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worm gear help

Froneck

Titanium
Joined
Dec 4, 2010
Location
McClure, PA 17059
I posted a while ago requesting information on the back-lash adjustment screws and received no replies. Simple mechanism I seen it used on another lathe. A worm gear is cut into a jam nut and 2 screws used as the worm. Loosen one, tighten the other will rotate the jam nut removing back-lash. However in my machine the screws will not tighten, little more than snug and they push away from the worm gear. Lathe runs great, cross fees screw shows little wear if any at all.I mentioned they were 3/8-16 but in checking they are 1/2-13. The hole they fit into is .550 so 9/16" will not fit. .550 gauge pin is snug fit. I don't know if P&W had special screws made. To help I used longer screws that extend past the gear and made a half round cradle with .500 on the same centers as the .550 holes to hold the screws on the gear but didn't help, better but not much! Gear looks to be in good shape!
What is the best way to measure the worm gear to determine what worm is needed and what centers are required.
 
The item is in the lathe under the cross slide next to the cross-feed nut. To take a photo I will have to disassemble the cross feed and not have the machine available. If I know what I'm doing then I'll plan it and have everything available to complete the project. Will a photo of the item in the parts manual work, it's an assembly drawing, pictorial type.
 
The item is in the lathe under the cross slide next to the cross-feed nut. To take a photo I will have to disassemble the cross feed and not have the machine available. If I know what I'm doing then I'll plan it and have everything available to complete the project. Will a photo of the item in the parts manual work, it's an assembly drawing, pictorial type.

Might help. Figure 42 in the late supplement section. If the "screw worms" push away does that not say the "nut" is stuck, not turnable?

Screws appear unsupported where their "worm" threads are - suggesting they are only supported in the .550 bores - suggesting that they are not off the shelf socket head cap screws

Probably should also post the related parts list on the next page

If it has yet to be apart, possibly you will find some helpful doofus pinned it in place - no longer adjustable
 
I dissembled the machine, had to remove the spindle because someone put a spacer in the wrong place, leaked oil is putting it lightly, more like oil poured out on the chuck side. Fixed it, now not a drop! While at it I noticed the bearing in the apron were rusty on the bottoms so all bearing were replaced but all other bearing in the machine were like new! In the process the cross slide was removed bearings also replaced. Since I had it apart figured it wouldn't hurt to replace the bearings! Nut is not worn out, seems to be in good shape, screw is also in good shape, no signs of wear. I think it's hardened and ground. Adjusting "jam" nut is also in good shape and turns freely. Adjusting screws will turn and adjust back-lash but can't be tightened. In another lathe a Sidney I think had the same adjustment style both screws could be tightened to prevent movement. The system works but screws can't be tightened so I too think some doofus put in the wrong screws, material list only has part numbers and why I asked help to determine what fits the worm. I'll get the manual, it has the supplement section, and make a few photos but there is nothing to see other than the assembly. I was thinking of getting very long 9/16 socket head cap screws and cut off the threads and re-cut the un-threaded portion to .550 and cut a "worm" to match the gear, only has to be about 1/2" of "worm".
 
Knowing P&W, (they never made anything half ass) I would expect both the "nut" and the pair of "screws" were made with proper worm style threads
 
Been a few years since I rebuilt the machine but I seem to remember looking at the worm gear and the tooth pattern was Vee and the 1/2 hex head cap screw threads fit but because of the way worm gears are only one "tooth" is full engaged so other threads might have fit better. At least back when this machine was made, I doubt the screw was a CNC generated worm. I didn't include the parts list a photo of the complete #12 line could not be read, photo of the description would not include the part number or item number. The description of item #12 is "Feed Nut Adj. Screw" exactly as I have written. CIMG1934.jpg
 
