153k101 binder plate question

[numbskull]

I ended up with an old Singer 153k101 walking foot cylinder arm machine that came with a box of attachments including a right angle binder setup.  The binder itself mounts on a modified bobbin cover slide plate (part #221174) that has two holes for the binder to screw onto and a welded on slotted 6" narrow plate that extends along the cylinder so that the slot aligns and ends above a hole in the cylinder arm that is 6" from the needle (this is not an oil point).  It looks like this hole should be threaded and a screw would go through the slot to hold the back end of the binder plate stable (while allowing it to slide and access the bobbin).
The hole (size 17 drill) is not threaded, however.  Does a missing pin or something go in there to hold attachments stable, or am I supposed to tap it myself ( a size 12-24 tap would fit)

Anybody out there familiar with this machine and know what that hole does?

Thanks.
George

[JuneC]

No clue, but I can tell you that the beds of my 3 old singers look like swiss cheese.  Over the years, different owners have obviously mounted different things here and there and at this point no telling what should go where.  All I know is that modern attachments I've bought didn't fit ANY of the holes already there and I had to drill and tap yet more. 

June

[Gregg @ Keystone Sewing]

numbskull,

I know this machine well, and more specific, this area of the machine well.  You say there are some welds up in there?  This means already some screws or part of the casting us busted out, and someone went and made some repairs.  It's not uncommon for cylinder arm casting where the needle plate set screws go to bust out.  The problem I would have now trying to help is not knowing what was broken, what was 'fixed', and where the current state of the machine is at now.  Do you have VERY detailed pics?  Poor quality images from a 1/4 mile away will  not help me here at all.

[numbskull]

I think I mislead you.  The cylinder arm is fine, as manufactured.  The hole was put there by singer and there are no welds or damage (the weld I was talking about is the attachment of the binder arm/plate to the bobbin cover plate.....it is a manufactured item that must have been sold to fit the machine at some point).  The hole is exactly 6" from the needle.  The binder arm is slotted to fit exactly over it while letting it slide to still be able to access the bobbin).  I'm having trouble attaching a picture (even with a small file size)....maybe I've not posted enough but will try again.

Thanks

[numbskull]

Lets try this since the regular upload path is blocked.  Sorry the picture is small.  The hole is centered on the arm although the picture distorts that.
First is the hole with a drill in it to mark it
second is the binder arm on the machine (without the binder itself mounted) again with a drill marking the hole

Seems a screw should go in that hole, but then why is it unthreaded and how do I stabilize the plate using that hole?  
Thanks for any help/advice you can offer.
George

[Gregg @ Keystone Sewing]

numbskull,

I just check machines I have here in stock...most close related I have in stock Singer 153W101.  In this hole where first drill bit is located (mounting hole for your custom binder attachment to bed of machine) is a is threaded hole that uses Singer attachment screw tap 13/64-32.  This is a common sewing machne screw that is not Standard, SAE, or metric.  

Check this hole, the threads could be covered in dirt, paint, or anything else you can think of.  Blow it out with compressed air, scape lightly with a screw driver or the such to see if there are threads. 

[numbskull]

Thank you, Gregg.
The hole on my machine is not threaded but obviously it should be or can be.  Maybe they missed it on construction or maybe it was usually done after sale only as needed.  Anyways, knowing that it is threaded on other machines gives me the confidence to just go ahead and tap it.  I'll check with my machinist friend to see if he has the right tap. 
Thank you again, your willingness to help is greatly appreciated.
George