Two Taps one hole

[gwb]

Had to bottom tap a few holes by hand as I programmed X5 tapping to shallow.

Wonder if I could do the following on a Haas VF3

Use MCx to tap a hole with a plug, and then run a bottom tap in the same hole.

Two different tool holders say T1 and T2 and two different taps.

Would the Bottom tap pick up the same threads or would it destroy the first set of threads and the render the threads useless?

Any Ideas?

thanks

[Mark and Poco]

In general machining I have done that on a CNC. You have to make sure you use a tapping head, and that the spring tension is very loose.

[DareBee]

Good chance for disaster.
Thread mill.

[littlerob]

From Mastercam point of view NO, from the machine I'd say not likely.

+1 on the threadmill

Robert

[gwb]

thanks for the info
Glad we kept the tapping head

[littlerob]

Originally Posted by gwb thanks for the info Glad we kept the tapping head

I meant to add -1 on this idea, a tapping head, like a floating tap holder? Make sure you try it on a set up piece first. I would be VERY, VERY curious to see if this works, I really doubt it. But if you go ahead with it, be sure to post the results regardless of the outcome.

Robert

[TXFred]

I've been wondering about this myself, and there's a method that I am pondering.

A Haas will repeat the tapping cycle on any thread, such that you can retap a hole using the existing tap, so long as you haven't removed the tap or the workpiece. I assume that it always starts the tapping cycle with the spindle indexer at 0.

It seems to me that you could create a fixture to clock the second tap to match the first.

First, you need a height gauge for measuring tools, like this one. This tool holder seats against the taper and the drive dogs, just like a mill's spindle.



Next, you need something to index the threads on the taps. I'm picturing a steel cylinder, perhaps 1" thick by 1" diameter, surface ground on both ends, with a threaded hole down the center the same size as the tap.

Put the first tapping tool, the one that made the threaded hole in your workpiece, into the fixture and install the indexer so that the end of the tap is flush with the top face of the indexer. Mark the face of the indexer with a line so you know how it was oriented. The more precise you can be, the better.

Now load the second tapping tool. Use the height gauge to measure the height of the end of the tap. Call this Measurement 1.

Install the indexer flush with the end of the tap. Turn the indexer counterclockwise (unscrewing it from the tap) until the mark is at the same orientation as it was for the first tap. Measure the height of the indexer. This is Measurement 2.

On your mill, set up the tool offsets. For the second tap, after you have entered the offset, subtract Measurement 1 from Measurement 2. You should get a positive number. Add that number to the tool offset.

Edit your tapping cycle for the second tap to increase the depth by the same number.

What should happen, I think, is that the second tap will start tapping higher in the air, and this height difference will ensure that its threads are aligned with the existing threads. Because you have also altered the tapping depth, it should finish at the right depth.

EDIT: One other thing. When you install the tools into the mill, you will need to ensure that you preserve their orientation based on how they were in the test stand. You don't want to install them 180 degrees apart from each other.

I have not tried it, but I'm tempted to get a piece of butterboard and give it a go. If somebody else does it first, please let me know how it goes.

Frederic

[psychomill]

Chase it by hand.... or can you use a spiral fluted tap to get to the bottom? (chip puller)..... or can you roll tap? can you threadmill? (Point is to get rid of the 2nd tap)

You have several problems with retapping using different tools... X5 isn't going to care if you program 10 taps in the same hole. The machine side is the problem...

Clocking your taps and setting the "right height" will be really difficult even with the elaborate description of the above post. Using a loose spring head (as mentioned before) might give you a slightly better chance if you go through the excersize of the set up like above. But depending on the material and tap size, it may not make a damn bit of difference... it'd just blow it all....

TxFred.... let me know how that works out.... sounds like fun up my alley to check out!

[nikolaiownz]

Highly doubt that this will work on most machines.. You will have to use a tap holder with very low resistance if you want this to work.. and its not guaranteed to work on every hole.