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In Need of Feedback - Dapra Power Biax Scraper

whizbang

Plastic
Joined
Dec 8, 2013
Location
Michigan, USA
Hey Guys,
I am looking for some feedback, as I cannot really find my exact question phrased anywhere and I am at a loss for words on how to describe it.
What I am looking for is confirmation that the strokes of my Biax are normal. I have attached pictures and a video below.

I currently have my Biax on setting 1-2, any more and it seems out of control. I have a 30-150 blade sharpened to a 60-55deg radius. I have been experimenting with 4-9deg rake angle for cutting. Reading something R. King wrote in another post for someone to try 10deg. I bought a 4x12x1 inch� block of gray cast iron. This is my practice block, similar to the one provided when I took King's class. It has been awhile, but I took his class in Kalamazoo back in 2013 I believe. I will admit that I did not pick up scraping very quickly in the class and I kind of rushed my time with the biax provided to work on the project I had brought with me. It has taken me 5yrs to acquire all the essential to really get into the scraping such as the Biax, hand scrappers, Accufinish grinder, and of course time.

Yes I know there are scratches in the part , I am not going to try and hide them, this is my first attempt at scrapping in 5yrs. I initially roughed using circles and crosses and worked to where I am now. However this is where I question if I am forgetting something.

In King's class I remember plowing of material with beautiful straight cuts, 7mm or wider cutting only on the forward stroke. Now with my current set-up, even with a 140mm radius blade, I get skinny 3-4mm wide scrapes and they are connected in a pattern that looks like a bunch of N's or W's connected. I am pushing forward and putting weight from light to more than I think I should to try to flex the blade.
I am looking for feedback:

Did I miss something very basic in set-up that is giving me these N patterns? Or is this completely normal?
I am looking to develop this skill and would really like to produce 4x4mm checker boarding. Even at slow speed less than 1 with pushing down in the radius 60 I get 2mm max width cuts. I think I am missing something fundamental. Perhaps I need higher than 600 grit on the Accufinish grinder?

20171015_173902.jpg
Camel Back Square done during class with R. King in 2013

Sample Scraping with Dapra Power Biax - YouTube
N pattern on current test piece (please note, when I uploaded the video it looked good but when I viewed link through phone it was fuzzy but I was able to select the quality which improved the image)

20171015_130635.jpg
Cast Iron test piece
 
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From the video your standing in the same place and not moving your feet that's why your lines are at different angles of attack. Also looks like your using your arms and not your body, thats why your not getting a straight line 45deg.

Get a machinist square and draw lines with a sharpie every 1/2 apart and use them as a a guide to aim at. The first photo shows you scraped 1/2 the part from one direction and the other 1/2 from the other. you need to scrape the part all the way from one side and then next time scrape from the other side all the way left to right / right to left to get the checker board look. Didn't you get a DVD in that class. I now give each student a DVD so you can learn at home before the class. Also you must have forgot my email address or phone number as I pledge to all my students free help on the phone or email for yours or my lifetime as long as you took a class.

I may have a photo to attach, let me see. Also their are dozens of my students who read the frorum who can help answer your question. One of my best and brightest students "Other Brother" is his forum name, he lives in MI and if your close I'm sure he would offer his help as he is retired now. Also now there are several You Tube shows made by former students showing the technique. Search Richard King Scraping on YTube. If you forgot my phone number send me a Private Message and I'll give you a call. Rich

20160826_114429_resized.jpgGA May class2.8.jpg20160316_111712.jpgDSC01116.jpg
 
Richard (by the way: welcome back! We missed you!) has pointed out pretty much the most important points. Another consequence of moving your arms, instead of your body is that you tilt the power scraper one side or the other, creating gauges well visible in your second picture and in your video circa 6 seconds in.
Beside strongly recommending you to watch Richard's DVD over and over, check if by any chance the shoe and blade attachment of your Biax are not worn allowing the blade to tilt some side to side. I believe that, up to a certain point, the ones on the 7 series are adjustable to compensate wear.
Last thing about your power scraper: is the rubber wedge in good shape? if not, it's harder to control the blade. A new one is rather cheap (I don't remember precisely how much, but in the single digit range).

Paolo
 
The N pattern is unavoidable. It has to be that way unless you can somehow time yourself to stop the scraper at every forward stroke and lift it up during the reverse stroke like some do in hand scraping.

The faster you run the scraper, the more the N shape starts to lean and look more "italic". If you want the checkerboard to be 45 degrees to the edge of the surface, you have to compensate. It doesn't really matter except for the cosmetic effect.

It looks like you need to put some pressure on the blade. It's barely making a chip.
 
The N pattern is unavoidable. It has to be that way unless you can somehow time yourself to stop the scraper at every forward stroke and lift it up during the reverse stroke like some do in hand scraping.

Also known as "the right way". :)
I'm quite amazed by the popularity of the Biax amongst the public at large. Sure, it's got it's benefits for production work but I have yet to see a proper surface scraped with a Biax. I'm sure it exists, it's just I haven't seen it.
 
