A home-made power scraper

[jhovel]

My entire scraping experience is a short demo about 10 years ago by an acquaintance of a friend one evening. I went home and ground the teeth of a large old file, annealed the end and forged it thinner and splayed on the end, then re-hardened it dead hard. I then ground it the way the the demo had shown and honed it on a stone. It worked, but went dull quite quickly. I later picked up an old 16" square Grade A cast iron surface plate and used that to scrape a small cast iron block about 3"x6"x1.5". That was a lot of effort and I never used the scraper again. :B

After recently reading lots about scraping here and on other forums, I decided to try again - this time with a carbide tip: I had previously broken a 1/4" soliod carbide endmill and siver soldered the shank of that to my 'file scraper', then ground it to the right shape on a diamond wheel. Now I was really making iron dust!
I then read up about power shapers and combed e-bay and other second-hand sources: way out of my budget!
A search for alternatives turned up a "Sawzall" adaptation described in one of the old threads on the PM forum (http://www.practicalmachinist.com/vb/general/power-scraping-anyone-tried-convert-makita-hk0500-metal-161099/#post925900).

I had bought a cheap reciprocating saw for a renovation job - and am unlikely to use it for sawing the future. Aldi had a special on at the time for $29.95 (I think).
So I opened it up, modified the stroke down to 8mm (all reversible if needed) by drilling a new hole in the drive gear which produces the reciprocating action (see photos of what I mean), and refitting the little needle roller bearing which drives the reciprocating slide. Mike "Holescreek" had milled an elegant dovetail for an adjustable stroke. I don't have the tools to do that - yet :;
I then made a scaper blade (more like a scraper 'lump' actually) from 3/4" square mild steel, with a tungsten carbide strip silver soldered to one end. The fitting at the power tool end is a milled 1/2" wide slot. To get the blade facing the right way (unlike the previous builder Mike, who chose to hold the powertool on its side).

Since I have never used - or even seen - a Biax, I have nothing to compare my tool to. It works like a charm!
Pushed, it really makes the cast iron dust fly. Just gently held in position, it makes nice gentle scrapes, just as I would with my hand scaper. Only it is not that exhausting and very quick. I use it at speed 2 or 3 out of 6.
I took me a little while to learn what angle to hold it at, so it doesn't jar my arm - and make gauges in the surface - and not skate across the iron.
It's pretty ovbious though and quickly learnt.
Anyway, here are a couple of photos of my effort:
http://i535.photobucket.com/albums/ee358/joe_hovel/interesting%20techniques/th_22052011264Large.jpg (http://s535.photobucket.com/albums/ee358/joe_hovel/interesting%20techniques/?action=view&current=22052011264Large.jpg)
http://i535.photobucket.com/albums/ee358/joe_hovel/interesting%20techniques/th_22052011265Large.jpg (http://s535.photobucket.com/albums/ee358/joe_hovel/interesting%20techniques/?action=view&current=22052011265Large.jpg)

Mike later decided that 1/8" stroke was the optimum for him and has left it on that setting since. I've corresponded with him and his $20 machine is still going after scraping lots of big machine ways.
Here is a short video of him using his "Scrapezall":
http://i290.photobucket.com/albums/ll279/CNCphotome/th_toPB.jpg (http://s290.photobucket.com/albums/ll279/CNCphotome/?action=view&current=toPB.mp4)
I may yet drill another hole for the little drive pin and try a shorter stroke.
GregQ has offered to show me a Biax in action and I look forward to that.
Cheers,
Joe

[Stustoys]

Hi Joe,
I've been working my way through a couple of the PM threads on "Sawzall" adaptation myself. I'd put it on hold while I get a few other things together.
The carbide strip you silver soldered, is it just something you had laying around or a special piece?

Stuart

[Anorak Bob]

Thank you Joe.

[jhovel]

The carbide tip was a chipped indexable threading tip. That's wat determined the width of my blade and is the reason why it's so thick at the end. If I need a thinner one (e.g. to get into a dovetail gap, I'll probably make another thinner one a bit like the twisted Biax blade I've seen on the DAPRA site.
Cheers,
Joe

[Stustoys]

Thanks Joe,
I'll see what bunnings have next time I go in there.

Stuart

[Greg Q]

I like this tool very much. In fact when that PM thread first appeared I planned to make one too. Then I found my Biax on ebay hiding in a dark alley of bad description/title/conditions. Consequently I never pursued it.

I have a couple of observations: On a Biax the blade is angled down about 15º so that the reciprocating action is less perilous to the work and your arms.

Second, on the advise of Forrest Addy, I found a tool balancer to suspend the tool. A 4.5 kg weight starts to get tiresome quickly...the tool balancer makes the Biax work effortless. You can rig something up with a bit of garage door track and a spring, or wait for one of the frequent listings on ebay.

Your machine looks fantastic...and it is variable speed. A genuine Biax typically fetches $500+ plus shipping. A modified sawzall is cheap enough that you could make two...one with a 10mm stroke, and another with 3 for finishing.

Anyway...well done Joe.

GQ

[jhovel]

Thanks for the observations Greg.
I'm hoping to talk to you in person on the weekend and see a Biax "in the flesh".
I had considered angling the blade down - asper Biax. Do you think that would work and improve the ergonomics?
About the tool balancer: would a movable pulley and counterweight away from the work area over a second pulley work?

I like the idea of a second "finishing" scraper. You could leave different blades in them permanently...
Joe

[Greg Q]

Anything you could rig up with pulleys etc would work well. The goal is just a counterweight. The ENDO balancer that I bought is a 5kg, so I had to clamp a pair of vice grips to the line to get the total weight up to a neutral balance.

