Proper Method for Making a Spider ?

P

pdhntr

Guest
I am getting ready to make a spider for the rear end of the spindle. I want to thread the spider to fit the threads of the spindle. I have some 3 inch OD aluminum for the frame, and I have been practicing cutting internal threads.

My delema is how to check the threads to see if they will fit. Or another way of putting it would be, if they don't fit, what is the best set-up to work from so I can re-index the spider to cut the threads larger? I realize you guys would hit the mark the first time, but I don't have that kind of experience or confidence at this point.

Checking with a dial indicator and using the 3 jaw, when I put the aluminum piece back in the same place, I am getting .0015 out of round. That is the best I can do.

I could guess my way through this and probably get something usable, but I would like to know what is the PROPER set up and procedure to use.

Thanks.

Jim
 
Make a copy of the male thread you want the spider to screw onto and use that as a gage to check your spider as you cut the internal thread. Look up the dimensions of the thread and calculate the thread depth. Better, thread wires and a micrometer would be a good thing to have for measuring the male thread. If you don't have one, get a copy of Machinery's Handbook - it will help you answer lots of questions like this. Any old edition is OK, you don't need a brand new one.
 
I had considered making a threaded copy, but (again) didn't know if this was the proper method.

I never thought of the Machinery Handbook. I may have an old one in the shed that I had forgotten about.

Thanks Henry.

Jim
 
While the spindle on my lathe is threaded, I made mine a good snug fit over it, and secured it with 4 set screws. Never had a problem. You can actually index those set screws with the 4 spider screws at the same time.
 
Or just make it a snug sliding fit to the spindle OD. After you put a barrel in it and tighten the spider screws on the barrel it isn't going anywhere.
 
Thanks Wayne and Jerry.

I never thought about the point you bring up Jerry. The spider is only holding the barrel in one spot in a circular plane and is pretty much just along for the ride.

If I feel I need to put set screws in to tighten the spider to the spindle, I can turn some delrin pads for the ends of set screws.

Thanks for making this job much easier.

Jim
 
If your going to be gun plumbin then eventually your likely going to want to clean up a receiver or two as well. Better to learn the skills on picking up a thread now on your tool than an action.

Mark the part and key it to one jaw on the chuck. Ensure you have a consistent edge to qualify from (like the back of the chuck) and give it hell. For a spider the runout really doesn't matter since your basically making a little 4 jaw chuck. Sure you want it nice to avoid excessive vibration and such, but at the spindle speeds most use for turning/threading it won't be enough to matter. .0015" is plenty good.

I'd encourage you to use a fairly stout wall thickness. I see so many that look like fence pipe. I have to think that's more for looks than function. Mass becomes quite important with machining.

Regarding delirin.

I tried this on the Harrison lathe I had at Nesika. I didn't have any luck with it. They smoosh and slip. (right when you need it to be still) Drill a hole 5/16" ID hole 1/4 deep in a 1/2"cap screw and sweat a puddle of brazing rod on the end. It'll last much longer.

Good luck!

Chad
 
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Gents,

My thoughts for pads to be used on the spider bolts would be brass acorn nuts. Same theory as using a piece of wire wrapped around the barrel, then gripping the wire with the chuck jaws (if one uses a conventional type chuck).

Justin
 
Zebra13 said:
Gents,

My thoughts for pads to be used on the spider bolts would be brass acorn nuts. Same theory as using a piece of wire wrapped around the barrel, then gripping the wire with the chuck jaws (if one uses a conventional type chuck).

Justin
Click to expand...

Well, that makes too much sense.

Good idea.
 
pdhntr said:
I am getting ready to make a spider for the rear end of the spindle. I want to thread the spider to fit the threads of the spindle. I have some 3 inch OD aluminum for the frame, and I have been practicing cutting internal threads.

My delema is how to check the threads to see if they will fit. Or another way of putting it would be, if they don't fit, what is the best set-up to work from so I can re-index the spider to cut the threads larger? I realize you guys would hit the mark the first time, but I don't have that kind of experience or confidence at this point.

Checking with a dial indicator and using the 3 jaw, when I put the aluminum piece back in the same place, I am getting .0015 out of round. That is the best I can do.

I could guess my way through this and probably get something usable, but I would like to know what is the PROPER set up and procedure to use.

Thanks.

Jim
Click to expand...

Hi Jim,

Here is a video link for re aquiring a thread. http://www.youtube.com/watch?v=FfwdsBYJN34

Just incase you want to make a spider that threads into your outboard spindle, check to see if it's a left hand thread. Since most lathe work is turning forward or towards you, usually the threads on the outboard side are left handed. I found this out the hard way after spending a very long night trying to screw right hand threads into a left hand threaded spindle.

Bob
 
NesikaChad said:
If your going to be gun plumbin then eventually your likely going to want to clean up a receiver or two as well. Better to learn the skills on picking up a thread now on your tool than an action.

Mark the part and key it to one jaw on the chuck. Ensure you have a consistent edge to qualify from (like the back of the chuck) and give it hell. For a spider the runout really doesn't matter since your basically making a little 4 jaw chuck. Sure you want it nice to avoid excessive vibration and such, but at the spindle speeds most use for turning/threading it won't be enough to matter. .0015" is plenty good.

I'd encourage you to use a fairly stout wall thickness. I see so many that look like fence pipe. I have to think that's more for looks than function. Mass becomes quite important with machining.

Regarding delirin.

I tried this on the Harrison lathe I had at Nesika. I didn't have any luck with it. They smoosh and slip. (right when you need it to be still) Drill a hole 5/16" ID hole 1/4 deep in a 1/2"cap screw and sweat a puddle of brazing rod on the end. It'll last much longer.

