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Best material for a spider?

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diamond

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#1
This is going to be for a PM 1340GT. This is my first lathe and I'm quite the noob here. Sure appreciate this site where folks who are willing to share their knowledge and are patient. :)

Lathe is 2-3 weeks from delivery still but I'm doing lots of research and trying to gather as much info as I can. I'm going to be pretty excited to get going on the thing when it gets here. A first project is going to be a spider.

I have read a number of great threads on here about various folks building spiders. I don't see many talking about using aluminum.

I've got a piece of 2.5" 6061 aluminum round bar. Plan to do a practice build with it. However I am wondering, do you think 6061 is too soft for a spider? Now wondering if it's going to be good enough to use as the permanent part. Note the spider will be primarily used to stabilize/align rifle barrels so work pieces will generally not extend far outside the spider.

Been reading all kinds of articles about thread strength in 6061. Seems like it would be quite sufficient with .5" of tube wall for thread contact. Maybe there are all kinds of other factors I'm not considering. (quite likely in my ignorance)

Given the choice, what would you feel is best to hunt down as a material for this project? (in other words, just track down a round bar drop and bore it out)

To get the right dimensions in tubing (at a sane cost) about all I'm finding is A513 DOM (2.5" OD, 1.5" ID). Thoughts on machining A513?

Learning where/how to source material I'm discovering is yet another part of this journey I've started.

Thanks and apologies in advance for such a noob question!

-dave
 

mksj

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#2
I would not use aluminum, too soft and also you can get corrosion/oxide formation where it slides onto the spindle and may not be able to get it off. The DOM A513 tubing will certainly work well, only downside is that you typically have to order 12" and cost of shipping if an online vendor. You can also get just about any steel in 2.5" OD and bore it out (which is what I did), but you need a good range of longer drills (MT3) to remove material and then come in with a 3/4" or larger boring bar. I am not a big fan of 1018 from a turning/machining point of view, if you can pick up some 1144, 4130, 4140 or 8620 steel, it all turns nicely. Some other threads with dimensions and information on the 1340GT spider. Make the brass tipped spider bolts yourself, don't waste your time/money trying to buy them. You may need to enlarge the belt cover spider hole, some covers are a little off center when mounted and may have a clearance problem. Make sure the spider bolts are far enough out from the cover so they do not hit the cover/cover retaining bolts.

https://www.hobby-machinist.com/threads/a-spider-for-the-pm1340gt-lathe.63222/#post-521344
https://www.hobby-machinist.com/threads/spider-for-pm-1340gt.54228/
https://www.hobby-machinist.com/threads/pm1340gt-spider-with-dial-test-indicator.45446/
https://www.hobby-machinist.com/threads/new-pm-1340gt-arrived.61803/#post-509976

Nice lathe, congratulation.
Mark
 

davidpbest

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#3
I'm with Mark - don't use aluminum, although I would recommend doing practice turning with aluminum before you tackle the spider to get some time on the machine. Aluminum is too soft for the spider. This might be helpful to you on the steel variants:

https://www.mcmaster.com/#steel-hollow-rods/=1dppx7f < click "About Steel" at the top.

I started with the steel pipe you have probably already found - 2.5" OD, 1.5" ID, from McMaster:

https://www.mcmaster.com/#6920t11/=1dppzdy

This is 4140 (A519), and worked well. I still have the off-cut from my project and willing to sell it - it's 2-7/8" long which is enough to make the spider, if you're interested, PM me. Photo here.

Attached is the drawing for my spider if that helps - verify your machine's dimensions, they may be slightly different.

If you're going to add a tach to your 1340, the spider is an ideal place to include a magnet for a hall effect sensor. Photo here.

Good luck.
 

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BtoVin83

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#4
Made mine out of aluminum, seems to work quite well. I have told it not to let any oxide form so I'm good there.
 

diamond

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Thanks for the tips guys.

I thought about 304 stainless but .5" wall tube in SS is really pricey!

This is 4140 (A519), and worked well. I still have the off-cut from my project and willing to sell it - it's 2-7/8" long which is enough to make the spider, if you're interested, PM me.
PM sent David thank you very much.

And yes, I do plan to put the magnet for the tach sensor in it. To go along with Mark's VFD control board. :)
 

dpb

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#6
I made my spider out of aluminum, for barrel work. It’s done about 20 barrels now, no problems. I’ll likely replace it with steel in the not too distant future, as I agree that it likely isn’t the best material, but it has worked fine. It also holds the tach magnet. Make your own brass tipped bolts, as already suggested.
 

Nogoingback

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#7
304 stainless looks nice but may give you trouble due to work hardening. 12L14 is
great because it machines nicely. I also like 1144 for strength and machinability. If you need a small piece you can sometimes find offcuts on ebay at reasonable prices. Depending on the dimensions, it might be better to make it from round bar and just drill and bore it rather than from tube.
 
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Janderso

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#8
Dave,
All Metals, in Oroville is a fabulous source for metal. Check out their “scrap” yard.
Last week I picked up several 7’ plus, pieces of scrap 2x2 square tubing 1/8”.
$28.
Hobby metals, online if no one mentioned it. Heard about them from Mr. Pete.
 

diamond

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Dave,
All Metals, in Oroville is a fabulous source for metal. Check out their “scrap” yard.
Last week I picked up several 7’ plus, pieces of scrap 2x2 square tubing 1/8”.
$28.
Hobby metals, online if no one mentioned it. Heard about them from Mr. Pete.
Hi Neighbor! :)

I was wondering about good sources of material around the area here in Northern California. I think you just gave me the answer. Free local delivery too. Nice! I will definitely drop in there to check their yard.
 

