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).

Picking the Correct Material Substrate for Tapping

Picking the Correct Material Substrate for Tapping

Like most cutting tools, taps can be manufactured from a variety of material substrates.  Generally, these materials can be broken down into a good, better and best system.  The materials break down as follows: High Speed Steel(Good), High Speed Cobalt(Better), Powdered Metal(Best).   The natural inclination may be to use the best material(powdered metal) as who wants to use something inferior when you can have the best.  This mindset does not always lead to the most efficient or most economical outcome.  The following are some advantages to each material substrate:

High Speed Steel(Good)

This is generally the least costly tap to purchase.  High speed steel is the workhouse of tapping, especially for low run volume jobs.  High speed steel will lack tool wear versus high speed cobalt and powdered metal.  However, high speed steel is more shock resistant than the other materials which means it is less prone to chipping.  If you have some alignment issues with your tapping application, high speed steel may be the least expensive tap per hole as it will not chip before it wears to the end of its useful life.

High Speed Cobalt(Better)

High speed cobalt is often the best choice for tapping.  Because it is harder than standard high speed steel it offers more wear resistance.  This wear resistance leads to longer tool life which means more holes being tapped before a tool change is required.  Generally, high speed cobalt is slightly more expensive than high speed steel but the extra tool life more than often makes up for the higher purchase price.  The one drawback of the harder material is that it is more prone to chipping.  If you have alignment issues then these taps may chip before they wear out which minimizes or eliminates the advantages it has for cost per hole being tapped.

Powdered Metal(Best)

Powdered metal taps tend to be used for specialty type of applications (i.e.  tapping stainless steel or exotic metals).  Often times these may be the only taps that will tap some of these materials.  These taps are often 2-3 times more than either high speed steel or cobalt.  Often times, these taps can be overkill when tapping some general mild steels, aluminum, etc.  In fact, while tap life in exotic materials may be excellent, tool life in some of the milder materials may not far surpass that of high speed cobalt.

In-die Tapping Advantages for Tapping Round, Small and Hard to Fixture Parts

Eliminating secondary tapping of high volume stampings by utilizing In-die tapping is a pretty easy decision to make.  What about those applications that are low to medium volume and may be borderline on cost justification?  There may be some other factors to consider that make secondary tapping even more expensive or inconvenient for specific applications.

Handling and fixturing round, small or cumbersome parts can be quite challenging for some secondary tapping operations.  For example, a simple round washer with one tapped hole may seem simple enough.  That is until you have to hold a round part in a fixture to try to keep it from turning while tapping and not distort the threads or damage the part.  Then there is the issue with very tiny parts or very large cumbersome parts.  It will take either a very patient or very strong operator to load these parts into the appropriate fixtures.   The frustration with dealing with these scenarios leads to increased costs and lower efficiencies.

The beauty of In-die tapping is that any part shape is already captured in the strip.  There is no need to do anything different than what would normally be done in any progressive die.  These round, small and hard to fixture parts come off the press complete with tapped holes and are ready to ship.

We look forward to working with you on your tapping projects.  Please visit us at http://www.hutchisontool.com/ or call us at 800-332-3230.

Tom Hutchison

President