[sooncheng]

I just referenced our job history. I'm in the US, so I am not current of your steel grade references, but in "low carbon" steel (1018, 1020, 4140 here in the US) we run that with a 4-flute tool, with modern coating, at:

75 - 107 M/Min Surface speed (stay on the low end here since I don't know what geometry)
75M/min = 23854 RPM
Feed per Tooth: 0.0044mm PER TOOTH (don't go above 0.005 IPT, and don't start below 0.0044"
Feed per minute = 458.016 mm/min (assuming 0.0048mmIPT, 74 M/min)

The feed has bee pre-adjusted for slotting conditions.

Again, runout and tool project are very important here. As short as possible, as concentric as possible.

You were rubbing the tool to death in your first 2 attempts, almost certainly. When your chip load is too low, not only will you build up heat, but your cutting edge will push off the material rather than bitting, so your effective shipload was actually much less than what you programmed. As you feed into the part, the end mill gradually falls behind and can't keep up, causing the carbide to break from excess deflection.

Thanks. I've worked my way around by using a 6mm diameter, 1mm tall slotting mill. I first tried with 60m/min (3183rmp) with 0.03mm/tooth/rev chip load (0.5% of tool diameter which is half of what joeavaerage suggested), then 90m/min (4774rpm) with same chip load. It worked great but the chip load is higher than what you've suggested (perhaps you've lowered intentionally on this?). What is your rule of thumb for choosing a chip load?

Cheng

[hpappsguy]

I used cheap ER32 collet with BT40 holder, TIR was around .05mm haha will using smaller collet and holder gives better runout (like ER16 collet, I prefer collet system because I have to change my tools quite often)

I think I had around 12mm stick out which was the minimum I can get before clamping on the coated surface of the tool (can I actually clamp on the coated part of the tool?)

Cheng

you can clamp on the coated surface, but it is not best practice as it hurts your TIR. In your case, choosing one over the other, I'd go for rigidity. 12mm stick-out is 12 x Diameter. A rigid projection is 3 x Diameter. A stable projection is 4 x Diameter.

We use only Swiss made Rego-Fix ER collets (they invented the product). There are other excellent options such as BIG Kaiser (Japanese), and Deibold (German). You get that you pay for in tool holders. There are others, but you always need to understand where their stated runout is measured at (collet nose, 2.5xD, 4xD?). Generally, if you can get 0.0002 -0.0004" in an ER, then you are doing fine. The ER collet business isn't real straightforward and there isn't a standardized reference for advertising runout. Although, I think 4xDiamter is the most practical because that is closest to the projection of a tools cutting tip in a real cut.

[hpappsguy]

Hi,


circumference = 2 x PI x r r=radius
circumference = PI x d d=diameter

tool diameter =1mm therefore circumference = 1.0 X PI=3.141mm

Craig

Craig, you are correct. Both formulas are the same. My apologies.

[deadlykitten]

First trial: 3500rpm, 15mm/min and the tool broke halfway...

Second trial: 2000rpm at 20mm/min, ...

you have increased your feed from 0.0042 to 0.01 mm/o; those are random numbers

... you should understand how to use different feed modes, like mm/min, mm/rot, then move to others types of feed :
...... inverse time feeds
...... difference between center/core feed and tangential feed, especially for small tools, thus look into speed difference between spindle center and cutting edge
...... interpolated feeds when rotary axis are used
*dont worry, some persons do just fine without knowing them
... you should use a hss disc, diameter 30mm, width 1mm, just like jim dawson said; also, with this tool, you should not worry about tir, and it is also cheaper then o1mm endmill / kindly

ps : bt40 is too rigid for tiny tools, especially how a mk1 is too small for a 10"chuck; if you wish to use the machine at such level, you have to know not only how to adjust tir, but also how to adjust it's rigidity, thus you need a more flexible, more gentle chucking method for your tiny tool ( the inertia of a heavy rotary axis is too big for small tools, making them to vibrate before begining to cut; also tir increases with rpm, and also it increases with spindle size ); just go with the hss disc ( attached )

[OrsonY]

I using HRC55 coating endmill milling XW41 high carbon steel without Harden,
4mm - 8000 RPM with feed 800mm/min
2mm - 12000 to 15000 RPM with feed 500 to 1000mm/min
1mm - 24000 RPM with feed 500mm/min

and
0.2 tapped endmill 24000RPM with feed 500/min

with 0.02 to 0.3 AP and AE


and it work fine for me..