I really do think that making an angled holder would work better. The biax has a kind of rectangular socket with a rubber liner. The blades are forked to fit around the single set screw which tightens everything up.

One thing an angled blade does is raises the machine above and parallel to the work. Gives better visibility and allows the user to twist the unit to get adjacent spots.

Greg

[Stustoys]

The ENDO balancer that I bought is a 5kg, so I had to clamp a pair of vice grips to the line to get the total weight up to a neutral balance.

Hi Greg,
Do you mean 5kg minium or that its not adjustable?

Being that you think a counter weight is a good idea, do you think it would help to add weight to the scraper? Say make it 10kg.

Stuart

[Greg Q]

Hi Greg,
Do you mean 5kg minium or that its not adjustable?

Being that you think a counter weight is a good idea, do you think it would help to add weight to the scraper? Say make it 10kg.

Stuart

Just had a look...it's a 4.5-9 kg unit, so it wouldn't quite go low enough. The vise grips were a quick and easy solution to the problem, but adding weight permanently would be a better solution.

[Bryan]

One thing an angled blade does is raises the machine above and parallel to the work. Gives better visibility and allows the user to twist the unit to get adjacent spots.

Greg

Doesn't it also make the stroke more horizontal, instead of trying to dig into the work? I dunno, maybe some angle is good, since you would press down somewhat when hand scraping...

[Greg Q]

The angle mimics the hand scraping angle, and it does allow you to bear down with some pressure on the blade during very heavy roughing.

Greg

[Stustoys]

Greg,
Sorry I meant my last post as two questions.
Do you think it would help with a Sawzall power scraper to add weight. Which is a little unfair to ask as you havent used one I guess. I'll just have to try it and see.

Stuart

[Greg Q]

Hi Stuart.

I don't think that I understand the question. The Biax weighs around 9 lbs, and it is tiresome to work for long periods without the balancer. I am scraping 8 different projects all at once, so my scraping takes about 20 minutes per cycle.

Since I am still recovering from surgery and can only do maybe two hours a day with breaks I couldn't use it at all without the balancer.

Greg

[Stustoys]

Sorry Greg I'm thinking aloud, maybe not typing questions so well lol
I'm guessing that the sawzall power scraper will weigh less than a Biax. I was wondering if you think it would be a good idea to add weight to the sawzell. It might help with vibrations?

Hope you are back to 100% soon.

Stuart

[RayG]

Hi Joe,

What a great idea, I'm not looking to do any scraping just yet, but that sounds to me like a good way to take some of the heavy labour out of the job.


and it does allow you to bear down with some pressure on the blade during very heavy roughing.

You could put the serrated "scraper blade" back in for some really heavy roughing..:rolleyes:

Regards
Ray

[jhovel]

Just went and weighed the "Aldi Power Scraper". It weighs 3.5kg.
So not a lot lighter than the Biax. Judging from photos, the modern Biaxes are likely to be around the same weight, because they have a much smaller motor than the older ones.

Greg, can you clarify if the motion of the Biax in in line with the blade or in line with the underside of the machine body?

Interesting idea, RayG, using a serrated blade. No idea at all. I guess someone will have to try. I would have a suspicion that the multitude of corners able to chip on a serrated tungsten blade could be an issue.

Joe

[Greg Q]

The Biax motion is parallel with the machine's centre line.

These photos aren't the best, but you can see the blade mounting block slides back and forth on the rod and guideway.

Greg

[jhovel]

Thanks for the photos Greg.
That clarifies that an angled blade on the "Aldi" is a straightforward modification.

Anyone else have any views on a serrated blade for faster stock removal? I kind of like the idea in principle for 'on machine' leveling something when an angle grinderwouldmaketoomcuh of a mess and you can't put the part on a mill (like a lathe bed). I'm contemplating scraping a couple of small flats on the side of my lathebed to mount leadscrew bearings on... and was also thinking about Anorak Bob'sbadly worn grinder ways...
Joe

[RayG]

Anyone else have any views on a serrated blade for faster stock removal?
Joe

Hi Joe,

Originally, it was a weak attempt at humor, I was thinking of the amount of rapid stock removal you could remove with the reciprocating saw...:)

But since then, you've started me thinking about toothed blades, like the sort you see on planes... You might be able to make something brazing bits of square carbide onto a backing, and then re-grinding the carbide "teeth"...

In my reading on heat treatment, I did come across something called "machinable carbide"... have you ever heard of that?

Regards
Ray

[Greg Q]

Just thinking about this as sleep beckons...

I have a chinois copy of a Fein multitool. I might try to make a carbide blade for it tomorrow to see if its rapid oscillation action would make an aggressive roughing tool.

I bought a cheap one thinking I'd use it an hour or two a year...it gets used more often than anything else I own.

Greg

[eskimo]

I bought a cheap one thinking I'd use it an hour or two a year...it gets used more often than anything else I own.

Greg

Ive only used my (a real Fein) 6 times :D...I got it to get in to some tight areas when I restored a wardrobe...its been sitting unused under the bench for the last 5 or so years

[jhovel]

An update: I modified the blade attachment to relocate it to the bottom of the tool. Much better with the slender and slightly flexible blade.
While I was at it, I also reduced the stroke. A little too far I fear - it is now only about 4mm now. Great for spotting, frustrating for roughing....

[jhovel]

Here it is in action. I compared it directly to the Biax sitting on the bench next to the vice.
You can see the Boax scrape marks between the blue stripes. It was set to a longer stroke.
The "Aldix" is not (yet) adjustable and set a littel too short for general purpose.
Aldi Power Scraper - YouTube