Good luck!

Chad
Click to expand...

Chad,

A puddle of brazing rod. What a time saver, instead of pressing a brass rod into a drilled hole, and it won't deform as easily. I hope someone is writing these ideas down. This is the kind of stuff that makes this forum so good.
 
I prefer drilling the holes in the spider screws and pressing a piece of grounding rod copper into it. Gene Bukys made 8 of them for me because I was lazy and didn't do it.
Butch
 
I should add something to my earlier comments.

The main reason I encourage using a heavy wall on the spider is for support of the 4 screws. A 1/2-13 cap screw for instance has a rather aggressive thread pitch. In a thin wall spider there isn't going to be a great deal of thread engagement- meaning the capscrew is going to be inclined to push around. I'd say a good formula is to use at least 1-1/2 times the diameter of the fastener for thread engagement. More engagement certainly won't hurt anything but you do get to a point of what's practical.(this will end up being the wall thickness of the tube) Going to a finer thread pitch probably won't hurt either if making it out of steel. For aluminum I'd still opt for the heavier pitch because the AL is a bit softer and will be more inclined to fugger up down the road. I like making tools-once.

The one I made for the Hardinge lathe I had (before the Harrison) used a split slip collar. I used 4140 prehard for that one. It'll be around after the cockroaches take over I bet. You could potentially combine the two. Make your threads a tad on the loose side and slice it then cross drill for a screw to clam it up once you have it threaded on.

One more thing then I'll shut up.

This is a bit "out there" as it deviates from the standard practice a bit. Anyone ever (dared) try just using a collet/sleeve assembly and fixture the muzzle end off the OD and the inside of the spindle tube?

It works guys. Pinky swear.

Hope this helped.

C
 
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NesikaChad said:
One more thing then I'll shut up.

This is a bit "out there" as it deviates from the standard practice a bit. Anyone ever (dared) try just using a collet/sleeve assembly and fixture the muzzle end off the OD and the inside of the spindle tube?

It works guys. Pinky swear.

Hope this helped.

C
Click to expand...
How much is this going to add to the distance through the headstock?
 
Bob Pastor said:
Chad,

A puddle of brazing rod. What a time saver, instead of pressing a brass rod into a drilled hole, and it won't deform as easily. I hope someone is writing these ideas down. This is the kind of stuff that makes this forum so good.
Click to expand...

Or...you could just order some brass tipped allen head cap screws from MSC. I ordered the 5/16-18 ones and they work great.

As for fitting the spider, try this. CHuck up a piece of stock large enough to mimic the OD on the spindle (back side) of your lathe. Measure the OD and TPI and go for it. Start the thread and with your dial calipers, measure the pitch diameter of the spindle. This will not be a true Pitch diameter but it will be close. Write it down and keep threading your test piece. When you get it to the pitch diameter of the spindle you are done. Take it out and when making your spider, use the test piece to check the fit on the inside threads. It works, believe me. And you don't sdneed to take it out of the lathe to check the fit or pick up the thread again.

Jim
 
jackie line bored his headstock and uses a tool/bushing/sleeve that fits the od of the bbl and the internal of the headstock.

me i did aprox .5 wall alum with fine pitch screws with copper tips. the spider is held on to the od of the headstock with 4 setscrews working on a single wrap of brass shim stock.

i use an internal tool from the spider to do shorter bbls. not as precise but better than nothing.

mike in co
 
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NesikaChad said:
If your going to be gun plumbin then eventually your likely going to want to clean up a receiver or two as well. Better to learn the skills on picking up a thread now on your tool than an action.

Mark the part and key it to one jaw on the chuck. Ensure you have a consistent edge to qualify from (like the back of the chuck) and give it hell. For a spider the runout really doesn't matter since your basically making a little 4 jaw chuck. Sure you want it nice to avoid excessive vibration and such, but at the spindle speeds most use for turning/threading it won't be enough to matter. .0015" is plenty good.

I'd encourage you to use a fairly stout wall thickness. I see so many that look like fence pipe. I have to think that's more for looks than function. Mass becomes quite important with machining.

Regarding delirin.

I tried this on the Harrison lathe I had at Nesika. I didn't have any luck with it. They smoosh and slip. (right when you need it to be still) Drill a hole 5/16" ID hole 1/4 deep in a 1/2"cap screw and sweat a puddle of brazing rod on the end. It'll last much longer.

Good luck!

Chad
Click to expand...

Hi Chad,

After thinking about what to do later yesterday, by the time I got to the lathe last night, I had decided to go with my original idea and try to thread the spider. I want it to be as much a learning experience as possible, even if it results in failure.

I am limited by the material I have on hand and that is 3" aluminum round stock. After cleaning up the outside, and boring the ID I should have a little less than .5" for the wall thickness.

Thanks for all the information.

Jim
 
Bob Pastor said:
Hi Jim,

Here is a video link for re aquiring a thread. http://www.youtube.com/watch?v=FfwdsBYJN34

Just incase you want to make a spider that threads into your outboard spindle, check to see if it's a left hand thread. Since most lathe work is turning forward or towards you, usually the threads on the outboard side are left handed. I found this out the hard way after spending a very long night trying to screw right hand threads into a left hand threaded spindle.

Bob
Click to expand...

Hi Bob,

I will watch the video asap. Thanks for the link.

I hadn't looked carefully at the thread direction yet. I know it is 1.5, and its on the outside.:D Thanks for reminding me to make sure before I start cutting threads.

Thanks for everything.

Jim
 
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