Atlas Pick-O-Matic Drive Gear 10-1213

[shadetreedad]

Blue,

That printed gear looks great! You're well on the way

Regarding the sliding gears. The small gear (10-1243A) is 20 tooth. The large sliding gear (10-1242) is 40 tooth and the same profile as a 40 tooth change gear. And this sliding gear has the female 20 tooth gear profile on the inside to mate with the gear (10-1243A) You will notice the gear (10-1243A) has a small groove for a snap ring. The snap ring/groove really isn’t necessary if you want to leave it out of the print. It is designed so you can't move the sliding gear “IN” too far. If you did, it wouldn’t hurt anything, only change the gearing.

Important Note:
The official exploded diagram (see image) has an error in assembly. Gear (10-1242) should be to the left side of the snap ring on gear (10-1243A). When I first put mine together (following the diagram) I struggled mightily with threading. After looking at actual photographs in the Pick-O-Matic manual the error was obvious. I've attached two photos on my lathe that depict the correct orientation of “IN & OUT”. You will also notice in those images I left off the Gear Link with Knob (10-1232) for clarity. Plus, I added a couple more pictures with just the gears in the same orientation. My gear (10-1243A) is very worn in the IN position!

The handwheel knob is designed so you don’t need a wrench to tighten down the complete gear set. That’s how Atlas could claim you can change into many different speeds/TPI without tools. I just use a regular 3/8” nut on my gear drive as it gives me more confidence the gear set is tight. The through bolt/stud (10-1230A) can be a standard 3/8” carriage bolt with half the head ground off if you don’t have the factory bolt/stud.

Another interesting note:
Your depicted tumbler set has a tin gear guard on the lower gear. This needs to be removed before the small Pick-O-Matic gear (10-1243A) will be able to engage in the OUT position. I think these tin gear guards were standard on gear change models, but I'm not sure about that. Nonetheless, that Pick-O-Matic gearbox probably was never operational, at least correctly, on your machine.

This is a lot of info and I'm sure I've overlooked a bunch. As you move forward, we'll iron out any issues that arise.

All the best!
Mike

 

[Blue]

Thanks Mike! The pictures are fantastic and should be enough to go on for drawing and making the 3D printed gears. Since I have already gone through the pain of making the involute gear teeth and can easily make gears of (nearly) any tooth count, making these two will hopefully be simple. Worst case, I assume that I could stack two gears and manually flip them around on the shaft if need be to serve the same function. But duplicating this will be much more fun.

To clarify - the 40T in-out gear is moved by hand by sliding the gear itself on the 20T "long" gear? The depicted knob is just to hold the stack tight? i.e. no loosening of the knob/nut is needed to do the in/out movement... just disengage the tumbler gear and slide it in/out as needed with your finger/screwdriver/tool? I was trying to figure out from the exploded diagram just how that knob allowed you to push the gear in or pull it out...


Referring back to the drive gear (that I will likely reprint since I printed the keyway in it and cannot broach that area) - Is the 10-1257 sleeve bushing actually used? The hole in my Pick-O-Matic for this drive gear is barely over 1" in diameter, meaning there is no room for said bushing to fit unless the drive gear shaft OD is reduced by the thickness of that bushing. Being a printed gear, the bushing seems like an excellent idea to prevent the housing hold from cutting down the OD of the plastic drive gear - unless the leadscrew naturally holds it dead-center.

(Yet another) question - I see a Phillips pan head screw at the top of your tumbler - used for holding the cover top half in place - what is the thread on that screw? I managed to damage my nice old brass threaded thumbscrew (don't ask...) and am now unable to check the threads. It seems like it should be 10-24, but my replacement screw binds up in the hole after a thread or two.

 

[Blue]

Normally I run gearing through a banjo with the final leadscrew gearing ~ A= 0.004, B= 0.008, C=0.002. With this setup there is always a “perfect” speed.

Is the gearing that you use for this 56 54 24 52?

If I am going to test the drive gear, I need to print a the in/out gears and few change gears to actually move the leadscrew... Might as well go for the ideal general use speeds

 

[shadetreedad]

Blue,

I've attached a series of photos that should shed some light on the sliding gear operation. #1 starts with the sliding gear IN. And #8 is ready to go in the OUT position. On most of the photos I removed the large washer that holds the sliding gear on & the Gear Link with Knob (10-1232) for better visibility of gear engagement. They both need to be installed for operation.

Referring to the Drive Gear bushing I've attached a photo of my bushing (10-1251). It is very thin and right at 1” so I assume yours is still in the gearbox. I don’t see the bushing number you reference (10-1257). Could that be a typo or am I looking at the wrong bushing?

I forgot to check the threads on that screw at the top of the tumbler. I'll look at it tonight.

I've attached the gear set up I normally run. There are other ways of achieving these lead screw speeds, but I have several spares of each of the gears depicted. So, if I broke one (hopefully not!) it would be easily replaced.

