Screw and Nut for Draw Bar

I am working on a Samhongsa engine with a similar screw. The thread is M3. Common pitch .5 mm. Most any hardware store will have a nut. You can make a shoulder screw by simply getting a full thread screw the same length and slipping a piece of brass tube over it for the shoulder.

Pete

I assume it's metric and somewhere between 2 & 3mm.  Do you have a set of calipers?  If so, use them to measure the diameter.   Except for 3mm, the number of threads per mm is fairly standard and I can probably help you out.

Jay

FYI, you can use 1mm = .03937”. 3mm=.118” . 1/8” = .125”

Pete

@Norton posted:

I am working on a Samhongsa engine with a similar screw. The thread is M3. Common pitch .5 mm. Most any hardware store will have a nut. You can make a shoulder screw by simply getting a full thread screw the same length and slipping a piece of brass tube over it for the shoulder.

Perfect! Just what I need. Now, need to check with my local ACE Hardware.

@Jay C posted:

I assume it's metric and somewhere between 2 & 3mm.  Do you have a set of calipers?  If so, use them to measure the diameter.   Except for 3mm, the number of threads per mm is fairly standard and I can probably help you out.

Jay

Jay, are you saying you may have a nut that will fit that you can offer?

Yes, I should.  I'm not a convert to metric but, when I started working on brass imports it seemed natural, to me, to keep things as original as I could.  As an example, 2mm is close to a 2-56 thread and I've observed hacks replacing one with the other.  To me it cheapens the whole process of doing it right.  For everything else I do in life, SAE is my go to.

As a side note, I find the digital calipers that toggle between inch & metric to be mandatory.

Jay

Let me suggest if you have a number of brass engines or even modern diecast that you get some metric screw/nut assortments. Amazon and eBay have scores for small money.

10-15 bucks will get you many sizes. Shoulder screws are more specialized though. Precision Scale has a few but you are more dependent on the importer for those. Lionel and MTH have some too.

Pete

@Jay C posted:

Yes, I should.  I'm not a convert to metric but, when I started working on brass imports it seemed natural, to me, to keep things as original as I could.  As an example, 2mm is close to a 2-56 thread and I've observed hacks replacing one with the other.  To me it cheapens the whole process of doing it right.  For everything else I do in life, SAE is my go to.

As a side note, I find the digital calipers that toggle between inch & metric to be mandatory.

Jay

Thanks for the offer. I will check with my local hardware store first. I like the digital caliper idea.

@Norton posted:

Let me suggest if you have a number of brass engines or even modern diecast that you get some metric screw/nut assortments. Amazon and eBay have scores for small money.

10-15 bucks will get you many sizes. Shoulder screws are more specialized though. Precision Scale has a few but you are more dependent on the importer for those. Lionel and MTH have some too.

Pete

This is a good idea. While I have tons of tools and hardware for larger stuff, I'm finding that I need a whole new inventory for trains.

May be build the shoulder with a piece of copper/or steel tubing.   Steel tubing is usually available as replacement automotive brake line.   

From the look of those threads I would get a die and chase them. Might be able to save that shoulder bolt.

Unlike Jay I have no problem going back to SAE threads.  Some driver crankpins accept 1-72 steel right off the bat.  But drilling and tapping for 2-56 is my go-to operation.

The hardware store option is your best bet.  Ten cents for a metric nut.  It will cost Jay a buck to get you one - post office does not like lumps in envelopes any more.

Metric fasteners are now dirt-common.

Thank you all for your advice. I manage to easily find the correct nut at my local ACE Hardware. Installed it this evening and went together pretty well.

On another note, after pulling the shell off for the first time on this loco (Samhongsa B&O Q4 2-8-2) I found that the motor was not screwed to the frame. Yes, the motor was just flopping around inside the shell. Only the coupling to the gearbox and the tight fit within the shell kept it running. Crazy. You never know what you'll find in a pre-owned item.

So, back to ACE to find a couple screws. I bought this loco in January and it needs some TLC. But, I really like the looks of it and I'll get it running properly and give it a good paint job.

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