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A Screw On Lead Extension Journals/Blogs
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Super User 5,905 posts Ken Rice Super User 5,905 posts
Ken Rice

The switching lead on my mini test layout would be pathetically short without an extension.  Since I expect to carry the module up and down stairs and round corners, the extension has to be removable.  I wanted it to lock nicely into place and be easy to install and remove.  I ended up using a threaded insert and a screw with a knob.

Here's a side view of the extension installed.

ure-7457.jpg 

And here's what it looks like when removed, with the layout flipped over to show the threaded insert.

ure-7456.jpg 

There's enough of the 1x3 going under the layout so the extension can't tip down.  The top piece the cork roadbed is glue to is also a 1x3.  In between a spacer of a scrap of 1/2" ply and a scrap of paneling made up just the right thickness to match the door.  When I tested clamping it on to see how much the extension would flex, I was surprised to see the whole door bow up along it's length as the inside end of the extension pressed up on the bottom of the door.  That's why I added the 1x2 stiffeners along the front and back edges of the door.  The extension itself flexes a little, but not enough to worry about with only the weight of an engine and cars on it.

The brass threaded insert has a 3/8-16 machine screw thread on the inside, and coarse wood screw threads on the outside.  You drill a 1/2" hole to screw the insert into.  I picked up both the insert and the screw with a knob for a head at a local hardware store.

Getting the insert screwed in right proved to be tricky.  My first attempt I used a washer engaged in the two slots at the top of the insert to screw it in, and it dug itself it several degrees off from vertical - enough that it affected how the board seated against the door.  Some experiments in scrap wood showed that it's very difficult to get it to follow the hole straight in.  What I ended up doing is getting some 3/8-16 threaded rod, which I threaded a regular nut onto and then the insert.  I wedged the top of the rod against a handy prop (my drill press) to keep it exactly vertical over the hole and held there firmly enough to resist the tendency to wobble when screwing in the insert.  I used a wrench to turn the whole thing to drive the insert straight in.  Not too hard once you know what needs to be done.  Here's the setup, doing a trial run on a scrap of 2x4.

ure-7448.jpg 

The end result is easy to remove, easy to install, and seems to align itself quite nicely.

(Copied from my blogspot blog  https://rices-rails.blogspot.com/2021/11/a-screw-on-lead-extension.html.)

My blogspot blog: http://rices-rails.blogspot.com/
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MikeHughes Super User 5,472 posts
MikeHughes

Lee valley sells these AWESOME

Threaded insert tools.

LeeValley Insert Nut Driver

Now, if you have a lathe …they are easy to make!
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Ken Rice Super User 5,905 posts
Ken Rice

The special tool

Thanks Mike I didn’t know those existed, I’ll keep them in mind if I need to do more.  There’s a special tool for everything!

Lee Valley only has the 1/4-20 size, Rockler has 1/4-20, 5/16-18, and the one I wish I’d had a couple days ago, 3/8-16:
https://www.rockler.com/power-drive-threaded-insert-tool-power-drive-threaded-insert-tool

My blogspot blog: http://rices-rails.blogspot.com/
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Bernd MRH Author 5,561 posts
Bernd

Using the tool

I would use a drill press turned by hand to to screw in the insert with that tool. The drill press will help keep the insert going in straight.

Bernd

New York, Vermont & Northern Rwy. - Route of the Black Diamonds - NCSWIC
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Brad Ketchen OSCR Regular poster 388 posts
Brad Ketchen OSCR

Support at other end

Great idea. How do you support the end? 

 

 

Ontario South Central Railway, Toronto, Canada. 
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Ken Rice Super User 5,905 posts
Ken Rice

Support the other end

You don’t support the other end, it hangs off into space.  The 1x3 that extends under the main module keeps it held firmly into place, so the only thing that affects the hanging end is the natural flexing of the top 1x3.  For the 52” length I have, that’s not enough to be an issue.  (Why 52”?  That’s how long the longest piece of 1x3 I had in my scrap pile was.)

Mind you if you ran a train out there, deliberately pulled down the end with a fair amount of force, and let go, you could probably bounce the cars up a few inches.  So don’t do that.  I think for normal non-malicious operation it will be fine.  Nothing will be stored on it, it will only have anything on it during an active session.

I will put some sort of edging around it to keep things from falling off just in case anything derails.  But I’m not worried about bouncing or sagging.