Richard (by the way: welcome back! We missed you!) has pointed out pretty much the most important points. Another consequence of moving your arms, instead of your body is that you tilt the power scraper one side or the other, creating gauges well visible in your second picture and in your video circa 6 seconds in.
Beside strongly recommending you to watch Richard's DVD over and over, check if by any chance the shoe and blade attachment of your Biax are not worn allowing the blade to tilt some side to side. I believe that, up to a certain point, the ones on the 7 series are adjustable to compensate wear.
Last thing about your power scraper: is the rubber wedge in good shape? if not, it's harder to control the blade. A new one is rather cheap (I don't remember precisely how much, but in the single digit range).

Paolo

I could use a new wedge myself, any leads Paolo? Dapra? It's for an old blue, single speed jackhammer, 7el IIRC...

But like others said, keep the machine high and tight like a football and do the feet shuffle. Like ewlsey said, looks a little "scratchy". Make sure your blades nice and sharp and put a little more into the Biax, although, working from your body rather than your arms, should make a more rigid setup/deeper cut anyway.

Corey
 
Also known as "the right way". :)
I'm quite amazed by the popularity of the Biax amongst the public at large. Sure, it's got it's benefits for production work but I have yet to see a proper surface scraped with a Biax. I'm sure it exists, it's just I haven't seen it.

Alex,
I'm no pro and don't claim to be a great scraping hand either. However, I find much easier and far faster to get a good enough surface with a Biax than by hand, especially with finish scraping and with problematic pieces.
I also enjoy the calm and peacefulness of hand scraping, whenever I can afford doing it.

This B&S surface plate was rather hard, at the point I had to use my 7ESM with the stubby blade holder in order to score it ~0.0002"




On the bottom you can see a round plate with a hole in the middle finished at ~50ppi with a Biax and above is the compound of a Hendey roughed-in by hand scraping (I'm not responsible of the scraping of the beautiful 24x24" B&S plate on which everything rests):


Bottom line, I find really great the fact that the machine controls the length of the stroke for you: it really makes a difference, at least for the crappy scraping hands like me. ;-)

Paolo
 
I could use a new wedge myself, any leads Paolo? Dapra? It's for an old blue, single speed jackhammer, 7el IIRC...
...
Corey
Corey,
I believe that the wedges are the same for both old and new (at least, I've used on both).
I've got mines from Ed Dyjak, who repairs Biax, sells spare parts, Canode inks, etc. and is a really nice person to deal with.

I'll PM his e-mail address.

Paolo
 
Thank You guys !

I plan on doing more reading and let the youngsters take over in the forum and add when I see something missing or I may learns some new tricks too.

It's nice to see my students answering questions :-)

Yes the the rubber "cushion" is what it's called caan be purchased from ED Dyjak..ES Dyjack Company in Milford MI. He and I have been friends for 40 some years. One man company now, before his Mom and Dad have passed away it was a family business and he runs the company alone now. Back in the hay-days Ed and His Dad sold more Biax Scrapers from DAPRA then anyone else in the country.

Rich
 
Alex,
I'm no pro and don't claim to be a great scraping hand either.

From what you've shown there you're very talented - that's some great work !
Re. Biax, it's just me - seen them used a couple of times ( 2-3 ) and didn't like the result which by the way was good enough for the purpose.
 
The return-stroke mark a Biax leaves doesn't have any depth to speak of. It's not the kind of thing to worry about.
 
Guys,
Here's a small update. I inspected the rubber cushion wedge under the blade and it looks like it needs to be replaced. While I know majority of the issue is operator error and being a novice I definitely see some rubber peeling back and the surface not being uniform because its worn in all places except where the U shape of the blade sits. I called ED Dyjak and ordered 3 rubber wedges they were a few bucks a piece. He is very helpful and knowledgeable. I ended up buying a 10-150 from him as well as that's the only size I don't have in the blade kit I got with my biax. I'm sure I'll find a use for it. Again thanks for all the feedback. I will update once I get the wedge see what difference it makes. Have a great evening fellas
 
I will second about everything mentioned here.

Great job with individual scrap marks and individual scrape lines.

My comment is it appears you are not putting too much pressure on the scraper?

If you do another video it would be good to see the positions of your hands and arms.

FWIW- I am a fly weight, 150 lbs, I scrap on about 4 or 5 on the dial.

I need to put all my energy and weight into scraping.
 
The return-stroke mark a Biax leaves doesn't have any depth to speak of. It's not the kind of thing to worry about.

I couldn't say - I haven't payed that much attention. My observation was that while with Biax they scraped A LOT, they had difficulty gaging depth and the pattern looked phony. I could not understand from the pattern how good the surface is. I'm sure they are wonderful tools but I wouldn't use one for real accuracy. But again, they are probably super for heavy removal and for creating the illusion of scraped surfaces.
 
I couldn't say - I haven't payed that much attention. My observation was that while with Biax they scraped A LOT, they had difficulty gaging depth and the pattern looked phony. I could not understand from the pattern how good the surface is. I'm sure they are wonderful tools but I wouldn't use one for real accuracy. But again, they are probably super for heavy removal and for creating the illusion of scraped surfaces.

