Help with P&W 10" engine lathe

[foxmxrcer]

So, I'm not the greatest at math... So I did this all by taking measurements and (hopefully) "common sense".....

Lead screw is 6tpi, square cut thread. I need a 24 tooth gear for the chasing dial. My gear will be 1.35" total od, and 1.135" od to the root of the teeth. I'm going to use 1/8" plate steel so I can cut the gear by hand (drill holes at the root, and band saw the rest, the file to final fit).... Can anyone verify my measurements? Or at least confirm if I'm close?

Thanks

Per the machinery's handbook I just looked at.... It looks like it will be 1.3" od.

Seeing as I've spent a few days looking for this answer and never finding it, but finding a lot of people asking the same thing... Hopefully this helps someone in the future.

[BCRider]

Fox, do you have a milling machine? Any way to index such as a cheap Spindexer?

Keep in mind that the "gear" you make will have to be cut to fit the square thread and not a gear rack. So it will not have the "usual" gear tooth angles and profile. It will, however, need some curve to the flanks of the teeth to roll into and out of the square cuts correctly.

How good are you at CAD? You could design a suitable one tooth fly cutter tool shape that you can use to cut the teeth of your gear. But you need a way to easily index it to 24 positions and hold it. And if you don't have anything more fancy that sort of screams for a 5c Spindexer and a mill.

PS, since you're making it so thin it occurred to me just as hit the Post button that you could do this in your lathe. But you still need a way to index the wheel to 24 positions.

[foxmxrcer]

Fox, do you have a milling machine? Any way to index such as a cheap Spindexer?

Keep in mind that the "gear" you make will have to be cut to fit the square thread and not a gear rack. So it will not have the "usual" gear tooth angles and profile. It will, however, need some curve to the flanks of the teeth to roll into and out of the square cuts correctly.

How good are you at CAD? You could design a suitable one tooth fly cutter tool shape that you can use to cut the teeth of your gear. But you need a way to easily index it to 24 positions and hold it. And if you don't have anything more fancy that sort of screams for a 5c Spindexer and a mill.

I wish I had a mill.... I've been keeping my eyes open for a j head, but haven't found a good deal on one yet. I Was more or less planning to cut the gear by hand, and file it to perfection (10 hours later...). However, I have a lead to a guy with a 3d printer, and if the price is right, might just go that route. I have no CAD experience, as I don't even own a computer or Internet (weird in this day and age for a 26 year old, eh?) All I have is my phone. I have a laptop that I use at work, but I'm not going to buy CAD for that haha.

[bytewise]

Threading dial gear

I suggest you make a lantern gear like those used in clocks. It can be made using a drill press and lathe. Twelve pins between the flanges are the teeth. The body can be mounted at the helix angle of the lead screw so the pin teeth mesh perfectly. I looked for a picture pf mine but could not find one. Sorry.
Hugh

[foxmxrcer]

I suggest you make a lantern gear like those used in clocks. It can be made using a drill press and lathe. Twelve pins between the flanges are the teeth. The body can be mounted at the helix angle of the lead screw so the pin teeth mesh perfectly. I looked for a picture pf mine but could not find one. Sorry.
Hugh

https://sites.google.com/site/anniesdtportfolio8a/_/rsrc/1299693218534/da-vinci-invention/lanter%20gear%20pic.jpg?height=200&width=185

Like that(but with 2 flanges as you said)? That would be a very interesting gear, but I can definitely see how it with work pretty good..... I'll keep that one in mind, thanks.

[BCRider]

The problem with making a lantern gear would be your lack of any indexing equipment again. And some extremely careful layout as well.

Given your tooling I think you hit the nail on the head with the idea of cutting and carefully filing to fit on a piece of your own.

Because it's a square cut thread keep in mind that the teeth will need to look very odd and not like a regular gear at all. They'll need to all look like short fat barrels with the fat dimension sized to just a hair less than the groove of the shaft thread. And the top and bottoms of the teeth narrowed to allow the teeth to roll into and out of the groove without binding.

If you carefully measure the width of the thread and width of the gap and the depth of the gap some kind soul might be persuaded to do a CAD drawing for you to aid in your layout.

I would also start with a turned part to work with instead of just some flat sheet metal. The part would be turned with a thinner outer portion where the diameter of the "shelf" at the base of the outer ring is the depth of cut needed on the teeth and the OD is the major diameter of the gear you need. The shoulder would then act as a guide for your sawing down into the ring to form the teeth.

[foxmxrcer]

The problem with making a lantern gear would be your lack of any indexing equipment again. And some extremely careful layout as well.

Given your tooling I think you hit the nail on the head with the idea of cutting and carefully filing to fit on a piece of your own.

Because it's a square cut thread keep in mind that the teeth will need to look very odd and not like a regular gear at all. They'll need to all look like short fat barrels with the fat dimension sized to just a hair less than the groove of the shaft thread. And the top and bottoms of the teeth narrowed to allow the teeth to roll into and out of the groove without binding.

