Threaded Inserts: Screw fit
Inserts are a great way to add threads to MJF and SLS parts. They secure, fast and good value. They are readily available in Brass (RoHS compliant), stainless steel and bright Nickel plated if bling is required. The inserts screw into the part using a coarse self- tapping external thread and are then retained in the part permanently.
There are advantages to screw fit inserts over other types such as press-fit, or heat-stake. These include:
- The ability to place them by hand in non square parts (press fit rely on force insertion so they need a stable part to be able to insert them, this can be tricky on round or uneven shapes)
- Quite quick to install
- Readily available in multiple sizes / configurations.
- Very secure once installed
- Multiple Screw / unscrew cycles without damaging the substrate.
Disadvantages compared to other types of threaded inserts:
- Press-fit can be quicker to insert
- Manual insertion of press-fit inserts is less "arduous"
- Marginally less secure than Heat-staked inserts
Incremental-AM recommends specifying Tappex Triserts for screw in thread applications. They are generally available in three types (for female threads) in each size:
Double ended / Reduced head / Regular head. We tend to recommend the Reduced Head type (Centre above) as they fit flush, the runout of the thread is not on display and they offer slightly higher performance in terms of "jacking out".
The hole definition is very easy to model into parts and in most CAD programs can be templated.
A full example of the hole definition can be found on the rather brilliant Tappex Website, in this case for the M4 - Reduced head.
When using the selected inserts Incremental-AM recommends the following additional guidelines when using the inserts for MJF or SLS 3D printed parts:
C - Hole diameter: Model the pilot hole to the on the bottom limit of the tolerance (it is easier to open the holes than to make them smaller after print).
Y - Pilot hole depth: Add 1mm to the minimum specified hole depth. Blind, narrow holes can be tricky to get completely clean and depending on print orientation can have some thermal bleed (solid white residue) trapped in the corners making the hole effectively slightly shallower.
These are Incremental-AM go to for permanent, fast and secure thread making in MJF and SLS parts. We are happy offer a quotation to fit them for you or for you to order and fit them yourself.
Top Tips:
- Hole size - bottom limit
- Tool - The tappex hand installation tool is great for ensuring coaxial insertion.
- Boss thickness - Don't forget to check the boss wall thickness!
For further thread making advice for HP MJF parts and SLS parts please have a look at other Technical notes:
For a no-obligation quote to have parts made with threaded inserts please contact Incremental-AM either by our contact form or request a quote through our online portal.
All images not of Incremental-AM origin are reproduced courtesy of Tappex Thread Inserts Limited