Clearing Bit Running Slightly Higher Than Finishing Bit

[Art Sign Works]

Recently started happening, we run a 1/16" end mill first, then change to a 1/2" end mill to clear and the 1/2" bit runs about .010" higher than the 1/16" bit did leaving a step up in the material. They were both Z-plate zeroed in the same exact spot on the table. We have tried changing to zeroing on top of the material with the same result. Any ideas on fixing this problem? Thanks.

[robtown]

Is it possible the 1/16" bit is slipping a bit when you z-zero? (worn collet)

If it's consistently happening and it's a consistent distance (.010) you could manually adjust your z after zeroing the 1/2" bit.

[jTr]

May not have as much to do with the machine's accuracy as you think. A 1/16" bit will pull much differently through the material vs 1/2". Even if you've had success doing this precisely the same way in the past, current material may be flexing upward more on that first cut, causing it to appear to cut deeper, or vice-versa, etc, etc....

Simplest way to rectify: Reduce depth of cut for the first bit by .016 - .020". This way, the larger bit will be cleaning 100% of the bottom of that groove, giving you that uniformity you are seeking.


Jeff

[Art Sign Works]

May not have as much to do with the machine's accuracy as you think. A 1/16" bit will pull much differently through the material vs 1/2". Even if you've had success doing this precisely the same way in the past, current material may be flexing upward more on that first cut, causing it to appear to cut deeper, or vice-versa, etc, etc....

Simplest way to rectify: Reduce depth of cut for the first bit by .016 - .020". This way, the larger bit will be cleaning 100% of the bottom of that groove, giving you that uniformity you are seeking.


Jeff

Thanks, I will try both suggestions. I appreciate your advice.