Having a Problem with Slivers from a Rollform Tap Operation?

Having a Problem with Slivers from a Rollform Tap Operation?

One of the biggest reasons companies choose rollform tapping is to eliminate chips during the tapping operation.  Some of the applications for rollform tapping include use in In-die tapping applications of stamped parts to keep chips out of the die or tapping of blind holes in machined parts which eliminates chips packing at the bottom of the hole.

Occasionally we will hear from customers about the formation of slivers during the rollform tapping operation.  Although these slivers are not the volume of chips resulting from a cutting tap application, these slivers can cause a problem when you are expecting a chipless tapping operation.  Generally, the cause of these slivers is the result of a hole size that is too tight.  Keep in mind that a rollform tapped hole size should be larger than a cutting tap and in addition trying to achieve greater than a 75% thread with a rollform tap can cause this sliver issue.  Please feel free to send us an e-mail to sales@hutchisontool.com if you would like us to send you a rollform hole size chart for metric and imperial size threads.

What is the Minimum Press Stroke Required for In-die Tapping

What is the Minimum Press Stroke Required for In-die Tapping?

What is the minimum press stroke required for In-die tapping?  The short answer is--it depends.  Because it depends is not a very helpful answer here are some general parameters to use when quoting or investigating new tapping projects.

The minimum press stroke required for In-die tapping is 3”.  Each tapping head generates a minimum amount of tap travel through the use of a gear ratio.  This gear ratio combined with the press stroke generates the total amount of tap travel from the open to closed position of the press stroke.  The 3” press stroke allows enough time to tap the part and allow time for feeding of the strip as well.

As the part thickness increases the more press stroke is required in order to get enough tap travel to completely tap the part.  The following are ballpark estimates of press stroke required with different part thicknesses.

Part Thickness    Minimum Press Stroke

.125” or less                            3”

.187”                              4”

.250”                              5”

.375”                              6”

.500”                              8”

What is the Proper Hole Condition for In-die Tapping?

What is the Proper Hole Condition for In-die Tapping?

We are often asked what the condition of the punched hole should be when utilizing In-die tapping.  In-die tapping does not require any special consideration in regard to punched hole condition.  However, the quality of the hole will have an affect on the quality of the thread whether you are In-die tapping or secondary tapping.

For example, when punching thicker material, it is common to see a bell mouthed condition due to material break out.  If this bell mouthed condition is not corrected it is likely that you will not receive a full thread through the entire thickness of the material.  This non full thread condition will exist in both In-die tapping and secondary tapping operations.  It is common practice to shave the punched holes in order to get a full wall thickness which in turn will lead to a complete full thread over the complete material thickness

Can Job Shops Qualify for an R & D Tax Credit

Can Job Shops Qualify for an R & D Tax Credit?

There is a misconception that the R & D Tax Credit is only for companies that are making a product line.  We all easily understand if Intel is developing a new microprocessor or Ford is developing a new hybrid engine that they are most likely using an R & D tax credit to reduce their costs.  Does this also apply for the tool & die shop that has to come up with a die design to manufacture a stamped part or CNC machine shop that has to develop a manufacturing process to mill a part to customer specifications?

The Precision Metalforming Association(PMA) hosted an interesting webinar on January 24 that highlighted that job shops indeed can and should take advantage of the R & D tax credit.  The webinar discussed several items that would qualify including any time spent to figure out methodology to manufacture dies, parts etc.  In many cases even time spent quoting could qualify for the credit. 

The speaker during the webinar was Mr. Scott Schmidt from Black Line Group.  You can contact Scott at scott@blacklinegrp.com for more information.

What is the Correct Wall Thickness of Extrusions When Tapping?

What is the Correct Wall Thickness of Extrusions When Tapping?

We are often asked what is the correct hole size for roll form taps.  This information is readily available through a variety of outlets including our website, tap manufacturer catalogs, wall charts, etc.   In addition to the correct hole size it is also important to have the correct wall thickness so the threads do not break through the extrusion walls.  So what is the correct wall thickness when tapping extruded holes?

The general rule of thumb is to have a wall thickness that is two times the pitch of the tap.  For example if a ¼-20 tap is required, each thread/pitch of a 20 thread per inch tap is .050.  If we multiply the .050 by 2 we arrive at a wall thickness of .100.  Determining wall thickness with metric taps is even more straight forward.  Just multiply the pitch of the tap by 2 and you will determine the wall thickness.  For example, an M6 x 1.0 tap would require a 2mm thick wall(1.0 x 2).

Improving Tap Life by Lubricating from the Bottom

We occasionally get calls about applications that are struggling to get adequate tap life.  Generally the issue is incorrect hole size or tapping speed that is too fast.  However, inadequate lubrication sometimes comes into play.  This would seem easy to resolve, just add more lubrication and the problem goes away—correct.  Well, not necessarily!

There are times we have to fight the law of gravity.  We will see applications were there appears to be plenty of lubrication on the part.  The problem is that Mother Nature does not always cooperate in getting that lubrication down into the holes that need to be tapped.  Subsequently, there is lubrication all over the place except down in the hole where it is needed most.  So what can be done?

Unfortunately, with blind hole tapping there is not much that can be done other that directing adequate lubrication down into the hole.  However, through holes offer the opportunity to send lubrication up through the bottom of the part.  By sending lubrication up from the bottom the lubrication is hitting the lead of the tap where it is most needed.  The end result is better tap life!

Settting the Correct Tap Depth with In-die Tapping

Setting the Correct Tap Depth for In-Die Tapping

One of the most common questions we receive when customers are new to In-die tapping is “How do we set the height of the tap?”  The ease of adjusting the tap depth is one of the favorite features of users of our In-die tapping heads.  The tap adjustment is all done through the quick change Lead Screw Assembly. 

The correct depth of the tap in the closed position of the press should be approximately 5 full threads through the part.   Using this guide line we can estimate the starting position of the tap in the open position of the press using this example.

Tap size:  ¼-20           Material Thickness:  .150”      Tap Travel:  .750”

If we take the material thickness(.150”) plus  5 threads through the part(.250”) we arrive at .400”.  With the total tap travel of .750” minus .400” we can assume the tap should start .350” above the top of the strip in the open position of the press.

These adjustments are made by removing the quick change Lead Screw Assembly from the tapping head, adjust the height of the Lead Screw by turning it inside the Lead Screw Bushing and locking the quick change Lead Screw Assembly back into the unit—it is that simple.  You can view this adjustment being done on our 8 minute video that is posted on our website(www.hutchisontool.com).