My sizes are out

[Desertboy]

Have you measured your backlash? You need to check backlash.

I ran Gcode to move X to 10mm then back to 0, 1000 times and same with Y and checked position everything seemed good.
http://www.mycncuk.com/threads/13525...399#post115399

I would have seen backlash with that check right?

[dazp1976]

I ran Gcode to move X to 10mm then back to 0, 1000 times and same with Y and checked position everything seemed good.
http://www.mycncuk.com/threads/13525...399#post115399

I would have seen backlash with that check right?

Not really no. Even if it has backlash it will still follow the same pattern back and forth so you wouldn't notice.
Have a look at some vids that show how to properly check it.

If your sizes are out by more than say 0.2mm I'd say it wasn't a backlash issue. I've never really seen backlash values of more than 0.08mm which would make a circle smaller by only 0.16mm.

[JAZZCNC]

If you had 1mm of backlash you'd feel it by shaking each axis, it would feel like it's falling off.!

[dazp1976]

If you had 1mm of backlash you'd feel it by shaking each axis, it would feel like it's falling off.!

Tell me about it!!
1 thing I'd say as well is I often use cheap nasty Chinese cutters for roughing through then swap a decent cutter for a finish.
Those Chinese ones can vary in size a chunk.
I can rough a new 6mm 3flute bit using it to finish as well and I won't fit a bearing in the hole.
Then next I'll leave 0.5mm on with the same cutter, swap it for a 4flute Cobalt bit for finishing and be able to just get the bearing in.
That's with my drawings modified where a circle is set 0.1mm lager than I actually want it.

My Benchtop only has 3000rpm at the spindle so I find Cobalt work better for me as I can hog it a tiny bit.
Those Carbide bits are designed for higher rpm and I've shattered a few so there used for finishing only too.

[pippin88]

I ran Gcode to move X to 10mm then back to 0, 1000 times and same with Y and checked position everything seemed good.
http://www.mycncuk.com/threads/13525...399#post115399

I would have seen backlash with that check right?

No, that will not show backlash.

Look up what it is and how to check it.

You need a proper measuring instrument, e.g a dial indicator. You move the axis in one direction into the dial indicator, zero the dial indicator then move the axis in the opposite direction a defined amount. You then check the dial indicator reading and compare to what it should be.