With every T.M. Smith Tool product you get:
Technology developed, tested and perfected.
Technology selected and optimized for real-world
special machine tapping.
Technology supported by the T.M. Smith service
policy and nationwide network of trained stocking
There is no substitute for quality. That’s why T.M. Smith tool is now the industry’s leading comprehensive single-source supplier for all your quick-change high speed spindle tooling systems.
• FITH-II Floating Tapping & Reaming Holders
• FITH-II RCI Floating Rotary Coolant Fed Holders
• ACTH Adjustable Tension / Compression
• LCTH Tension / Compression with Radial Float
• CCTH Close-Center Tap Holder with Tension
SUIT YOUR APPLICATION!
⇒ Contact our engineering department with your specifications, samples or drawings. We have
over 120 years combined manufacturing and engineering experience to serve you.
⇒ Tap Adapters are available with special error proofing options to suit your specific application
Why use a holder with radial float?
A holder that provides radial float should be selected for tapping or reaming applications where the hole that is to be tapped, or reamed, does not lie exactly on the machine spindle centerline. Typical examples of this may include the following types of equipment or operations.
• Transfer line type equipment
• Dial type machines
• Reaming through bushing plates that are not aligned with the spindle’s centerline
• Tapping machines that only tap a hole that is prepared somewhere else
• Tapping castings that have “As cast holes” and are not qualified by additional drilling on the same machine where tapping takes place.
However the misalignment occurs, it must be compensated for before tapping or reaming to provide optimum results.
In tapping, a holder that provides radial float, allows the tap to find the center of the prepared hole and produce a
higher quality thread and better tap life. No binding to the tap, or angularity of the tapped hole to the spindle centerline
is introduced by the tapping operation if the holder compensates for the misalignment.
In reaming, the same things are true. Holes are sometimes guided by bushing plates that are not in alignment with the spindle’s centerline and would cause binding, or rubbing, of the reamer going through the bushing. The floating holder compensates for this.
On applications where there is no bushing plate used, the holder must allow the reamer to “Find” the center of the hold or “Bell Mouthing”, which is an imperfection to the diameter at the entrance of the reamed hole can occur. The
reamer, without a radial floating holder, has to engage a sufficient amount of the reamer into the hole before it stabilizes in cut. During this time it can produce an oversized hole at the entrance, or “Bell Mouthing”.
Either tapping or reaming works best when the cutting tool is not forced in any direction, but allowed to cut freely on it’s own.
Why use a length compensating tap holder with radial float?
The LCTH tap holder provides both radial float and length compensation for tapping operations. It has the ability to
“Float” parallel, off the machine spindle’s centerline, to the center of the hole to be tapped. It also provides compensation,
tension and compression, for spindle speeds and feed rates not matched to the pitch of the tap you are using.
The two features perform separate and distinct functions.
1. Radial float is desired when the hole you are trying to tap does not fall on the same centerline as the spindle.
This happens when transfer type machinery produces a hole at one station and then another station does the tapping operation. Some misalignment of the holes to be tapped can occur when the pallet fixture moves from the drilling station to the tapping station. The floating holder compensates for the misalignment. Another example is when tapped holes are made in cast parts where the holes are not finished machined in the same fixturing as where
the holes are to be tapped. This is sometimes referred to as tapping “As Cast Holes”. For a high quality thread to be
produced, the tap must find the center of the hole and then tap without any angularity or binding of the tap. Floating holders accommodate the misalignment. Tap life will be improved as well as a higher quality thread being produced.
2. Length compensation in the holder is the ability to shorten, or lengthen, itself during the tapping cycle. This allows the tap to feed at the proper pitch or its own pitch, without any pushing or pulling forces on the tap. Pushing or pulling, (compression or tension), actions will result in the flank angles of the thread to be shaved and distorted.
This is a common source of over-sized tapped holes, or holes where there is crest damage to the thread form.
Some sources of the mismatch of feeds and speeds may include worn components on the machine, or the inability to accurately control the feed and speed of the spindle to the pitch of the tap.
3. Compression is necessary when using a torque control type of tap adapter. This is a tap adapter that has a clutch inside it. When a torque value is reached during tapping the clutch disengages from driving the tap and the tap stops rotating. The torque value is usually set at a pressure just before the tap breaks. The clutch re-engages on
reverse of the spindle and backs the tap out of the hole. If the clutch disengages during the forward tapping operation, the holder must have the ability to compress on itself to compensate for the still advancing spindle. Not having this feature will result in a crash.