CNC Shark Forum

For those of you that have never operated a machine like this in the past there are maintenance practices you might need to develop.
A trim router is normally used for 10-15 minutes and they can go for many years without much maintenance at all. With the machines
like we are using we are punishing the normal trim router into hours of running. Now this is not detrimental to the life of the router
but it does deserve more attention when it comes to preventative maintenance. The Bosch colt has two brushes that need to be looked
at from time to time. If they are not looked at you might hear a horrible noise as the springs are pulled into the armature. Below
shows one brush cover that can removed with a straight slot screw driver. (Be sure to unplug the router first) After the cover is removed hook the end of the brush guide (brass in color) with the tip of the screw driver and slide the brush assy.
out and you can see the amount of brush life you have left. Below show the worn brushes on the left and new ones on the right. As you can see mine where ready to be replaced. I got a years worth of running out of them but I did not run the machine as much as some
of you might be so it would be good to check them.
I bought mine right from the BOSCH website for about $8.50 a set. Below is a picture of the package you can use for reference.
I have found that all of the specialty stores in my area have closed due to the economy and can not buy the brushes locally anymore. The last
store closed two weeks ago. Happy CNCing . . . .

Here is the web address to order brushes. https://www.boschtoolsservice.com/Searc ... Order.aspx Part # 2610008121.

I noticed my Bosch was making more noise than usual and it seemed to be losing power. One day it didn't want to start without a nudge, I realized it was time to look at the brushes. Replaced the brushes and all is well now.

I had good luck here when I needed to replace bearings
http://www.ereplacementparts.com/
Jim

Thanks for posting, I have read about this, but did not know what all was involved in it.

Is there a good estimate about how many hours of machine time can be done until they need to be swapped?

-Eric

Hi Eric,

I'm finding 125-140 hours is my norm for brush replacement. Certainly the window to be checking.

hdtheater wrote:Thanks for posting, I have read about this, but did not know what all was involved in it.

Is there a good estimate about how many hours of machine time can be done until they need to be swapped?

-Eric

It also depends on the speed you run the router (rpms). I use to run mine wide open throttle which meant 30,000 rpm say 16 - 20 hours a week versus 18,000 - 24,000 (no exact way of knowing the rpm without a tach.). Trick is set the rpm based on what you are cutting and what type of bit. You can tell by the router pitch and the cut if the rpm is too low.
Also note that Bosch recommends replacing the bearings at every brush change. They didn't have the collet end bearing in stock when I ordered my brushes but I will certainly change them the next time.

Bobby

If you do change the bearings some people have reported better performance and noise with higher grade bearings like:

ABEC Grade 7
http://www.vxb.com/page/bearings/PROD/Kit7747
http://www.vxb.com/page/bearings/PROD/Kit7655

Or for the crazy full ceramic
http://www.vxb.com/page/bearings/PROD/Kit8219
http://www.vxb.com/page/bearings/PROD/Kit7726

Can't speak from personal experience but I have talked to a few people that have done grade 7 with great success.

John,

I clicked on those links for ball bearing. I'm a Mechanical Engineer with 23 yrs. experience with a bearing manufacturer. The bearings in the link are stainless steel with ceramic balls. I would strongly recommend not using ball bearings with stainless steel races. Stainless steel used in bearings does not come close to the hardeness of Through hardened bearing steel (AISI 52100) and will have a much shorter life.

While ABEC 7 bearings are manufactured to closer tolerances, most of them will not affect the performance of a router. The critical specifications in my view would be to properly specify the radial internal clearance and choose a bearing with an EMQ ( Electrical Motor Quality) rating for noise. These EMQ bearings will be manufactured to tighter specs for raceway (ball path) roundness and usually have higher grade (better roundness) balls. Those items are not covered by ABEC tolerances.

Finally, most bearing fail to perform correctly due to improper installation. Keep them clean and do not cross load the races during installation, ie. apply load only to the race being press fit at the time.

Say hello to Ron for me.

BillK

Thanks for the info. Don't know about the quality of those bearings. They are just the links I was giving by a customer. Said he had run them through 2 brush changes and they were still good. I will pass on that info though no point making a system worse.

I'll let Ron know you said hi.

Edit:

Bill, it says in the description "the quality is set to EMQ (ABEC-7 quality) to ensure high speeds" is that what you are referring to or is there something else I should look for?

John,

That description implies that the two, EMQ(ABEC 7) go together or mean the same thing. In fact, they are independent. An ABEC 1 bearing can be manufactured to EMQ (Electric Motor Quality) levels.

Caveat Emptor: True ABEC 7 and ABEC 9 bearings are very rare and usually only manufactured for Aviation and Aerospace applications.

One other thing to note in the link description: the radial internal clearance is listed as C3, which is the most common and for this size range is .0003-.0009 inch. Bosch does not specify this in the manual, so you have to be careful as this could be either too loose or too tight depending on the fit ups.

I have not tried to disassemble either of my Colts yet, but I have checked the Bosch Manual. 1st it recommends bearing replacement every other brush replacement. 2nd it suggests sending the unit back to Bosch for bearing replacement which may indicate that the bearings are somehow preloaded to remove radial play thus lowering spindle runout.