Monday, September 6, 2010

A Spindle Option for Operation: OVERKILL & a Few Details on My Emco Unimat 3 Multipurpose Machine Project

A member of the Taigtools Yahoo group had asked me about spindle upgrade options in a message there today.  I had purposely been pretty vague on this topic because I've had SO many options and plans, but I'm pretty sure I'm going to use the spindle I had originally started building for the Emco Unimat 3 project after acquiring that lathe bed some time ago.  MEWorkshop group members that have browsed through my pic folders from the MEWorkshop files may recognize this spindle:

Figure 1: ER32 spindle blank with LM67048 tapered
roller bearing and race, L44643 tapered roller bearing
and race, and decent quality Chinese digital caliper for
size comparison.  The LM67048 has an inside diameter
of 1.250" and the L44643 above the spindle has an
inside diameter of 1.000".

The bearing journals on it, indicated by the blued portions in the center of the spindle, are roughed to 1.280", leaving a little less than 0.0300" material to remove on the cylindrical grinder for the bearing at the nose end, which will be a press fit, and right at 0.0305-0.0310" material to remove at the rear journal for a tight fit not requiring a press (the rear bearing must be able to be removed by hand at room temperature and freely move along the journal to allow for proper preload adjustment).  The bore has not yet been roughed out, special washers (probably at least a single needle bearing or ball bearing thrust washer between the preload nut's first conventional washer and rear bearing race and protective covers or custom "washers" to keep chips and swarf out of both exposed bearings) and a nut will be needed to set and adjust the preload on the pair of LM67048 tapered roller bearings in the custom headstock housing, threads for the preload nut will need to be cut, a keyway will need to be cut at the rear of the spindle to retain the timing pulley with a square key, the internal 8-degree (16-degree included angle) will need to be ground to the proper size and length, and the M40x1.5 threads to retain a standard ER32 collet nut will also need to be single-pointed once the grinding operations are completed.  I'm sure that most if not all of the grinding operations to the spindle itself can be performed without disturbing the spindle in the cylindrical grinder's chuck to ensure concentricity to extremely tight tolerances.  Threading will then be single-pointed with the spindle's ground surfaces protected where it will be secured in jaws of my Sherline 4-jaw chuck and centered to within 0.0001" with the aid of my Starrett #25-511 indicator, and the 1/4" 60-degree carbide threading tool (included with the Sherline threading attachment, a quality USA manufactured brazed-carbide bit, not a generic imported version) will be mounted in a custom holder in the Sherline compound rest to keep the cutting edge facing up while the compound will be rotated to the proper 29.5-degree angle in the correct direction as would be used on a conventional lathe.

If you look closely in the pic above or in any below, you can see some chatter marks left in the radius cut behind the nose of the spindle.  A fresh, sharp HSS form tool had been ground to cut this radius, but the material didn't want to cooperate at any speed.  I'm pretty sure the material this spindle was turned from is a 41XX alloy or some variant of that because it doesn't cut well at all with HSS lathe tools and had even required smaller depth of cuts and lower feed rates with the carbide tools used for all other machining operations.  The original blank used for this had been in service in some previous point as a type of roll or roller in what I presumed to be an industrial machine, though it didn't look like it had come from any kind of slip roll machine that I'm familiar with.  This spindle was formed from the end of that part, not the area that appeared to be a hardened roll but a smaller diameter section that had left-hand threads resembling acme threads only with a radiused floor.  The "roll" was scrap that had been collected from the local oil refinery and showed no obvious signs of rusting despite being exposed to the elements while being stored outside for many months if not years; I would have liked to see the machine it had come from.  Anyway, I saved a few of the chips produced from turning this piece and had planned on sending them out for analyzation, but I have since misplaced them.  There will be more swarf from this part after roughing out the inner bore, so I'll make sure to send them off shortly after they're collected.

The dimensions for this component were originally based upon a spare Taig 3/4-16 spindle and headstock I had previously purchased to convert into a dividing head for the mill.  After acquiring the Emco Unimat 3 cast iron lathe bed, I reviewed multiple options for attaching a spindle to it including using stock Emco products, but the Taig headstock was a very good match to the Emco bed ways.  At the time, my only other lathe was the Sherline 4400 and my immediate goal was to have a machine with a larger diameter turning capacity, so I dismissed the option of using the Taig headstock even though I could've achieved the desired 5-5.5" swing with a few custom components and possibly a small spacer but had elected to build my own spindle and headstock to provide the larger swing with a minimum spindle bore of 0.750".  Now that I have the 7x10 lathe (well, it will be a 7x14 after completion of it's mods and upgrades), my goals for the Emco project have changed; though it's more than just "on the back burner" now (I could say that it's figuratively still in the freezer awaiting its chance to be de-thawed so that it can be placed on the "back burner"), it will one day sport a stock Taig headstock and 3/4-16 spindle, but the spindle will be supported in that headstock via two 30203 tapered roller bearings (17mm ID x 40mm OD x 13.25mm thick) and possibly a combination of 5203 dual row deep groove angular contact ball bearings and stock-style 6203 17x40x12mm ball bearings.  Yes, I know that's a bit of OVERKILL for any size of spindle, but any followers of mine here or on any of the groups or forums I frequent that get to know me should understand that I'd rather not take chances when it comes to the modifications and upgrades of my machine tools.

