I'm seeing about 20 thousands of error in the Z and 15 thousands in the X axis

[Indigenous]

E.G. This is a photo of a pocket that was located at .723 but actually cut at .703 as shown in picture.

I have a similiar discrepancy on the Z

Is .020 the expected error in the machine?

Thanks for any help.

This is kind of critical as I wanted to do blind dado construction.



29837

[knight_toolworks]

it depends on how you cut it and how fast. slop in the machine and cut direction can do it or a dull bit. usually for dados I will do a climb and regular cut if they need real accuracy.

[Indigenous]

It is already .020 small, IOW it is not because flex in the machine. Otherwise it would be .723 or bigger.

[Gary Campbell]

There are a few things that will cause undersized cuts:
Worn pinions (or loose pinions while climb cutting)
Undersized bits
Machine flex due to climb cutting. Which will return equal undersize results to oversize cutting using a conventional direction.

[Indigenous]

There are a few things that will cause undersized cuts:
Worn pinions (or loose pinions while climb cutting)
Machine flex due to climb cutting. Which will return equal undersize results to oversize cutting using a conventional direction.

That is Counterintuitive to me, it would be the opposite

Undersized bits

Again Counterintuitive, undersized bits = larger parts

[knight_toolworks]

I find especially on baltic birch the big getting dull gave give me .02 even with a combo of climb and regular cut. a climb cut will bring out more slop in a machine then regular cut.

[Indigenous]

How deep do you cut on the climb cut? On 3/4" sheet goods for instance.

[Gary Campbell]

"That is Counterintuitive to me, it would be the opposite

Undersized bits

Again Counterintuitive, undersized bits = larger parts"

I defer to your greater knowledge.

[steve_g]

http://www.talkshopbot.com/forum/attachment.php?attachmentid=29842&stc=1

[Indigenous]

http://www.talkshopbot.com/forum/attachment.php?attachmentid=29842&stc=1

Thanks Steve

[Indigenous]

"That is Counterintuitive to me, it would be the opposite

Undersized bits

Again Counterintuitive, undersized bits = larger parts"

I defer to your greater knowledge.

I'm not trying to be argumentative, and appreciate the input.

I was thinking the deviation was from the out side profile not the 1/4" deep pocket.

[gundog]

If your machine is out of tram it will also affect pocket size the longer the bit the more under size it can be and also be off in position. Have you swept your spindle using an offset indicator? Think about the force put on the bit and if it has slop the pockets will be under size and outside profiles over size.

Mike

[Joe Porter]

I t looks like you are plunging straight into the cut and then cutting. I would do a spiral cut and give the bit a chance to eat away a smaller bit of material as it progresses. What type of bit are you using? Which machine do you own? It looks as if the initial plunge is the size of the bit, but the dado is smaller which would make me believe that, as said before, there is some flex in the machine, worn bit, etc. Why don't you try running the same toolpath again (over the same cut) and see if the dado starts to get better.....joe