Author Topic: Pennsylvania A3 Switcher (Kozo)  (Read 97062 times)

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1320 on: October 14, 2021, 12:09:28 AM »
Chapter 16.2 – Guide Yokes

The next part is the Guide Yokes themselves.  There are two of these – a left-hand and a right-hand version, one for either side of the tie plate.

A few episodes back I cut the guide yokes from the same 1/8” sheet of steel as the tie plate.  But they are still rough cut, right off the bandsaw.

I took them and double sticky taped them together.  I use this SpecTape double-sided tape.  It works really well to hold parts together.  I find it better and easier to use than CA glue or Loctite for this kind of thing.  It cuts easy, goes on well, and holds quite well.  I’ve never had an issue with parts staying together using it.


With the pieces together like this, I squared them up and took the width to exactly 1.5”.  The length is nice and square, but it is less important.  I just wanted to make sure it was ‘long enough’.


Then I spent a full shop session figuring the exact locations of all the holes I wanted to make in the guide yokes and checking them twice (and thrice).  I’m using the top edge and the right side as my references.  And I shifted all the features 0.030” down from the top so that I have a little bit to shave off after soldering the extra parts in place (stay tuned for future episodes!)

But for now, I’m going to make all of these features with the two plates together like this.  The left-hand one is on top (with the markings you see) and the right-hand one is on the bottom.  The fronts both face out so that they are mirror images of each other.


Here I’ve drilled all the holes and countersunk the three that require it (but only on the left side – we’ll CSK the right side later).


Next, I chain drilled for the slot.  The slot is supposed to be 1/8” wide. But in my experience, if you drill 1/8” wide and use a 1/8” wide mill, you get really ugly looking edges.  So, to fix this I’m chain drilling 3/32”, and will mill it at 3/32”, then at 7/64” and finally at 1/8”.  This tends to give me pretty edges along my slot.


Here I’ve just completed cutting full depth (1/4” in this case) with a 3/32” 2 flute end mill.  I took this slot slowly.  Only 0.025” per pass, lots of passes, to remove the rest of the material in the slot. But look at the edges of the slot – really ugly.  Not sure why.  It might be because the 3/32” drill wanders and doesn’t cut super clean holes.  Or it could be because the mill bit flexes back and forth as it mills the extra material between the holes.  I’m not sure.  But the multi-stage slot milling here will clean it up.


Now, here's after I used the 7/64” end mill.  I did this one in ONE pass, at full depth.  It was only taking off 8 thou per side, so full-depth wasn’t a problem.  You can still see a few marks on the side of the slot, but it is certainly a lot cleaner than the 3/32” pass.


And now, finally a single full-depth pass with a 1/8” 2 flute end mill.  The slot looks quite good now, all that roughness and gouges from before are now gone.  I’m happy :)


And finally, I flipped the part over (well, the two parts) and used a gauge pin to index on the three holes that need countersinking…


And got the countersinking taken care of for the righthand yoke.


Now, after prying the two pieces apart (I generally pound old box knife razor blades – carefully – between the two parts to get them separated.  It's harder than you think!) I have the two guide yoke plates.  The one on the left is the left-hand version and matches the drawing.  The one on the right is the mirror image of the drawing and is the right-hand version.


Next will be to make the little add-on parts for the yokes and silver solder them in place.

Thanks for looking in!
Kim

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1321 on: October 14, 2021, 12:13:09 AM »
Very nice!
 :popcorn: :popcorn: :popcorn:

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1322 on: October 14, 2021, 12:33:46 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: Looking good Kim.

Question/thoughts for you re slot roughing finish- when doing the cut, were your table gibs locked? On my old mill, if I don't lock the gib on the axis that doesn't need to move, I get a slot that looks like I cut it with a Cockshutt 3 bottom plow rather than a mill. Also, if the endmill is held in a collet I get much better results than if I do a light cut with it held in the drill chuck. (yes, sometimes I cheat and do a small slot cut with a endmill in the drill chuck - even though it is a no no and I should know better  ::) )

Your final slot cut looks just fine anyway. :cheers:

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1323 on: October 14, 2021, 05:12:56 PM »
Thanks Chris & Cnr!

