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Discussion Starter #1
I got a 4/40 tap and bit from Ace Hardware

The bit is a couple sizes larger for a over sized hole




I positioned the coupler to drill the holes




The holes drilled




Taped the holes



Prepare the coupler with spacers.

# 4 washers Six on each screw.

Something I determined earlier








Using the Kadee height gauge I determined how many washers I needed

The screws can be cut to length now


 

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JJ,
Isn't the Oversized bit for clearance through the draft gear and a smaller one for a pilot hole for the tap?
Taps usually have a specific drill bit to use for each one.

John
 

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Discussion Starter #3
Posted By Totalwrecker on 21 Apr 2013 07:38 AM
JJ,
Isn't the Oversized bit for clearance through the draft gear and a smaller one for a pilot hole for the tap?
Taps usually have a specific drill bit to use for each one.

John
I really should not have said that when taping plastic.


I drill a slightly over sized hole when tapping metal to make it easier to tap.,

Less meat for the tap to cut into .

On softer metals I actually use a drill to do the tapping.

JJ
 

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Are you using nuts to secure the screws in place?

If so why not run the screws down through from the top and put the nuts underneath the couplers for a cleaner look.
 

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Discussion Starter #5
Posted By rlvette on 21 Apr 2013 09:10 AM
Are you using nuts to secure the screws in place?

If so why not run the screws down through from the top and put the nuts underneath the couplers for a cleaner look.
No Randy I am not using any nuts. The plastic is tapped for the 4/40 screw.

In the pictures I have not cut the screws to length yet.

In other applications I have done what you suggested.

I have actually dune what you said.

I also have put nuts between the rolling stock and the coupler as spacers to get the height I needed.

Then I put nuts to old the coupler in place.

JJ
 

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Typically a #43 drill bit is used for a 4-40 tap. But it varies depending on how much or how little material you want to tap into.
 

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Discussion Starter #7
Posted By San Juan on 21 Apr 2013 10:47 AM
Typically a #43 drill bit is used for a 4-40 tap. But it varies depending on how much or how little material you want to tap into.
Exactly. In harder metals I drill a over sized hole to make it easier to tap taking off less metal. There is a less chance of breaking off the tap.


Castings can be difficult to tap .

Depending on the hardness of the metal I have been known to use a drill motor as a tapping wrench.




JJ
 

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Good points about taping into metal JJ.

I recently drilled and tapped two Precision Scale 1:24 tank cars for Kadee couplers. Wow that was some thick brass to get through. And I drilled by hand using a large pin vise
 
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