View Full Version : Scraping with an Asian flare

02-13-2011, 09:51 PM


Wonder which country?Taiwan,Korea or China?

J Tiers
02-13-2011, 10:11 PM

I could not figure out what the operator was after in the first one.

he had spotted the surface, and there were marks visible. But rather than scrape off the marks, he was scraping the entire surface.

if the part had not spotted along the entire length, I'd understand, but it did appear that the entire way was spotted, although not exceptionally well for a slide-way. I could not get a feeling for the bearing spots per sq inch, simply because teh medium seemed to be thick.

In any case, he seemed to leave no area un-scraped, despite there being a number of area with no spots, yet he scraped them.

I'll have to take another look.

The second one shows not "medium spotting" but "wear spotting". The operator takes about 50 strokes of the mating part, and then scrapes the worn spots.

If teh first spotting was any good, the wear spots showed a LOT less bearing than was present originally.... there were probably less than 30 spots on the whole length, as opposed to 10 or 15 per square inch as for a slideway. he was apparently much closer originally.


02-13-2011, 10:23 PM
It must be the Grizzly factory, the green floor might be years of overspray.

02-13-2011, 11:20 PM
Ahh,the finished producta CNC slotter,neat.

Caption says Taiwan,wonder what one costs?



02-13-2011, 11:22 PM
It looked like he was missing several of the wear spots he was supposed to be eliminating.

Mike Burdick
02-13-2011, 11:33 PM
I don't see any use of "standards" anywhere! The guy is not scraping for a precision fit, parallelism, squareness or perpendicular, etc. He's just rubbing two surfaces together to see if it hits anywhere.

Another thing...one should scrape the material to where one's been, not pile it on to where one's going.

And... oh well....

02-14-2011, 12:18 AM
If I'm reading it right,the slides have already been machined square and parallel.The scraping is being done for a running fit oil retention etc.The front ways will most likely be fit with shims.

02-14-2011, 12:23 AM
'But but.. Its scaped, Its gotta be better!'

J Tiers
02-14-2011, 12:39 AM
If I'm reading it right,the slides have already been machined square and parallel.The scraping is being done for a running fit oil retention etc.The front ways will most likely be fit with shims.


What was the spotting for then? He spotted it, and then did what amounts to "scraping straight down", which eliminated any precise alignments that were machined-in. No standards used, so no idea what the effect was, other than, apparently, to mess up the bearing bigtime, if the subsequent "wear marking" is anything to go on..

Possibly we are not seeing the whole sequence, but I have never heard of "wear spot scraping", like that.

I have heard of (but not done, except as an experiment) the use of alcohol as a marking medium. That would "look like" what was done, except that alcohol would have been wiped over the surface, the mating part (or other reference) would have been carefully laid on, and moved back and forth a short distance maybe twice.

The "haze" would be marked by small areas of burnishing, which represent the high spots to be dealt with.

In the video, some red stuff was put on, then wiped off (lube?) and then the mating part was 'ground -in" about 50 long strokes (I counted). The very few bearing spots were then scraped. No testing of alignment, which you would think was important for a slotter in the plane perpendicular to the ram rotation axis.

As for machining to square and parallel, if ground, the surfaces should have spotted better, and wear marks should be different, and, of course, "why scrape at all?". If otherwise machined, where are the tool marks?

if done for oil, the best method would probably be to scrape a checkerboard of spots, or to simply "flake".

it's goofy if considered as 'scraping for bearing and alignment", I'd want to know more about the goal.