A Real Dirty Job
Moderator: Harold_V
Re: A Real Dirty Job
After forming the donut end, the other end of the part has to be drilled and tapped 1-72 NC.
The problem is now how to hold the part so this operation can be performed and to keep everything centered as the extra length of material used to hold the part in the 4 jaw chuck was cut away after forming the donut. One end of the part is now the donut and the other end a short circular stub only 1/8" long.
These miniature parts really need to have their own unique holding pieces that, likely, are going to be only used once to make the number of parts needed. It is whatever one can come up with and better still keep it simple.
A scrap piece of 3/8" dia. brass was drilled in a collet at one end to be slightly under size on the donut end (3/16") and on the other circular stub end (1/8"). The piece was then taken out of the collet and sawn through on one side. Put the piece back in the collet and bore each end to be a close slip fit on each end the part. Now slide the part through the part "holder" and draw in the collet. The stub end of the part will now be held securely and will turn truly central. Now, one can proceed to face, drill and tap the stub end.
The attached photos show how this was done.
The problem is now how to hold the part so this operation can be performed and to keep everything centered as the extra length of material used to hold the part in the 4 jaw chuck was cut away after forming the donut. One end of the part is now the donut and the other end a short circular stub only 1/8" long.
These miniature parts really need to have their own unique holding pieces that, likely, are going to be only used once to make the number of parts needed. It is whatever one can come up with and better still keep it simple.
A scrap piece of 3/8" dia. brass was drilled in a collet at one end to be slightly under size on the donut end (3/16") and on the other circular stub end (1/8"). The piece was then taken out of the collet and sawn through on one side. Put the piece back in the collet and bore each end to be a close slip fit on each end the part. Now slide the part through the part "holder" and draw in the collet. The stub end of the part will now be held securely and will turn truly central. Now, one can proceed to face, drill and tap the stub end.
The attached photos show how this was done.
Re: A Real Dirty Job
Further machining on the tiny brake parts. One has to be patient here with the setup's as any little error will be seen.
Last edited by Carrdo on Fri Jun 21, 2019 4:03 pm, edited 1 time in total.
- JBodenmann
- Posts: 3865
- Joined: Sun Oct 26, 2003 1:37 pm
- Location: Tehachapi, California
Re: A Real Dirty Job
Hello My Friends
I have been enjoying your threads on the Hudsons and have been admiring your fine work. Hopefully someday you can bring your engine to the Alcalde & Coalfield.
Jack
I have been enjoying your threads on the Hudsons and have been admiring your fine work. Hopefully someday you can bring your engine to the Alcalde & Coalfield.
Jack
Re: A Real Dirty Job
J. Bodenmann says that he enjoys making all of the little fiddly bits on a locomotive - well I don't - just to hold them for machining is a real problem. Setup after setup.
But I do it...
The Hardinge square collets are amazing for holding square pieces but so is the price.
Making another single use holding fixture for the front eyebolt which I really don't want to do.
Making a second split holding fixture for the same part which I REALLY don't want to do. This is a one time use only fixture as one has to hand file the slot in the fixture so that the tapered part on the eyebolt is a nice push fit in the now tapered slot. And the eyebolt must lay flat, be on centre and square in the fixture for the drilling operation. Almost impossible to do.
One has to find centre here by eye, using an eye loupe, very good lighting and check, check, check. And if anything moves during drilling...
But I do it...
The Hardinge square collets are amazing for holding square pieces but so is the price.
Making another single use holding fixture for the front eyebolt which I really don't want to do.
Making a second split holding fixture for the same part which I REALLY don't want to do. This is a one time use only fixture as one has to hand file the slot in the fixture so that the tapered part on the eyebolt is a nice push fit in the now tapered slot. And the eyebolt must lay flat, be on centre and square in the fixture for the drilling operation. Almost impossible to do.
One has to find centre here by eye, using an eye loupe, very good lighting and check, check, check. And if anything moves during drilling...
