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INDICATION MARKS ON PULL STUDS ​IS NOT NORMAL

5/25/2021

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by Bernard Martin
There have been some who claim that drawbar gripper fingers and/or ball marks that appear on retention knob head after several tool changes is normal.
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It is NOT.  
​THAT IS FALSE. 
​

According to Haas CNC, ball or gripper marks on the edge of the pull stud indicate that the drawbar does not open completely.

​If you see these indication marks you should check your drawbar and replace these pull studs immediately.

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Don't Take Your Retention Knobs for Granted

2/16/2021

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​by Bernard Martin
Retention Knobs are the critical connection between your machine tool and the tool holder and they are the only thing holding a steep taper tool holder in the machine’s spindle.

​Techniks has recently introduced their MegaFORCE retention knobs that have some rather unique features when compared to standard pull studs.  Before delving into the features of the MegaFORCE pull studs, let's review some things that you may not know, or think about, on a daily basis. 
1 Retention knob pull stud casues of failure

Retention knobs go through thousands of tool changes which means that they are subjected to the very high pulling forces from the spindle’s drawbar.

This force can be up to 2300 ft. lbs. for 40 taper toolholders and up to 5000 ft. lbs. for 50 taper toolholders.
​According to Haas, you should expect a service life of about 6000-8000 hours for a retention knob.  

​Most all rotary toolholder manufacturers state that you should be replacing your pull studs at least every three years.

However, if you're running multiple shifts, 24-7, making lots of tool changes, making very heavy cuts with long reach or heavy cutting tools, and/or have ball lock style grippers instead of collet type grippers used on the retention knob, you will probably need to replace your studs at least every six months.

Given the spindle speeds that we are running at to remain competitive, retention knobs are not an item that you want to take a chance on breaking.  I can tell you firsthand that 5 pound toolholder with a drill in it flying out of the spindle at 23,000 RPM is not something you want to experience. 

METAL FATIGUE: WHY THEY FAIL

Pull studs encounter catastrophic failure as a result of metal fatigue. The metal fatigue can be caused by a number of reasons including poor choice of base material, engineering design, machining process, poor heat treatment, and, sometimes, they have just met or exceeded their service life. We're going to dig into each of these reasons below but first let's look at some threading fundamentals.
The threads on your retention knob will stretch slightly when load is applied and the loading borne on each thread is different.

When you apply a tensile load on a threaded pull stud, the first thread at the point of connection sees the highest percentage of the load.
Percentage of Load on a Retention Knob Thread
Percentage of Load on each thread of a Retention Knob.
The load on each subsequent thread decreases from there, as show in the table. Any threads beyond the first six are purely cosmetic and provide no mechanical advantage. ​

Additional threads beyond the sixth thread will not further distribute the load and will not make the connection any stronger. 

That is why the length of engagement of the thread on a pull stud is generally limited to approximately one to one & a half nominal diameter. After that, there is no appreciable increase in strength. Once the applied load has exceeded the first thread's capacity, it will fail and subsequently cause the remaining threads to fail in succession.

​RETENTION KNOB DESIGN

Repetitive cycles of loading and unloading subject the retention knob to stress that can cause fatigue and cracking at weak areas of the pull stud.

What are the weak areas of a standard retention knob?  ​
For the same reason we put corner radiuses on end mills, sharp corners are a common area of failure for any mechanical device.

​The same holds true with your pull studs:  The sharp angles on the head of the retention knob and at the minor diameter of the threads are common locations of catastrophic material failure.
Retention Knob Metal Fatigue
These are the two weakest points of any retention knob.
The most common failure point for a retention knob is at the top of the first thread and the underside of the pull stud where the grippers or ball bearings of the drawbar engage and draw the toolholder into the spindle.

Remember, bigger Radii are stronger than sharp corners. ​More on that soon.
Styles of Retention Knob for Rotary Toolholders
Styles of MegaFORCE Retention Knobs

MATERIAL

Not all retention knobs are made from the same material, however, material alone does not make for a superior retention knob. Careful attention to design and manufacturing methods must be followed to avoid introducing potential areas of failure.

