Turning BT40 into sorta CAT40, referencing the cuts on a manual lathe (?)

Hi,

I have about 20 BT40 holders that I'm turning into CAT40 and will be using them to hold drill bits and other stuff to run relatively slow, figure sub 5000 RPMs. As you know the tapers are the same and if you get the right pull studs a standard BT40 can be used in a CAT40 spindle. The only headache is that they will not go into the automated tool changer.

It turns out that there is enough material on the BT40 that you can turn a channel and make it work. I tuned one and, at least in my machine it works fine.

The question I have is a beginners question: "How do you reference your cuts so that you get them consistent and within tolerance"

The critical dimension is the width of the "V" section of the channel. If it is too narrow it is too tight of a fit, if it is too loose the holder will still be picked up by the tool changer, but it will be a sloppy fit.

BT40


BT40 with a channel so that it will fit a CAT40 changer


Holding it between centers


With this fixture


First Op is the flat section of the channel. This is not critical and we can put the parting blade against the shoulder with the spindle stoppled and index it that way. The depth of the cut is not critical either and is about 0.320" of the original surface of the holder. The compound is at 0 degrees (perpendicular to the cross slide) and feed is done with the cross slide


... continuing on the next post

This is the second Op and I do not know how to best reference the tool. It does not show in the picture, but the compound is at 62.5 degrees (90-27.5) and feed is done with the compound. How do I make this cut consistently and always take the same amount of material so that the taper will be of the correct length/depth?????


This is the last Op and it is a similar question. However, on this one I guess I could get two drill bits and use them as measuring pins on the taper, similar to what is done with gears. See what the distance is on a real CAT40 holder and then feed the cutter straight in till it matches it. If the previous cut was done correctly we should end up with it being symmetric enough. Also because it is a thin wall I can just feed the cutter straight in. And as luck would have it the taper I'm using is 27.5 degrees. So a 55 degree diamond insert works great. But if someone has a better suggestion I would appreciate it. In this Op the compound is at 0 degrees (perpendicular to the cross slide) and feed is done from the cross slide. Thoughts?


Sorry, if this is a silly question. I just do not know how to do it well and do it consistently for about 20 holders. Thanks!

Well, after a lot of head scratching I'm going to use gauge pins to measure the depth/width of the half "V" taper in Op 3. Then the same idea for the full "V" in Op 4. The distance in Op 4 will come from an actual CAT 40 holder and I the distance in Op 3 can probably calculated with some trigonometry.

Phase said:

Well, after a lot of head scratching I'm going to use gauge pins to measure the depth/width of the half "V" taper in Op 3. Then the same idea for the full "V" in Op 4. The distance in Op 4 will come from an actual CAT 40 holder and I the distance in Op 3 can probably calculated with some trigonometry.

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Some folks would just:

- standardize on one holder or the other, horsetrade the odd-ones-out OUT.

- assign CAT and its drawbar / studs to one (group of) machine(s),

- assign BT and family to another (group of) machine(s).

Or mebbe change tool changer grippers now and then.

Doubt you are the first Pilgrim to see a need.

Fair-certain all holders you modify will become unpredictable, bastardized - AKA 'scrap metal' - to any other user not in the room on the day you conjured them up.

Perhaps even your own good self will be among those folk in the fullness of time?

Bill

Phase said:

I have about 20 BT40 holders that I'm turning into CAT40

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Can't be done! BT holders have Metric threads for the retention knob. CAT are English. You can make them fit, but you can't change them.

You must have a lot of time. Most shops would not bother. They'd either sell or trade for other holders.
JR

I have close to 100 BT holders everything from end mill holders, ER collet holders and a bunch of Universal Accur Grip holders. I have at least five face mill holders with cutters.

About five years ago I got a great deal on two Arrow 750 machining centers with tons of tooling, I paid 15 grand for both and all the tools. All my other mills are CAT-40 but the Arrows are BT-40 The mills are on the way out and will be replaced this year. The machines are worth nothing more than what the parts might bring at this point, actually one of them has not run in the last two years and I have used parts from it to keep the other going.