Question/thoughts for you re slot roughing finish- when doing the cut, were your table gibs locked? On my old mill, if I don't lock the gib on the axis that doesn't need to move, I get a slot that looks like I cut it with a Cockshutt 3 bottom plow rather than a mill. Also, if the endmill is held in a collet I get much better results than if I do a light cut with it held in the drill chuck. (yes, sometimes I cheat and do a small slot cut with a endmill in the drill chuck - even though it is a no no and I should know better  ::) )

Your final slot cut looks just fine anyway. :cheers:

Good advice, CNR!
In this case, the Z and Y axes were locked (the X is the one I was moving to make the slot).  And I was using a collet for holding the end mill.  I always (well, always like you always apparently :) - meaning everyone in a while, for a light cut I've been known to use the drill chuck if it was already in place. But as you said, I know it's not ideal so I generally don't do that  :embarrassed:).

I've been thinking about it more and I'm leaning toward it being flexing of the small 3/32" mill as the forces change as it cuts through the bits between the chain drilled holes.  The side gouges seem to line up with those places. 

If I cut the entire depth in one pass, I'd likely get less flexing at the tip of the 3/32" mill.  But I worry that a 1/4" deep pass would be too much for a dinky mill like that and I'd break it. (I've done that before and it's not as fun as it sounds  :-\)  So I only take a little each pass (only 25 thou).  And that seems to correlate to the strata of the gouges too. They go in stripes all the way down the sides. In that picture I show, you only see the first row of gouge marks.  But they repeat all the way down the side.  Maybe only every 50 thou, meaning when I go one direction it makes marks on one side, and the other direction makes marks on the other?

But as I said, I don't really know. Those are just my guesses.  I got the same on my taig, and I see it using my (much more rigid) Grizzly mill too.  But the 3/32" mill bit didn't change between the two setups.  Maybe that's the problem?  Maybe my 3/32" end mill isn't very sharp?  That's also a possibility.

Anyway, I'm pleased with the end result!

Thanks for your thoughts on this!  I appreciate it. This is how I learn!
Kim


Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1324 on: October 14, 2021, 09:46:13 PM »
With the main yoke plates drilled and slotted, I need to make the various little add-on doodads for it.  There’s a wider spot along the top of the yoke that will eventually hold up one end of the running boards, and there are the two protrusions that will hold the back end of the crosshead guides.

I started with the simpler one – the running board support.  It only needs to be 1/4” wide, but I chose to make it from 5/16” 1018 CRS because I want to be able to mill down the top so that it is flush and doesn’t have that ridge/divot thing at the joint.  So I cut a couple of short pieces of 1/8”x5/16” CRS and drilled a pair of 1-72 clearance holes to match the ones I made on the top of the yoke plates.  These are for solder holding screws.  The holes are mirror images to match the two yoke plates.


Then I cut 4 little blocks of 1/4" square 12L14 and squared them up so they were all 3/8” long. Next, I drilled a hole in the end for a 1-72 thread – these are to hold them on the yoke plates for soldering.


Next, I rotated them 90o and reamed a 3/32” hole all the way through.  This will eventually be widened to a #3-48 clearance hole for mounting the crosshead guides.  But for the soldering process, it will be used with a 3/32” rod to keep these blocks properly oriented.


Finally, I cut some short chunks of 3/32” stainless steel rod to slide through those 3/32” reamed holes.  Here are all the parts of the guide yokes.  I also put punch pricks on the parts to be soldered to maintain a gap for the solder to flow.


I did a test assembly to make sure it all fit together appropriately, and thankfully, it does :)


Next step will be to take it apart, clean, flux, and solder. But that will be a project for another day.

Kim

Offline 90LX_Notch

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1325 on: October 15, 2021, 12:40:01 AM »
Looking good Kim.

-Bob
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My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Don1966

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1326 on: October 15, 2021, 12:46:31 AM »
Awww the smell of success a loos great Km and a little closer to completing……  :Love:




 :cheers:
Don

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1327 on: October 15, 2021, 05:59:24 AM »
Thanks Bob and Don!  :cheers:
Kim

Offline kvom

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1328 on: October 15, 2021, 07:18:03 AM »
As for slotting, I use carbide endmills, and for small slots like  these chain drilling doesn't make sense.  Using a drill chuck for plunging an endmill seems perfectly OK.

When I made the yokes I seem to remember milling out of one plate each.

