Biax Power Scraper

[John WallerParticipant @johnwaller42747]

Hi Bill – Thanks very much for your message – always appreciated.

I've already now got two Biax scraper

KR

John

[peak4Participant @peak4]

Posted by John Waller on 17/01/2020 23:34:12:

Hi Bill – Thanks very much for your message – always appreciated.

I've already now got two Biax scraper

KR

John

I realise that, but thought someone else might be interested in adapting it .
I'm not sure I could justify a real one, or the time involved making one, though the Instagram link is interesting.

Bill

[Jon HolmesParticipant @jonholmes92873]

I converted a cheap variable speed reciprocating saw ( re-drilled the pin to a new location to reduce the linear movement). Quick and easy to do and works well. I then decided the variable stroke idea was very good/necessary, but difficult to implement. Solution? Buy another cheap reciprocating saw and convert to the stroke you want. Still much much cheaper than the real thing!

[jaCK HobsonParticipant @jackhobson50760]

I thought I'd try making one as a small holiday project. I bought the cheapest reciprocating saw from screwfix (titan) and put a new pin in centred on the diameter of the shaft which then gives 10mm stroke. Would be really easy to do next time now I know…The original pin is pressed in so it might even be possible to press the pin back out and the conversion is then reversible. Now to attach the scraper…

[Pete RimmerParticipant @peterimmer30576]

Hi Jack,

On a Biax the blade does not point forward in the direction of reciprocation, it's angled down at some 15-20 degrees. I can measure it of you like. There is also a rubber wedge block under the blade to give it some cushion.

You'll find that 10mm is quite a long stroke. It will do for roughing but you'll want it much shorter for finishing work.

[jaCK HobsonParticipant @jackhobson50760]

Thanks. I will bolt on a scraper at 15 degrees… and then I could add a layer of rubber underneath if needed.

I should have asked before I hacked. 10mm just seemed about half way on the Bax.

If this works, and I need a shorter stroke, I may just buy another … rather than try to engineer an adjustable stroke (there is an example on youtube but it isn't exactly easy to adjust, and not sure it would work on the Titan). Does one find they change stroke often, and is it critical? What stroke would be good for finer work? 5mm?

[Mark RandParticipant @markrand96270]

I go down to about 3mm for finer work, slightly less when aiming for the most possible points per square inch.

Start with the 10mm and see how it goes!

[mike barrett 1Participant @mikebarrett1]

this might be a stupid question but what do you use them for?

mike

[jaCK HobsonParticipant @jackhobson50760]

So I think the main conclusion is, I don't know what I'm doing with a power scraper. I guess it's good I didn't splash out on a Bax! I'm not sure it is any faster.

Here is a vid taken one handed (I hold phone with other).

https://www.youtube.com/watch?v=3avg-jqRKCo

 

They are used for scraping things flat. The final fit on machine tools. Scraping doesn't take much material off!

 

Edited By jaCK Hobson on 28/07/2023 11:35:42

[Pete RimmerParticipant @peterimmer30576]

Jack I watched your video. First off your blade is blunt. If you push it gently across your thumbnail and it doesn't easliy shave a thin layer of nail, it's not sharp. Your stroke is OK for roughing but not anything finer. Your blade could do with being somewhat shorter for better control and with a bit more spring, it looks a bit on the stiff side. And you could do with a bit more radius on the end.

It's a good start though I'm sure you'll find it useful.

[jaCK HobsonParticipant @jackhobson50760]

Thanks for the tips – the blade doesn't last long if you fall off the edge and then hammer drill it square against metal! This happend a few times while one handed scraping and holding the phone. A rough grind really made a difference. The blade profile is as new, but I agree more radius on end is needed for my skills and this much brute power.

I will shorten by 1/3 I think. The scraper is a sandvik and the material is really hard and inflexible. And difficult to drill…

I might halve the stroke, but I'll play with this for a bit.

The thing is prone to leaving cutter marks perpendicular to the stroke. I think when adjusting the cutting angle there is a fine line between too shallow and no cut, and too steep and plough lines.

Edited By jaCK Hobson on 29/07/2023 10:16:28

[Mark RandParticipant @markrand96270]

Cutter lines perpendicular to the stroke are chatter. See Pete's comments about sharpening the blade. A cast iron disk turned smooth and flat on the lathe, with diamond paste pressed into it with a ball bearing makes a good lapping fixture. Use 5µm diamond maximum for sharpening. Make a rectanglar or square bar with the top sloping down by 3° towards the plate to support the blade and give you a consistent angle. You want a mirror finish, if possible, and no visible transition between the front and the bottom faces. The Sandvik inserts have far too large a radius for power scraping, which makes control harder.

This is my every-day blade for the Biax:-

The material is 3mm x 20mm ground flat stock, which is more flexible than Sandvik's hand scraper and is the same size that Biax use.

[jaCK HobsonParticipant @jackhobson50760]

Modified to 5mm stroke and fettled the scraper. Much nicer to use. Another poor video of the scraper in use with one hand only,  and then a shot of one of the passes for size

Edited By jaCK Hobson on 29/07/2023 19:11:30

[Pete RimmerParticipant @peterimmer30576]

Looks a lot better now. Turn your speed right down Jack and use more weight if the machine will stand for it. You want a gap between the scrapes equal to the width of the scrape at least, and the same for the ends if you hope to achieve a points pattern. Only when roughing a lot of material down do you want the scrapes joined up, if you do that when trying to achieve a flat plane you'll just keep moving the contact points about the place without achieving your goal.

Switch directions every pass to cross the scrapes across each other and stop you ploughing furrows.

Doing well there keep it up. If you are nearby me in Kent I could give up a couple of hours that would work wonders for you.

[jaCK HobsonParticipant @jackhobson50760]

J6 M25! I would love some tips!

[Pete RimmerParticipant @peterimmer30576]

Ok so you're not far away. I can certainly spare a couple of hours tuition but not today, perhaps next weekend.

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