Parts seem to be hard to get and service even harder. The machine have paid me back many times over and as I said they are heading out the door.

The tooling is in great shape. Is there a market for them or should I just scrap them along with the machines and be done with it ? BT tooling is not very common in this neck of the woods but I would hate to just dump them or give them away if I could get something for them.

Make Chips Boys !

Ron

Dupa3872 said:

I have close to 100 BT holders everything from end mill holders, ER collet holders and a bunch of Universal Accur Grip holders. I have at least five face mill holders with cutters.
....

The tooling is in great shape. Is there a market for them

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Uhhh.. new ones cost about the same, either race. Sure is a market 'somewhere'.



Or .. you could make a hundred eBay scroungers happy.

Manual 40-taper machine users (guilty as charged..) don't much care.

We don't have to.



Bill

Hi, thanks for the comments! The holders are not worth much on eBay so I'm not worried if there is no resell value. I did get the right pull studs for the specific thread/machine and I did test that the mod works on my ATC. So really the only problem I was having was how to cut them not too tight or too wobly. Most of them are ER16 so they will be good for drill bits.

Phase said:

Hi, thanks for the comments! The holders are not worth much on eBay so I'm not worried if there is no resell value. I did get the right pull studs for the specific thread/machine and I did test that the mod works on my ATC. So really the only problem I was having was how to cut them not too tight or too wobly. Most of them are ER16 so they will be good for drill bits.

Click to expand...

Even so.... I'd sure rather keep in stock [1], or if need be, modify, last-choice fab from scratch - gripper fingers ONCE.. OK, a second set as spares - than bastardize 40-taper TWENTY times.

And, of course, you could then make use of as many standard BT as you wanted to, not just the 20 red-headed-stepchildren.

Folks as want to run different tire sizes on a motor vehicle than OEM may have to change the wheels. Mayhap stock different sizes on-road/off or winter/summer.

They do NOT ordinarily alter the rubber at the rim of each set of tires. Them's 'consumables'.

So are 40-taper tool holders.

Bill

[1] Not as if BT-40 were never utilized with a changer, after all...

Honestly this is a pretty basic turning exercise, if you have a repeatable quick change tool post and a DRO. Leave the top slide set at the needed angle for all operations, turn it and you lose all your positions!!!! and either use the tool setting option in the dro or simply use some ofset values. If the top-slide does not have the DRO read out, simply set the dial to zero and a simple sharpi reference mark gets you back to the same spot every time allowing for lash. Then use the dial or DRO on the cross slide and do the same, either zero it or make note of the location on the dial and a simple sharpie tick betwen slide and fixed part of saddle to know which turn of the dial its at.

Basicaly you need to be able to repetably park the saddle then the cross slide in a known X,Z spot, (DRO, the dials or some clocks are all std ways of doing this) you then know were you are and the topslide machines your angle in the same place each time.

Just consider it as a cnc 2 axis milling job, work off fixed locations and a given amount of offsets. Once you get your head around it its fast and easy, getting the first holder right is a few minutes work after that, you should be knocking the next 20 out in but a couple of minutes each.

After that you just need to figure out how to pick up a easy datum from the existing part your modifying each time if your holding method ends up diffrent Z distance and your away.

This stuff any competent lathe hand should be able to show you in a few minutes, seams real hard the first time, but after that its a walk in the park, secrets just breaking it down into simple coordinated moves and if need be doing the simple trig to work out what to open the width of the tapered grove by. Trust me if i can do it anyone can, just requires you to take on the coordination the cnc mill control normally does for you. I turn a lot of complex features using multiple X and Z locations on my lathe, lots of diffrent semi circular groves for pipe formers and all sorts of contoured manderals - rollers. So long as you can keep the tool in a known repeatable location your half way there, its why you realy never want to have to adjust the cross slide angle mid part. or you lose your referance.