doctor
11-29-2002, 09:58 AM
We use the Biax power scrappers alot. As to their being faster that cuts both ways. While they do reduce fatique in some ways and are really useful on large jobs like scrapping beds on crankshaft grinders it is REALLY easy for the inexperienced to take too much off. For the finish work we still rely on hand scraping, just wish we could still use white lead though. Connelly,s book MTR is first rats. Taught me the trick about use alochol as a base coat 'cept the light has to be right.

Forrest Addy
11-29-2002, 11:45 AM
Watch it there Spin, you can chill the face using alchohol to raise a haze and if you don't allow time for equalibrium you work will come out convex.

As for the Biax being 5 times faster m-m-maybe, but you have to be a pro with the machine working against a run of the mill scraper hand. It is a labor and fatigue saving gadget.

I scraped three big straightedges in rotation to develop their flatness. I hung the Biax from a crane using a screen door spring as a tool suspension. Using the crane controls and by gripping the tool from the slide I could glide it from spot to spot with little effort a real plus when the final picking cuts took over an hour over 4" x 10 ft reference face bumping the crane as I went.

As with scraping by hand the productivity of a Biax power scraper derives from the will of the hands using it. You can "push the blue around" as readily with a $2000 Biax scraper as you can with a home made hand scraper. You can also make the chips fly.

I watched an old timer scrape 0.030 rainbow out of a milling machine table in an afternoon. That's dovetails, flats, and top. He had a long scraper he pushed with his hip. When he nudged the scraper cast iron fountained up in little gray clouds.

It's like digging a ditch: the ditch won't dig itself. Someone has to work the shovel. There is no escaping skill and willingness to work if you want to expeditiously accomplish a task.

Tibertus
11-29-2002, 06:52 PM
Spin Doctor
I have friends that scaped a way flat to 100 angstroms (4 angstroms in an atom). They used alcohol for the final scraping and an autocollimator to check the work. They noticed they had some slight curvature to the way and couldn't figure it out, turns out the heat from the guy's hand doing the scraping deformed the scraper enough that it caused the arc (I thought they said it was off by a portion of an arc second). I was reading connely's book and can't figure out how to make crescent marks. I've tried to follow his instructions just ain't smart enough or something like that.

Thrud
11-30-2002, 10:24 PM
Tibertus:
100 angstroms = .o1 microns = .oooo1mm = .oooooo39375"

The finest gage blocks made - Starrett/Webber Grand Masters are only to .ooooo1". They are kept in a vacuum to prevent atmospheric damage to the surfaces. The blocks are recognised as "master standards" verified with frequency stablized laser light.

Your friends are yanking your chain - there is no way they could get a surface that flat by any human means. And if they did - they should expect their Nobel prizes shortly.:P

Forrest Addy
12-01-2002, 06:16 AM
[QUOTE]Originally posted by Thrud:

"Your friends are yanking your chain - there is no way they could get a surface that flat by any human means."

Not entirely. I dunno about angstroms but given time and control of conditions (body heat radiation is only one variable) one can hand scrape to amazing degrees of accuracy. Remember the equipment used to develop gage block accuracy and certify them were hand scraped. Also the gimbaling that uses hand scraped circular arc hydrostatic bearings used on astronomical telescopes are associated with angular measurements accurate to 0.01 arc second. At least the ones made before 1970 were. I don't know about present day ones.

Hand scraping accomplished to fit and align small manual machine tools is at the rougher end of the spectrum. I've personally scraped a set of three straightedges about 10 ft long flat and straight to 90 millionths. My last few cuts were with a hard Arkansas stone. Took a week of part time effort and there's a lot of guys done closer work than me.

How do I know 90 millioths? That's what the cert papers from Northwest Calibration Laboratories said. There was a nice little map that came with it too. The contours were mapped in 20 millionths increments. They were shaped like woodgrain in a flat sawn clear pine board.

gizmo2
12-02-2002, 12:37 AM
And I thought inletting a rifle stock was a pain in the butt; you guys are definitely sick, but not twisted.

tonydacrow
12-02-2002, 10:20 AM
The average amature astronomer can easily (with a little practice) grind glass plates flat to within 1/4 wavelength of light. I know: I've done it and I'm not very good! Those with more practice can go to 1/8 wavelength or better. That's about 500 angstrom using violet light. I see no reason why a very good machinist couldn't better that by a factor of five or more (although I don't think "hand-scraping" will produce that kind of accuracy).