VM has the parts book so I did some screen shots
 

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Thanks John, that is exactly what is in my book. Unfortunately a part number is used for the screw #12. Looking at the manual standard screws that are used to attach various items are not numbered nor included in the part description so it's probably not a standard screw. I am at a loss to determine what thread if Vee threads are used for the worm. I'm thinking they are Vee from my memory of the worm gear cut into the #11 Feed Screw Take-Up Nut. The diameter of #11 is about 1-3/4". In the drawing john provided the feed screw looks easy to remove in that it is connected the the handle via a spline. Simply remove the screws holding #9 and rotate the handle enough pushing #9 bracket back enough so it the bearing and screw can be turned and feed screw removed but not shown is the view with machines having a taper attachment, it becomes a bigger issue in that the assembly has a series of balls in a track to provide movement. What would help the most is if someone has the newer Model "C" machine can unscrew one of the #12 the Adjusting screw and measure it. I can if necessary remove my 2 #12s and rotate #11 with #24 cover removed and be able to look at #11 and possible determine the type tooth that has been cut in it. Someplace in my pile of used taps I do have a 17/32-13 tap. Probably can make a 1/2assed gauge to turn a 9/16" Allen Cap screw and thread it to fit better.
 
Not especially late model - serial 1349 is before they changed to five digit serial about 1952. Any 16" serial 1350 up will have those screws

Note the VM version of the manual is from Cincinnati - so it may be worthwhile to contact the folks that sell Cincy parts with that part number. cmike - who posts in the Cincy / USA Heavy Iron forum, knows who sells those parts

Here you go from one of his posts

The Fives 800.934.9735
 
Thanks John, I didn't think parts might still be available. Over all the P&W is a great lathe, heavily built and easy to operate. Thread stop is a bit of overkill but it works. Need to get the thread selection plate redone it looks quite worn as if possibly an air hose was hanging from one of the gear selector handles and rubbed numbering off. Otherwise lathe is in great shape. I do think my Hendeys are easier to operate but the lead screw reverse on the P&W is far better! Can reverse the feed or lead screw at top speed of 1000RPM! Previous owner must have use it for large hole drilling, tail stock spindle screw was very worn to the point it would be very hard to turn when backing out after drilling. Found a nut on ebay from what looks like a company making bronze accurate machine nuts, it was 3.5" long old nut was only 1.75", re-bored the spindle for longer 10TPI nut. Though 8TPI screw was in great shape no signs of wear (probably hardened and ground) I replaced it with McMaster 10TPI precision screw. Handle was broken and welded, good job turned with almost no wobble but found another from South Bend Carriage on ebay. It's slightly bigger in diameter so pushing large drills with 10TPI screw and bigger hand wheel is easier. While at it I found a 100 graduations dial from B-P knee and fitted it to the handle so not only do I have the scale on the spindle I have a dial on the handle. Feed clutch handles don't engage quickly especially on slow spindle and feeds, handles are a little short too so I did make an extension for X feed one day Y too.
 
Available probably isn't the right word - could be they have the drawing and can get some made, but not especially cheaply - but it never hurts to ask
 
Yeah I think so too and why I said might be available. Knowing what kind of prices they charge for those type items I think I'll be making my own but calling them will not hurt. Some time ago when I had quite a few turret lathes I called for replacement turret locator tapered cups about 1" in diameter X 3/4" long hard steel with taper for the pin ID. I was floored by the price! 6 of them would be more than 3 times I paid for the machine! If I knew what the worm was I can make it and why I was asking how to determine what the gear required.
 
Up-Date

Hi John: I called the number you provided (800.934.9735) to check on the adjustment "screws" for the P&W lathe. Number is a working number but it's to magic track a kids car track. I asked if the number I dialed is correct and they confirmed that I was connected to the number provided.
 
Hi John: I called the number you provided (800.934.9735) to check on the adjustment "screws" for the P&W lathe. Number is a working number but it's to magic track a kids car track. I asked if the number I dialed is correct and they confirmed that I was connected to the number provided.

You could private message cmike and ask if he has a current number

Looks like 800 - 934- 0735, or a little off from what cmike posted

Easy to look up

Online Parts Store - Fives Metal Cutting-Composites
 
up-Date the Up-Date

I called the new number, I can see the simple mistake. Simply a 9 in place of a 0. Got to the right place but no option to get anything for P&W. Messaged cmike this morning, no reply yet.
 








 
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