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Newbie scraper in Japan

Bakafish

Hot Rolled
Joined
Feb 21, 2022
Location
Tokyo Japan
Greetings PM team, I live in Tokyo and have started gather tools and materials for scraping an old cast iron surface plate to be used as a machine base. I'm located in Japan which creates challenges but has offered potential opportunities as well, as there is some unique solutions over here.

What I have so far is a set of domestic Tungaloy scraping handles and a good number of spare blades.

scrapers.jpg

They are about 40CM in total length and I have all 4 widths, 30, 25, 20 and 15mm blades. These are still sold new here in Japan, the handle part number is HCS-xx and the blade is CST-xx (the xx is width in mm)in case anyone wants to attempt to order them. They are pretty chunky, with virtually no flex, so they aren't really the latest style I think is recommended, but I'm lucky to have them.

I also just rebuilt a 44 year old, domestic carbide tool grinder that I'm hoping will help me get the blades into shape.

grinder2.jpg

This is a 3-phase unit, so I added a VFD and forward reverse switch. It has a nice tilting bed so I can get the bevel right, I will make a jig to set the radius.

The questions I want to pose today are specific to the blade radius. The Tungaloy blades come factory ground at about 5 degrees, but the curvature is around 150mm. I don't know if that's due to the way they are used over here, or because it is easier to reduce the radius than it is to increase it.

My perhaps naive assumption is that the wider blades are for roughing, and the narrower blades are for finishing. And maybe more wrong-headedly, that the bigger the curvature, the deeper the cut and more material removed.

I want to have a clear strategy for if and how I prepare these different blades. The question I have is:

  • What radius and angle should I grind on each of these blade widths (for cast iron)?
  • How does blade width and curvature affect the material removal?

I did read through a lot of the existing threads here, but may have missed an existing answer, so I apologize in advance if these questions have already been clearly answered.
 
The radii turns out to be 250mm, seems like there are some who believe that these large curves can keep you out of trouble.

A link to the PDF for Tungaloy scrapers and blades is here.

It looks like people sometimes have trouble finding these blade for home built scrapers. They are highly mirror polished and should be very good quality.

blades.jpg
 
Given how expensive the Sandvik blades are, if you get a chance please let us know how much yours cost. It might be worthwhile to get some imported to the US if the price is right.

I'm too much the noob to help with your questions, but I'm sure Rich will notice the thread at some point.
 
Thanks for the welcome, it's actually Bakafish, 'Baka' being Japanese for idiot.

The current price range of the 15mm to 30mm single blades is 3104-4820yen. About $30-$40USD each. The handles are about $50-60, but are much easier to make yourself. Although I would warn people that trying to buy professional items like this isn't even easy if you are here in Japan, but sometimes knowing that things exist is half the battle.
 
Welcome Bakafish,

It’s nice to see someone from Japan posting!
Don’t dwell too much on the blade radius just start scraping. I think I use a 150 to 120 for roughing and maybe a 60 to 90 for finishing. My advice would be to get a piece of class 40 grey cast iron barstock or some other piece of iron and practice. A piece perhaps 80-100 mm wide by 150 to 175 long is a good practice piece size. I have an unimportant piece of cast iron that I have at the ready to try a different geometry on blades or to take a few swipes at before scraping something important.

Also, read all of Rich Kings posts, he is the teacher or master. I think the Japanese say one becomes a master after 50,000 hours of practice. He is most likely the only one on this forum with that much time behind the blade.
 
Also, read all of Rich Kings posts, he is the teacher or master.

Yeah, he's a legend I'm well familiar with. I've been researching this for a long time, just trying to nail down some of the details behind some of these specific radii recommendations (found on the gauges.) Maybe it has more to do with power scrapers, I just haven't found it clearly documented anywhere. The good thing is that the base for my machine (750x500mm) doesn't really need to be all that accurate, there will be larger sources of error I expect, but the closer I can get it to flat, the happier I will be.

Base_Plate.jpg
 
How'd I guess?... :D

It looks like you're using round-rail for guides? if so, I'd encourage you to look at proper profile rails, which can be fully supported by machine elements and therefore vastly stiffer.

Unless you're only planning on cutting plastics or very light passes on aluminum, round rails really don't have a place on milling machines. 3D printers yes, torch or plasma cutters sure, but contact cutting tools? No.
 
How'd I guess?... :D

It looks like you're using round-rail for guides? if so, I'd encourage you to look at proper profile rails, which can be fully supported by machine elements and therefore vastly stiffer.

Unless you're only planning on cutting plastics or very light passes on aluminum, round rails really don't have a place on milling machines. 3D printers yes, torch or plasma cutters sure, but contact cutting tools? No.

The pictures here get resized to the point of uselessness, it is sporting 25mm Hiwin heavy duty rails in all axis. Those cylinders are 28mm NSK precision ground ball screws (also on all axis.) But again, I don't want to get off topic here if at all possible. I'll try to create a dedicated thread for the CNC soon.
 
Welcome on board, Bakafish!
Regarding the radius of the blades, especially at the beginning, it is easier to use sharper radii, since they are more forgiving if you do some mistake in controlling the lateral tilt of the blade.

Sharpening: for cast iron you generally use approximately between -3° and -5° depending on the hardness of the material: more negative rake if it is soft (otherwise you dig too much into the material and you get more chatter), shallower (till more or less neutral) if the material is hard.

For the makers of those blades it is more convenient to make them as straight as possible, since they have to remove the least amount of material.

