# Why not 50 mm when i tell him so :)

Hey Guys need some wisdom for you all!!! Why is it like that, when telling in Vcarve pro or any other CAD programm a circel of 50mm and tell him to cut in the inside, why its the finisht circle not 50 mm in the inside, but is about 52.76 even if i have put the stepover at 0.1 mm 1.8% ???

have you measured your bit? run a cut in scrap and measure the width of the cut, is it exactly 5.5 mm? it only needs to be 1.36 mm off to make the difference.

Have you calibrated your steppers?

Ok that is new for me, how do you do that calibrated stepper motors ??

if you have calibrated your machine (place a bit with a fine point in it, and move the machine an amount, measure the distance the machine moved. calibrate the stepper to move the amount requested). there are several post in this forum on the exact procedure to do this, some with spreadsheet with the math equations built in, and you are sill off then check your bit diameter, just because you bought a 5.5 mm bit doesn’t mean that the bit is exactly 5.5 mm. The best way to measure a bit when you need precise cuts is to make a cut with the bit in scrap material and then measure the width of the cut, rarely will it be exactly what the bit was listed as, sometimes more sometimes less. Take that measurement (width of cut) and place it in as bit diameter. (5.415 mm for example) instead of 5.5 mm. hope this makes sense.

When cutting a circle or a box you have to take the “difference” in bit diameter and double it. when you have a bit that is .1 mm bigger it will make the object a total of .2 mm wider .1 mm on each side. again hope this makes sense. I am sure there are some mathematician out there that will correct this but that is what I have found.

I have dont that already some weeks ago calibration of the steppers like Robert is showing in his videos but my was fine so i did not need to change somthing. I just noticed that i lost some steps the other day when i dont some more circles.
But i think it just was to fast freed rate that i put in I still have the old power supply unit not the X controller cost to much to send it the Sweden.
Because sometimes i feel i need a new one because my x carve works for hours !!

Ok and if i understand Kenneth right you mean that when i have my 5.5 mm bit i need to take off the 11mm right since you say double it.
when you look at my first pic where its says stepover i thought that is what makes it more accurate the it will cut more from the waste to the inner chenter ( in my case the circle )

so you mean i just put that infon in to my machine or check it one more time ?!

ok z is fine or what do you say

what is what my machine insp. says \$102=188.976 how come yours and my are so much different ?

just my X is of by 0.45 mm i run 400 mm but it went 400.45mm

ok so so i need to put \$100 or 101 the one for X and then enter 39.955 and hit enter ok will try later need some hewat in my garage is -2,6 getting colder

i see you got to one of the nice dust boot. like to make my own wonder if i can find some drawings on here like this one
https://www.suckitdustboot.com/purchase

Thanks Phil

If that was your x axis and it currently says
\$100=40.00

Then you should enter
\$100=39.955

Your x and y will probably be different from each other. Do the test in both directions.

oh ok i did not look what is say at \$100 i just look on my ruler put it to 100mm when then i told the machine to go 400 mm i will try again

oh Phil i seen that you start your dewalt router with Easel how did you do that ? i thought of doing a normal switch in between.

no maybe i say it wrong on the ruler i start at 100mm told him to go 400mm and it stop on 500.45

so everything works fine again !! did not do any cuts yet but i need to give the steppermotors more power too. and x and y are fine too.

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