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  1. #1
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    Default Looking for Information on Pratt and Whitney M-1803 Dividing Head

    I just got a Pratt and Whitney M-1803 dividing head with tailstock and some good collets, no gears, arms/quadrants or dead center. Hopefully I can get some information to make some pieces, as I need them, to compete the kit over time.

    Is there a manual that shows its care, feeding and parts/disassembly? If anyone has one, can I get a copy? My dividing head is quite stiff, probably congealed lubricant. I don’t want to force anything, I have an amazing ability to break things.
    ,
    If anyone has the arms/quadrant and the dead center assembly can I get a sketch with critical dimensions? From the pictures I have seen, it appears the dead center assembly is a shaft, likely 1/2” diameter at least on the tail end, through a collet shaped sleeve, maybe with some sort of thrust bearing and bronze bushings in the sleeve.

    From the threads I have found, I believe the change gears are 24DP, 3/8” thick and have a 1/2” hole with a 1/16” keyway, is that correct, and is it a single keyway?

    Due to my head’s stiffness, I can not figure out what the collar behind the hole plate locks/disengages and when it is clamped or loose.

    Probably related to the above question, how does the input shaft (via, a mounted gear) turn the gear train to rotate the collet/chuck?

    Also, how is the spindle play adjusted, in my case loosened?

    I will post some pictures, as I can, of disassembly as I clean and adjust.

    Thanks,
    Bob

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    Vintage machinery website has a reprint of pratt whitney line catalogues. Maybe you'll find it in a catalogue?

    Newest catalogue appears to be 1941.

    Here's a link:

    Pratt & Whitney Co. - Publication Reprints | VintageMachinery.org

    Regards,
    Steve.




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    Steve,

    Thanks, I tried that, unfortunately it did not turn up anything I needed.

    Bob

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    You must be the one who bought the recent one on eBay. I also have the P&W 3C horizontal mill. I recently bought a dividing head but I only got one collet and two dividing plates. I am keeping my eyes on eBay for a set of collets and a tailstock. Do you have a 3C mill too or did you buy it to use on another small mill?

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    discodan,

    Yes, that was me. I don't have a 3C mill. I intend to use it on another mill, unfortunately, not a universal table.

    Bob

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    By any chance in the collection of collets you bought did you get any duplicates? I only have one true 4pn collet, a 3/16. I have a 3/4" but it looks like it may be shop-made because it has no markings and is longer than the true 4pn collets.

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    I did find one duplicate 3/8", Private Message being sent.

    Bob

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    Quote Originally Posted by rwilliams View Post
    I just got a Pratt and Whitney M-1803 dividing head with tailstock and some good collets, no gears, arms/quadrants or dead center. Hopefully I can get some information to make some pieces, as I need them, to compete the kit over time.
    You can "adapt" rather a lot of the needfuls so there is less to "make". Dividing plates of "comparable" size and attach method, crank, quadrants - all are sold for the many "modern" DH and rotabs as separate kits, and in several sizes - brand-new.

    Even if not US-made, they mostly work OK and can be had "now" not after four-plus years of scouting used ones, giving up and buying a whole 'nother DH, the day comes you actually NEED one [1]..

    Altering shaft or hole diameters, fabbing spacers, bushings, and brackets should be far less work than making plates and quadrants from a cold start.

    2CW

    [1] Many shops, a rotab with dividing adapter kit is far the wiser investment anyway. Bugger will actually be USED more often, as "DH" also means "Dust Holder".
    Last edited by thermite; 07-22-2019 at 05:08 PM.

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    During this dialog, there are references to a Pratt & Whitney 3C mill. Newbies may be confused because they don't use 3C collets. The only thing that I can think of is the adjustable vertical head which came with my #4 Burke. It uses 3C collets too. Perhaps the P&W included a vertical head which used them. It would be a great addition to a smaller horizontal and the folks using them would know it was a popular collet.

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    thermite,

    Your quite correct about being creative, "work smarter not harder". The three original plates I did get, it is the gears and quadrants I will have to be creative about. I think you are on track about the more common usefulness of a rotary table.

    Bob
    Last edited by rwilliams; 07-22-2019 at 06:03 PM. Reason: remove duplicate

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    Quote Originally Posted by rwilliams View Post
    thermite,

    Your quite correct about being creative, "work smarter not harder". The three original plates I did get, it is the gears and quadrants I will have to be creative about. I think you are on track about the more common usefulness of a rotary table.

