[coyoteboy]

Hi all. I recently managed to get hold of a well priced used small mill (AMA25LV) and having had a little play with it I'm pretty pleased with the overall construction and rigidity for what I need it for. I plan to convert it to CNC over the coming months but first I'd like to get some tooling bought in that I can use with it manually for the time being.

I don't plan to use this machine as a production line item so saving 30 seconds on a tool change doesn't bother me, though repeatable consistent tool heights might come in useful when the machine is computer controlled. I have an MT3 taper in the spindle which can take TTS tooling via the TTS adapter, or I could use ER collets, but considering it has a self-ejecting drawbar it doesn't seem to gain me much over just using bog standard MT3 collets (which would surely inherently have higher stiffness and larger working throat due to the lack of adapters?). I could be missing something vital that for an extra bit of cash will make my life 100x easier - can anyone provide me guidance in this process?

[dkowalcz]

I'd stick with the fewest adapters and interstitial pieces you can manage, having better concentricity on an endmill is key to tool life and easier machining. It's a problem if one flute in four is doing 60% of the work and the rest "go along for the ride, doing 20%, 20% and 0%" as is likely with the finer feeds on a small mill when the tool is eccentric.

Any decent control should let you "touch off" the tool and set zero before cutting, it doesn't add that much time with 5x changes a day (about once an hour) to do that vs. 500x (less than a minute per toolchange).

Hope this helps.

[coyoteboy]

Thanks, yes you confirm my suspicions but have upset my "buy shiny tools" urges

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[RCaffin]

Seriously biased opinion: the words 'Morse Taper' and 'CNC' should not be in the same sentence. For that matter, 'Morse Taper' and 'Milling Machine' should not either.

Cheers

[coyoteboy]

That's not really helpful unless you explain why. It's very common, cheap and there's loads of mill compatible tools sold in mt3 and other than slow tool changes I can't see a reason against it.

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[RCaffin]

That's not really helpful unless you explain why.

OK.
Morse taper relies on friction and the taper angle to get both retention and torque. So for drilling holes where the thrust helps drive the taper inwards, this is great. And since drilling is fairly constant torque, no problems. So fine for drills and lathes.

Now with milling, the thrust is usually sideways, and there is vibration. This is a bad combination. The nightmare when milling with Morse Taper is when the vibration shakes the taper loose and it starts to edge out. Bad scene, damaged machine, broken tools. It can be prevented by using a drawbar of course, but there are many better solutions: R8, ERnn, ISO-nn etc. That's what professional machines use.

Yes, I know a lot of little drill/mills use Morse Taper. That does not make it smart. It's cheap, and many of those machines do little more than drilling anyhow. But that's just my advice: take it or leave it.

Cheers

[coyoteboy]

Don't have much choice, I have what I have but I've never had (and my father has never had) an mt3 come loose with the drawbar done up reasonably?

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[coyoteboy]

Don't R8 use drawbars too? Making it a moot point?

And unless you can find a replacement spindle for your machine, there's absolutely no point using an mt3>er type converter as all of the issues of the mt3 still exist, only you're adding additional concentricity errors and losing stiffness?

[dertsap]

I've got two small mt3 mills that are in constant production when I'm not at work and I've got a load of these holders collet holders
They work great , and the one or two times that I've forgotten to crank the draw bar tight , they on their own managed to suck themselves damned tight into the taper while taking fair cuts .
The only issue that I find with mt is the fact that they get so tight and it takes a heavy hit to break them loose , I've blown thru a few draw bars because over time the threads break down

[RCaffin]

Don't have much choice, I have what I have but I've never had (and my father has never had) an mt3 come loose with the drawbar done up reasonably?

With a draw bar is OK. Never run without the drawbar done up tight. If it rattles it can damage the socket.

Yes, R8 uses a drawbar too, but there is no temptation to try to use R8 without the drawbar! :-)

If you find the taper jamming too tightly it might be worth while putting the barest smidgeon of copper anti-sieze paste on the taper just once. Just a touch of it, spin it around, and do the draw bar up tight every time. That may be better than hammering the ball race in the column.

Cheers

[coyoteboy]

With a draw bar is OK. Never run without the drawbar done up tight. If it rattles it can damage the socket.

Yes, R8 uses a drawbar too, but there is no temptation to try to use R8 without the drawbar! :-)

If you find the taper jamming too tightly it might be worth while putting the barest smidgeon of copper anti-sieze paste on the taper just once. Just a touch of it, spin it around, and do the draw bar up tight every time. That may be better than hammering the ball race in the column.

