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Powermatic 12” Planer Bed Flattening


New member
Hello! This is my first post on the forum and I’m happy to hear all of your thoughts :)

I recently bought a used Powermatic 100 planer that was built in 1960. It appears to have served a busy former life and there is a fairly uniform dip in the infeed, outfeed and Center bed sections of between 0.004 to almost 0.006. From my research so far, I’m led to believe that those tolerances would probably not be an issue for a woodworking application, nevertheless I have always been interested in the art of hand scraping and was wondering whether this could be a candidate. As I’m sure some of you already know, the thought of restoring quality machinery to its former glory can be a fun pursuit.

I was considering getting either a 12”x9”x3” or an 18”x12”x3” granite surface plate off of Amazon as they seem to be a great value with good reviews and accurate to 0.001. Would one be more advantageous than the other in this application?, Other than that I also wouldn’t be opposed to buying a good carbide scraper.

I also plan to upgrade to a byrd shelix helical cutterhead for the unit as part of my restoration.

Any thoughts on this approach as a means of flattening the tables?
I assume you have or are going to dismantle the machine. As the mdl 100 is pretty numerous in all conditions I'd suggest posting on the OWWM site for a non worn donor table. You can of course have it machine shop surfaced. However, if your interest is in doing it your self it can be done quiet successfully with a hand sander and precision straight edge. Cast iron works much like hardwood only its not at all as pleasant to work, i.e. dirty for you and tools. Getting to a factory standard within 1-2K's can be achieved with a standard 5" random orbital and a 3' descent straight edge. Less than 1K will require more precision tools. Preferable a Festool or Bosh turbo 6" dual mode oscillating sander and a Starrett or Brown 3-4' straight edge with fine feeler gauge stock. Hook n loop abrasive is desired as you will be doing a lot of changing. And you'll want the best industrial abrasive, i.e. 3M Cubitron II. Most all your leveling work will be with 80 grit. The final surface finish is just dependent on your personal finish. Like flattening a work bench mark-sand-check-mark-sand-check. Change paper often-very often it wears fast. This is a tedious task as is bluing-scraping-checking-(lifting-flipping), but much faster though more obnoxious due to the flying metal dust. My method when truing large jointer tables 4'+ to less than 1k tolerance. For flat woodworking machine surfaces that are prone to surface corrosion and hard to treat and wax like thickness planer tables its preferable to have a smooth surface versus a flaked or planned surface more desirable for a large hand surfacer /jointer or band saw table.


New member
I've watched a guy flattening a granite surface plate by going over the plate spinning a 12" x 12" x .5" steel tool with a turning handle near one corner with some grinding powder under his tool. Upper body work that beautifully showed the high spots in the plate and when the high spots disappeared he used a Talysurf connected to a laptop. Perhaps you can improvise the same tool and do a similar job on your table with no expense. I wouldn't expect you to have a Talysurf but then you don't need 0.0001".

stephen thomas

Active member
are you also a proficcient scraper?
All the people who suggest abrasive methods have never become proficient scrapers with good tools.

Scraping is faster to a precision goal, and it is far less deleterious to the gages.
Among the lesser evils of abrasive belt sanding include localized heating and differential heating which results in poor inspection practice without long (serioulsy long) cooliing periods.

I was co-presenter in a class for a turbine rebuilder. They needed to learn how to scrape, to make steam tight joints, since grinding & hand lapping was unreliable for that effort. IOW, scraping can yield a finer finish that grinding, if that is one of the intended goals.

That said, i have used an angle grinder, used with stabbing motion to create spots, as a scraper on things like hardened jointer lips. Never swing with full contact as when auto-body grinding or steel fab or similar. Just rapidly peck the spots, rinse, repeat.

Per your question- Yes.
As is so typical one goes to the trouble to respond to the original post & the individual goes missing. I did follow your post and your link and as always found it a good read. Scraping is a very relevant topic and definelty applicable to this site. Having just recently joined this site as a contributor I thought my contribution to the site would be most beneficial
addressing the concerns of woodworkers. I often come to this site when trying to help facilitate a local metal worker or machinist. I realized years ago I needed, because of means and time as well as choice of desire, to narrow my vocational practice and inventory. That resulted in doing away with most all my metal related shop tools/equipment. Sad to say I had no idea when making that decision that most all the metal shops & services would disappear in this coastal region of northern CA. And now its a required collaboration with those few individuals that still have metal shop equipment & tooling to fulfill the metal working needs I still have working/modifying my woodworking machinery/accessories. So knowing that most woodworkers have limited metal or mechanical experience I try to advise on this assumption and what I believe as woodworkers the tools/skills they may have or should have/acquire. Stephen, as you are aware, only the unique woodworker today is going to be dedicated in time & effort to become sufficient in metal scraping, however, within there medium abrasives is a way of life. Spoken by one who believes in woodworking being a preferred occupation/life style of making shavings rather than dust!


New member
Not to worry, I have not disappeared! I had a member on this forum reach out to me (lives in my local area so I stopped by for a visit) and he gave me an overview of scraping and we had a really good chat about my intentions when it comes to woodworking precision. After doing quite a bit of research online about machine tolerances for woodworking, it’s clear that there are MANY opinions about what is considered precise enough.

Im currently in the process of cleaning off the rest of the rust on the beds, at which point the forum member kindly offered to come by with some measurement equipment so that we can get a sense of the flatness situation.

From my reading, it doesn’t seem like being “out” 0.005” is reason for concern, as that is below the factory specs of many companies today. It will come down to whether I feel I will see a noticeable improvement by improving beyond 0.005”