Why Can't I cut a round circle?

[flyguy]

I am trying to make some small circles, on Parts Wizard they look like circles, but usually they cut like ovals with tool marks or maybe lash marks in places. The circles are only 1/2" to 1 1/4" circles but it would be nice if they were much more round. I am using a slow speed, and 1/2 MDF and two it in 2 passes.

[paco]

Hi Michael!

Are you using the arc post?


10709.jpg

What tool bit are you using; can it be flexing (if long and small CED)?

What about holdown?!

Tell us more if possible...

[flyguy]

I'll check today when I go over to see about the arc post as I am unsure of that.

The bit is a rather long 4 fluted 3/8" bit. We've ordered some much shorter bits to try and mimimize this as a problem.

The project is clamped AND screwed in place so I'd have to say no hold down problems.

I'll get some pictures and post as well.

Thanks
Mike

[richards]

Mike,
I had to REALLY slow down my alpha to get round circles when cutting smallish holes. When I use a 1/4-inch cutter to 'drill' 8mm holes, I drop the feed speed down to 1-ips instead of the normal 5-8 ips that I use to cut most things. At slow speeds I get circles. At higher speeds I get ovals.

[gerald_d]

Michael, if you grab your router by the collet, and shake the router around with 20 to 50 lbs of force, does something flex, move or have play? Typically this could be loose v-rollers on the z-slide....

[mikejohn]

Don't grab it whilst its working

[gerald_d]

Mike, I thought of adding that, but then I remembered Ted saying we give advice with more pizazz.