How thick are Biax scraper blades?

[Tillie]

I just got a used biax BL 40 and I'm learning the basic scraping "strokes"(?) from Richard king's video.
The two blades that came with my scraper are the type that hold sandvik 630 type inserts, which is what I prefer. The drawback is that they are the short extra-thick type 4mm or 5/32" that I expect are for heavy roughing. What is the thickness of the general purpose blade? I will be making my own insert style blades, probably a 6" long 3/4 wide to take sandvik inserts and eventually another to take narrower inserts.

 

[Peter from Holland]

Your biax is a flaker I think To make those V shaped finishing marks
I had one and it had a special blade with a radius on one flat side


Peter

 

[lucky7]

That’s not a flaker, it is a light weight scraper. I have a medium weight 7 series, and if helpful could measure the thickness of my blades this evening.

 

[Tillie]

nope it's a BL40/7ELM. The flaker is the HM-10. In any case this tool makes regular scraping marks not half moons.

 

[Tillie]

sure lucky 7 that would be a big help. Biax lists the length and width of their blades on the website but not the thickness.

 

[dcsipo]

I just got a used biax BL 40 and I'm learning the basic scraping "strokes"(?) from Richard king's video.
The two blades that came with my scraper are the type that hold sandvik 630 type inserts, which is what I prefer. The drawback is that they are the short extra-thick type 4mm or 5/32" that I expect are for heavy roughing. What is the thickness of the general purpose blade? I will be making my own insert style blades, probably a 6" long 3/4 wide to take sandvik inserts and eventually another to take narrower inserts.

The thickness of the blade is only relevant if you want to get into very tight places. The critical geometry is the sharpening angle and the radius. All else is irrelevant for the roughing or final passes. The brazed Biax blades are thinner. I would say 2mm. And there is no bulky clamp. None of that makes any difference on flat surfaces, but a big issue if you have to get deep into a dovetail.

 

[Richard King]

Those tool holders are made out of Cold Roll steel; and milling them to the silver soldered carbide tip blades won't work as the those blades are made from HSS. I tell students to mill those insert blade holders .020" and test it. Thinning blades holders tomuch will made them bend. So thin them slowly and test them as big strong vs. small weaker people affects the blade.

 

[Richard King]

Lucky is Right, That is a scraper. BL-40 is the European number, here in the USA its called a 7-ELM. A flake in the old days was a 8-EM, it was the same size as the 7-ELM. Now, new 1/2 moon flakers are the same size of a BL-10 scraper. The new flaker is called a HM-10. You can zoom in on the blade holder on the left and see the ways. A scraper was ways, a 1/2 moon flaker doesn't have ways. They do different things and you can't use them to do the others purpose. There are several of my in person students who are members here who know.

 

[stephen thomas]

I used S7 and hardened/tempered it for one of my insert holders.
Thinned (on surface grinder) the part that is not gripped in the Biax until it "looked right"
Must have guessed ok. It's not my go-to blade, but use it with a (shop ground) HSS pos rake insert for cutting steel.

smt

 

[Richard King]

If you need help learning how to scrape, I am hosting a scraping / rebuilding class the first week of October in my shop in Cottage Grove, MN. Email me and say your a Practical Machinist member and I'll give you a discount. [email protected]

 

[Mark Rand]

I posted this on the other forum, but here it is for complete saturation:-
20mm x 3mm is what fits my BL40 and what I use for all my blades. Brazing/hard (silver) soldering a carbide blank onto the end of a bit of metric gauge plate makes a good blade. My go-to blade is here. The sort of eliptical shape allows finer points to be worked on by tipping the scraper slightly and also prevents gouging in moments of inattention.

 

[Tillie]

Thank you for all the replies, I am mainly interested in the blades I intend to make being more flexible than these 4mm blades. These that I have now are all too rigid . Yes I figure that since I'm making my own they can be whatever thickness I want. I might start at 3/16 and thin it down further from there.

Thanks Richard, if I understand correctly, you're saying that the brazed carbide tipped blades are made of HSS, and that they would be too thin and deform plasticly if they were of a softer alloy?
BTW I do plan to take your class. I'm thinking sometime next spring.
I want to get more practice hand and power scraping- at least to the point where the skill of scraping for (reasonable) flatness is somewhat taken care of and I can move on to considering allignments.

 

[Bakafish]

The brazed BIAX blades I have are made from some type of spring steel brazed to (what I assume is a mild steel) on the mount side, and the carbide blade on the other. The mount side uses a 6mm deep 2.5mm wide slot for the spring steel body and the blade side uses a V groove for the brazing surfaces.



So the brazed blades that I have look fairly complicated to replicate, both mechanically and the difficulty identifying the correct spring rates of the flex section, and likely worth buying. The non-flexible type are a different story, I've made a couple of them and I don't think they are difficult to make.

 

[Richard King]

Yes... the black Biax holders are soft and the Biax silver soldered carbide blades are harder HSS. . I now teach power scraping on Day 1 & 2 as it's easier to understand scraping when you get the same stroke length with a power scraper, compared to sporadic length when pushing a hand scraper. When someone is standing behind you showing you how, you will learn to scrape a flat plate in a few hours. I always say scraping flatness is simple to learn, knowing where to scrape and knowing how much to take off on different brands and types is a trade. Over the years I have taught the tricks of the trade in 5 days,,so you can have the confidence to go home and rebuild your machines. Plus you cam call me for help.

 

[Mark Rand]

There is no significant difference difference in stiffness (young's modulus) between mild/carbon steel and HSS. There is a difference in strength, but you aren't going to be pushing hard enough to bend the blade holder whatever you do. So the only reason not to use 12L14, for instance, is that it rusts as soon as you look at it!

You get a more flexible blade/holder by making it longer.

 

[Bakafish]

There is no significant difference difference in stiffness (young's modulus) between mild/carbon steel and HSS. There is a difference in strength, but you aren't going to be pushing hard enough to bend the blade holder whatever you do.

As I said in my post, it appears to be a 'spring steel' insert and I'm pretty sure that BIAX says that as well. Certainly you could attempt to make it out of some other material, but if you are trying to replicate (or improve) the factory design, you should at least be approaching it with this in mind. I also believe that by substituting mild steel and thinning it down to match the characteristics of the factory version, you are risking bending the resulting blade. The downward pressure and reciprocating loads of these power scrapers is not trivial. I'm not sure why you think mild steel that must be thinner than the 2.5mm thick spring steel (to achieve similar flexibility) wouldn't get bent after any serious usage. BIAX went through a lot of trouble to make these blades out of 3 pieces, I expect if they could have made the entire shank out of the same material they would have.

You get a more flexible blade/holder by making it longer.

This sounds like you may not have first hand experience with a BIAX. Making a longer hand scraper might be a viable option, but that's not great way to add flexibility in this part. The length of the factory blades and their mass affects the reach, stability and balance of the tool and is something I would want to keep consistent and compact. If the OP is trying to make their own, sticking as close as possible to the factory part would seem best.

 

[Mark Rand]

I've rebuilt two machines with my BL40 so far. Worst piece was scraping an average of 0.010" off the 48" x 10" top and bottom of the of the milling machine table to bring it back to straightness from 20 thou of hogging. That's a lot of metal...

All my holders are home made and vary in length between short (stiff) and long (flexible). The steel I use is un-hardened O1 ground flat stock and it doesn't bend.

As I said, there is no significant difference in stiffness between any of the steel alloys. Strength is a different thing, but un-hardened O1 or 1080 etc, will be enough for normal mortals.

 

[Bakafish]

Cool, it sounds like you've got some experience. Can you show us some of your home made blades and give some pointers, and specifically dimensions on how you made them? Getting the spring right is what has been stopping me. I'd be quite interested in making some of the flex type if I was confident that the effort would be worthwhile, it's what I believe the OP was requesting details on.

Have you ever have the chance to compare your homemade blades to an actual BIAX version? In my experience the difference in feel between the rigid holders and the flexible ones was pretty dramatic, I'm all for homemade but you may be missing out on some of the utility the original blades provide.

 

[Bakafish]

Just to add a data point that you could use to compare to your homebuilt tools (or for other makers), I put a BIAX 20/150 blade on a mass block with the edge of the mount section aligned with the edge. I then put a digital dial indicator 100mm from that edge and hung a 1kg block of carbide from that same 100mm measurement point on the blade. The cross section of this blade is uniform (the other blades are scalloped for clearance) and 20.2mm wide and 2.5mm thick. I measured 0.615mm of deflection with the weight applied.



These numbers should be pretty close, but these are not in temperature controlled conditions or anything, YMMV on the usefulness.

 

[Bakafish]

Using an online calculator the moment of inertia of that cross sectional load is 26.3021mm4, with 9.81N of force (the 1kg load) at 100mm deflecting 0.615mm gives a Young's Modulus of about 200GPa.