Techniks MegaFORCE retention knobs are made from 8620H. AISI 8620 is a hardenable chromium, molybdenum, nickel low alloy steel often used for carburizing to develop a case-hardened part. This case-hardening will result in good wear characteristics.  8620 has high hardenability, no tempering brittleness, good weldability, little tendency to form a cold crack, good maintainability, and cold strain plasticity.

There are some companies making retention knobs from 9310. The main difference is the lower carbon content in the 9310. 9310 has a tad more Chromium, while 8620 has a tad more nickel.  Ultimate Tensile Strength (UTS) is the force at which a material will break. The UTS of 8620H is 650 Mpa (megapascals: a measure of force). The UTS of 9310H is 820 Mpa. So, 9310H does have a UTS that is 26% greater than 8620H.

​That said, Techniks chose 8620 as their material of choice because of the higher nickel content.  Nickel tends to work harden more readily and age harden over time which brings the core hardness higher as the pull stud gets older. The work hardening property of 8620 makes it ideally suited for cold forming of threads on the MegaFORCE retention knobs.

​It should be noted that some companies are using H13. H13 shares 93% of their average alloy composition in common with 9310. 

ROLLED THREADS VS. CUT THREADS

5. Cut thread vs rolled thread retention knob
A cut thread, image 1, has a higher coefficient of friction due the the cutting process, while a roll formed thread, image 2, has a lower coefficient of friction which means that it engages deeper into the toolholder bore when subjected to the same torque. You will notice that Cutting threads tears at the material and creates small fractures that become points of weakness that can lead to failure. Rolled threads have burnished roots and crests that are smooth and absent of the fractures common in cut threads.
Rolled threads produce a radiused root and crest of the thread and exhibit between a 40% and 300% increase in tensile strength over a cut thread. The Techniks MegaFORCE retention knobs feature rolled threads that improve the strength of the knob by 40%.  
6. LMT Fette - Thread rolling with F2 Rolling head on CNC lathe
Shown here is a Fette head cold forming a thread. Note how the three roller forms center and maintain near perfect concentricity of the pull stud shaft.
In cold forming, the thread rolls are pressed into the component, stressing the material beyond its yield point. This causes the component material to be deformed plastically, and thus, permanently.

There are three rollers in the typical thread rolling head that maintain better concentricity by default than single point cutting of the threads.

Also, unlike thread cutting, the grain structure of the material is displaced not removed.
Rolled threads produce grain flows that follow the contour of the threads making for a stronger thread at the pitch diameter which is the highest point of wear. 

The cold forming process also cold works the material which takes advantage of the nickel work hardening properties of 8620.
7. Fette Turning Concepts Thread Rolling Magnaflux
Photo courtesy Mike Roden at Fette Tool. www.turningconcepts.com
By comparison, cut threads interrupt the grain flow creating weak points.

MEGAFORCE GEOMETRIC DESIGN

MegaForce Retention Knob features vs standard pull stud
Overall Length
There are some claims that a longer projection engages threads deeper in the tool holder preventing taper swelling. While a deeper thread engagement can help prevent taper swelling, applying proper torque to the retention knob is an effective way to reduce taper swelling.

An over-tightened retention knob may still cause taper swelling regardless of how deep it engages the threads of the tool holder. Additionally, the longer undercut section above the threads presents a weak point in the retention knob.
Blended Radii
With the new Techniks MegaFORCE pull studs, stress risers of sharp angles have been eliminated through the blended radii on the neck where the gripper engages under the head of the pull stud.
9. Techniks MegaFORCE Pull Studs
Ground Pilot
There is a ground pilot, underneath the flange, which provides greater stability. The pilot means the center line of the tool holder and pull stud are perfectly aligned.

