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Discussion Starter · #1 ·
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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Discussion Starter · #3 ·
There's no question that a smooth running router is nice as far as tactile feedback goes, but when it comes to using the router for joinery, rigid is king. Round over bits other edge decorative routing won't be so much effected. Straight bits doing template cut out work would be adversely effected since a spinning bit in wood wants feed in a certain direction. The only way I can see light template work being successful is if the operator takes a light pass, adjusts the router depth a little and makes another pass and so on. Because of centering error, there's a big risk of making the slot wider than needed.
I would think that when the side load is particularly heavy, the armature will tilt into the field coil and poof. The magic smoke rolls out.
 

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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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"seven fairly recent Porter Cable 3701 laminate trimmer routers"?
BUT I thought PortaCable had stopped making routers since around year 2007.
Owners Black&Decker (now Stanley-B&D) had decided that only DeWalt will continue making routers.
 

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The Proter-Cable Co. Makes only the 1 3/4 hp 690 and their little trim router. Another company that used to make good stuff being bought to get the brand name to stick on so-so gear.
 

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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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What you have are Porter Cable laminate trimmers. They are ment to be used to trim laminate when building counter tops. They work very well for this task, but are not meant to perform as "routers". Having owned a cabinet shop and a top fabricating shop I have used many or these over the years and they are excellent for their intended purpose.
 

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Discussion Starter · #9 ·
What you have are Porter Cable laminate trimmers. They are ment to be used to trim laminate when building counter tops. They work very well for this task, but are not meant to perform as "routers". Having owned a cabinet shop and a top fabricating shop I have used many or these over the years and they are excellent for their intended purpose.
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.

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They use the PC 310 in Castle pocket hole machines, etc. I have the 310 and 7310. The 310:has become expensive to replace , even used. The 7310 is a bit more common in shops , but not as trustworthy.. Commercial shop have stopped using them for cheaper, more droppable model routers..
 

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Discussion Starter · #11 ·
They use the PC 310 in Castle pocket hole machines, etc. I have the 310 and 7310. The 310:has become expensive to replace , even used. The 7310 is a bit more common in shops , but not as trustworthy.. Commercial shop have stopped using them for cheaper, more droppable model routers..
A friend has one of those Castle machines. I seem to remember that Castle went to the 7310s after the 310s got hard to get. There was a mounting part change so a new part had to be ordered for the 7310. I remember my friend bringing me his 310 part and wanted me to see if I could modify it so he wouldn't have to buy the new part. I don't remember whether I was successful or not. It was about 10 or 15 years ago. Nicely designed machine.
 
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