What Where and How of Metal Shims

What, Where, and How of Shims and Shim Packs

I am excited about our new Free 3D CAD Models ordering service on Rentapen’s web site.  I know I promised to talk more about the simple weld fixture (weld jig), this week,  however I am delaying that because this is (I think) so COOL!!

Our line of tooling components are now even easier to use.   I invite you to play with this new 3d model downloading service.  These files are Free!  Since we are still discovering kinks, be sure to let us know if you find any problems.

The videos I have for you today are about how to use this service.  But there is so much more to learn. These videos aren’t polished, but you will get the idea.

First, I talk about shims and show how they are placed in a real fixture. You might want to turn the volume down a bit, I start in the shop…

I know I go on and on about shims at times. I am a big advocate for shimming in weld fixtures.

With so many variables involved in how much heat will be created during welding and therefore, how much distorting will occur on the product being welded, shims and shim packs are essential. They help the production group set up the fixture before full production begins. So that when the weld jig or fixture goes into full production it is putting out a product that works.

In this next video I  show you how to download a file for a RAPid Block(TM) and a RAPid Riser(TM).

And in THIS video, our team member, Kory, tells you how to get your Pro/E parameters into your STEP file.


I hope you have fun trying out the new 3d models and seeing how you can use them. I’d love to see what you come up with! Didn’t you like playing with legos??

Send images of your designs using RAPid Tooling Components to news@rentapen.com

The Queen of Lean Machine Design


6-Questions RE: Locating Pins in Weld Fixture Design


In weld fixture design we often use the holes in the product for locating the product part in the fixture.  What do you  think designers should ask when considering pinning a hole?

Welded Product Parts With Critical Dimensions Tween the Holes



The location of the hole in one product part can be precisely located in relation to the other product parts it is being welded to.  This is done by using the right design methods.



Major design difficulties can occur if some questions are not addressed before starting the 3D modeling process.

What do you  think designers should ask when considering pinning a hole?

What comes to mind for me is:

1) Is the hole location critical to the other parts it is welded to?  If it isn’t it doesn’t mean I WON’T pin the hole, just that maybe I can use a looser tolerance between the pin and the hole diameters, and I won’t need to use an adjustment shim pack to fine tune the locations of the pin.

2) Will you be able to get the product out of the fixture if you pin the hole?   Or, do you have to remove the pin before you are able to remove the product from the fixture?  We will be going over how to use a straight action clamp in weld fixture design for removing a pin in future blogs.

3) Are there other holes in that same product part that are pinned?  You need to take care here because you need to understand that there will be tolerance issues between the holes.  Yet , two holes makes it easy to locate the part at just the right angle.

4) Will you need to rough locate the part before it is pinned so that it is easier and faster for the pin to find the hole, or the hole to find the pin?

Rough Locator

Pink Rough Locator helps position the Product Part


For example, The product parts are dark gray.  In this picture, the pink round part is a rough locator, along with other locators it gets the product part in close proximity to perfect.  Then the removable purple pin with the help of a straight action clamp moves into place to hold the part in the perfect place while it is being welded.

5) Will you use a shoulder pin that can also act like a rest pad?

Shoulder Pins Can Be used as Rest Pads.


In this picture the left pin is a shoulder pin.  The product plate (in dark gray) rests on the shoulder.  The yellow part underneath it is a metal precision shim pack.



6) How will you prevent weld splatter from making the pin get stuck or welded into the hole?

As you see in the picture, the pins have chamfers on the ends where they protrude through the product plate.  The pins should be harder than the material you are welding.  That makes them last longer in the fixture and reduces the likelihood that the weld splatter will stick to them.  The material of the pin depends on the material you are welding.   In some instances you will need to add guards or shields to protect the pin from the weld splatter.  There is also a protective coating that can be added to protect the pin from the weld splatter sticking to it.

Did I miss some questions?  What else would you consider?

Please share this with a manufacturing engineer or machine builder that you know. We always can learn from the welders, assemblers, machinists and managers who work with our designs every day.

Susan Straley, Queen of Lean Machine Design at Rentapen

Susan Straley
Queen of Lean Machine Design


Do you know someone with some singing or rapping talent? Video tape them singing our Shim King song and we will post it on our shim page and tweet it!