Magnetic Particle Tested
Each Techniks MegaFORCE retention knob is magnetic particle tested to ensure material integrity and physical soundness. MegaFORCE retention knobs are tested at 2.5X the pulling forces of the drawbar.
MegaFORCE Technical Specs
  • Material: SAE8620
  • All knobs are case carbrized, hardened, and tempered to:
    • Case depth: 0.025” – 0.030”
    • Surface hardness: HRc 56-60
    • Core hardness: HRc 44 minimum
Torque Specs
The following are the guidelines for torquing your pull studs according to Techniks.
  • BT 30 36 ft. lbs.
  • ISO 30 - 36 ft. lbs.
  • 40 taper - 76 ft. lbs.
  • 50 Taper - 100 ft. lbs.

RETENTION KNOB BEST PRACTICES

In order to maximize the life of your retention knob and prevent catastrophic failure here are some technical tips to keep your shop productive and safe.
  • Regularly inspect retention knobs for signs of wear. Wear may appear as dimples or grooves under the head or visible corrosion anywhere on the retention knob. 
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  • If the retention knob demonstrates any signs of wear replace it immediately
  • Make sure to properly torque the retention knob to the manufacturer’s specifications. Use a torque wrench and retention knob adapter to ensure proper torque. 
  • Overtightening can overly stress the retention knob leading to premature failure and can cause the tool holder taper to swell leading to a poor fit between the machine spindle and the tool holder.
  • Apply a light coat of grease to the retention knob MONTHLY to lubricate the drawbar. If you use through-spindle coolant (TSC), apply grease to the retention knobs WEEKLY.

Special thanks for Greg Webb at Techniks and Mike Roden from Fette Tools/ Turning Concepts, for providing technical insights. 
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Some Drilling Tips to Keep-in-Mind

6/13/2018

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We've assembled a few tips on drilling that you may want to pass along to your team.

Drilling Tip 1

OSG EXOCARB ADO-SUS
During drilling operations, chip formation is very important to keep an eye on. If you are getting long unbroken chip with jagged edges, your feed rate is too high. If you are getting tight spirals but the chips are not breaking apart, your feed rate is too low.

The Ideal chip shape is small tight curls, Like little "6's and 9's". When you are getting these shapes of chips then you will get best tools life and finish on your part.

Drilling Tip 2

Drilling Tips tricks
If your drill is getting chipped only on one edge or if your drill has more wear on one cutting edge than the other, the cause could be bad run out of the drill or bad alignment of the machine.

This means one side of the drill is experiencing more axial forces than the other. If you correct the run out of the drill and alignment of machine spindle, the problem will be solved.

Drilling Tip 3

OSG Tap Die Drill runout
If your drill has too much run out, you will have issues such as hole expansion, bad hole perpendicularity, and poor surface finish.
Drill run out should be less than 0.0008"(0.02mm) when setting up. The run out increases with the speed, thus, when drilling a deep hole.

OSG recommends making the pilot hole 0~0.003"(0.08mm) oversize and inserting a long drill at 0~500rpm so that the drill is fitting properly in the pilot hole .

Drilling Tip 4

OSG V-Series HELIOS dri
The V-Series HELIOS® drill is the 1st drill to process deep holes 10X-20X diameter, without pecking and without the use of internal coolant supply.

Flute form, point thinning and compound lead construction are all patented technologies developed by OSG to make this drill do what no other parabolic HSS-Co drill can.

The addition of our exclusive WXL coating technology makes non-peck drilling repeatable, even in the longest of production runs.

Drilling Tip 5

Last but not least, don't forget that now through August 31st, save 12% on select A-Drills!l
OSG Drill Promotion 2018
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Alternatives to Steep Tapers

12/13/2017

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Below are excerpts from a Cutting Tool Engineering article by the same title. To read the entire article please click HERE.
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Author Kip Hanson, Contributing Editor, Cutting Tool Engineering
(520) 548-7328
khanson@jwr.com
Kip Hanson is a contributing editor for Cutting Tool Engineering magazine. Originally Published: September 12, 2017 - 3:00pm


Shopping for a machining center was simpler when buyers had only two basic spindle choices: CAT or BT. Both of these “steep tapers” have an angle of 3.5 in./ft., or 7" in 24" (7/24), and are based on the 1927 patent by Kearney & Trecker Corp., Brown & Sharpe Manufacturing Co. and Cincinnati Milling Machine Co. 
​
With the development of automatic toolchangers in the late 1960s, machine tool builders in Japan modified the patented design and invented the BT standard. In the 1970s, tractor manufacturer Caterpillar Inc., Peoria, Ill., changed things again with a flange design now known as CAT, or V-flange.

