We are very busy at Rentapen.  That means that I, the Queen, get pulled into helping to get the weld fixture designs out on time by using Pro/ENGINEER.  And what THAT means is I don’t have much time for blogging.  

We are also very busy cutting and packing metal adjustment shims.  So I would like to be doing two things at once, helping to pack shims and CAD drafting.

But that is OK, actually, that’s a good thing!   We are busy because manufacturing in the USA and especially the MidWest is busy. 

So this week we will discuss only ONE tiny topic….

When do YOU use extra fine thread (UNEF) in machine design?

I posed a question on Linked In asking where is a good application to use an extra-fine thread on a screw.  And the response was great….

“I use them to mount electrical components to back planes in electrical cabinets. The back plate is thin so the thread pitch has to be high.” Ron L.

“We use them a lot as adjustable dead stops for small cylinders in our custom built machines where space or reach does not allow us to use a micrometer head. Not and elegant but a functional solution. “ Scott M.

“Fine thread grade 8 screws, bolts & Locktite are surely hard to move or break. SAE, High vibration, holding strength, less movement . Coarse thread are great as lag bolts for wood. As comparing coarse thread are most likely to vibrate loose unless backed by a locking nut due: to distance between threads”layman’s terms” . Fine thread is closer together giving More Thread TO lock down Harder, and hold under high vibrating areas.” Brad D.

“Finer threads have a “flatter” slope than coarse threads, so that has two effects. First, they are a little less likely to back off under vibration. Secondly, since the finer thread has a higher mechanical advantage (it travels less distance axially for a given amount of rotation), so you get more clamping force for the same amount of wrench torque. This is really important to consider when specifying torque settings.” Eric K.

“Extra Fine threads are stronger than coarse/fine threads because of larger cross section on mean dia. It is also use when you need adequate thread engagement i.e. on thin plates.” Ernesto V.

“Most of the time I use fine threads in lead screw positioning applications that require a high precision along the thread axis.” Italo V.

“I’ve used UNEF threads on firearms and scope mounting tasks or wherever the vibrations would be sufficient to loosen UNF and especially UNC thread systems. When I do machine design I prefer standard metric fasteners (or the fine series of metric threads in high vibration situations) as the thread angle is flatter than UNC threads of comparable diameter and hold better. When having to use Unified fasteners I prefer UNF unless a soft material is being tapped, such as Aluminum or Brass because of the greater possibility of stripping out the tapped hole by over-tightening.” David F.

So, do YOU have something to add?  When have YOU used Extra Fine thread or even Fine threaded screws? 

’til next time,

The Queen


Check out this slide show I put together as a quick over view of Rentapen’s capactity and history.


As you may know, I ride a catrike a lot.  (Rode it to work today in fact!)  This video shows how to adjust the disc brakes.  I love my brakes!  They have saved my life more than once.  (Recently I got caught riding in the rain after dark.  At an intersection I slammed on the brakes and the car coming at me slammed on the brakes.  We both slid a bit on the wet pavement, but avoided a collision due to fast reactions and good brakes!)  Yet disc brakes on trikes need adjusting from time to time. So if you are interested, watch and learn.



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