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Thread: CAT40 vs. BT40 on new machines
03-18-2009, 10:27 AM #1
CAT40 vs. BT40 on new machines
I was talking to a gentleman awhile back who retrofits older machines with new controls and motors, and sometimes spindles and toolchangers. He swears by BT-40 due to the symmetrical drive dog configuration... potentially less hazard for the ATC? This was surprising to me since most of the big VMC makers I talked to spec'd new orders with CAT unless otherwise specified.
I was under the impression (based on talking to local shops) that people bought BT machines only if they already had an arsenal of older BT machines and didn't want to buy all new holders.
For those of you who have recently (last 5 years) purchased new machines, were they configured with CAT or BT? What's the breakdown of BT vs CAT machines in your shop?
03-18-2009, 11:02 AM #2
We use CAT because thats all we have for spindles. If we were to buynew it would be CAT as well. ATC hazards depend on the machine. They are both symmetrical to my knowledge. Older or even newer Taiwan machines use a hydraulic cylinder to change tools and sometimes if the hydraulics stick it tears the pocket out of the carousel (vert. mill). Other machines have a check valve that sends a signal to the computer and tells it "OK time to raise the head". This is referring to the carousel style changers...that are slowly getting phased out.
03-18-2009, 11:21 AM #3
CAT for sure
The big advantage to CAT in my opinion is the availibility. I have found a lot of good used CAT holders on ebay and the like. BT are much harder to come by
03-18-2009, 12:05 PM #4
I don't think you'll find a late model machine that gets mad at you if you put the CAT holder in any certain way. Yes, the keys are cut a little deeper on one side of the CAT holder, but I've never seen it cause a problem.
CAT40 availability seems to be outpacing BT40 quite a bit too.
03-18-2009, 02:31 PM #5
Cat 40 vs BT4- on new machines
If the keys are correct and the machine is a CAT 40, and you put the tool in the spindle reversed, you will jam the tool holder hard to one side. I have seen this damage the taper and/or damage the bolt holding the key on the side that got jammed.
I believe the BT tooling key slots are equal. I believe this may have been what the rebuilder was talting about. However, if you put a boring bar in a BT reversed, you have a completely different set of problems. (Orient the spindle and pull the boring bar out of the hole.)
03-18-2009, 03:17 PM #6
Although, with the way MTBs work, I guess nothing is really surprising!
03-18-2009, 04:31 PM #7
The changer on my cat40 hurco jams when it puts the tool in the spindle if you put the holder in the magazine the wrong way round. I assumed all cat40 machines were that way. If you look on a cat holder there is a pretty big difference in the depths of the keys so I'm surprised to learn that there are machines that will accept them both ways!
03-18-2009, 05:39 PM #8
CAT40 vs BT40 on new machines
I just looked at the machinerys handbook and the only thing they show is National Standard Spindle Nose. As well as the National Standard Tool Shanks ANSI B5.18-1972 (1998).
I have looked a few other places and I am unable to come up with a CAT40 or CAT 50 spindle and or tool holder specification.
However, I do remember quite well putting a tool holder in a CAT 50 spindle taper backwards (180 wrong) and it jammed the holder real tight. It was tight enough that it egged the freshly ground spindle and I had to open up the containers, remove the grinder, go through the setup procedure again and regrind the taper to bring it back into specification. This was at a Caterpillar plant, I remember very well, I was awarded the awshit award for the day.
If you look at a CAT spindle, you will notice the holes and drilled and tapped at a different distance from the centerline of the spindle.
On some spindles, I think maybe Ingersol, or G&L they use different sizes of keys. All of these variations are to ensure the tool holder is placed in the spindle in the proper position.
Maybe Mari Tool can help us here.
Maybe I'll EMail him for some help.
