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Kato unitrack assembly tolerance

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  • Member since
    January 2024
  • 1 posts
Kato unitrack assembly tolerance
Posted by Stillkickin on Friday, January 19, 2024 11:13 AM


I’m new to this form but it’s been 30+ years since I have done any model railroading.

I plan on using Kato Unitrack. While designing my small layout I have a question about how much tolerance is between track junctions. How far off can I be if I can’t find the perfect Kato track section?



  • Member since
    July 2006
  • From: Central Vermont
  • 4,565 posts
Posted by cowman on Friday, January 19, 2024 7:24 PM

Welcome to the forums.

I have not used Kato unitrack, but have used another brand of pre-ballasted track.  I would say there was just about zero tolerance the way the pieces lock together rather tightly.  

If you have a spot that you absolutely cannot rearrange to match up the wide variety of Kato offerings you could cut a piece of flextrack to fit and put cork under it.  I believe the Kato base is the same thickness as cork roadbed, if not, shim or sand it to match.  For looks yoou might want to cut off the locking ends on the Kato pieces.

Good luck,


  • Member since
    April 2023
  • 27 posts
Posted by Lost in A2 on Friday, January 19, 2024 8:00 PM

Unitrack joiners can be removed without cutting. Kato has a plastic tool specifically for that purpose. 

  • Member since
    February 2018
  • From: Danbury Freight Yard
  • 456 posts
Posted by OldEngineman on Friday, January 19, 2024 9:34 PM

Tolerances for Kato track are quite close. Not 100%, but again, close. You could be off, perhaps a very few mm, but not much more.

You might consider using one of the "track planner apps" out there, at least the free versions that are available. I believe they'll have templates for Unitrack that can be used to get an idea if things will fit together properly.

RE the comment about Unitrack joiners. I've found that the "tool" Kato provides for popping out the Unijoiners works, well, so-so. I'll use a VERY small flat-bladed screwdriver, the kind that come in eyeglass repair kits. This works for separating adjoining track sections, as well. This stuff fits together tightly.

  • Member since
    December 2021
  • 63 posts
Posted by NScale4x8 on Sunday, January 21, 2024 12:13 PM

Kato Unitrack has ajustable sections to fill any gap.

Kato Unitrack can be modified. Cut it like flex track to remove part of the middle while preserving the rail joiner indents.

The roadbed can be notched to enable creation of S-curves etc.


In this picture, you can see how a segment of Untrack roadbed was cut out of the middle (to the left of the bridge) and the rails extended accross the bridge to the other end of the original segment.

Cut Unitrack

  • Member since
    January 2014
  • 1,500 posts
Posted by ROBERT PETRICK on Sunday, January 21, 2024 2:17 PM

You didn't say if you're N Scale or HO Scale. I'm N, so this info applies to N. There may or may not be similar stuff available for HO Scale.

Kato Unitrack is available in sets of uniform lengths of straight track based on multiples of the shortest unit length.

The curved sections are available in sets based on 15-degree, 30-degree, and 45-degree arcs of various radiuses (radii). The curves can be fudged a little without losing the integrity of the joiners by bending the ends a little. That is to say, for instance, a 15-degree curve can be splayed out to about 17- or 18-degrees or scrunched in to about 12- or 13-degrees. The actual track and plastic base are not deformed, only the end joints are fudged. Then the adjoining sections are jiggled a little to smooth out the alignment. This activity can have a large effect on other sections of the layout.

Kato makes two sets of short filler pieces to insert anywhere they are needed on the layout. Here's a photo:


Section No 1, No 2, and No 3 are from one of the Kato filler sets. No 5 shows a standard 62mm straight (the standard base unit of the ordinary Kato N Scale straight sections). Section No 4 and No 6 are two pieces I cut using a jeweler's saw. The hand-cut filler sections can be placed in the layout using the standard Kato UniJoiners.

Hope this helps.



  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 13,873 posts
Posted by wjstix on Monday, January 22, 2024 10:37 AM

Main thing with Kato Unitrack is to read all the info about the pieces and how they go together. The track design isn't random, the smaller pieces are designed to fit specific situations, like say getting the track ends to come out even when adding a passing siding. If you buy HO electric no.6 turnouts, the reverse curve and short straights you need to come out even come with the turnout; if you buy the manual no.6, you have to buy those separate pieces yourself. Otherwise, the two tracks won't come out even.

One problem I think people have with the gizmo to remove the joiners is they may not realize it's one-sided; if you try to do it wrong way around it won't work.

  • Member since
    December 2004
  • From: Bedford, MA, USA
  • 21,442 posts
Posted by MisterBeasley on Tuesday, January 23, 2024 4:07 PM

If you do decide to insert small sections of flex-track, it might be a good idea to get a Ribbon Rail gage for the minimum curvature you'll accept and use that to help shape the curve.

It takes an iron man to play with a toy iron horse. 

  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 13,873 posts
Posted by wjstix on Monday, January 29, 2024 10:59 AM

In HO, Kato's code 83 track is a bit narrower than other manufacturer's, but other rail joiners (like Walthers) will still work with them - but it's not a snug fit, so you might want to solder the joint.

Note that the Unitrack rail isn't glued into the roadbed pieces, you can slide the rails out to use them with regular ties (like if you were handlaying track or in a building with grooves for rails). You might be able to slide the rails into ties from other brands of flextrack, but I've never tried it.


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