If you carefully measure the width of the thread and width of the gap and the depth of the gap some kind soul might be persuaded to do a CAD drawing for you to aid in your layout.

I would also start with a turned part to work with instead of just some flat sheet metal. The part would be turned with a thinner outer portion where the diameter of the "shelf" at the base of the outer ring is the depth of cut needed on the teeth and the OD is the major diameter of the gear you need. The shoulder would then act as a guide for your sawing down into the ring to form the teeth.

There is my "CAD drawing", haha. Each line represents the center of a tooth, equally spaced every 15*. I figured I'd I measure the width of the grooves in the lead screw, then slightly under size, that would give me an acceptable tooth width. As far as actually making it, I was thinking of cutting a disc and attaching it to the shaft, then Chuck it up in the lathe and turn it to the appropriate od, and then score a line with the tool bit for where the root of the teeth will be. Then mark every 15* for location. I wonder if I could use that gear maker/tool grinder attachment/indexing thing I posted a picture of, to make indexing it easier? I'll have to take a closer look at that.

[foxmxrcer]

Little bit of an update in case anyone cares, or potential future Pratt and Whitney lathe owners that want a chasing dial. As I said, I had found a guy that does 3d printing, and I got him to help me out. He sent me measurements of a dial for an atlas 10"lathe, because it looked as though it would be easily adapted to my carriage and about the correct size. Well, it seems it will be a perfect fit, aside from the fact that it's a 16 tooth gear. So, after talking with him (Dennis), he came up with a 24 tooth gear to fit my lead screw, and sent me a drawing with measurements of it, plus this 3d drawing. The price was very reasonable (under $75 for the entire thing), so I went ahead and ordered it. It should be here next week some time and I'll mount it up and post some pictures of it. If anyone is interested in purchasing one, or any other chasing dial or parts, his email address is on the dial in the picture.

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[foxmxrcer]

Exciting news update! My chasing dial arrived yesterday, and looks fantastic. Very good print quality. The gear meshes perfectly with my lead screw, and was very easy to mount. I drilled and tapped a 5/16"-24 home in the side of the carriage for a allen head cap bolt I had laying around, along with some random washers. After clocking the dial, every hash mark lines up perfectly with the engagement points of the half nuts. I highly recommend Dennis ( [email protected] )for any of your 3d printing needs, he's great with communication, very intelligent, and does very good work. Now, onto the pictures. Please ignore the mess, as my shop is also my garage. I included a picture of the entire lathe as well, to show it in its updated form, and I also built a shelf on the tail end after seeing another p&w with one (had a tool box and collet rack however)

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[foxmxrcer]

.

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[foxmxrcer]

So, I managed to score a set of collets, collet centers, and arbors pretty cheap on eBay tonight. Unfortunately the shipping cost more then the items, but oh well. Not sure what the arbors would be used for? Different machine? Mainly bought that lot for the centers. I'm excited though!




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[reggie_obe]

In the first image, the second through fifth items would be of interest to a P&W milling machine owner. Appear to be: 2 face mill holders; a stub milling cutter arbor; end mill holder.

[alanganes]

Any way to index such as a cheap Spindexer?

If you look back through the photos the OP posted in post #17, the sixth or seventh one down sure looks to be some sort of dividing head or fixture. I'd bet one of those circles will get you the number of teeth you need for a dial.


Edit - Oops, missed the update posts. Sorry about that. Never mind, nice job on the threading dial. That dividing fixture will still be nice to have around the shop for when you have a mill and get to that sort of thing. Hang on to it and clean it up. It will make a handy piece of gear.

[foxmxrcer]

In the first image, the second through fifth items would be of interest to a P&W milling machine owner. Appear to be: 2 face mill holders; a stub milling cutter arbor; end mill holder.

I was kind of figuring they were milling collets. I mainly wanted the lot for the centers (assuming I get around to making a face plate). Know anyone interested in the (potential) milling collets?

If you look back through the photos the OP posted in post #17, the sixth or seventh one down sure looks to be some sort of dividing head or fixture. I'd bet one of those circles will get you the number of teeth you need for a dial.

Unfortunately I've come to the conclusion that none of the fixtures are for my lathe. Likely most are for the m head Bridgeport that the guy had for sale also. So, they sit in a box in my garage until I can 100% confirm what they are so I can sell them to someone that can use them.

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[alanganes]

Unfortunately I've come to the conclusion that none of the fixtures are for my lathe. Likely most are for the m head Bridgeport that the guy had for sale also. So, they sit in a box in my garage until I can 100% confirm what they are so I can sell them to someone that can use them.

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You are correct, they are not for the lathe, but things like that indexing head are pretty versatile and not necessarily machine specific. They can be used with most any mill or grinder. I would not necessarily be in a hurry to unload them if they were mine. Unless you really need the room or the money raised from selling them, you may want to just sit on them for a bit until you get feel for what they can be used for.

Overall you did pretty well for 200 bucks, I think. That looks like a really stout machine for a 10" lathe. I'm guessing you have easily gotten $200 worth of fun messing with it already.