A home-made power scraper

**jhovel** · 26th June 2011, 08:12 PM

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.

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.

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:

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":

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** · 26th June 2011, 08:35 PM

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** · 26th June 2011, 08:49 PM

Thank you Joe.

**jhovel** · 26th June 2011, 10:56 PM

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** · 26th June 2011, 11:25 PM

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

Stuart

**Greg Q** · 27th June 2011, 09:35 AM

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** · 28th June 2011, 01:34 AM

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** · 28th June 2011, 02:45 PM

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** · 28th June 2011, 02:54 PM

Originally Posted by Greg Q

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** · 28th June 2011, 03:16 PM

Originally Posted by Stustoys

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** · 28th June 2011, 03:36 PM

Originally Posted by Greg Q

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** · 28th June 2011, 03:47 PM

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** · 28th June 2011, 09:33 PM

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** · 28th June 2011, 09:42 PM

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** · 28th June 2011, 10:34 PM

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

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