End mills not accurate?

Machine design, rails, bearings, screws, nuts, couplings, ...

End mills not accurate?

Postby svberg » 18 May 2013, 19:34

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
svberg
 
Posts: 80
Joined: 15 Oct 2012, 17:50
Controller: Mk3

Re: End mills not accurate?

Postby Andrej » 19 May 2013, 09:06

I find this hard to believe. Where do you get your bits?

I measured mine and they are exactly like they should be.

Perhaps something is wrong with your caliper?
Andrej
 
Posts: 2489
Joined: 10 Jan 2012, 16:09
Controller: Many controllers

Re: End mills not accurate?

Postby RubonNY » 19 May 2013, 17:53

To me it sounds like your bits have been resharpened/renewed/refurbished, etc.
If this is the case, you just have to account for this difference in your CAM programm by measuring accurately every bit before usage.
If the depth of your (or work piece thickness) lies within the LOC of the bit, there should be no worries.
Just my thoughts
RubonNY
 
Posts: 22
Joined: 25 Nov 2012, 23:45
Controller: Mk2

Re: End mills not accurate?

Postby svberg » 20 May 2013, 00:18

Yes, its unbelievable.
As I said, i got the bits from different Suppliers in the UK, USA and Norway.
I have three calipers. All measuring the same.
But i really do not need them, as making a hole With inside cut, and then a "plug" With the same dia and outside cut. They do not fit..... before I put in the measured values.
Using the measured values on all my bits, I always get good results (+- 0.02mm)

On the Vectric forum they sugested i had used cheap resharpened bits. I certainly have not intended to, and have payed some 10-30 usd a bit. Is that cheap?
Maybe I have just been unlucky and that the main bulk of my bits bought from a Norwegian supplier (1F general purpose end mill), are all crap.
But still, All my other bits are also not correct.

I Guess I just have to keep measuring the bits, and put in the measured value. But its time consuming.

Anyway, thanks for Your reply!
regards svein
svberg
 
Posts: 80
Joined: 15 Oct 2012, 17:50
Controller: Mk3

Re: End mills not accurate?

Postby RubonNY » 20 May 2013, 11:51

With a 100 bits it won't be fast, but the good thing is that you have to measure it only once.
p.s. We probably all went through this situation while choosing the right supplier, just stick with the proven ones (though, at times it's might be more expensive, but as you mentionned - our time is more valuable)
I use 1/8 shank bits mostly from the drillman1 on ebay (no affiliation:), just good prices on great bits)
RubonNY
 
Posts: 22
Joined: 25 Nov 2012, 23:45
Controller: Mk2

Re: End mills not accurate?

Postby dbsharp » 19 Oct 2013, 21:48

I've never gotten a new endmill more than .002" or .05mm off the advertised size, even cheap ones. I do however measure each one as I enter it into my tooling database.
dbsharp
 
Posts: 16
Joined: 24 Jan 2013, 03:55
Controller: Mk2


Return to Mechanics



Who is online

Users browsing this forum: No registered users and 1 guest