Porter Cable 444 Sander Will Not Convert to Power Scraper

I finally got around to attempting Forrest Addy's suggestion to convert a Porter Cable 444 Profile Sander into a light-duty power scraper. I put about $80 CDN into this project, but found the results disappointing. The data, however, is useful for the ongoing community effort to find an accessible alternative to Biax power scrapers.

In essence, the linear mechanism isn't sufficiently rigid to allow the scraper to dig in and then shovel off material. The rigidity of the blade tang was not an issue. The cutter was salvaged C2 carbide ground to the usual specs: -5º rake, 100mm radius.

Addy suggested modifying the plastic adapter to receive scraping blades while retaining the sanding functionality. I don't recommend this because it's already too flimsy. I machined a holder out of aluminum to gain rigidity, as well as make a more robust clamping surface. I would recommend machining away much more material than I did because the resulting holder may have been too heavy. The plastic holder, with profile inserts, weighs about 120g, but my aluminum holder weighed 210g. Trying to adjust the counter-weight didn't help. The sander is extremely unpleasant to hold in use (I'm a cabinetmaker and have tried numerous sanders, and the Porter Cable 444 is the worst I've held), but the additional balance error made it a bit worse.

This same balance error also increased the strain on the plastic housing mounts. Within 10 minutes of use, the plastic housing had cracked at the anchor point for the linear motion mechanism. I did not attempt to correct the balance error because the idea does not seem worth pursuing further.



At the time of posting, I haven't received the speed controller to reduce the tools RPMs by at least half. I'll update the thread after I'd tried it.

I didn't read Forrest's writeup, but I bet you'll see a difference with a longer blade, thinned a bit in the middle. Biax also has a block of rubber as part of the blade coupling, should be plenty of images here in Biax threads. A little springiness helps a lot when power scraping.

To follow up, reducing the 444's stroke rate down from 4000 strokes per minute (OEM spec claim) to <1000 dramatically improves the ergonomics of the tool. It's much easier to hold, even for sustained use. Following Screwmachine's advice to change the blade form with a longer, more flexible shank did not improve the performance of the tool; it actually made it slightly worse. The pile of cast iron dust at the end of the stroke was reduced compared to the shorter, more rigid tool holder.

Either way, the scraper still fails to remove as much as I can manually. Nick Mueller used to end his videos with the exhortation: "Scrape, don't scratch!" This tool seems merely to do the latter. Power scrapers should be faster, not slower, so I consider this tool largely to be a failure. I may, however, use it for finish scraping. Its stroke length is relatively short, about 1.8mm/.07", and it takes a consistently light pass.

...and to update the price, the controller cost me about $15CDN. It was some cheap and cheerful little thing shipped from the Netherlands. The speed controller brings the total cost up to about $100CDN. Even though I believe it reduced the power of the motor in addition to its speed, the power loss didn't seem to affect the depth of cut.