Last edited by Carrdo on Mon Jun 24, 2019 12:32 pm, edited 1 time in total.
Re: A Real Dirty Job
And when you are all done...
Days and days of work, concentration and tense setups for... not much!
Then you discover that the parts won't fit together as the Langworthy drawings say drill a 1/16" hole in the front and rear eyelets and when you do that the 1/16" dia. threaded brake adjusting rod won't pass through!
I guess that my 1/16" drill drills tenths undersize so then one has to do the cross drilling all over again with a #52 drill which is 0.0635". Also, threading the ends of the brake adjusting rod increases the rod dia. slightly on the threaded section. And don't try and file the threaded ends down as the thread here is so fine (a 1-72 NC) there will be insufficient thread depth left.
A small point but - the Langworthy drawings are excellent but whoever did the drafting was an excellent draughtsman but it becomes obvious (he/she) never made the parts.
Days and days of work, concentration and tense setups for... not much!
Then you discover that the parts won't fit together as the Langworthy drawings say drill a 1/16" hole in the front and rear eyelets and when you do that the 1/16" dia. threaded brake adjusting rod won't pass through!
I guess that my 1/16" drill drills tenths undersize so then one has to do the cross drilling all over again with a #52 drill which is 0.0635". Also, threading the ends of the brake adjusting rod increases the rod dia. slightly on the threaded section. And don't try and file the threaded ends down as the thread here is so fine (a 1-72 NC) there will be insufficient thread depth left.
A small point but - the Langworthy drawings are excellent but whoever did the drafting was an excellent draughtsman but it becomes obvious (he/she) never made the parts.
Re: A Real Dirty Job
The major diameter of a 1-72 class 2A thread is .0724/.0689, therefore a #52 drill is still undersized. If it does allow the parts to fit, your major diameter is woefully out of tolerance.Carrdo wrote: ↑Mon Jun 24, 2019 12:26 pm Then you discover that the parts won't fit together as the Langworthy drawings say drill a 1/16" hole in the front and rear eyelets and when you do that the 1/16" dia. threaded brake adjusting rod won't pass through!
I guess that my 1/16" drill drills tenths undersize so then one has to do the cross drilling all over again with a #52 drill which is 0.0635". Also, threading the ends of the brake adjusting rod increases the rod dia. slightly on the threaded section. And don't try and file the threaded ends down as the thread here is so fine (a 1-72 NC) there will be insufficient thread depth left.
If your rod diameter is 1/16", the thread size should be an 0-80, and even for that thread the major diameter of the rod is oversized (should range between .0595/.0563).
H
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: A Real Dirty Job
Harold is entirely correct but the parts now fit together well enough as modified.
The Langworthy drawings said produce a 1/16" x 72 thread on a 1/16" dia. rod. I used a split and adjustable 1-72 NC die and the 1-72 NC nut fits well enough even though it is out of tolerance. To make a custom, non standard dia. rod of that length, that small and have it come out on size, straight and not tapered - that is not going to happen. And to turn down a 1/16" dia rod to the correct OD for an 0-80 thread, one would need a 1/16" dia. collet (which I have), but since one end of the 1/16" adjusting rod is threaded 1" long - this is not going to happen either. Even I have my limits.
We are not making Boeing MAX 737 parts here.
The Langworthy drawings said produce a 1/16" x 72 thread on a 1/16" dia. rod. I used a split and adjustable 1-72 NC die and the 1-72 NC nut fits well enough even though it is out of tolerance. To make a custom, non standard dia. rod of that length, that small and have it come out on size, straight and not tapered - that is not going to happen. And to turn down a 1/16" dia rod to the correct OD for an 0-80 thread, one would need a 1/16" dia. collet (which I have), but since one end of the 1/16" adjusting rod is threaded 1" long - this is not going to happen either. Even I have my limits.
We are not making Boeing MAX 737 parts here.
Re: A Real Dirty Job
Endless end rounding here for me.
End rounding on the brake shoe hanger links.
End rounding on the brake shoe hanger links.