--- title: "Choosing a Shaft Grounding Ring: Part 2" description: In Part 2, we cover bolt-through and press fit mounting, most often used to install AEGIS rings inside electric motors. image: https://blog.est-aegis.com/hubfs/pressfit-endcap.jpg --- [![Electro Static Technology](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/electro-static-technology.svg "Electro Static Technology")](https://www.est-aegis.com/) [![Aegis](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/Aegis.svg "Aegis")](https://www.est-aegis.com/) - [+1 866-738-1857](tel:+1%20866-738-1857) - [Products](https://www.est-aegis.com/products/) - [AEGIS® SGR – for motors under 500 HP/375 kW](https://www.est-aegis.com/product/sgr/) - [AEGIS® uKIT – for common NEMA/IEC frame size](https://www.est-aegis.com/product/sgr-ukit/) - [AEGIS® RPPR – for reactor recirculating pumps](https://www.est-aegis.com/rppr-resources/) - [AEGIS® EV and EVO Rings - for electric vehicles](https://www.est-aegis.com/product/ev-evo-rings/) - [AEGIS® PRO Series – for motors over 300 HP/225 kW](https://www.est-aegis.com/product/pro-series/) - [Shaft Voltage Testing and Accessories](https://www.est-aegis.com/product/mounting-accessories/) - [Online Product Catalog](https://catalog.est-aegis.com/) - [AEGIS® 2-Year Extended Warranty](https://www.est-aegis.com/product/extended-warranty/) - [Applications](https://www.est-aegis.com/applications/) - [Electric Vehicle Solutions](https://www.est-aegis.com/applications/electric-vehicle-solutions/) - [Food & Beverage](https://www.est-aegis.com/applications/food-beverage/) - [HVAC](https://www.est-aegis.com/applications/hvac/) - [Industrial & Chemical](https://www.est-aegis.com/applications/industrial-chemical/) - [Other Industries](https://www.est-aegis.com/applications/other-industries/) - [Power Generation & Renewable Energy](https://www.est-aegis.com/applications/power-generation-renewable-energy/) - [Transportation](https://www.est-aegis.com/applications/transportation/) - [Water Treatment](https://www.est-aegis.com/applications/water-treatment/) - [Bearing Protection](https://www.est-aegis.com/bearing-protection/) - [Shaft Voltage & Bearing Currents](https://www.est-aegis.com/bearing-protection/shaft-voltage-and-bearing-currents/) - [Fluting & Bearing Inspection](https://www.est-aegis.com/bearing-protection/fluting-and-bearing-inspection/) - [Best Practices & Installation](https://www.est-aegis.com/bearing-protection/best-practices-and-installation/) - [Resources](https://www.est-aegis.com/resources/) - [AEGIS® Bearing Protection Handbook](https://www.est-aegis.com/resources/handbook/) - [IEEE-841, Hazardous Locations, & AEGIS®](https://info.est-aegis.com/technical-codes-and-ieee-841-standards) - [Recorded Webinars Library](https://www.est-aegis.com/resources/recorded-webinars/) - [Installation Instructions](https://www.est-aegis.com/resources/installation-instructions/) - [Videos](https://www.est-aegis.com/resources/videos/) - [Technical Papers](https://www.est-aegis.com/resources/technical-papers/) - [Case Studies](https://www.est-aegis.com/resources/case-studies/) - [Specifying AEGIS®](https://www.est-aegis.com/resources/specifying-aegis/) - [Request Training](https://www.est-aegis.com/resources/training/) - [Product Sheets](https://www.est-aegis.com/resources/product-sheets/) - [About](https://www.est-aegis.com/about/) - [News](https://blog.est-aegis.com/) - [Tradeshows](https://www.est-aegis.com/about/tradeshows/) - [Blog](https://blog.est-aegis.com/) - [Where to Buy](https://www.est-aegis.com/where-to-buy/) - [Distributors](https://www.est-aegis.com/where-to-buy/distributors?type=Distributor) - [Trained Installers](https://www.est-aegis.com/where-to-buy/installers?type=Installer) - [Explosion