Pattern bit burning MDF???

[Stobe]

Has anyone had this problem before.  I was trying to cut a second side from a pattern, using the pattern but/router process.  Luckily I clamped on a scrap peice of wood to test the procedure before using my target peice of wood.

I'm using 3/4" MDF, with a 1.5 HP router.  I have a stronger router as well, but this one was more handy.

My pattern bit worked fine for a couple inches, and then it started burnging the wood.  Also, it seems that the bearing got fused to the shank.  Are you supposed to oil those bearings before you use a bit the first time.

Another thing that may have lead to my unsuccessful tracing is that I did not pre-trace the pattern with a jigsaw first.  I have read that it is probably better to cut close to the pattern, then route.

My pattern bit is now a little "blackened", and after working the bearing loose, it still does not roll freely.  Have I toasted this bit?

Thanks,
Stobe

[wintermute]

If possible I try to leave less than half the diameter of any straight cutter type router bit (includes pattern / trim bits), so if I have a 1/2" trim router bit, I try to leave 1/4" or less after jig sawing / rough cutting with some other means.  The cutter has a lot less tendency to bounce or try to move away from your pattern piece if it doesn't have to cut on the outboard half of the cutter.

Another thing that may affect wether you get burn marks or not is how fast you move the router, and how fast the router is spinning.  MDF is quite soft, so you will probably want the router set close to it's maximum speed.  As long as the router has the power, try cutting a little faster (you shouldn't have to push too hard though, so if you're already giving it firm pressure then don't overdo it).  If the router sits in one spot too long it will heat up the material and cause the burn marks.

good luck,

wm

[Bones]

Be careful when trying to re-lubricate the bearing. They are grease packed for life and although the steel shield can be removed, it is not designed to be.

Also, bearings are pre-packed with a grease that is designed for a wide range of operating temperatures and speeds. Mixing with different types of lubricants tends to degrade the lubricant rather than make it better.

Why these router bits don't come with bearings that have rubber seals installed is beyond me. The rubber seal makes contact with the inner & outer ring and offers much better protection around fine dust.

You can probably get a brand new bearing for less than $5.00.

[Sensei]

Oh, and you may want to sharper your router bit.

That along with going with the fastest rotation speed and moving along as quick as you can will reduce the temperature on the MDF board.