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1329 on: October 15, 2021, 06:42:50 PM »
Thanks for the input Kvom.  Just a few questions to help me understand what you're saying:

As for slotting, I use carbide endmills, and for small slots like  these chain drilling doesn't make sense.
Interesting... why is that?   My thinking was that chain drilling reduced the side load on the end mill - which seems especially important for those tiny end mills.  Seems like no chain drilling would lead to much higher sustained side loads. which is how you break them.  Or at least, that's how I break them!  :embarassed:

Using a drill chuck for plunging an endmill seems perfectly OK.
Sure.  But  I thought it wasn't best practice to use end mills in a drill chuck (at least, if you have a choice - I know some small mill/drills ONLY have a drill chuck).  They are held more firmly and with better concentricity in a collet vs drill chuck.  If I'm wrong here, that would be good to know!

When I made the yokes I seem to remember milling out of one plate each.
Not sure what you mean here?  I milled out one plate for each side, I just did them together.  But that might not be what you mean?

Kim

Offline Dave Otto

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1330 on: October 15, 2021, 07:50:39 PM »
Hi Kim

A couple things about milling with a drill chuck, they lack rigidity which equals crappy finish on your part. The second most important thing is most drill chucks are mounted on their arbor buy a taper fit, side loads and vibration may cause the drill chuck to fall off the arbor and dance around on top of your part. If you want to mill with a drill chuck it should be modified so that it can't come apart; this would be done by taping a hole in the end of the arbor and adding a socket head cap screw inside the the chuck that pulls it onto the arbor. If there is enough meat in the chuck body it can be counterbored for the cap screw.

Straight on pressure as in drilling doesn't cause a problem, so if you wanted to say, flatten the bottom of a hole or add a counterbore that would be acceptable. 

Dave

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1331 on: October 15, 2021, 11:57:58 PM »
Ah... Thanks for the explanation, Dave!  Makes a lot of sense.   I think I'm following you there now Kvom.

Kim

Offline Kim

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1332 on: October 16, 2021, 12:06:53 AM »
Today is silver solder day.  So, I took things apart, cleaned them to get rid of oil and grease, buffed the important parts on the 3M Scotch-Brite wheel, added flux (I used the black flux) and bits of silver solder.  Then it was up to the hearth for it:


Here’s the after-soldering picture.  This is 4130 which is higher carbon steel than 1018.  So, I was sure to let it cool more before tossing in the pickle bath (didn’t want to accidentally harden it!)



Chapter 16.3 – Guides

While those parts were soaking in the citric acid I decided to move on with the crosshead guides themselves.  These are very simple parts.  Just a short piece of bar with holes at each end.

I cut them from 1/8” x 1/4" 1018 CRS.  I carefully cut four pieces to just over 3 1/16”.  I try not to cut too much extra because it just gets machined away and wasted.  Unfortunately, the parts need to be 3 3/16” long. Guess I just misread the drawings or misremembered what I read. :embarassed:

Anyway, once I discovered that, I cut some more bar to just over 3 3/16” long (checked, re-checked, and re-re-checked the drawings  :-\).  Then I double sticky taped them together and cut them to length and to thickness.  They need to be 0.235-0.236” wide.


With that done, I promptly separated the parts... then remembered I still needed to drill holes in each end!  Of course, I meant to do that before I separated them.  Ah well. I was able to line them all up in the mill vice to drill them all together.  I pushed them up against a gauge pin to make sure they were all aligned.  Plus, I stuck a chunk of cardboard (the kind on the back of a tablet of paper, not the corrugated kind) between them and the edge of the vice to help make up for any possible slight width difference there might be (since I no longer had the help of the sticky tape).


And drilled 2 holes; 3-48 tapping hole on one side, and a 3-48 clearance hole on the other.


With that, the guides are complete:



After fishing the guide yokes out of the pickle bath and washing them off, they look pretty good.  The black flux seems to leave more of a mark on the parts.  But that’s OK.  I’ll be cleaning them up more as we go.


Next will be to finish up the yokes.

Thanks for looking in,
Kim

Offline cnr6400

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1333 on: October 16, 2021, 01:05:28 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Offline crueby

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Re: Pennsylvania A3 Switcher (Kozo)
« Reply #1334 on: October 16, 2021, 01:19:03 AM »
Great progress, following along...  Got a nice fresh bottle of white popcorn (no kernel shells to get stuck between the teeth)


 :popcorn: