# What speed should I run my Biax at?



## loply (Jul 22, 2013)

Hi folks,

I have an older single speed Biax 7ELC which I grabbed off eBay about a week ago.

I practiced scraping with it for a week using full-speed but today I fitted a variable speed control.

I'm wondering what speeds I should be running at what times during the scraping process?

When should I be using it at full speed? And when at really low speeds?

Cheers,
Rich


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## Richard King (Jul 22, 2013)

loply said:


> Hi folks,
> 
> I have an older single speed Biax 7ELC which I grabbed off eBay about a week ago.
> 
> ...



I have no clue what the SPM (Stroke per Minutes) is on the old scraper.  The newer Biax scrapers when running on 6 the SPM is 1600.  I very seldom ever run it that fast unless I am roughing and moving fast in a circular motion or a Z motion moving the blade forward into the work to cut off the burrs.  I usually run it on 5 and I estimate that at 1200 SPM.  But I have been scraping with a Biax since 1972.  If I were you I would slow it in 1/2 from the sound of the motor and give it a try  The secret is to move fast enough on diagonal lines to get a scrape and then an opening or no scrape and then another scrape.  Be sure your blade has a radius on 60 to 90 mmR.  This way if you eye hand coordination should cut a scrape mark about 1/8" wide.  and about .0002" deep.  If you get file looking marks the also look like fish scales you are not moving fast enough and digging holes.  I also suggest you use a high ligher and I use the Yellow Canode mixed with glass cleaner.  Put it on and wipe it off so it dulls the shinny metal surface.  Years ago when it was legal we used red lead. But now only paint companies can buy it, is what I have heard.  

Does that answer your question?  Maybe some of the students can post a picture.  I have some someplace, but I scraped all day at work and I am whipped.     

Rich


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## komatias (Jul 23, 2013)

Start out with pretty damn slow until you get the feel for the movement, just remember to let it cool down every now and then. As Richard says in every post to newbies, individual strokes, spaced apart.

You need to be able to traverse at a comfortable speed and the biax should take care of the strokes.


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## loply (Jul 23, 2013)

Hi guys,

Thanks for the replies.

So is the speed really just a question of the operator's comfort and skill, rather than fast/slow being required for different phases of the scraping process?

I've had best luck running it at about 50%, they run at 1200spm at full speed. Any faster and I find I get chatter if it's a wide cut (large radius), and I scrape the same spot over and over rather than getting the scrape-gap-scrape effect.

Thanks for the help!

Just about to complete my compliment of scraping tools which I've been working on since Christmas! Made a small 9" dovetail/wedge reference, an 18" scraped parallel, a 12" master square reference, and cut a 36" knifeedge camelback down to 24" so that I could check it on my plate. Gave the whole lot a matching paint job but just putting finishing scrapes on some of them, will post pics when finished.

Cheers,
Rich


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## Richard King (Jul 23, 2013)

I see both of you are in the UK, can you guys meet up or talk on the phone.  Over here we now have cell phone and pay a monthly fee for service, so basically  no long distance fee's.  I would think it's the same over there?  Komatlas should be able to teach you as he had chatter too, until he figured it out.  So many variables, the speed, the blade radius, the flex of the blade.  I only recommend for roughing and finishing the 150 mm long blade.  I tell folk with the clamp on 6" blade holder to machine it thinner 1/32 off each side and you will see a world of difference.  Bill made a blade holder and has it in a thread here.  Another HUGE issue can be sharpening the blade.  A dull blade or to flat a blade will chatter like crazy.  On some of the super soft cast iron I have seen in some imports I tell my readers to grind it at  neg. 10. deg. ===>
For regular iron grind it at ====> neg. 5 deg.   Good luck and happy scraping.




loply said:


> Hi guys,
> 
> Thanks for the replies.
> 
> ...


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## loply (Jul 24, 2013)

Hi Rich,

Thanks for the help.

I have one genuine Biax blade which came with the machine, it is 2mm thick on the main shaft and 20mm wide and 150mm long, the part which inserts into the clamp on the Biax itself is thicker though. Do you mean to mill some material off each side so the blade isn't as wide, or off the top/bottom so that it isn't as thick?

I've also made a blade of similar proportions but with a clamp to hold my other carbides which I used for hand scraping previously.

Cheers,
Rich


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## komatias (Jul 24, 2013)

your blade is fine. if you do not overlap the stokes, then chatter is usually down to the relief angle. To shallow and the blade bounces, to acute and the blade just polishes the surface.


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