    Bob
    Quadrants are sooooo easy to adapt - off the back of several sizes in the market. And soo wasteful of raw stock if cut from the edge of plate.

    Gears? Think on that. How often would you actually USE those even if you had a brand-new mill and the OEM full set for it?

    Even if/as/when you DO have the need, how much TIME would that take, and at what potential scrap rate, compared to a drawing and an RFQ, CNC shop that is in that end of the bizmess, all-day, all year, and has to be cost-competitive with the rest of them?

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    Here's a link to some pics of a 3c mill, and you can see a pic of tooling that was available along with a vertical head.

    Steve.

    Pratt & Whitney 3C Precision Bench Miller

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    I also found a 9 year old thread discussing this model head, and there they said it uses "4pn" collets.

    Steve.

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    Quote Originally Posted by stevewatr View Post
    I also found a 9 year old thread discussing this model head, and there they said it uses "4pn" collets.

    Steve.

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    Doesn't really much matter. Not as if it was a Hardinge running three shifts, 24 x 6 with its tongue hanging out as it turned and parted-off one widget after another from rapidly-advanced rod or bar stock.

    My Yuasa rotab is #2 MT, the Ellis DH/indexer combo # 9 B&S (plus threaded nose). "native" collets exist for both (and 40-taper..). All of mine stay in the drawer as "last choice winners".

    In either case, a body would only have to make ONE - and solid, no split - to adapt to "whatever' - from dirt-common 5C "nose closers" to (n) jaw chuck.

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    A bit more information and pictures, unfortunately I could not figure out how to sequence the pictures.

    The “new to me” Pratt and Whitney M-1803 is very stiff, cannot be turned by the worm/dividing plate shaft. Soaking in solvents has not helped so I am trying to disassemble it to clean dried grease and find out why it is so tight and what is needed to free it up.

    I am trying to be slow and cautious in order to not do harm, something I am highly qualified to do. So far I have been able to safely get it partially disassembled.

    The tail shaft housing comes off easily after removing the threaded collar (using a small pin spanner) around the input shaft. The tail shaft housing is held by four screws and located by two dowels. The tail shaft is removed by removing the nut on front end and sliding it out the back. Burrs or dried grease can make this a bit more challenging. The keyed helical gear slides off the shaft as it is removed. There are needle bearings fore and aft in the housing supporting the tail shaft.

    The access plate on the side opposite the tail shaft housing covers a ND 5200 bearing and its retaining screw. Three of the plates retaining screws go through the base uprights and clamp the head when it is horizontal. The bearing is a close, but slip fit to both housing and the worm shaft. I was able to remove the worm and its shaft by unscrewing it out of the worm gear toward the bearing side provided there are no burs or raised area on the shaft, most likely near the end where the index pin is clamped. I suggest not removing the spindle housing support (held by three screws) behind the tail shaft housing. It is a precise, tight, doweled fit into both the support housing and spindle housing.

    The square cover and bushing on the backside of the spindle housing supports the back end of the spindle and protects a pin spanner nut and other inside pieces parts. I made a pin spanner wrench to reach into the recess and remove the nut. The nut covered another ring/plate with a dowels and four screws, two fillister head and two with a tapered head and shank. This plate rotates with the worm gear and spindle when the spindle is rotated slightly using a wood dowel.

    This is as for as I have been able to get. I have not figured a way to get the second ring/plate out. If anyone has gotten the spindle out please tell me what to do. If anyone has been into something similar I welcome advise.
    Attached Thumbnails Attached Thumbnails pin-spanner-nut-input-r.jpg   spanner-wrench-1-r.jpg   parts-side-rear-r.jpg   spanner-wrench-2-r.jpg   ring-behind-spanner-nut-r.jpg  


  17. #16
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    More Pictures.worm-shaft-r.jpgtailstock-housing-r.jpgworm-shaft-partialy-r-unscrewed.jpg

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    Do you have the drawings that show what is inside the thing? I think I have a set of prints for it.

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    Rivett608,

    I only have the sketches I am making as I get pieces apart and guesses about the internals I can't see yet, especially what holds it together. I appreciate anything you can find, if anything turns up I will give you my email or what ever to get it to me. Also, I sent you a PM a few days ago, before I got this far, with questions based on a post you made earlier about these and the wood case.

    Thanks,
    Bob

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    Bob, I sent you a PM with my phone number to call me. I’ll go look for the drawings.


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