Important Update:
I have one more correction/addition I just realized for removing the upper shaft in the Pick-O-Matic gearbox. There is a set screw holding the shaft in place as depicted in the attached photo. On the gearbox I took apart it was already loose, and I didn’t realize it was even there until taking a couple more photos.
Sorry if that caused anyone confusion.

I'm still learning too!

Mike

 

[Blue]

Thanks for the in/out gear "demo". That was really helpful. I assume that the gears installed are not the 2/4/8 configuration, since there are no "F" gears installed.

But, to clarify, your preferred "normal running" configuration is:
D = 64
E = 36
F(B) = 32
F(F) = 64
In/Out = IN

The parts diagram in my 1st post shows the bushing as 10-1257, and is the bushing that appears to already be in your "Output Shaft Bushing" picture. Maybe my diagram has a typo, or the 7 is really a 1? Hard to say, but we are definitely talking about the same bushing.

Spoiler: Output Shaft Bushing Picture

I was referring to the bushing the bronze bit that the calipers are touching.

I will need to clean some grime off of mine to get a better look. Based on my quick measurement yesterday, the bushing is probably still in mine, so all should be good

 

[shadetreedad]

Blue,

You are correct. I removed the “F” Position gears to minimize confusion.
My normal setup is exactly as you described.
D = 64
E = 36
F(B) = 32
F(F) = 64
In/Out = IN

The thread pitch on the panhead screw at the top of tumbler is indeed 10-24.

Since starting this conversation with you I have looked closer at the Pick-O-Matic manual/drawings than ever. After our confusion over the 10-1257/10-1251 part numbers and the issue with the sliding gear I decided to scan all five of the different Pick-O-Matic exploded drawings that I have (attached). Turns out Atlas had the typo with our bushing confusion. The oldest drawing lists it as 10-1257. The later four list it as 10-1251.

Another major discrepancy in the drawings is the sliding gear setup. The oldest drawing has the gear 10-1243 without a snap ring or groove which I'm sure was correct. And would have worked fine. Then the snap ring/groove was added, and Atlas updated the part number to 10-1243A. However, they incorrectly oriented the image with the snap ring to the left instead of the right side. This is the drawing I used when setting my gears up and caused much confusion why I couldn’t thread properly. On the last two drawings Atlas oriented the gear 10-1243A correctly but didn’t concurrently move gear 10-1242 to the left of gear 10-1243A. So, the only drawing that is actually useable as depicted, is the oldest one.

I'm sure the snap ring was added because users would have slid gear 10-1242 in too far thinking that was the IN position. It would have worked but the gear ratios would not have been what was expected. Exactly my issue.

Anyway, this has been quite a fascinating discovery/journey for me.
And on we go!

Mike

 

[Blue]

Fantastic info! (as always ) Definitely clears up the 1251/1257 confusion.

Thanks very much for the thread size. I figured it was likely 10-24, but the 10-24 screw I tested bound up quickly. It could be dirty or the threads slightly damaged... (don't ask), so I might just need to chase the threads to clean them up. Worst case, it becomes the next size up
What is interesting is that neither the (thumb) screw, nor the threaded hole on the tumbler bracket that holds the top cover in place is not shown on any of the 5 versions of the documentation. Based on the changes between 1944 & 1945, my Pick-O-Matic is not from 1944.

My printed in/out gears are "not bad", but need improvement. I tried a different resin, and it did not go all that well because this resin did not want to come off of the base surface, and some features were damaged during removal. But, this was just a "Concept Test Print" and the dimensions seem good. Best of all, the teeth appear to mesh properly from gear to gear. The inside gear fits into the outside gear just fine. If the inner diameter of the inside looks too large, I designed it to use an off the shelf leaded bronze sleeve bearing to press put inside so that the sleeve rides on the bolt instead of the printed plastic. Seemed wise.

I made an educated guess as to where the c-clip goes on the inner gear by scaling your picture. Appears to be "close enough" to work. It might be a good idea to print the movement limiter/clip as part of the piece, since the outer gear can slide over from the nut side for installation. Should be easy enough to add that feature instead of needing a c-clip that will go flying upon removal.

 

[shadetreedad]

Blue,

That was the first time I noticed the screw or threaded hole at the top of the tumbler wasn’t represented on the drawing. I had to look at the actual photo again to verify. Amazing the amount of errors that can be on a document.

The sliding gear setup looks excellent!
Your idea to print the limiter/clip is the absolute correct thing to do.

You will probably need a bushing in a bushing for your idea to work. Once you tighten down the bolt it will stop the inner bushing from turning. At least if I'm understanding your intentions correctly. If not feel free to disregard.

And I should have included those two dimensions of the 10-1243A gear. So here they are!

Mike

 

[Blue]

My guess was pretty close... I had .580" & 0.60" for the notch

And yes,the idea is a bushing inside a bushing (flanged post over the bolt). The bushing inside the inout gear will be smaller than the gear itself

Updated (just a sketch):

 

[shadetreedad]

Blue,
That in/out gear should work perfectly!
Also, I didn’t see in your pictures a Gear Link with Knob (10-1232) and thought you may want to print one of those as well (see attached). With your skillset that should be pretty easy.
Mike