Drilling Holes and skipping steps

[wb9tpg]

I'm having issues drilling holes with my Shapeoko 3 in MDF and looking for options.

I was using a 0.25 EM to try and peck drill a 0.25 hole and losing steps near the bottom of the hole.

I checked with the other Shapeoko users and they recommended I pocket the 0.25 hole with a 0.125 EM. I did try that and it was a little better but still ran into issues most of the way through.

Both those options seemed to go smoothly the first 0.375 or so before I ran into skipped steps deeper.

I think I could try (1) finer increments of peck drilling using the 0.25EM or (2) trying to add pocketing using a ramp and the 0.125EM or (3) pocket the hole and customize my passes so I get finer passes the deeper I go.

I'm looking to see that you guys think.

[Rcnewcomb]

Is your end mill downcut, upcut, straight, compression?
What are your RPMS and move speeds?

[wb9tpg]

ShapeOko #201 0.25" Upcut Spiral
3/4" Length of Cut
3 Flutes
2.5" Overall Length
0.111" Pass Depth
0.113" Stepover
16,000 RPM
Feed Rate 75 Inches/Minute
Plunge Rate 12.5 Inches/Minute

[Rcnewcomb]

Both those options seemed to go smoothly the first 0.375 or so

How deep are the holes?

3 Flutes
...
16,000 RPM

A 3 flute bit doesn't have very large gullet for clearing chips. My guess is that the combination of high RPMs and poor chip evacuation is causing things to get plugged up. While cutting small holes the router isn't moving through the material very quickly. If the chips don't get cleared from the slot or hole they end of getting re-cut into even finer particles and get pulled back into the cut and actually start blocking the cutting action of the bit.

First I'd try slowing your RPMs down if that is an option.

I'd also recommend switching to a 2 flute bit, particularly for cutting holes. You may even find a single flute bit like an Onsrud 48-007 bit works better for your machine.

The image was taken from Router Bit Basics for CNC

[wb9tpg]

I bought a Whiteside RU2075 2 Flute 0.25 Upcut Endmill and will try Peck Drilling again tomorrow. I created a separate profile for drilling for this bit that has a pass depth of 1/16". I report how it goes.

[wb9tpg]

I thought I'd let everyone know that it worked perfectly. I was holding my breath but it worked great. Thanks everyone for the suggestions; you can through again

[Rcnewcomb]

woo HOO!

Can you show us some photos?