I have scraped 40 to 60 PPI and with in .00002" using the Biax Power Scraper. The advantage of it, is the stroke lengths are the same and all it takes is good eye and hand co-ordination. Seeing someone is not the same as doing. Many of my students on here can testify to this. BIAX is also coming out with a newer and better scraper line soon and things will get better.

Also the BIAX scraper will increase productivity by 50% or more. I admit that a Swiss hand scraped way is a beautiful art. Sip used to use the BIAX up until the last couple of passes when they hand scraped to get their signature hand scraped look. G-Day. Time to go fishing, leaves are beautiful up here too. Rich
 
I have scraped 40 to 60 PPI and with in .00002" using the Biax Power Scraper. The advantage of it, is the stroke lengths are the same and all it takes is good eye and hand co-ordination. Seeing someone is not the same as doing. Many of my students on here can testify to this. BIAX is also coming out with a newer and better scraper line soon and things will get better.

Also the BIAX scraper will increase productivity by 50% or more. I admit that a Swiss hand scraped way is a beautiful art. Sip used to use the BIAX up until the last couple of passes when they hand scraped to get their signature hand scraped look. G-Day. Time to go fishing, leaves are beautiful up here too. Rich
Glad you are back on the forum, hope you enjoy the cottage and relaxing
Edgar

Sent from my SM-G935V using Tapatalk
 
I couldn't say - I haven't payed that much attention. My observation was that while with Biax they scraped A LOT, they had difficulty gaging depth and the pattern looked phony. I could not understand from the pattern how good the surface is. I'm sure they are wonderful tools but I wouldn't use one for real accuracy. But again, they are probably super for heavy removal and for creating the illusion of scraped surfaces.

Alex, talking as the cheapskate hobbyist that I am, I think the main issues most of us find with the Biax could be mainly summarized in two main points: worn out power scraper, and illusion that the blade will cut forever without sharpening.

The least worn Biax scraper I have is a very old 4EBC that has "only" ~.003-.005" between the blade holder and the harden steel shoe.
My backup machine (similar model, now being rebuilt) in the middle of the stroke there was almost a .020" gap, causing the blade to tilt enough to gauge the piece (with 90mm radius blade) or, anyhow, to land the stroke where you don't want it. It took me quite a while to realize that it was not only operator error, despite I had watched a video from Jan describing the very same problem (when I watched the video, I didn't believe it was a real problem and I thought he was exaggerating things).
The second issue, that could yield to the misconception that you cannot control well the depth of cut with the Biax is that you have less (or, better said, a different) feedback on how the blade cuts, since the grunt work is done by the scraper itself.
Definitely, you need to develop a feeling on how much pressure you're putting on the blade: I don't remember who suggested it, but a great advice is to train yourself in pressing against the top of a scale, and develop a muscle memory of what a light, medium and heavy pressure is.
Now, with your body delivering more or less constant pressure, you need to be very attentive of the scraping marks: if they become narrower, it's time to return to the grinding stone.

Later, if I find the time. I'll post a couple of pictures of scraping marks made with same setting and blade just sharpened and blade begging to be resharpened.
It's hard to establish a rule after how many square inches you need to resharpen the blade: some cast iron is rather abrasive and dulls the blade very quickly (and I'm talking about the great Sandvik scraping blades!).

Paolo
 
Alex, talking as the cheapskate hobbyist that I am, I think the main issues most of us find with the Biax could be mainly summarized in two main points: worn out power scraper, and illusion that the blade will cut forever without sharpening.

The least worn Biax scraper I have is a very old 4EBC that has "only" ~.003-.005" between the blade holder and the harden steel shoe.
My backup machine (similar model, now being rebuilt) in the middle of the stroke there was almost a .020" gap, causing the blade to tilt enough to gauge the piece (with 90mm radius blade) or, anyhow, to land the stroke where you don't want it. It took me quite a while to realize that it was not only operator error, despite I had watched a video from Jan describing the very same problem (when I watched the video, I didn't believe it was a real problem and I thought he was exaggerating things).
The second issue, that could yield to the misconception that you cannot control well the depth of cut with the Biax is that you have less (or, better said, a different) feedback on how the blade cuts, since the grunt work is done by the scraper itself.
Definitely, you need to develop a feeling on how much pressure you're putting on the blade: I don't remember who suggested it, but a great advice is to train yourself in pressing against the top of a scale, and develop a muscle memory of what a light, medium and heavy pressure is.
Now, with your body delivering more or less constant pressure, you need to be very attentive of the scraping marks: if they become narrower, it's time to return to the grinding stone.

Later, if I find the time. I'll post a couple of pictures of scraping marks made with same setting and blade just sharpened and blade begging to be resharpened.
It's hard to establish a rule after how many square inches you need to resharpen the blade: some cast iron is rather abrasive and dulls the blade very quickly (and I'm talking about the great Sandvik scraping blades!).

Paolo

Come on, you are quite a bit better than a cheapskate hobbyist. Some great work there ! I'm sure it's a good tool and one can do some serious work with it. I wasn't impressed but that means nothing. In the end, what do I know ? Very little.
 








 
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