Large Scale Central

Replacement for Split Jaw Insulated rail joiner

Over the years I have had problems with my split jaw insulated rail joiners.

The problem is that because of the design the plastic piece tends to break.

Because of this I had my son and Al redesign the insulated part

Several improvements were made

  1. The profile of the rail was used for the insertation rather then an angled cut so that it fits better.

  2. the insulated part now goes under the rail to help prevent the stress caused by the insulated part tilting down.

  3. the insulated part was strengthened

  4. there is now an insulated part between the rails that prevents the two rails from touching each other.

Still needs some minor adjustments but if anyone is interested we can share the 3d design.


Very cool. I’ve not had any failures, but I think I use about 4 on my whole RR where you probably have 400!

Hi Stan,

At Split Jaw, we are huge believers in innovation. So, congratulations on you and your Son’s idea! Before I comment, I’d like to point out the history of the product line:

The original Split Jaw company was formed in the 1990’s, and lasted until 2018 when the founders decided to call it quits. As a new, reincarnated Split Jaw Products, we only opened our doors in April 2021, and sold our first insulated rail clamps in Summer 2021. So here in February 2023 I’d like to clarify any problems you have had “over the years” with Split Jaw insulator clamps were very likely not our products. Hey, not everyone knows or cares about our little company’s history, so the mistake is easy to understand.

You are 100% right about the ‘old’ Split Jaw’s insulated rail clamps needing more strength and better insulating design. That’s why we intentionally made a big change to the design. Starting with an improved design, after some good initial customer feedback in our first few months, we continued with product evolution. For insulated rail clamps, Split Jaw now has our crush strength exceeding 100 lbs/in2. Plus, we are using a proven reinforced polymer that holds up to Sunlight and weather. We have this fun, weather-accelerator gizmo for this durability test.

Today’s Split Jaw uses the strongest stainless screws we have seen in our hobby. But realistically speaking, plastic will never be as strong as metal. So definitely it is still possible, as with any plastic-to-metal combination, to crush the plastic against the metal. Users should remember the main purpose of insulators is electrical, and not mechanical. Our insulating clamps provide some of the famous Split Jaw rail-aligning features, but not with the holding power and toughness of a 100% metal rail clamp.

That said, anyone who purchased our Split Jaw insulating rail clamps, and got a little overzealous with screw tightening, is very welcome to contact us at for a free replacement.

Keep up the good posts!




Welcome to Large Scale Central. Its always great to hear from manufacturers about their products.

I really like your new design for the insulated portion. The main problem with the previous companys version was that the grove did not fit the rail so it tended to put the presure in the wrong place causing it to eventually fail. Gad to see your new version fixes this.

You are of course welcome to our 3d version if you would like it,

Looking forward to meething you at the North East Large Scale Show in april


PS selling just the insulated part your new design might be an interesting addition for those that have damaged previous companies version.