Attaching an outboard spider

I need to attach a spider to the LH end of the spindle on my EMCO Super 11 for dialing in barrels through the headstock. The spindle has a section about two inches long on that end that appears to be ground and uniform. I don't want to mess with removing the preload nut and threading it on so I need to affix it to the smooth portion. What would be the best way to go about this? I've got a hunk of 8620 that would give me a wall thickness of about 3/8" over the spindle. I've considered using two sets of three or four set screws an inch and half apart with brass or copper tips to connect it, or possibly splitting it lengthwise once or twice and installing clamp bolts or a split clamping collar. Obviously a near slip fit to begin with is desirable for either method. Am I overthinking this like I usually do or is there a significant benefit to either way, or something I haven't considered? There is a slot in the end of the spindle probably for the lever collet closer I don't have that a pin/bolt could go into to drive the spider. I've found some pics online but it seemed that all of them were threaded onto the end of the spindle.

For all practical purposes there's no load on this piece. I'd split it and put a couple 8-32's to clamp it on. And aluminum would be fine as well.

Mine is simple like you mentioned making. A nice slip fit for however far you can slip it on, enough sticking out to be able to work around and four 1/4-20 set screws holding it in place. I actually ordered soft one from mcmaster that had silver in the tips to form and not mar the spindle. They worked quite well.

I also used 1/2-20 fine thread with copper tips I put in them. The fine is nice for smaller adjustments. I drilled out the set screws and got grounding wire from Lowes and basically poured them in with a hammer. I believe you can buy them that way too but mine seem to have bigger copper in them which I like because it seems to give more purchase on the barrel.

I've never seen one threaded on but maybe there are some like that. Would have to be threaded against the direction you're turning.

If you make it a nice fit on the end of the spindle, a single setscrew is plenty to hold it in place. Brass tipped if the spindle is soft.

Figured I was overthinking it. Hopefully be able to get it fit tomorrow and will use some number of tipped set screws to hold it, based on how close I can get it.

There are varieties of "keyless bushing" that are used to transmit torque between a shaft and pulley/gear, etc.

One style is:



On ebay, price is reasonable.

And they won't leave a mark.

OP doesn't give a diameter, so let's say 50-75 mm.

ebay has:

B Loc Series B112 65 I D mm x 95 mm O D Keyless Bushing | eBay
B602203 Keyless Bushing Dia 2 1875 in 8 Bolt | eBay
B402108 Keyless Bushing Dia 1 5 in 14 Bolt | eBay
B602200 Keyless Bushing Dia 2 in 7 Bolt | eBay


I suspect a determined person could start with a collet and make the compression frame. That's not me

Or, cut a pipe (tapered) thread, then slot the male, and create a matching (perhaps tapered) nut.

And we all know someone who would just weld something on. And that's definitely not me

I built a spider for my lathe. Attached inside the spindle and it expands outwards. Just like a split bushing, except in reverse.

Mine just slips on when needed. The four 3/8-24 adjustment screws hold it on the barrel, and the barrel is held in place by the chuck side cathead.

SteveBausch said:

There are varieties of "keyless bushing" that are used to transmit torque between a shaft and pulley/gear, etc.

One style is:
View attachment 162518


On ebay, price is reasonable.

And they won't leave a mark.

OP doesn't give a diameter, so let's say 50-75 mm.

ebay has:

B Loc Series B112 65 I D mm x 95 mm O D Keyless Bushing | eBay
B602203 Keyless Bushing Dia 2 1875 in 8 Bolt | eBay
B402108 Keyless Bushing Dia 1 5 in 14 Bolt | eBay
B602200 Keyless Bushing Dia 2 in 7 Bolt | eBay


I suspect a determined person could start with a collet and make the compression frame. That's not me

Or, cut a pipe (tapered) thread, then slot the male, and create a matching (perhaps tapered) nut.

And we all know someone who would just weld something on. And that's definitely not me

Click to expand...

This has potential. I'm very familiar with these taper lock bushings. The spindle is about 1.5" OD so I'd need a lager diameter hunk of material than if using set screws, but it would be very rigid.

I have made hundreds of these in the last 10 or 12 years and there is no need
over thinking.

All the spyder does is keep a rifle barrel or whatever you are running thru the
spindle from banging around.

It does nothing toward driving the barrel and there is no tendency to turn
either way.

I usually thread 1/4 X 20 flat face set screws to hold it on the left end of the
spindle, and four 3/8" X 1" nylon socket drive set screws to hold a barrel.

I have threaded a few that do not have enough spindle sticking out.
A couple threads is all that't needed if that's all that's available.

I have threaded over 100 1 & 1/4 X 20 for a little unmentionable lathe.

If anyone wants to use any 3/8" nylon screws, I can sell you a few and not have
to buy 25 or 50 to get 4. Just PM me.
A word of warning. When threading for the nylon screws, run your tap in and out with a power screwdriver.
many times and grease the screws or they will freeze up if left in. Kenny

I made up an add-on outboard spider but when I realized how easy it is to drill and tap the spindle end itself that became my preferred solution. It reduces the minimum barrel length by around 2 inches when compared to the spider.