Back Spindle Spider

[Jinx-)]

Thinking to add spider to my lathe, so I'm planning on building one from 4140. The back spindle is threaded, its metric thread 1.5 the OD is 1400. So I'm thinking to bore out hole for ID thread so I can screw it on the spindle and add setscrews to hold it in place. Well if anyone done this before I'm open to any suggestions...
Here is picture of the back spindle with one nut removed to expose threads.

Thank you ;-)

 

[shortgrass]

Plain ol' cold roll will work just fine, no need for chrome moly, here.

 

[Jinx-)]

Then I got 2" OD piece of rusted 1020 just for this
And I made quick sketch what I think I'm going to make... Without CNC and them can-cycles it will be a challenge to get that ID thread...

change of plans... this would make threading less complex

 

[Jinx-)]

odd thread it is, looks like m39x1.5, I think its extended metric thread... still working on it

 

[shortgrass]

The pitch isn't hard to figure, as long as you have a metric pitch gauge. The O.D.,,,,,, well, you can (and should) mic it, then convert to metric. It's not like you can thread this spider part way, remove it from the chuck and try it 'till it fits. So, you have the jam nut from the spindle. I'd use the jam nut as a gauge and make a threaded stub, 'till the nut fit right. I'd use that threaded stub as a gauge while making the spider. Basic manual machining that it didn't take a program to figure out. A mark on the threading bar for depth will tell you when to dis-engage the split nut. 'Canned cycles" are nice, but, not needed for every job.

 

[Jinx-)]

I can't disengage half-nut for metric threads.... have to stop then reverse...

 

[bigngreen]

I would make it as compact as you could to reduce any out of balance the spider could bring. shoulder it out on the spindle as well so the set screw is not taking the brunt of the pressure and just needs to act as a fail safe. Clock it with your front chuck, makes life easier.

Use a dial indicator on the carriage to stop dead on the same number each time, set it to touch at 0 then disengage at 0+ one rev, puts you nuts on each time.

 

[msalm]

I would thread a stub the same as your spindle using one of the spindle nuts as a test thread so you would have something to 'try' your thread on the spider without removing it from your chuck. Shouldn't be too bad to make. I would also be more inclined to machine it to the first drawing as it offers more support for your spider bolts...maybe even add a 45 degree chamfer to the inside shoulder so you could thread it on snug and it would self center before tightening your set screws.

 

[Jinx-)]

Well after I got my 4 year old and 9 month old to bed I continued with my project. The lathe I have in my garage is not professional, its just G0602 benchtop from Grizzly, so according to their manual "Note: Since this lathe has an inch leadscrew, do not use the thread dial when cutting metric threads. Instead you must leave the half nut engaged from the beginning until the threading operation is complete." So when threading I have to stop the spindle, back the croslide, then engage reverse, then stop spindle, backup croslide, then move compound and engage forward. So when I press stop, spindle will rotate and since lead screw is engaged, carriage will move and on 1.5 metric thread I get about .150 - .200 until it completely stops. Yeah I hate it, but I can't buy another lathe at this point
Anyway, I got half way through, I decided to go with the original drawing, good thing threading is done and its perfect tight fit. I still have to cut it to size and tap them holes, but it shouldn't be complicated.

 

[J E Custom]

While you are set up to cut Metric threads I would cut one more coupling and install a handle on it
to turn the spindle.

A friend on this site did this and I liked the idea of having total control of the spindle and not worrying about the
coasting down of the spindle. If your lathe is in a tight space, a 1/2'' drive ratchet will work well and can be reversed
easy.

I also made a threaded nut with 1 1/16 x 16 tpi inside to screw a short threaded barrel in and install the extension nut
in the spindle to hold the back of the barrel. It works well and uses the shoulder of the spindle and the receiver for the
best alignment.

It is a little more work but it gives you total control when you can,t disengage the half nut.

Just a thought.

J E CUSTOM

 

[SidecarFlip]

Oftentimes I believe the 'half nuts' populate this forum........

 

[shortgrass]

Oftentimes I believe the 'half nuts' populate this forum........

But,,,, what about the split nut????

 

[Jinx-)]

I can call mechanism to engage lead-screw or lead screw engager something... About the lathe its 10x22 and it missing some features I would like to have. Let see if you ever worked with Hardinge toolroom lathe, when threading once lead screw engaged it stays that way, but it has a break and special lever on crosslide to get in and out of thread, love that feature... Of course Hardinge toolroom lathe no longer made, but there are many replicas still build today and they still cost 20 times more then grizzly

Here's one made by EISEN

And the one from Grizzly

Specifications:
Swing over bed: 9-5/8" Swing over cross slide: 6-1/8" Distance between centers: 22" Spindle bore: 1" Spindle thread: 1-3/4" x 8 TPI Spindle taper: MT #4 Motor: 1 HP, 110V, single-phase Number of speeds: 6 Range of speeds: 150, 300, 560, 720, 1200, 2400 RPM Leadscrew: 3/4"–12 TPI Compound travel: 3-1/2" Cross slide travel: 6-1/2" Carriage travel: 18-1/2" Maximum tool size: 1/2" Tailstock barrel travel: 2-1/2" Tailstock barrel taper: MT #3
Standard Equipment:
5" 3-Jaw chuck with two sets of jaws 6-1/2" 4-Jaw chuck with reversible jaws 8" Faceplate Steady rest with 1/4"–2" capacity Follow rest with 1/4"–2" capacity MT #3 dead center 4-Way tool post Chip tray and backsplash Hardened & ground V-way bed
Oil-bath gearbox Tool box with service tools Number of longitudinal feeds: 9 Range of longitudinal feeds: 0.0023–0.013 IPR Number of inch threads: 33 Range of inch threads: 8–72 TPI Number of metric threads: 26 Range of metric threads: 0.25–3.5mm Overall dimensions: 46" L x 22" W x 16-5/8" H

 

[shortgrass]

I've just always known, what you call a half nut, as a split nut. I've not had the pleasure of the Harding machines. But I've experienced Clausings, South Bends, Warner & Swaseys, Brown & Sharpe single spindle automatics, Acme-Gridley multiple spindle automatics, New Britain multile spindle automatics, Summit engine lathes (you can dis-engage the split nut on those when metric threading), Monarchs, Lymans, Sydneys and now HAAS. Thats just turning machines, the list is about as long for the mills I have set-up and operated. Punch presses,,, yes, for the part punched and for broaching, precision grinders, no centerless or bore, but pleanty of surface and tool & cutter grinders (making & sharpening). Heat treating,,,,, only on a one one one basis in the tool room. True "job shops" will show you alot in 35+ years. Never a boring moment,,,,,, unless it's with a 'bar'!