Tibertus
12-02-2002, 08:20 PM
Ok Thrud you made me get out my book (they put this in writing) and found that you are right, the tool has to be positioned to within that spec. I'm sure that in the book somewhere and along with conversations with the old boys they did say they scraped it that flat. If one of them wasn't on the international board of standards I would of laughed it off. They are also old friends of Henry Moore (Moore tool company). They old guy that actually did the scraping said he was sent to Pratt and Whitney for a few months to learn how to scrape. I didn't measure it myself so who really knows? Still would like to know how to make crescent marks while scraping.

Spin Doctor
12-02-2002, 09:30 PM
Thurd, your right about letting the temperature equalize. If you place your hand just above the alochol you can definetly feel the temp difference. The primary reason I started using alochol is the base coat we were forced to use after the feds put the kaybosh on white or red lead is some crap called gear compound. We used to use in our production deptartments to check rear end sets for pitch line pattern after lapping. One thing though is if your in the process of rebuilding a machine that you have leveled out yourself and then the machine movers come and pick it up, horse it around to get it in place on the shop floor, and then level it I'll garanty it isnt going to be as straight as when it was finished in the shop. If your doing the job in place your still subject to a lot of variables. Temperature for one, vibration from fork truck traffic, and god knows what else with the primary one being the boss breathing down your neck wondering why the job isnt done. And yes when I started in this racket my boss wanted to see chips and smoke coming off the end of the blade.

lalatheman
12-03-2002, 12:59 PM
Spent $75 on The Biax scaping Video watched it 10 times so far and now once a week it's helping alo their radius gage for tool grinding helps.
Would any of you accomplished scraperguys consider doing a little personal instruction . . . for pay ?
I'm thinking two or three hours with someone wh actually knows how to operate would save me months of scratching around.

Thrud
12-05-2002, 02:38 AM
Forrest

I might have been better served wording my response to "extremely unlikely".

I agree with the comments made about 1/4, 1/10, or even 1/20th wave surfaces. A 1/20th. wave surface would be 250 Angstroms or 9.84E-7" or just under 1 millionth of an inch (presuming infra-Red light). Which explains why a 1/20th wave optical flat is so expensive. But these are only a few inches in diameter at most.

The HST Mirror made by Kodak (low bidder) was tested to 1/20th of a wave (90+ inches). The Kodak (best) mirror never went up because they were low bidder (huh?) So the defective Morton Thiokol mirror went up instead. Good thinking. http://bbs.homeshopmachinist.net//frown.gif

ckalley
12-06-2002, 04:40 PM
I have some news for you...
The HST main mirror blank (the one that was actually used) was cast by Corning and then "rough" ground and then finish polished and coated by Perkin-Elmer Corp in thier Wilton and Danbury, CT plants. If memory serves me, the mirror has an OD of 96" and a clear aperture of 90". The big difference between the 2 mirrors was how the metrolgy was done. Kodak calculated what the force of gravity on earth compared to it in space would do to it and ground it to copmensate for the deflection due to gravity. P-E used a system that simulated the actual forces that would be seen in space.

Even if the final radius wasn't exactly right, it was the most perfect surface of that size. Too bad NASA wouldn't do the testing they wanted to do so that problem could have bee avoided.....

mattdrag
12-07-2002, 01:07 AM
Hey lalatheman i would like to see that tape , i think we are not to far apart? Maybe we can work something out?? mattdrags@earthlink.net

Thrud
12-08-2002, 02:23 AM
ckalley:
Corning made both of the blanks. I was sure it was Morton Thiokol - whoever the turds were they made military spy sats and they figured they never make mistakes. And yes, NASA could not get the NSA to test them in their Optics facility because they were afraid the "other side" might figure out how good the spy sats really are. Have to keep making military suppliers look good...

One of the most important scientific tools ever built by mankind and it was almost totally screwed because of blind favoritism.

[This message has been edited by Thrud (edited 12-08-2002).]

lalatheman
12-09-2002, 10:24 PM
mattdrag,
Yeah lets try to get together , I can loan you that video. I'm sending you an e- mail