Scraping: I second the suggestion of getting a piece of scrap cast iron to practice with. If you get a block somewhere near 150-200 x 70-100 x 40-70 mm, you can machine it into a small dovetail straightedge and your practice piece will become a precision instrument that you can keep forever.

At the beginning it is easier to do two mistakes: digging holes (e.g. you insist in trying to hit a certain spot and you keep digging next to it) and "chicken scratching" (i.e. not applying enough downward pressure on the scraper and/or not sharpening the blade frequently enough-some cast irons, although "soft" are rather abrasive due to the amount of iron carbides and they wear out the edge of the blade very quickly): when scraping, you should always hear/feel the "crunch-crunch" sound and see a reasonable pile of cast iron crumbles forming in front of the blade.

Scraper: I completely agree with Richard that a light springy scraper is by far superior to the Sandvik or the ones you have. Personally, I have made my own with a piece of flat 1018 low carbon steel bar, approximately 25-30 mm wide and ~3 mm thick. Obviously, if you press too hard, you get permanent deflection, but it hasn't happened to mine.
Cut the bar to a length proper for the distance between your belly/chest and the workpiece and put a flat pad at the back. On mine I brazed a short piece of 1/4" all-thread and screwed on a rubber flap disk designed to be mounted on a hand drill for sanding.

If Saturday I manage to go to Tuckahoe, I will take a couple of pictures of mine and post them here.

Paolo
 
I just saw this and can't write much now, I have a class going in my shop in 20 minutes. 2 more days. I willpost some photo's later. We have a Axelsone compound were scraping ...plus a couple of surface plates... There is a great company in Tokyo called Captain Scientific, who sell scraping tools all over in Asia. They sell in Taiwan where I taught there salesmen to scrape. I'm sure they sell Biax and other tools. My assistant teacher in Taiwan was trained to scrape the Japanese style. I have to go. Thanks Matt and Paolo for the compliments... This group has a lot to offer now....Welcome to the group. Thos handles look like Anderson Scrapers, I'm not a big fan of them though...LOL got to go.. Rich
 
I just saw this and can't write much now, I have a class going in my shop in 20 minutes. 2 more days. I willpost some photo's later. We have a Axelsone compound were scraping ...plus a couple of surface plates... There is a great company in Tokyo called Captain Scientific, who sell scraping tools all over in Asia. They sell in Taiwan where I taught there salesmen to scrape. I'm sure they sell Biax and other tools. My assistant teacher in Taiwan was trained to scrape the Japanese style. I have to go. Thanks Matt and Paolo for the compliments... This group has a lot to offer now....Welcome to the group. Thos handles look like Anderson Scrapers, I'm not a big fan of them though...LOL got to go.. Rich

I think you mean Captain Industries the domestic Biax distributor. I'm sticking to hand scraping for now, since my needs will likely be limited for some time. I've been keeping my eyes open for any good values on used Power Scrapers of course, but they are pretty uncommon over here.

I've seen the "Japanese Style" and it is downright lewd :-D But they do a pretty good job from what I've seen. I have several domestically scraped reference surfaces and they are lovely.

cb4.png


I know this handle design isn't the most desirable due to the rigidity, I've seen that the cool kids machine a long central relief in them to loosen them up a bit. I'll try and make due with what I have first, the scraping is the first step in my journey, I don't want it to be the main focus. Just trying to tighten up the tolerances on an old neglected plate before I start bolting a machine to it.

When your training is finished and you have a chance, my question is basically trying to understand the relationship of the blade curvature and width to the specific scraping application. There seems to be conflicting opinions (gasp, who would have guessed?!) about it, and I suspect that power vs. hand usage has a lot to do with it. It would be nice to get a well reasoned explanation of the relationships though, seeing as the Tungaloy and Sandvik blades seem to ship with very large radii compared to the 4 profiles found on the ubiquitous scraping gauge.
 
I'm not sure there are conflicting opinions on blade radius so much as different preferences. To get more points per inch, you have to focus on cutting just small spots you pick out. You simply cannot do that with a large radius. It shaves off a wider spot and it's difficult to aim.

Conversely, when you have to bring a surface down two or three thousandths, it's just a lot of shoveling material off. Close location doesn't matter, just get the majority of the excess off and then start refining the surface. Here a small radius is a pain to use since it's cutting narrow tracks and so you choose a larger radius and maybe even a wider blade and get that part of the job done.

I think you'll find pretty broad agreement on the large to small radius progression as you move from rough cutting to producing a fine surface. Forest Addy's references were first curve like a two pound coffee can, then move to a soup can radius, and finally to frozen juice can size.
 
I'm linking to the full images for the items posted above since it won't allow me to edit these posts.

The Tungaloy Scrapers:

scrapers.png


The refurbished Japanese carbide hone:

grinder2.png


Close up of the Tungaloy blade:

blades.png


The future victim:

Base_Plate.png


The end goal state:

Kaiju.png
 
I have a simple website with info about getting started openscraping.com, the site needs a bit more work but it will give you an idea about preparing blades etc and the other equipment needed.

As for the router project that is a different thread altogether, for a router using aluminum extrusions there is no need to scrape that plate (and doing so would be profoundly difficult without a large reference surface plate and a crane)

Luke
 
As for the router project that is a different thread altogether, for a router using aluminum extrusions there is no need to scrape that plate (and doing so would be profoundly difficult without a large reference surface plate and a crane)

Luke

The OP seems to not be interested in discussing his machine design, unfortunately.

We should presume he has a reference flat, he's evidenced enough understanding of the process to not have missed that. And if he's strong enough to lift and mate either that plate or the flat, I'm not going to argue with him!
 








 
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