The Emco project will only have one Emco part: the bed casting.  I thought about building a fully functional small scale version of an industrial sized lathe from it, even complete with a quick-change gearbox, auto longitudinal feed, auto cross feed, and possibly even a scale standard taper attachment, but I'm no modeler.  I'm sure it will be of much more use to me if I use its bed casting, the 3/4-16 Taig headstock and spindle, and a multitude of custom machined parts and components as well as a few readily available precision items to construct a 5-5.5" swing by 8-10" between center capacity lathe and also use the stock Taig ER16 headstock and spindle from my Taig mill (with the same bearing arrangement as the Taig headstock used for the lathe spindle) mounted to an extremely versatile and adjustable vertical milling column (VMC) somewhat similar to a Bridgeport series 2 milling machine (but not identical-current plans will require a bit more complexity) that will usually remain attached to the stock Emco VMC attachment points (permanently attached in other words, but most of the VM parts will be removable if so required) to cut down on set-up time and reduce errors caused from transferring parts between machines when multiple turning and milling or radial drilling operations such as keyways cut in shafts, cross holes needed in screws or custom turned and threaded bolts, concentric geometric features must be milled in turned parts, or various other related  operations are required on workpieces.  Each Taig spindle on this machine will be powered by its own motor and my original intent of using the 3/4-16 headstock and spindle as a dividing or indexing head will also be utilized in the lathe's headstock to allow for expanded and somewhat complex operations to be completed in a single set-up, without requiring the part to be moved from one machine to another and back again.  A miniature multipurpose machine, built to my specifications and tolerances to suit my needs better than any commercially available Smithy-style 3-in-1 machine, with a great deal more features and functionality could prove invaluable in nearly any shop.  To shorten this post a bit, I won't go into many details of the additional features planned for it, but I will say that the cross slide will be fairly long and wide with several Taig-sized T-slots for multiple work-holding options, the headstock and motor mounted to the VMC will also have the ability to be mounted in a horizontal milling configuration with rigid mounting locations for horizontal milling arbor supports for using (smaller) conventional horizontal milling cutters, and many other features that I won't mention here just yet.  I'll lay out more details for it sometime later when I can afford to take a break from the Taig mill mods...

Some additional pics of the spindle:

Figure 2: An alternate view of the spindle blank and

Figure 3: This view shows the rear of the spindle

Figure 4: This view shows the caliper measuring the
diameter of the nose, the mistake I had made while
turning this part by not leaving additional material
to grind here to ensure the nose threads will be con-
centric with the bore and bearing journals.

The mistake I had made while turning this piece is outlined in the picture above.  While I ensured that I left approximately 0.020-0.030" material to remove from the outer diameter over the remaining length of the spindle,  I had turned the nose to almost exactly 40mm (or actually less than two thousandths larger at 1.5765").  I don't forsee this as a real problem because I can grind away over 0.008" from a part this size and still retain more than enough on the outside diameter for the threads to be in excellent shape as long as the pitch and minor diameters of the threads are within specs.  I could grind away even more from the nose if needed, but I'm going to only remove a thou or two at a time until I reach 1.570" (38.878mm).  Removing another 0.005" would still be acceptable for most applications, but I'm not going to take more than needed from the nose to ensure the threads will be well within specs instead of at the lower limit of the major diameter.  I warned you guys that I was anal! 

Anyway, it's past my bedtime so I'd better catch some "Z's."  If I don't update these pages tomorrow, you'll know that I've been hard at work designing, engineering, and building more parts for this soon-to-be "Mini-Beast." 

Oh-I added an "adult content" warning to this blogspot page; I can promise you that I won't post pictures of my penis or any nude or lewd pics of exgirlfriends here, I just wanted a warning for the inevitable foul language that I often feel is necessary when writing.  I may not write G-rated children's stories, but I seriously doubt the FCC would rate any of my posts worse than PG-13, and those would be rare.  I felt the warning was appropriate in case any children were reading along with their fathers (or mothers even?).

Until next time, happy machining and do your best to find solutions to your project problems that are "outside the box," or at least a few steps away from the "norm!"

1 comment:

  1. good work,good job,good blog,and good workshop haa