Proof Installers](https://www.est-aegis.com/where-to-buy/installers?type=Explosion%20Proof%20Installer) - [Motors & Seals with AEGIS® Installed](https://www.est-aegis.com/where-to-buy/oems-with-aegis/) [Contact Us](https://www.est-aegis.com/contact/) - [+1 866-738-1857](tel:+1%20866-738-1857) # How to Choose a Shaft Grounding Ring - Part 2 [Home](https://www.est-aegis.com/) » [Blog](https://blog.est-aegis.com/) » How to Choose a Shaft Grounding Ring - Part 2 [AEGIS](https://blog.est-aegis.com/author/estaegis) Mar 20, 2023 In[Part 1](https://blog.est-aegis.com/how-to-choose-an-aegis-ring-part-1?hsLang=en-us)of this series on selecting an AEGIS Shaft Grounding Ring, we discussed solid vs. split ring design, clamp-on, and conductive epoxy mounting. Those rings are all meant to be installed on the outside of an electric motor. This time, we'll look at mounting options for installing the grounding ring inside the motor. ## Why Install an AEGIS SGR and Mounting Options Installing an [AEGIS SGR](https://www.est-aegis.com/product/sgr/)inside a motor is the best choice in most situations. Inside the motor, the ring is protected from water, dust, grease, and other environmental contaminants. The most common mounting options for internal installation are bolt-through and press-fit. ### Internal Installation Internal installation is the *best* option, but it is not necessarily easy. These methods are used mainly by motor repair companies and manufacturers who factory-install AEGIS rings in their motors. For the most part, these are not rings end users would install themselves.![bolt-thru](https://blog.est-aegis.com/hs-fs/hubfs/bolt-thru.jpg?width=250&height=250&name=bolt-thru.jpg) ### Bolt-through SGRs Bolt-through SGRs have two or four bolt holes in them to allow them to be directly bolted to the motor without any mounting clamps or brackets. There are a few part number suffixes for bolt-through rings:  -3FH rings come with 6-32 x 1/2” flathead screws, the -3 has M3 x 14 mm cap screws and washers, and the -3MFH has M3 x 12 mm countersunk flathead screws. Like clamp-on mounting, bolt-through mounting requires drilling and tapping the motor with threaded bolt holes.  Because manufacturing them takes additional machining, bolt-through rings are more expensive than clamp-on rings. And just like do-it-yourself split rings, we highly recommend against screwing through a clamp-on style ring. Driving a screw through an ordinary SGR will likely cause the conductive fibers to fall out. ### Press-fit Rings ![pressfit-endcap](https://blog.est-aegis.com/hs-fs/hubfs/pressfit-endcap.jpg?width=250&height=250&name=pressfit-endcap.jpg) Press-fit rings have a much tighter tolerance in their outer diameter than ordinary SGRs.  This increase in precision comes with an increase in cost, but it allows you to press them into an aperture bored into the motor bearing endcap.  You can't get a much more secure fit than that! Boring the aperture is beyond the ability of most end-users, so press-fit mounting is done mainly by motor repair companies and motor manufacturers.  The second image shows a press-fit ring installed in a bearing end cap.  This work was done in a motor repair machine shop.   AEGIS Shaft Grounding Rings also have a [2-year extended warranty](https://www.est-aegis.com/product/extended-warranty/) against bearing fluting damage. No other form of shaft grounding offers a warranty like this. [![2-Year Extended Warranty](https://no-cache.hubspot.com/cta/default/20974229/3b258d08-3058-4c7f-a866-2991b627f2e0.png)](https://cta-redirect.hubspot.com/cta/redirect/20974229/3b258d08-3058-4c7f-a866-2991b627f2e0)     To learn more about AEGIS shaft grounding and best practices for electrical bearing protection - for motors and generators - [sign up for a training](https://www.est-aegis.com/resources/training/). We offer monthly live training webinars, and we can also visit your facility to review your exact application.   [![Sign Up For Training](https://no-cache.hubspot.com/cta/default/20974229/69dd56c7-bbd1-4ad0-ae5c-29de322039f0.png)](https://cta-redirect.hubspot.com/cta/redirect/20974229/69dd56c7-bbd1-4ad0-ae5c-29de322039f0)   [How-To](https://blog.est-aegis.com/tag/how-to), [Motors with AEGIS Installed](https://blog.est-aegis.com/tag/motors-with-aegis-installed), [Motor Repair](https://blog.est-aegis.com/tag/motor-repair) ### Subscribe To Our Blog ## Read On ### [New AEGIS-Installed Motor Catalog](https://blog.est-aegis.com/new-aegis-installed-motor-catalog?hsLang=en-us) Over the past twenty years, variable frequency drives (VFDs) have been used to control more and... ### [Five Reasons You Should Use Motors with AEGIS Shaft Grounding Factory-Installed Inside](https://blog.est-aegis.com/five-reasons-for-aegis-inside?hsLang=en-us) **1. Motors run on variable frequency drives (VFDs) need protection against bearing current ** ### [Electrical Bearing Protection Q&A - Part 21](https://blog.est-aegis.com/electrical-bearing-protection-qa-part-21?hsLang=en-us) **Q1.  I've heard that AEGIS® Ring you've made, to date, was 44" (112 cm), for a hydroelectric...** [![Electro Static Energy](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/logo-est-alt.svg) ![AEGIS](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/logo-aegis-alt.svg)](https://www.est-aegis.com) 31 Winterbrook Road Mechanic Falls, ME 04256 Phone: [+1 207-998-5140](tel:+1%20207-998-5140) Fax: [+1 207-998-5143](fax:+1%20207-998-5143) Contact Us: [Send Message](https://www.est-aegis.com/contact/) ## Subscribe to Our Emails - [Products](https://www.est-aegis.com/products/) - [AEGIS® SGR](https://www.est-aegis.com/product/sgr/) - [AEGIS® uKIT](https://www.est-aegis.com/product/sgr-ukit/) - [AEGIS® PRO Series](https://www.est-aegis.com/product/pro-series/) - [Testing & Accessories](https://www.est-aegis.com/product/mounting-accessories/) - [Custom Static Solutions](https://www.est-aegis.com/product/custom-static-solutions/) - [Product Catalog](https://catalog.est-aegis.com/) - [AEGIS® 2-Year Extended Warranty](https://www.est-aegis.com/product/extended-warranty/) - [Applications](https://www.est-aegis.com/applications/) - [Electric Vehicle Solutions](https://www.est-aegis.com/applications/electric-vehicle-solutions/) - [Food & Beverage](https://www.est-aegis.com/applications/food-beverage/) - [HVAC](https://www.est-aegis.com/applications/hvac/) - [Industrial & Chemical](https://www.est-aegis.com/applications/industrial-chemical/) - [Other](https://www.est-aegis.com/applications/other-industries/) - [Power Generation & Renewable Energy](https://www.est-aegis.com/applications/power-generation-renewable-energy/) - [Transportation](https://www.est-aegis.com/applications/transportation/) - [Water Treatment](https://www.est-aegis.com/applications/water-treatment/) - [Resources](https://www.est-aegis.com/resources/) - [Request a Training](https://www.est-aegis.com/contact/request-a-training/) - [AEGIS® Bearing Protection Handbook](https://www.est-aegis.com/resources/handbook/) - [Videos](https://www.est-aegis.com/resources/videos/) - [Technical Papers](https://www.est-aegis.com/resources/technical-papers/) - [Case Studies](https://www.est-aegis.com/resources/case-studies/) - [Specifying AEGIS®](https://www.est-aegis.com/resources/specifying-aegis/) - [Product Sheets](https://www.est-aegis.com/resources/product-sheets/) - - - Copyright 2022 Electro Static Technology. 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