End mills measures not correct?

[svberg]

Hi.
Some weeks ago I discovered the parts I made was slightly out of dimentions.
To make a long story short, I ended up measuring my bits. NONE were even close to their designated values.
A 6mm end mill was measuring 5.62. Putting this value in Vectric aspire, and the part was spot on!
I have some 100 bits, ranging from 1mm to 6mm, from some 6 different Suppliers. End mills With 1, 2 and 4 flutes, Ball nose With 2 and 4 flutes. ALL were some 10% to 5% smaller than what I had ordered. The shank of all bits was very accurate.

I have searched the net, but found very little about this.
I have also searched the websides of all the Suppliers, but found nothing similar to;
"When ordering a 6mm (Shank) bit, the actual cutting With of the bit have to be measured by the user!"

Feeling like a Complete idiot, as the very reason for CNC seems wasted if the bits are all over...

Have anybody else experienced something similar??

best regards svein

[gdb]

Only on a resharpened end mill.

[Leo]

svberg,

Are they 3 flute? If they are - HOW - are you measuring them?

[zeeway]

Getting your machine to exactly cut a dimension is a function of the calibration of the machine, the repeatability of your machine, sharpness of the cutting bit, the material, and the size of the cutting bit, among other things. After making sure your machine is well calibrated, you can cut a simple groove (on the vector) with a sharp end mill in your material, and measure the width of the groove - this is the effective diameter of the tool. This will vary as the tool loses sharpness, the material changes (sometimes in the same piece). Wood is a special challenge because it is non-uniform, and will also change because of humidity.

Angie

[David Rueth]

Only being a little bit past new kid and still using "cheep" bit I find that all the bit are off including the V bits. I found the easy way to check a bit is to lay out a 1.5" square and inside of that a 1" square. This works well for a EM or V Bit. Use a V-Carve tool path with the depth set to 0.125 When the cut is done measure the depth of cut. If you are testing a V bit this must be correct before you measure the size of the two squares. If the larger square is less than 1.5" and the smaller square is greater than 1" your bit is less than what it is rated at. If the two square are the correct size and you are using a V bit do the sides and corners look good? I have found one V bit that my best guess is the blade has a bow in it. It will cut good to a depth of about 0.125 but if I cut to a depth of 0.25 the side bow in and the cornes look bad.

[Leo]

I am confused.

Sounded like the poster was asking how to measure the cutter - not how to make an accurate cut.

I am usually wrong - but that is how I read the post.

End mills are a bit difficult to measure - and 3 flute or 1 flute mills or any odd number flutes for that matter cannot be measured with calipers or micrometers.

Hence - my question - Are they 3 flute?

[Adrian]

Svien says the parts are correctly sized now he has put the correct diameter into the database. Seems a bit of a coincidence if Svein's machine was off by exactly the same amount that the bits were undersized so I expect he is measuring the bits correctly and they are undersized.

I have a plate that I machined out of tufnol that I use to check the diameters of the tools I use. I get mine from the same supplier and they are always spot on to what I order. I had my fingers burned early on with cheaper undersized bits. Only takes one undersized bit that is missed to ruin a sheet of parts and wipe out any savings.

[Leo]

I do not understand.

If we have a CNC router - spent significant money to acquire it - bought software to program the nice piece of equipment - spend significant money for that - then we want to produce great things ----- all cool in my book.

But - the thing that confuses me is this.

We go out and buy the cheapest cutters that can be found?? This is where the rubber meets the road.

Kinda like having a high performance sports car with the cheapest used junk yard tires we can find. Then we want to run the course???

I just don't understand.

I don't buy cheap cutters - so I don't ever experience these problems.

I should just keep myself silent (lurk) in these matters.

Sorry ----

[rscrawford]

measure the endmill by cutting a slot in the wood species you will be using, and measuring the slot. Different substrates will have different widths of slots using the same bit.

Also, you'll find that the angle on V-bits is rarely exact. This will cause problems with your v-carving. There is a tutorial on these boards somewhere showing how to adjust the angle settings for your v-bits to get perfect v-carvings.

[Jozua]

We go out and buy the cheapest cutters that can be found??

Ditto!!!

I will most certainly take this opportunity to keep my Big Mouth Shut!!!

As an afterthought – I never had any problems with Onsrud or Amana cutters.

Joz

[Leo]

We go out and buy the cheapest cutters that can be found??

Ditto!!!

I will most certainly take this opportunity to keep my Big Mouth Shut!!!

As an afterthought – I never had any problems with Onsrud or Amana cutters.

Joz

I wish I could keep my mouth shut.

[svberg]

Hi.
Thanks all.

First. As stated my bits are 1, 2 and 4 flute bits. I measure With a caliper. Laying the bit and the caliper flat on a table. My maschine should be OK, as I always gets good results (+- 0.02mm) when using the measured value, instead of the "delivered" value.

"Cheap bits?" I certainly did not intend to. And I have never bought resharpened bits, at least the supplier have never stated they were resharpened.
I pay from USD 10 to 30 each. Is that cheap?
Some I bought from a Norwegian supplier who claime his delivering to all the main mechanical shops in Norway. He said its impossible to measure his 1 flute bit, "they are always correct, so its my machine, the material or some gremlins at work."

V-bits doesnt bother me much, as I only use those for decorative purpose, wich really dont need much accuracy.

Jozua had never had any trouble With Onsrud or Amana cutters. Thank you for the tip.
I will buy my Next bits from them.

Thank you all!
regards svein

[Leo]

svberb,

Sorry for sounding off like that.

SGC, Robb Jack, Amana, Onsrud - there are a lot of decent names out there.

I have a lot of experience in the metal cutting industry and we depend on cutters cutting to exact size. I know it's difficult to know what is best.

I generally pay from $15.00 to $50.00 USD for cutters. In general a 1/4 inch SGS 2 flute end mill at a discount place will cost between $15.00 - $20.00 I am SURE that the .250 SGS end mill will measure .250

[4DThinker]

I'll throw in another vote of Onsrud being the most reliable in dimension. I've had bad luck with Freud, MLCS, CMT, and most other manufacturers. Not a crisis when the bit can be easily measured or the part dimensions aren't critical. Annoying as hell though.

I found Freud 1/16" endmills were cutting oversize (wider than 1/16"), and it turned out they were not centered on their 1/4" shank.