Rich V

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#10
I used 7075 aluminum for my spider and it works well. 7075 is a very strong and relatively hard aluminum alloy similar to some mild steels. I under bored the spider, heated it and slipped it onto the spindle for a very secure shrink fit.
It helps that I already had the 7075 stock on hand.
 

wrmiller

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#11
I used 7075 aluminum for my spider and it works well. 7075 is a very strong and relatively hard aluminum alloy similar to some mild steels. I under bored the spider, heated it and slipped it onto the spindle for a very secure shrink fit.
It helps that I already had the 7075 stock on hand.
I will use 7075 if/when I decide to do a spider for my 1340GT. 7075 is more than strong enough, and a spider isn't carrying that much in the way of centrifugal force if correctly set up anyway.
 

Janderso

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#12
I just checked out your new lathe. That is a nice machine!
My old 13X42 South Bend is still making parts even after 71 years. You are gonna love that lathe!
What add-ons did you get?
Back to the post. I made a spider out of aluminum, my fault, bad design. My spindle hole is just a tad over 1". I have no way of attaching it to the spindle OD. I decided to make a slip-in but, that's just not practical. It was a good lesson.
I have seen plenty on this forum and youtube using 7075 though.
 

diamond

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I've got a number of pieces of 6061 to play with/practice and mess around with. Got that piece of 4140 from David to make the permanent spider.

Janderso I got the preferred package in 3-phase. It's coming from Matt with a DRO and an upgraded 4-jaw chuck. Going with the full-on Mark Jakobs VFD control system upgrade with his proximity stop design as well. Can't wait to get that all set up.

Lathe is still a few weeks out, don't have a confirmed delivery date yet. Still working on setting up the shop area. Basically enclosing one corner of a 40x50 metal building to be my shop area. Building is too dang hot this time of year. I'll want to be able to have some climate control in there.
 

Dabbler

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#14
You can use any material at all thaq will hold a thread. I use wooden collets instead of a spider and they work very well. Even junk aluminum will hold the pressures if the length of the thread is greater than 2 times the diameter of the thread.
 

Bamban

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#15
For chambering, the outboard spider is just there to dial in the barrel, if you loosen any of the outboard spider screws and the runout as indicated on the chuck side spider moves, you are bending the barrel. The outboard is not there to tightly hold the barrel, snug is all you need, aluminum is plenty good. There are a few schemes out there that allow the chuck side barrel to pivot or gimbal. Find out for yourself what works best for you and your machine.

If you are interested I can send you a copy the compiled chambering discussions on benchrest forum, it is too large to post. Send me an email bambanbarrelbarn@gmail.com
 

diamond

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#16
Thanks Bamban. I'll take you up on that because I like to learn from others. FWIW I ended up making one out of aluminum and it's working great and I'm really happy with it. As noted a lot of force is not needed for this specialized purpose (rifle barrel chambering). Just light finger pressure on the screws (which I tipped with brass) is really all that's needed to support the muzzle end and dial in the chamber end. Then I just snug up the lock nuts to keep anything from moving. I'm using a bit of #4 copper wire wrapped around the chamber end to allow it to pivot and not put any bending forces on the barrel. If I'm concerned about anything with the aluminum it's the 1/4x20 set screws that lock it down on the spindle. That area of the part is only about 1/4" thick so there's not a lot of thread there. But for now they seem to be doing well and again, not a lot of force is really needed. I have to just remember not to go all out when I tighten those. It only needs to be snug to keep stuff from moving.
 
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Bamban

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#17
Document sent.

One way to check how solid is your workholding, after dialing the barrel, part of small section, face it off, and check the bore for runout. In my case, the finger clamps with ball bearings provide the best holding power with no change after parting. Another check is after threading, run your dial test indicator tip on the thread, with the same threading set up run the lathe backwards at slow speed and see if the runout is the same at bore runout. Just an unsolicited input.
 

P. Waller

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#18
I would not use aluminum, too soft and also you can get corrosion/oxide formation where it slides on
Mark
Absurd, this has been installed and removed from this lathe many times in the last 25 years or so, being made from aluminum has never caused a problem. I have only used this machine for the last 5 years but remove it and reinstall once per week or more.

This is an extension to the stop for a long part.
 

Dabbler

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#19
nice work, Mr Waller!
 

mksj

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#20
Not your typical thin walled spider. To each their own, you may have had one experience with aluminum, others may have had a different experience. I have had numerous cases where aluminum has oxidized and frozen onto other metals. It can also gall when threading screws and does not hold up as well as steel with regard to deformation, in particular when the spider wall is like 1/4"and you thread and add lock nuts. I have not seen any commercial spiders that fit onto/thread into the spindle made out of aluminum. If your spider is not heavy walled, I would use steel.
 

Tozguy

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#21
Been reading all kinds of articles about thread strength in 6061. Seems like it would be quite sufficient with .5" of tube wall for thread contact.
As mentioned above, an outboard spider does not have to work hard. To indicate a barrel it requires very little pressure on the screws.
There is no reason not to use the 6061 that you already have. You will have to do a ton of barrels to wear it out.
Re the risk of corrosion, unless you use the spider regularly why not just remove it from the spindle when the barrel work is done.
 
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