Mill bits last 200 pieces one day and 20 the next

[SaltyPotato]

Running a tormach milling machine and milling out a ~.250 deep detent with a 5/16" 4 flute TiN ball end mill. Using SFM 350 and .002 IPT. We run two different types of mild steel, a forged piece which runs great all the time off 2 stepdowns, and a cold rolled steel which we anneal before to soften it for this machine which we run with 3 step downs. The hot rolled part works great some days, getting 160-200 pieces one day and then 20-30 the next with no changes. Any help or ideas why this variation might happen day to day would be greatly appreciated!
Thanks in advance,
SaltyPotato

 

[michiganbuck]

Guess I would quickly eyeball inspect the cutters with a loupe to see the cutting edge and that the back off comes right up to the edge. ball noises can have a sloppy grind.

Check a few cutters after a short number of parts to see that there is no heal rubbing.

QT: (which we anneal before to soften it for this machine) might file check those parts.

 

[FredC]

1) The light duty machine could have a hick up one day that damages the cutter.
2) The part might move a little and damage the cutter one time and not the rest.
3) Material could have random inclusions. I have found inclusions in 1 inch round cold rolled that stopped the spindle on a screw machine. Hot and cold rolled steels can have a lot of junk in them these days.
4) What michiganbuck said about cutters. Just because they came out of the same box does not mean they are all equal.

 

[DDoug]

What's a "Mill Bit" ???

 

[michiganbuck]

What's a "Mill Bit" ???

A small part of a milling machine?
A funny mill story or a mill joke.?

 

[Shipp]

A small part of a milling machine?
A funny mill story or a mill joke.?

No, it's the part attached to the reins for steering the mill when you ride it.

 

[Vancbiker]

What's a "Mill Bit" ???

It’s a tool for folks using a machine they think is a mill but is really a chintzy drill press with power steering.

 

[michiganbuck]

It’s a tool for folks using a machine they think is a mill but is really a chintzy drill press with power steering.

Never ran one but see some used ones $4 and 16k are they all poor/light duty?
They did give up on making a surface grinder.

 

[Cole2534]

chintzy drill press with power steering.

this gave me a sensible chuckle.

 

[13engines]

What's a "Mill Bit" ???

All I know is if you had two of them you'd have Two Bits. Which may say you finally have some value to work with.

 

[plastikdreams]

All I know is if you had two of them you'd have Two Bits. Which may say you finally have some value to work with.

Well then you could get a shave and a hair cut...

 

[Mtndew]

and a cold rolled steel which we anneal before to soften it for this machine

What type steel is it? CRS can be anything from 1018 to 6150 to 1060.

 

[Milland]

I don't understand the need to anneal the CRS. And if it is higher carbon, a "home shop" annealing may just harden it.

 

[Mtndew]

I don't understand the need to anneal the CRS

I don't either.

 

[dandrummerman21]

Maybe it's normalized?

 

[mhajicek]

Are you using coolant? Could be cutting out.

 

[plastikdreams]

I don't understand the need to anneal the CRS. And if it is higher carbon, a "home shop" annealing may just harden it.

Why would you anneal something that's in a soft state already? I do know it's easy to case harden that stuff with a torch lol.

 

[Orange Vise]

Where are you buying your endmills?

 

[Orange Vise]

We run two different types of mild steel, a forged piece which runs great all the time off 2 stepdowns, and a cold rolled steel which we anneal before to soften it for this machine which we run with 3 step downs. The hot rolled part works great some days, getting 160-200 pieces one day and then 20-30 the next with no changes.

Assuming this means you're not having trouble with the cold rolled. Only the hot rolled.

The mill scale is probably wearing down your cutters. They can have hard spots. Good cutters will breeze through the scale. Get better ones.

 

[Milland]

Wimpy spindle and machine stiffness will do-in the best carbide cutters...