Floating tap holder

KeithB

Resident Half Fast Machinist
There have been several recent threads about tapping devices for a lathe and a references to collets and collet chucks/extensions. I needed a better way to hold taps in my CNC lathe. I have a tooling setup for my lathe that can hold 1" diameter round tool holders accurately. I tried using a rigid collet holder to hold a tap but kept getting ragged threads. I decided to buy a floating tap holder from Shars.com. It allows me to use regular ER32 collets to hold taps. It holds taps firmly against torque but allows the tap head to float forward about 1/4" or backward about 3/16".

You see, on a CNC lathe the rotation of the spindle and the motion of the carriage are controlled independently by sensors and motors and computer circuitry, they are not geared together in some fixed ratio by a gear train such as that on most manual lathes. If the process of slowing, stopping, and reversing the spindle rotation at the same rate that the carriage is slowed, stopped, and reversed in the Z axis isn't perfectly coordinated then at best you will get torn and ragged threads and at worst you will spend all day replacing taps and expanding your vocabulary. A floating tap holder provides enough axial freedom (under a spring load, it's not sloppy) to make up for a little mis-coordination.

They make special collets that have a square profile on the back end of the interior hole and have a diameter appropriate for the tap size. It provides a positive drive and is necessary for larger taps and harder materials. For small taps (IMHE up to about 1/4-20 in steel or 1/2-13 in aluminum) I have found that friction is enough.

I use ER16 and ER 32 collets, the former covers diameters up to .375", the latter up to .75" There are also ER11, ER20, ER25, and ER40 sizes. One of the next toolholders I plan to buy is an R8 shank that uses ER32 collets, so I can use my collet set on my manual vertical mill. I needed to use a 7mm ball nose mill on a job last week and didn't have an R8 collet in that size.

Not at all useful on a manual lathe but I thought I'd show you my new tool.

Floating tap holder w/1" round shank.
floattapholder1.jpg

Nicely marked on the nut.
floattapholder2.jpg

You can see the keyway type slot that provides the "float"
floattapholder3.jpg

An ER32 collet with a 1/2" bore. This was laying on my desk because the bore was damaged when we broke off a carbide endmill. You can see the damage on the left side of the mouth of the bore. I'll get after with a Cratex wheel and put it back in inventory as a spare.
floattapholder4.jpg
 
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KeithB

Resident Half Fast Machinist
Got a job starting Monday that requires tapping a 1/4-20 thread about an inch deep in aluminum. I ordered a his tool knowing that was coming up. We’ll see how it works.

A CNC machine that is advertised as having “rigid tapping” usually doesn’t need this type of tool; my lathe is supposed to have that but since I’ve had trouble tapping in past I hought I’d try this.

I think it has to do with the quality of the control system and sensors and such.
 

Brad

Benevolent Overlord and site owner
Staff member
Getting all those motions in sync every time would take some very precise controllers and sensors. Doesn't take much error to mangle a thread.
Never thought about that very much Keith. Interesting solution.
 

KeithB

Resident Half Fast Machinist
I don't need this type of tool on my CNC mill, the mass of the rotating and reciprocating parts is much less than on my lathe. Imagine reversing an 8" or 10" chuck holding a part while reversing the motion of all of the mass of the carriage. At 600 RPM, 10 revs a second!

My CNC machines have a resistor that looks like a massive hot plate element in a cage on top of the power/control box. All the energy from dynamic braking is converted to heat and radiated away there. And it does get HOT after numerous spindle reversals.
 

Pistolero

Well-Known Member
I see it is from Shars, too. Everything I have gotten from them has been good
quality, and they have great prices most of the time, too.

Bill
 

KeithB

Resident Half Fast Machinist
They've replaced MSCDirect at the top of my look-here-first list for machine tools. Ebay is now second. When MSC merged/took over Enco their prices went up, service is still good.
 

Pistolero

Well-Known Member
I was sad to see Enco go, and the prices go up, too. I had purchased from Enco for
years. My tool and die maker friend pointed me to Shars.
Prices for cutting tool inserts on eBay are truly unbelievably low.

Bill
 

smokeywolf

Well-Known Member
Keith, wouldn't a tapping head negate the need to reverse your spindle? I certainly may be wrong about this, but if memory serves, Tapmatic made a tapping head specifically for lathes.
 

KeithB

Resident Half Fast Machinist
Not familiar with the Tapmatic product you are talking about. It may have been designed for manual lathes. On my CNC lathe and mill the only way to get the tap out of the hole is to reverse the spindle rotation and the axes motion driving the tap. For manual mills Tapmatic heads are great for power tapping. We have been doing a lot of lathe work that we have to finish up on the CNC mill simply to tap a center hole. I'm hoping the new floating tap driver will eliminate that problem of more handling, machine time, and mill congestion.
 

Pistolero

Well-Known Member
I have seen the Tapmatics for a drill press/mill, really impressive, never saw one for a lathe.

Bill
 

smokeywolf

Well-Known Member
Keith, I think you're right that that particular tapping head was made for manuals. I still have it somewhere. The one or two times I used it, I think I mounted it in a 5C collet on a KDK toolpost. I do remember that once was on a 15" Cincinnati Hydrashift.

The floating tap holder looks like a swell addition to your inventory of tooling.
 

Brad

Benevolent Overlord and site owner
Staff member
I don't think can is the right word. You WILL spend more on tooling than you did for the machine.
It is awful easy to look at things and think of all the tooling you would like. Then reality and finances come into view and you find ways to make due with less.
As a hobbyist I can trade time for money. Keith can't due that as his time IS money.
 

smokeywolf

Well-Known Member
I have easily half again and probably closer to double the money in tooling, than I do in machinery.

Would love to be able to justify an Accurite Millpwr NC retrofit for the Bridgeport.
 

KeithB

Resident Half Fast Machinist
Finally got a job that requires a 1/4-20 tapped hole in the center so we finally got to try out our new floating tap holder. Note the
in-and-out action of the tap holder. With a rigid holder the tap would have broken or the threads would have stripped out. This is the second piece, the apprentice will tune the program to limit the extra travel and do some other time saving measures. Even so, it takes less than a minute to face, chamfer and tap. And no tool changes!

 

Brad

Benevolent Overlord and site owner
Staff member
Time is money.
In production would the chips on the tap need to be removed between parts or will they be pushed aside when the next part is tapped?