“Sticking” Together

During the late ’80s, machine tool builders began offering vertical and horizontal CNC mills with spindle speeds higher than the 6,000 to 8,000 rpm common at the time. As rpm increased, so did problems with steep-taper toolholders.

​Chief among them is the tendency for the mating spindle and toolholder tapers to stick together. This is caused by the expansion of the spindle housing at high speeds, which allows the toolholder to be pulled upward into the spindle taper, jamming it in place.
HSK spindles, like the one shown in the illustration below, offer advantages steep-taper styles can't.  

​One way to eliminate this problem is by extending the toolholder flange upward, thus creating a hard stop against the spindle face and preventing further Z-axis movement. ​
HSK Ibag Spindle Cutaway
HSK spindles, like the one shown in the illustration above, offer advantages steep-taper styles can't. Image courtesy of IBAG North America.
This is the approach taken by BIG KAISER Precision Tooling Inc., Hoffman Estates, Ill. Jack Burley, vice president of sales and engineering, said the BIG-PLUS system—developed in 1992 by BIG Daishowa Seiki Co. Ltd., Osaka, Japan—relies on a bit of elastic deformation in the spindle to provide dual points of toolholder contact at its face and taper, eliminating upward holder movement as the spindle expands.

He said it’s also more rigid, with tests showing that the deflection on a CV40 BIG-PLUS toolholder measured at 70mm (2.755") from the spindle face is only 60µm (0.002") when subjected to 500kg (1,102 lbs.) of radial force, roughly half that of a traditional V-flange toolholder.
For people who think they can’t take advantage of this technology because they don’t plan to buy a new machine, they might want to check with their distributor, as their machine may already be equipped for BIG-PLUS.
Big Plus vs Standard Steep Taper contact
​“There are now roughly 150 machine builders that either offer BIG-PLUS or have it as a standard,” Burley said. “The beauty of the system is that it can use either standard toolholders or BIG-PLUS interchangeably. So for drilling and reaming work, you can use a conventional collet chuck, but for heavy milling cuts or profiling operations at higher spindle speeds, BIG-PLUS improves accuracy and tool life.”

Revving Up

Burley does not recommend BIG-PLUS for older machines that have never seen these toolholders, because CAT and BT taper-only contact holders tend to bellmouth the spindle over time, leading to undesirable results.

BIG-PLUS, like any dual-contact toolholder, requires particular attention to cleanliness, as chips caught between the spindle face and the toolholder can cause serious problems.

​He also recommends staying below 30,000 rpm when using 40-taper holders, noting that higher speeds are better handled by HSK spindles and holders.

Keep It Clean

clamping mechanism for HSK toolholders
The clamping mechanism for HSK toolholders is distinctly different from that of steep-taper holders. Image courtesy of BIG KAISER Precision Tooling.
Bill Popoli, president of IBAG North America, North Haven, Conn., said the company started building steep-taper spindles in the late ’80s, but 95 percent of its work has since transitioned to HSK spindles. As mentioned earlier, the extreme accuracy needed to guarantee near-simultaneous contact between the spindle face and taper is challenging, requiring micron-level tolerances in toolholder and spindle alike.
​
These requirements were impossible to meet when steep taper was first developed, Popoli said, resulting in looser standards overall for CAT and BT spindles than the ones applied to HSK spindles and toolholders. Because of this, purchasing an HSK or equivalent toolholder automatically makes one “part of the club” when it comes to balance, accuracy, repeatability and tool life.
That’s not to say, however, that shops firmly married to steep tapers should settle for less. Popoli recommends purchasing the highest-quality tooling possible and paying close attention to the stated tolerance.

