Penny wise and dollar foolish

[Bill the Cat]

Well, after a number of months of interuptions, I finally got a chance to start working with my CNC mill. I purchased some bits from Precise Bits based on the things that I had read about them on the forum. In addition, I bought some "cheap" bits from a guy on eBay. I figured I could use the cheap ones for roughing out pockets and use the Precise Bits for finishing. I just got done with some test cutting in the shop and found that the cheap bits I bought were a waste Two of them broke almost immediately. After cranking the feed waaaaay down, they didn't break...they just looked like a beaver chewed out the pocket. I reprogrammed and put in one of my Precise Bits. It cut like a dream and I was able to crank the feed back up to a reasonable rate.

Needless to say, I just finished placing another order with Precise Bits:thumbup:

I'm sure any of you guys that have been CNC for a while already knew this, but I thought I'd post it for the guys just getting into CNC.

 

[conetip]

Having the correct type of cutter for the job can make a big difference.
Ar work we tried a mitsubishi 4mm end mill with 20mm cut depth, cutting a pocket 19.8 mm deep and 4.2 mm wide and 200 mm long is toolsteel,35 Rc hardness.
The new cutter running at the recomended speeds and feeds did the job in just under 8 mins. Made 17 parts. The previous cutters were taking 19 mins a piece and only getting 4 parts per cutter.Even though the new cuter was nearly 3x the price,it was cost effective in making 38 parts.The time saving alone more than paid for the cutters.
There are a bunch of different cutters on the market, and it pays to look around and sometimes outside the square to find them.
DHF from asia also make some very specialised cutters with very wear reistant coatings.
Most of the new style we use now are the type with either unevenly pitched cutting geometry or variable helix cutters that efectively become unevenly pitched cutters.The reason is to reduce harmonics and also adds to cutting life for some reason.
Cuters for ali work really well on wood and most materials used in cuemaking.

 

[Mc2]

Check the cheap bits under magnification

Bill, the cheap bits that you got may in fact be drill bits. They look almost the same. Under magnification you can see that they are not bottom cutter (fishtail bits). This could cause alot of issues including breaking.

If you don't mind me asking, what kind of setup do you have? I am always interested in the machines and software that others are using. I have a Storm machine that I built myself running with Mach3, Gecko 540, and Bobcad V23. Also I have a 50K rpm Kavo spindle with an ATC.

The bits at Precise are great as they will come with stop rings. I can change out my bits in less than 5 seconds and don't need to touch off the bits every time as they all have the same length.

Jim.

 

[Bill the Cat]

I thought that might be it too....

Bill, the cheap bits that you got may in fact be drill bits. They look almost the same. Under magnification you can see that they are not bottom cutter (fishtail bits). This could cause alot of issues including breaking.

If you don't mind me asking, what kind of setup do you have? I am always interested in the machines and software that others are using. I have a Storm machine that I built myself running with Mach3, Gecko 540, and Bobcad V23. Also I have a 50K rpm Kavo spindle with an ATC.

The bits at Precise are great as they will come with stop rings. I can change out my bits in less than 5 seconds and don't need to touch off the bits every time as they all have the same length.

Jim.

Hi Jim, thanks for you input!

I've got the CNC ready Taig 2019 with ER16, Keling steppers, Gecko 540 controller and using Mach3. I use BobCAD V19 to create my designs and generate the Gcode. I've also got one of the Wolfgang Engineering TB350 spindles, but I've been doing my initial tests with the stock Taig spindle.

All of the cutters I have use depth rings....even the cheap ones. I couldn't imagine having to change cutters (mid-program) without them.

The cheap cutters I bought are .040" and I started with a .030" overlap between paths. The pocket (paricularly the bottom) was very rough, so I reprogrammed for a .018" overlap. It was a little better, but the bottom still showed ridges like there wasn't enough overlap in the cuts.

That's when I checked the cutters under magnification like you mentioned. They are fishtail end mills and not drill bits. At least that's when I looked at a new one. When I looked at the one that I had just used to cut ONE pocket, the fishtail was gone. The corners of the cutter had worn or broken off and it DID look more like a drill bit at that point Less than impressive tool like.

I switched to the Precise Bits that I had (.035"), used the same program (.018" overlap) and the pocket is as smooth as a baby's butt