Cheers

Note taken, thanks! I will see how I get on, of its a problem I may consider a change. I have a self ejecting drawbar on the mill so I'm hoping I only have to do minimal beating to remove them!

I've got two small mt3 mills that are in constant production when I'm not at work and I've got a load of these holders collet holders
They work great , and the one or two times that I've forgotten to crank the draw bar tight , they on their own managed to suck themselves damned tight into the taper while taking fair cuts .
The only issue that I find with mt is the fact that they get so tight and it takes a heavy hit to break them loose , I've blown thru a few draw bars because over time the threads break down

What's your reasoning behind using the ER adapter when you could use just the mt? I'm just curious as it seems a very common thing to do but seems counter to everything I knew, certainly if you don't change regularly?

[dertsap]

What's your reasoning behind using the ER adapter when you could use just the mt? I'm just curious as it seems a very common thing to do but seems counter to everything I knew, certainly if you don't change regularly?

I certainly do
As I mentioned , these mills are running production , some tools run longer than other but I use multiple tools and I'll do a lot of tool changes in a day . Constantly re-qualifying tools wouldn't be efficient and has other potential problems that may occur . I've got tools that were set months ago and the offsets are saved in the control , nothing changes and everything works as expected , plus tool changes are rapid , well , as rapid as they can get by hand .
As far as beating on the draw bar , it's not necessary to beat the living snot out of them , one good blow usually does it , my point was that the chances of them them working loose and or damaging the taper is slim to none and probably less so than any of the other tapers out there .

[RCaffin]

What's your reasoning behind using the ER adapter when you could use just the mt?

Probably the same as with R8 to ER. I can only get a very small number of sizes with the R8 (6, 10, 12, 16, 20 mm), whereas with ER I can get every millimetre step. This matters for two reasons:
* with ER collets I don't need to move to a large height-consuming chuck for drilling
* modern carbide milling cutters don't have the 'standard' shank sizes one gets with HSS.

The latter is quite important: by way of example, a modern 8 mm carbide end mill usually has an 8 mm shank, and this cannot be held by R8, MT3, etc.

So I have a good ISO-30 to ER25 adapter in my CNC. Runout (measured) is very low.

Cheers

[dertsap]

you forgot one point , er collets are dirt cheap

[RCaffin]

you forgot one point , er collets are dirt cheap

To be honest, that was not really a consideration. What mattered was being able to handle the carbide cutters: ER collets can, others can't.

Cheers

[coyoteboy]

I certainly do
As I mentioned , these mills are running production , some tools run longer than other but I use multiple tools and I'll do a lot of tool changes in a day . Constantly re-qualifying tools wouldn't be efficient and has other potential problems that may occur . I've got tools that were set months ago and the offsets are saved in the control , nothing changes and everything works as expected , plus tool changes are rapid , well , as rapid as they can get by hand .
As far as beating on the draw bar , it's not necessary to beat the living snot out of them , one good blow usually does it , my point was that the chances of them them working loose and or damaging the taper is slim to none and probably less so than any of the other tapers out there .

Is that purely because the bits bottom out in the collet? Does wear not affect this and need calibrating?

[coyoteboy]

The latter is quite important: by way of example, a modern 8 mm carbide end mill usually has an 8 mm shank, and this cannot be held by R8, MT3, etc.

So I have a good ISO-30 to ER25 adapter in my CNC. Runout (measured) is very low.

Cheers

Pretty reasonable selection of sizes available in mt3?
http://www.arceurotrade.co.uk/Catalo...llets---METRIC including 8, unless I'm missing a point? (Always possible!)

[dertsap]

To be honest, that was not really a consideration. What mattered was being able to handle the carbide cutters: ER collets can, others can't.

Cheers

that would be dependent upon the circumstances , on non production machines they work ok , but for real cnc production macinhing I'd never use a collet unless it's the only thing available . I've never liked er for milling and have had more trouble with them than any other tool holding system out there . Er collets are far to prone to slipping , I'll take tg well above er when it comes to holding a mill well enough that it won't slip , aside from that there are much more expensive collet systems out there that are far superior to both of those

[dertsap]

Is that purely because the bits bottom out in the collet? Does wear not affect this and need calibrating?

I have a multitude of those holders , I don't change the tool in the holder , i change holders and never remove those tools from the holders

[coyoteboy]

I have a multitude of those holders , I don't change the tool in the holder , i change holders and never remove those tools from the holders

Oh that's interesting, I would have thought the taper insertion depth was more variable than that. You learn something new every day!