Flycutter woes...

[dmcmd]

Hi all,

I'm having problems flycutting.

I'm trying to put a finish on some HRS (I think) I got at a scrapyard just for practice.

I have an X2 mini mill I bought from Little Machine Shop about 4 years ago.

I have a flycutter with an R8 shank.

I cut a left hand cutter out of 5/16 HSS blank. Really, all I did was cut a relief angle on the bottom so it wouldn't rub.

What is happening is the cutter is getting ground down by the workpiece instead of the workpiece being cut by the cutter.

As you can see from the pics, the corner has been shaved off of the cutter, and minimal cutting was done to the steel bar.

I'm using a fairly low speed.

What gives? Any ideas as to what I'm doing wrong?

Thanks,
Darren

 

[pjf134]

Try rounding off the cutter at the contact point and increase speed and light cuts also. Maybe it is a hard metal and thats why it is having a hard time of it. Try the rounded end bit on some known metal and see what happens. Your bit should look like mine in the pic.
Paul

 

[Bill Gruby]

I agree, you need at least a small radius at the contact point. If the metal is hard a sharp edge will just wear right off or even chip off. Cuts must be light.

"Billy G"

 

[Tony Wells]

You need some rake and some positive lead also on that cutter. Depending on how deep the scale it, it could be part of the problem. It can be pretty hard and abrasive.

 

[12bolts]

Can you drill a hole in the steel with reasonable ease? Maybe it isnt what you think.

Cheers Phil

 

[xalky]

Sometimes with HR steel, the mill scale is hard. I've found it better to take a heavy first cut, just a bit deeper than the scale, to get into the soft stuff. Then take a light finishing pass after that.

Marcel

 

[Deny1950]

As mentioned cutter should be sharpend differently look on utube for the proper way to sharpen, also what rpm are you running? do not skim on the scale it is very hard. Make sure you have the right rotation on mill, sounds like oxmorone but ti has happened before , I know trust me lol Denis

 

[dmcmd]

Re: Flycutter woes... Updated with second try

Hi all,

Thank you for all of the advice.

I tried it again today. I reground the bit, this time with a small radius and a lead angle. Also, I ground off all of the mill scale with my angle grinder. I also used a faster speed.

Unfortunately, the tip of the bit got ground off again...

Then I put a little remnant of the steel that I had from a hole saw into my lathe and faced it with a HSS right hand tool I made. It cut through it like butter.

I'm thinking that my mill is just not stiff enough to handle steel. Any thoughts?

Thanks,
Darren

 

[burtonbr]

I did kinda the same thing a while back, first time using a fly cutter had some Hss bits but didn't know they should be ground to a cutting bit, got the same results as you, a dull flat corner on the bit I needed to face off and square up several faces so I got a few of the cheap brazed carbide tipped tool bits to use in the fly cutter and was able to get the parts I needed made it worked well for me, could get a nice finish even, but still haven't learned how to grind a proper bit yet, I need more practice.
i used something like these:

 

[kd4gij]

I agree brazed carbide bits work much better in a fly cutter. At least for me.