Always stay below 20,000 rpm with 40-taper holders, and reach no more than 30,000 rpm with 30-taper ones. Use balanced holders and high-quality retention knobs that have been properly torqued—otherwise distortion at the small end of the taper may occur. And whatever the taper type, keep the spindle and toolholder clean at all times.

Bob Freitag agreed. The manager of application engineering at Minneapolis-based metalworking products and services provider Productivity Inc. said the lines are evenly split between traditional 40- and 50-taper CAT or BT tooling (much of which is BIG-PLUS) and HSK. 

“It really depends on the application,” Freitag said. “Most of our die and mold machines in the 20,000- to 30,000-rpm range will have an HSK63A or HSK63F. When you get up around 45,000 rpm, you’re probably looking at an HSK32. But in horizontal machining centers and lower-rpm, high-torque verticals, you’ll see mostly steep tapers, as this is generally preferred for deep depths of cut and lower feed rates, where you’re removing a lot of material at once.”

For shops that want to make the leap to an HSK machine but are leery of investing in new toolholders, Freitag advised:

​“Anytime you buy a new machine, you should buy new toolholders to go with it. If not, the imperfections of the old toolholders will soon transfer themselves to the spindle on the new machine.”
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Next Generation Tooling Now Offers Technical Training!

6/14/2017

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We are very excited to announce that we are now able to offer on-site technical training to YOUR machinists at YOUR location!  This is offered at no charge  to customers who use any of the manufacturer's whom we represent in California and Nevada.  

However, just because you don't purchase things from us, don't feel left out! We also offer on-site topic specter training on any of the following topics for $150/hour.  

Each presentation lasts about 2 hours.  The presentations last approximately 45-60 minutes with the remaining time for Q&A and discussion about unique applications in your facility.
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Training Classes Available:
Machining 101
  • Basic Boring
  • Basic Chamfering
  • Basic Drill Training
  • Basic End Mill
  • Basic Indexable
  • Basic Tap Training
  • Basic Tool Holders
  • Basic Work Holding / Fixturing​

Advanced Part Manufacturing:
  • Programming Tool Path – Climb versus Conventional
  • Material Machinability – Cubic Inches of Stock Removal
  • Part Set Up / Work Holding / Fixture 
  • Tool Holder Selection, Collet, Solid, Hydraulic, Shrink Fit
  • Cutting Tool Selection – Substrate, Geometry, Coating, Speed and Feeds 
  • Estimating Part Cycle Time
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Rotary Toolholders: Understanding the problems to watch

12/12/2012

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CNC machines feature high-capacity tool changers that automatically swap toolholders in and out of the spindle as needed, by means of a high speed swing arm or a rotary carousel. Periodically, toolholders should be examined for wear and if necessary replaced to maintain cutting performance.
You lose 10% of cutting tool life for every “tenth” (0.0001”) of ru
You lose 10% of cutting tool life for every “tenth” (0.0001”) of ru
New operators should be taught how to properly evaluate toolholders so they can recognize when toolholders need to be replaced to prevent premature cutting tool failure, or even expensive damage to the spindle.

​Many operators do not know why it is necessary to replace their tooling, or have the experience to tell when it is time to do so.

Determining if toolholder components need to be replaced is not a difficult task, but does require that the operator knows what to look for. Here's a few things you should be aware of when checking your rotary toolholders.

Checking For Spindle Mouth Wear

Inspect Fretting Steep Taper Toolholder where to look
A worn spindle can cause runout issues that affect toolholder accuracy and reduce cutting quality and productivity. This is a condition known as bell mouthing. If toolholder issues can be eliminated by bench checking T.I.R., then the source of the problem is often a worn out spindle mouth. A trained professional will be required to check and repair bell mouthing.

