I recently purchased a Powermatic PM100 planer after extensively researching modern planers and concluding that most are Chinese junk and not worth the money. My Father has a PM100 which he used and uses as a finish planer, so I set out looking for one. I tracked one down earlier this year. It's an earlier model, made in 1966 and had the traditional 3 knife cutterhead that it came with when new. After converting it to single phase and cleaning and adjusting it, I put it to work.
I work in a lot of figured woods, mostly because I can get them at cost from my brother (curlymaple.com) and while the straight knives worked, you had to be very diligent about grain direction and depth of cut. While the planer is a tank and can hog off quite a bit of wood with each pass, tear out was pretty bad. After chatting with my brother who planes this stuff daily, he told me that he uses insert carbide type cutter heads on all his production machines. He is located in Lycoming County, PA, and it just so happens that Hermance Machine, which has been in business since the 19th century is still in business and actually makes their cutter heads in house right in Williamsport.
I did quite a bit a research and came to the conclusion that their heads are the best made. They actually patented the design which is a true, helical, shear angle type cutter head. The knives are angled in two directions, along the length of the axis but also tilted with respect to the surface of the head. Further, the knife is completely pocketed and supported on all 3 sides unlike other clones which screw the knife to the surface of the head.
After some discussions with the folks at Hermance, I put one on order. They make each one to order and it took about 2 months. Keeping in mind this was during the days of Rona, I don't think that is unreasonable. The beginning of last week it arrived. I decided to send my old cutter head to them so they could remove the bearing inserts from the old head and then press new bearings onto the shaft and into the cutter head housings.
As it arrived and after taking out of the crate:
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The computerized balancing readout which I didn't even realize was part of the deal:
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After removing the cling wrap and rust proof paper:
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After installing into the machine. Putting it into the PM100 is a really simple affair. The left side of the head contains a double 2 belt pulley and the right side contains a single pulley which runs the drive system (as indicated by standing in front of the infeed side). The entire assembly is slid into the machine casting and clamped with two pointed screws with jam nuts. Shown here installed with cutter installation in progress:
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The carbide inserts are made in Germany and they even supply a constant output torque wrench to properly torque each cutter. 5 Nm is equivalent to about 45 inch pounds. First class all around:
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Close up of the pocketed arrangement:
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Knife install complete:
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Adjusting the infeed and outfeed rollers, chipbreaker and hold down bar was very straightforward and easy. After some experimenting, I determined that the apex of the cutting edge of each knife was a uniform .040" away from the surface of the cutter head. As it's much easier to use that round surface as a reference point than the edge of the knives, and also considering that unlike a straight knife arrangement, that relationship will never change with knife replacement or rotation, I used the cutterhead as the index measurement. Since the knives stick out .040" and the manual says to adjust the infeed and outfeed rollers .030" below the arc of the knife, .070" is the number to shoot for for all but the hold down bar. Adjusting the outfeed roller as seen from the outfeed side:
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After putting the rest of the machine back together and taking a test cut, the only thing that needed adjusted was the pressure bar. It was rubbing a little so I raised it .002". The finish is second to none. I test planed a knarly piece of hard maple burl and there was not a hint of tear out. Not one bit. After planing some wood through the last week, it's apparent that worrying about grain direction is a thing of the past. Doesn't matter which direction you feed it, it just doesn't tear out.
For those interested, the head has 60 knives in 4 spiral chevron wings of 15. The chevron pattern directs the chips into the middle of the head where they can be more efficiently collected. I do notice a big difference in the amount of stray chips that are not collected. It also runs very quiet. It cost just under $1000 which is not cheap, but considering the planer it went in is 54 years old, it will be a lifetime investment. By comparison, a similar head by Byrd which doesn't have many of the same features as the Hermance such as fully pocketed knives and double shear angles is almost $1300.
So, if you are in the market for an insert carbide replacement cutterhead, give Hermance machine a look. The best US made head on the market and cheaper than some!
Pete
PS. There is a very nice PM100 planer for sale in the classifieds. If you buy it and want to upgrade to a Hermance Head, PM me. It's a fantastic machine and completely adjustable to be perfect.