03-18-2009, 06:27 PM #9
I rememebr when we bought our first new cnc mill. It was a little fadal 4020 and they set it up telling us the spindle orients to the toolchange position which uses one of the keys. Since then we install the cat 40 tools any orientation into the spindle and have for 19 years. I know that the key slots cut into the cat 40 tooling are cut deeper on one side than the other. It appears that on our Fadals the keys are equal. I dont know maybe we have been lucky..LOL That might explaint he belleville washer syndrome though
03-18-2009, 07:43 PM #10
On our 05 Okuma MCV4020 with a cat 40 spindle, you have to put the tool in the right way or it will not seat right. I did this once by accident. Nothing was damaged but the tool didn't pull into the spindle all the way and was wobbiling around. Now I make sure I put the tool in the correct way.
On our 94 Fadal with a cat 40 spindle (reground by walt ) it doesn't matter which way the tool is inserted into the spindle. Probably the reason I put the tool in wrong in the okuma in the first place. Anyway I got my self in the habit of putting the tool in the same way in this machine too so I don't screw up on the okuma again.
03-18-2009, 08:56 PM #11
We run mostly BT-40, thats the spindle on our Matsuura's. And to my knowledge, on brand new Matsuura 40-taper machines, they are still only available in BT-40. Ran CAT-40's on a new Cincinnati Arrow we bought new about ten years ago... Terrible time!! Can't balme the tool-holders really, the machine was just a weak piece of elephant pooh. I'll take my Matsuura and BT-40's anyday thank-you!
03-18-2009, 09:39 PM #12
All CAT tapered tool holders have offset drive notches. This feature is to help orientation in case you are for example using a boring bar where you stop the spindle, offset with a I or J command and then come up. If you did an insert change and put the boring bar 180 deg apart then the I or J offset will be wrong and you can break the tool. Another situation is tolerance. Sometimes when holding tenths rotating the tool 180 deg can throw you off. But this is one of the reasons why I like BT40. Sometimes if a hole is just a hair too tight or too loose before I try anything else I try to rotate the holder 180 deg and make another piece. Many times it doesn't help but sometimes it does.
Most machines do not have offset drives to require you to watch how you put in the holders, but as Walt said some do.
CAT 40 holders have a .985 offset drive slot and .890 offset drive slot from the centerline
CAT 50 holders have a 1.485 and 1.390 offset.
Standard is to drill a 3/8 hole .015 deep ( not including the tip). on the tall offset drive notch to bring the holder back to a decent balance.
03-18-2009, 10:40 PM #13
CAT 40 vs. BT40 on new machines
Wow, thgat fmari guy really knows his stuff.
Thanks for your help. I knew there was a difference but for the life of me, I couldn't find it printed anywhere.
Now then, that kinda takes care of the different depth of key slots on CAT tooling.
Now to compare the difference in length of a CAT 40 and a BT 40....
I don't know why but measuring from the gage line to the end of the taper, their is a difference of about .115 inches. The CAT 40 toolholder will be longer than the BT 40 holder. Usually the CAT 40 holder will have inch threads and the BT 40 holder will be metric. However, the holders can be ordered either way. This could explain why the matsuura did not run too good with CAT 40 toolholders. Anytime you reduce the compression on the belleville springs by .115 inches, the retention force will be lessened way too much to provide for satisfactory operation.
If you are going to just switch from one type toolholder to another, tool retention should be measured.
That's my story and I'm stickin to it.
PS this difference of .115" only shows up in 40 taper tooling....
Not 30, 35, 50 55 or 60......Don't know why... Walt.
03-18-2009, 10:46 PM #14
Yep the CAT40 taper gets to a smaller diameter than the BT40. Thus most of the time pull studs for CAT40 pull studs will have a .115 shorter stem than its sister version in BT40. This is why I see more pull studs breaking on BT40 machines than CAT40 machines. The pull studs are slightly longer. BT 40 pull studs for HAAS machines are the worst. Long and skinny. Shortly I will have some special pull studs that will address this situation.
03-20-2009, 04:55 PM #15
CAT 40 vs BT 40
The difference in length is usually separated by the metric and inch threads however, aint always the truth. You can order Cat tooling with metric as well as BT tooling with inch thread. Standard is inch for CAT and metric for BT but, it aint writ in real hard stone.
03-21-2009, 12:57 AM #16