End mill squiggles

[Jerry In Maine]

i get light "squiggles" on the surface of areas I mill out...usually with my .25" down spiral but it'll happen with most end mills I've tried. Otherwise no issues with the machine. It seems to be accurate enough and is built pretty solid.

Anyone know what might cause thus? It's just light traces or scratches that the mill leaves behind.

[Rcnewcomb]

There are several possibilities:
1. Spindle is slightly out of plumb
If the head assembly is not square, the tool will cut with one edge/tip and leave swirl marks. To check squareness/spindle sweep, mount a dial indicator to the spindle so it will swing about a 24" diameter circle, bring the indicator down to the table and slowly spin the indicator 360 degrees; you should not see much more than .002 total. More than that and you probably need the head squared up.

2. Chips are being recut
This is more likely with a downspiral bit. Try changing your feed rate. You may need to go move faster or slow down your RPMs.

3. Bit geometry
Both Onsrud and Hartlauerhave 66-300 series bits designed for bottom surfacing. They have a very slight radius on the corners. This radius is designed to give a smoother bottom surface when hogging out large areas. Sharp tips will leave a slightly deeper cut on one side leaving the appearance of scratches. The rounded corners of this series don't leave harsh lines, making surfaces optically much smoother.

[Jerry In Maine]

Thanks. This gives me something to look at...


+/- .002" over a 24" circle would be pretty accurate!

[dhellew2]

If you don't have a micrometer but do have a large diameter planer bit or end mill put it in your chuck just tight enough to keep the bit from falling out, lower it down against the table, if the two opposite sides don't lie flat on the table the router/spindle is not aligned properly. A small LED flashlight will help spot even the slightest gap under the bit

Dale

[eph210]

I use a little jig I cobbled up from a 1/4 bolt with the head cut off and a piece of stiff wire. The wire is clamped between two nuts on the end of the bolt. I mount the shank of the bolt in the collet and the wire extends sideways 9 or 10 inches and then the tip is bent down 1 inch. Lower the router so that the tip just touches the spoil board. Swinging this around reveals any out of tram condition very quickly.
Euan