[4DThinker]

I use a Dewalt DW611 router on my Probotix CNC. Yes, I'd love to have a true spindle but there is no easy way to add 220v outlets where my CNC is parked.
While cutting a project for a student a few days ago my router just stopped running while the CNC kept moving. This was a VCarve job and most of the carving had been done when this happened, so no apparent damage was done to the job.
The router simply would not power on any more. I checked the router outlet on the controller in case a relay had failed, but that outlet still worked.
A quick google search found replacement brushes for that router, so by yesterday's mail I had new brushes in hand.
It took 4 tools which I fortunately had to get the router top off and brushes replaced. Mind you I wasn't absolutely sure new brushes would fix it. I put it back together then held my breath for a few seconds while I plugged it in and hit the ON button.

Now as much as I've used my CNC I had expected the router to eventually fail. I'd had a new one there to replace the failed one with just a few minutes after discovering the failure. Job finished fine and student was happy with the results. The smile on my face arrived when that old router started up again with new brushes. This is the second tool in my shop that has been revived with new brushes this year, First was a Dustless Shop Vac. In both cases I was delighted to find replacement brushes for them. Replacing brushes wasn't "easy" in either case, but also not rocket science.

So don't throw out your failed router, or shop vac, or anything with a brushed motor in it. There may be new life for it in the form of new brushes.
4D

 

[jdowney]

That is interesting, I've only ever worked with hand held routers, so I don't associate brush replacement with the revival of a dead one - usually I've had the bearings go first and you then see the limitations of modern manufacturing that keeps things like routers so affordable (the bearings have a very light press fit in their pockets and the pockets are lightly cast so they wear out in the blink of an eye once the bearing goes).

Which is all to say a CNC setup is probably one of the best uses for a router motor in terms of long term utility. Consistent loads likely equal motor longevity. Inconsistent loads from hand held routing equals bearing wear and the heavy arcing at the brushes that erode the commutator. I've been looking at spindles if I go with a CNC, but this is good info to remember and not rule out router motor options.

I have had good luck replacing brushes on drills and a chop saw however, both of which probably see consistent loads compared to routers. You are right in that brush replacement is usually a bit of a pain. There is often a little hole to be seen in the brush holder - for those that don't know that hole is for a bit of wire or a pin to be inserted to hold the brush back away from the commutator during assembly. Once assembled the wire is pulled out through the back of the case and the brush springs forward to make contact. I first noticed these holes when rebuilding an alternator for my car in college - had to do it a couple times and on the second reassembly I realized what the holes were for. Most brush holders I've seen since have them. Probably if one has a service manual (and reads it!) this stuff doesn't come as such a revelation

 

[4DThinker]

I found that the bearings in the Dewalt routers are rated for 18,000rmp yet the router can run faster than that. So I always keep my routers set on 5 not 6 to keep them running longer. You're right though that if you get bearing failure then it is best to replace the whole router.

 

[jdowney]

I've noticed the same thing about router bearings - whenever I see rubber seals in them I look up the rated speed for that bearing and find it lower than the router's max speed. I would imagine its a bit of a dilemma for manufacturers, they can spec a bearing that is up to the speed requirement but will quickly fail in dusty conditions (generally sealed bearings run slower than shielded) or they can spec a sealed bearing that will wear out due to running over speed throughout its life. That they seem to have consistently chosen the latter over the last 20 years makes me think they've looked into it and come to a conclusion

In some cases true high speed bearings are available in the right sizes, but at many times the cost so they aren't used. I bet that is some of the advantage of spindles over routers, just one of several features that make high duty cycles possible.

 

[TimPa]

interesting thread. we run two porter cable 7518's in the router table. we run them often and long. it always seems the bearings go bad first, but i replace both bearings and brushes at the same time (~ $25). takes about an hour. have done them about 4-5 times each. stepped up to timkens this last time, will see if they last any longer...

 

[4DThinker]

It may be the cost of the faster bearings or the availability, but I'll bet on engineered obsolescence. Design a router than never wears out and eventually the market for them will dry up.

 

[DsKnees]

It may be the cost of the faster bearings or the availability, but I'll bet on engineered obsolescence. Design a router than never wears out and eventually the market for them will dry up.

I am a skeptic about the whole "engineered obsolescence" thing. The idea is opposite from how the design and engineering process actually works. They aren't designed to fail...they are designed to last long enough without being prohibitively expensive!

Maybe it's just a pet peeve of mine, but...the vast majority of routers (and power tools in general) sold to consumers get very little use over their lifetime. And the market for tools is competitive, meaning everybody has to work hard to keep costs down.

But to summarize what could be a quite lengthy rant, there is nothing about a handheld router that is designed around being used in a CNC router. So I think it woud be better to remark about how surprisingly well they can work in that application.

But anyway, it is a good point to make, that brushes are replaceable even in modern tools. All my corded milwaukee tools have brushes that can be replaced without opening up the tool, which is remarkable. But to be honest, I have never used one of them enough to wear out the brushes! I suspect that wearing out brushes is highly unusual in any consumer grade power tool, so it is notable that they still design in that feature.

 

[jdowney]

I don't think the idea is the opposite of design and engineering at all. Its just a somewhat jokingly pejorative phrase that gets people hung up like its some conspiracy theory or something.

What 4d is talking about is simply the cost/benefit balancing decision process that is intrinsic to all engineering and design. The "no downside" aspect to a manufacturer of tools wearing out is just a bit of a running joke.

I don't call it engineered obsolescence, personally. I just call it acknowledging reality - there are tradeoffs to be made in all design and engineering work. In general, lowering costs make the tool more accessible to more people, thus making their work a bit easier to accomplish, but also tends to reduce the tool's useful lifespan.

I hope it was clear in my initial reply that I was impressed that his router was revived with new bearings. Normal hand held use in my experience leads to heavier cuts, inconsistent feed rates, and lots of arcing at the brushes, wearing out both the brushes and the motor. It is impressive to me that a CNC setup wore out just the brushes like it was a drill or something.

 

[4DThinker]

No matter what it is called, or it being intentional or just inevitable, the fact that routers seem to want to wear out is still there. I just added a Milwaukee brushless battery powered trim router to my collection. Not sure what will wear out first but it won't be the brushes that it doesn't have. I've got cordless drills that would still run save their batteries have failed and are no longer made. The curse of living a long life I suppose.
4D