T.I.R. (total indicator runout) is the measurement of axial deflection of the cutting tool in the toolholder assembly. Techniks toolholders are manufactured to minimize runout and extend cutting tool life. You lose 10% of cutting tool life for every “tenth” (0.0001”) of runout. That's what the chart above depicts.

Automatic Tool Changer Alignment Issues

Measuring Runout TIR Rotary Toolholder wear
It’s crucial to maintain proper ATC swingarm alignment. If the ATC does not insert the toolholder perfectly, damage to the spindle and toolholder may result. Also poor cutting tool performance and reduced tool life will be evident. A trained professional will be required to check and repair ATC issues.

Evaluating Toolholders for Wear

A worn out toolholder will not provide good accuracy and will quickly wear out your cutting tools. Worn tooling can also cause poor surface finish, and may even damage your spindle. Keep and eye out for these issues and your tool life, surface finish and cycle time will all improve to help you make more money on every job in your machine shop.

Special thanks to TechniksUSA for providing this detailed information!
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Tap Troubleshooting

12/15/2010

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Troubleshooting problems with new taps.
Taps are very free cutting and will easily cut oversize threads if overfed or pushed. For the best results use a Tap Holder with built-in tension, compression.

Always utilize your holder's tension feature by programming spindle feed to 95-98% of the calculated feed rate.

