All I can think of is vibration control but building a better balanced system would be the way to go, I would think.
Question about modern hand router construction
I recently got a bunch of portable power tools that were destined for the scrap bin. Among them were seven fairly recent Porter Cable 3701 laminate trimmer routers. This would be easy enough, I thought, until I took them apart and found a disturbing and unfamiliar construction detail
The top (commutator) bearing was inserted in a soft rubber cup. This cup is inserted in a socket in the plastic body. Is normal construction for portable power tools these days?
When side pressure is put on the bit, the top of the armature is going to deflect one way and the bit is going to deflect the other. Clearly the armature is not rigidly held in the housing like all of the routers I’m familiar with. Besides the performance issue, this condition imparts alignment issues with the larger fan bearing.
While this construction seems to make a little smoother feeling at idle, it does little to keep the bit perpendicular to the base when cutting.
What got me is that some of the other tools (not routers) I took apart also had that rubber cup on the armature bearing. Coopfab’s recent problem with a full depth mortise cut wandering horribly got my attention. That isn’t supposed to happen with a what I thought was a well built router. I checked the parts illustration for his router and sure enough, there was that rubber cup holding the top of the armature.
There seems to be a lot of experts on routers here, so I’m hoping to hear from someone else that has seen this rubber cup bearing holder. I’ve rebuilt a lot of routers over the last forty years. All I have ever seen had the commutator bearing in a solid housing. My deficit here is that I haven’t rebuilt any newer version routers or other newer portable power tools.
Any illuminating comments?
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The top (commutator) bearing was inserted in a soft rubber cup. This cup is inserted in a socket in the plastic body. Is normal construction for portable power tools these days?
When side pressure is put on the bit, the top of the armature is going to deflect one way and the bit is going to deflect the other. Clearly the armature is not rigidly held in the housing like all of the routers I’m familiar with. Besides the performance issue, this condition imparts alignment issues with the larger fan bearing.
While this construction seems to make a little smoother feeling at idle, it does little to keep the bit perpendicular to the base when cutting.
What got me is that some of the other tools (not routers) I took apart also had that rubber cup on the armature bearing. Coopfab’s recent problem with a full depth mortise cut wandering horribly got my attention. That isn’t supposed to happen with a what I thought was a well built router. I checked the parts illustration for his router and sure enough, there was that rubber cup holding the top of the armature.
There seems to be a lot of experts on routers here, so I’m hoping to hear from someone else that has seen this rubber cup bearing holder. I’ve rebuilt a lot of routers over the last forty years. All I have ever seen had the commutator bearing in a solid housing. My deficit here is that I haven’t rebuilt any newer version routers or other newer portable power tools.
Any illuminating comments?
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I first got in to commercial woodworking in 1975 when laminate work was a big fact of life so I'm well aware of laminate trimmers. My point is that the build quality has hit the skids compared to the laminate trimmers I was used to like the Porter Cable 310. These modern trimmers don't appear to be able to handle much more than the stubby carbide trimmer bits. Long trimmer bits with a ball bearing guide would probably stress this inferior design way too much. If you can find the old 310 model, grab it. Its worth the effort to rebuild. They are my favorite and I'm not alone with that attitude.
Below is a photo taken in 2011. The four 310 models are on the right. I've accumulated several more 310s since then. The 310 will handle a 3/8" round over bit with no problem but that's about all I'd want to put in it. That 1/4" shank is a little whippy. Full size routers are better for the 3/8" round over bit particularly with a 1/2" shank.
The Black and Decker trimmer on the left has surprised me with its rigidity and durability.
The 7310 pictured was something I picked up for cheap. I generally relegate it to lighter work. Compared to the other routers, it just isn't up to snuff.
LOL. That shows my age.
Most of my 310 trimmers that I use were made in the 1980s. I probably should be buying orthopaedic router bits for them
The 7301, from my perspective, is modern or at least the most recent design. I really should have qualified that.
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