My blogspot blog: http://rices-rails.blogspot.com/
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eastwind Super User 3,588 posts
eastwind

Nice!

I noticed you had some very nice looking straight-grain 1x3s there. 

Others who try this might not get your results if they do anything less well than you have as far as controlling humidity, getting the thing together before the pieces cup, using superior lumber,  etc.

 

You can call me EW. Here's my blog index
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Jim at BSME Prolific poster 2,087 posts
Jim at BSME

Another driver option

Looking at the Lee Valley Tools site and I saw the offer both 1/4-20 and 5/16-18 inserts, no 3/8-16 though. So made me wonder about a driver for the 5/16-18 and the offer that too, but a different style (and cheaper) than the first one.

https://www.leevalley.com/en-us/shop/tools/hand-tools/screwdrivers/bits/110061-insert-nut-driver

My question is where did you get the knob?
- Jim B.
Baltimore Society of Model Engineers, Estd. 1932
O & HO Scale model railroading
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MikeHughes Super User 5,472 posts
MikeHughes

Lee Vally sells tons of different knobs as well

Also an amazing selection of cabinet hardware and numerous first rate tools.
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Ken Rice Super User 5,905 posts
Ken Rice

The Knob

I got the knob at my favorite not quite local hardware store, O’Connor’s True Value Hardware in Billerica, MA.  (That’s the same Billerica as the nothern terminus of the Bedford & Billerica RR, the first 2 foot gauge common carrier in the US.)
https://www.oconnorhardware.com
/> (Not good for online ordering, just can’t resist a little plug for my favorite hardware store.  And the other point is other True Value hardware stores with reasonably complete fastener sections probably have the same stuff.)

I’d guess you should be able to find the inserts and knobs in other hardare stores with a reasonably comprehensive screw and misc hardware section.  When I’ve got a problem like this I’m not quite sure how to solve I make the drive up there and just browse around through all the sections until ideas start to percolate.

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Jim at BSME Prolific poster 2,087 posts
Jim at BSME

re: The Knob

Guess I'll have to look closer I haven't seen a knob attached to a threaded rod, and didn't find one at Lee Valley.

And it looks like O'connor's doesn't have online inventory just general department info.

Doing a little more googling looks like they might be call hand knobs.
- Jim B.
Baltimore Society of Model Engineers, Estd. 1932
O & HO Scale model railroading
Check out BSME on: Facebook, Instagram
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Ken Rice Super User 5,905 posts
Ken Rice

The Knob

Sorry Jim, didn’t mean to imply the O’Connors site was good for online ordering.  But they are a True Value hardware store, so I’d guess that you could find the same stuff at any true value store with a reasonably complete fastener/hardware section.

My blogspot blog: http://rices-rails.blogspot.com/
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Jim at BSME Prolific poster 2,087 posts
Jim at BSME

No worries

I was more concerned with trying to find the name so i could look locally.
- Jim B.
Baltimore Society of Model Engineers, Estd. 1932
O & HO Scale model railroading
Check out BSME on: Facebook, Instagram
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MikeHughes Super User 5,472 posts
MikeHughes

Lee Valley Jig and Fixture Parts

https://www.leevalley.com/en-ca/shop/hardware/jig-and-fixture-parts

https://www.leevalley.com/en-ca/search#q=knobs%20for%20fixtures&t=product-search-tab&sort=relevancy&layout=card&numberOfResults=25
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Ken Rice Super User 5,905 posts
Ken Rice

Homemade insert jig

I just came across an article with a pretty simple homemade jig for installing the inserts:

https://www.woodsmith.com/article/threaded-insert-jig/

My blogspot blog: http://rices-rails.blogspot.com/
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Graeme Nitz OKGraeme Prolific poster 1,695 posts
Graeme Nitz OKGraeme

Just Google

1/4" threaded knob and you will find plenty of them.

For example:-

 

https://www.lowes.com/pd/Hillman-Replacement-Knobs/3903340?store_code=1500&cm_mmc=shp-_-c-_-prd-_-hdw-_-ggl-_-LIA_HDW_126_Fastening-_-3903340-_-0-_-0-_-0&ds_rl=1286981&gclid=EAIaIQobChMIwN_ciOuZ9AIVFmxvBB131wWIEAQYAiABEgJStfD_BwE&gclsrc=aw.ds

Graeme Nitz

An Aussie living in Owasso OK

K NO W Trains

K NO W Fun

 

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Those that understand Binary and those that Don't!
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