Most drill size charts are based on using standard job drills which can drill over size by approximately .003". The charts are based on .003" over size condition to achieve the proper percentages of thread.
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With today’s high precision drills, they are now capable of drilling to near net size. When using a high precision drill or a “G” drill you should refer to the drill size formula’s in the “Tapping Formulas” section of the catalog.
  • Tapped holes deeper than 1.5 diameters often call for a larger tap drill. 
  • Blind holes often require larger tap drills to reduce loads on the tap caused by chip build up in the hole.
  • Materials that tend to gall when tapped or when fasteners are installed should have larger drilled holes.
    Under tapping pressure, soft materials tend to extrude and enter the root area, necessitating a larger drilled hole.
  • Materials that don’t readily dissipate heat, should have larger holes to reduce the tooth contact area and minimize heat build up.
  • When making threads with high helix angles using a larger tap drill will help reduce tap breakage. 
Problem: Tapping oversized threads (no-go gage too loose)
Possible Cause Possible Remedy
Improper tap for material and thread application. · Use a suitable tap for the hole style and material being tapped. 
Cutting speed to high. · Reduce cutting speed.
· Improve coolant/lubrication.
Cold welding on the flanks of the tap (loading). · Use a new tool.
· Use surface treated taps.
· Improve coolant/lubrication.
· Grind away chipped and damaged teeth.
Chip packing in flutes. · Use tap with different flute geometry/angle.
· Possibly use set of taps.
Grinding burr. · Remove burr with soft wire or fiber brush.
Incorrect fixturing or positioning of part. · Use tap holders with axial and parallel floating.
· Check clamping of part for correct alignment.
Inconsistent feed of tap. · Tap with controlled feed.
· Check CNC programs.
· Check lead screw for backlash.
· Use compensating tension/compression tap holder.
Problem: Tapping oversized threads (no-go gage loose)
Possible Cause Possible Remedy
Tap selected too large for class of thread fit required. · Review markings on tap and determine if it is suitable for the class of fit required.
· If in doubt, contact us!
Improper reconditioning of tap. · Reconditioning of tap requires that all ground surfaces maintain the original geometry put on by the manufacturer.
Problem: Tapping bellmouthed hole (first few threads gage oversize)
Possible Cause Possible Remedy
Wrong initial starting pressure. · Work with controlled tap feed.
Axially hard working spindle. · Use a tap holder with length compensation.
Incorrect fixturing or positioning of part. · Use a tap holder with axial and parallel floating.
· Check clamping of part for correct alignment.
Problem: Torn and rough threads
Possible Cause Possible Remedy
Improper selection of tap for material and thread application. · Use a suitable tap for the hole style and material being tapped. 
Cutting speed too fast or slow. · Select proper cutting speed.
· Improve coolant selection to assist the effects of tap speed.
Cold welding on the flanks of the tap (loading). · Use a new tool.
· Use surface treated taps.
· Improve coolant/ lubrication.
· Find away chipped and damaged teeth.
Chips packing in flutes. · Use tap with different flute geometry/angle.
· Use set of taps.
Grinding burr. · Remove burr with soft wire or brush.
Tap drill too small. · Use correct size drill.
· If in doubt, contact us!
Insufficient coolant/ lubrication. · Selection of suitable coolant/lubrication for material being tapped.
· Use adequate amounts of coolant lubrication.
Tool overloading due to coarse pitch, hard materials or short chamfers. · Use a set of taps.
Problem: Tapping undersized threads (go gage won't enter/binds up part way into hole)
Possible Cause Possible Remedy
Tap selected too small to do multiple regrinds. · Limit the number of regrinds a tap has.
· Use a new tap.
Area of wear not removed when tap was resharpened. · Grind tap again.
· Use a new tap.
Improper tap for material and thread application. · Use suitable tap for the hole style and material being tapped.
Go gage binds up part way into hole. · Tap is dull - recondition or replace tap.
· Avoid too much axial force during tapping operation (this caused the tap to cut out of lead)
· Use tap holders with length compensation.
Tap selected too small for class of thread fit required. · Review markings on tap and determine if it is suitable for class of fit required.
Problem: Tap life too low
Possible Cause Possible Remedy
All reasons stated in torn and rough threads. · See torn and rough threads.
Loss of tap hardness by excess hear during regrinding. · Change the specification of the grinding wheel.
· Use coolant while grinding.
Loss of surface treatment from regrinding. · Retreatment of the tap surface.
· Check suitability of surface treatment for material being tapped.
Work hardened drill hole and hole chamfer. · Change or regrind tap drill more frequently.
· Check proper drilling speed and feed.
· Anneal part before tapping.
Problem: Torn and rough threads
Possible Cause Possible Remedy
Improper selection of tap for material and threading application. · Use a suitable tap for the hole style and material being tapped.
Tap drill too small. · Use correct size drill. Note that cutting and roll form taps use different size tap drills for same size thread.
Tap hole not deep enough. · Check actual drill depth, drill may have slipped back into holder.
Missing tap drill hole. · Ensure tap drill hole is present. Common problem in multiple spindle applications on transfer lines.
Chips packing in flutes. · Use tap with different flute geometry/angle.
· Use a set of taps.
Cutting speed too high or low. · Select proper cutting speed.
· Improve coolant/lubrication to assist the effects of the tap speed.
Cold welding on the flanks of the tap (loading). · Use a new tool.
· Use surface treated taps.
· Improve coolant/lubrication.
· Grind away chipped and damaged teeth.
Overload of the chamfer teeth. · Use longer chamfer.
· Increase number of tap flutes to provide more chamfered teeth.
Incorrect fixturing or positioning of part. · Use tap holders with axial/parallel floating.
· Check clamping of part for correct alignment.
Tap hitting the bottom of hole. · Use tap holder with length compensation and torque overload system.
Tapping hard or high tensile materials. · Check selection of tap, carbide tap may be more suitable then high speed steel taps.
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    Technical Support Blog

    At Next Generation Tool we often run into many of the same technical questions from different customers. This section should answer many of your most common questions.

    We set up this special blog for the most commonly asked questions and machinist data tables for your easy reference.

    If you've got a question that's not answered here, then just send us a quick note via email or reach one of us on our CONTACTS page here on the website
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    Authorship

    Our technical section is written by several different people. Sometimes, it's from our team here at Next Generation Tooling & at other times it's by one of the innovative manufacturer's we represent in California and Nevada.

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Established 1995
​

Next Generation Tooling
10240 Cavalletti Drive
Sacramento CA 95829
916.765.4227
Northern California
23 Maxwell Street
Suite B
Lodi, CA 95240
Southern California
22343 La Palma Avenue
​Suite 126
Yorba Linda, CA 92887
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