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Draw tube material?

twr

Hot Rolled
Joined
Mar 18, 2014
Location
Kitchener Ont. Canada
Hi I am changing Chuck's and need to make a new draw tube for my Mori lathe, what material should I use? Right now tube is 3" OD and it has .375 wall because the threads on each end are a different size. I am planning on DOM tube but what material should I use? Thanks TWR
 
Hi that is what I was thinking 1018 I see some companies that make draw tubes from 1026 when it's a heavy wall or 4340 on thin wall tubes. I will call and see what steel place has in stock. Thanks
 
I just checked with Alro and they specify 1010-1026 for all DOM depending on diameter. Don't think you can choose.

The reason for 4340 for thin walls is because of the added strength.
 
Considering the work that you'll put into the drawbar and installation, I'd go with a stronger material for the reliability of the threads.

Saving $20 on the metal to spend it on a remake isn't the best idea...
 
Considering the work that you'll put into the drawbar and installation, I'd go with a stronger material for the reliability of the threads.

Saving $20 on the metal to spend it on a remake isn't the best idea...

Yup, and don't forget the problems with failure (catastrophic)
"Repeated loading" is one of the problems, I would go with something "tougher"
and take care for any stress risers (undercuts, sharp corners, etc.
 
Considering the work that you'll put into the drawbar and installation, I'd go with a stronger material for the reliability of the threads.

Saving $20 on the metal to spend it on a remake isn't the best idea...

My bad, I thought he wanted to make an draw bar extension for his lathe. Got him mixed up with david n. Hardinge GT27.........I wanna run 4' bars w/o a feeder

In that case, yes, go with 4340 or something similar.
 
Hi it looks like it's going to be 1026 because that is what they have in stock. Using thin wall would not help that much because the thread on the actuator is 2 7/8 so using thin wall would only Open the hole a .100 or so and they don't stock 4130 in that size.
 
Hi it looks like it's going to be 1026 because that is what they have in stock. Using thin wall would not help that much because the thread on the actuator is 2 7/8 so using thin wall would only Open the hole a .100 or so and they don't stock 4130 in that size.

You sometimes have to actually go BUY what you need.....
 
Unless you heat treat the 4130, there is not a huge advantage in using it over 1026 DOM. Cold work that happens in the drawing process increases the yield and tensile strength a lot.

1026 in that size is 60 ksi yield, 70 ksi tensile. 4130 is 70 ksi yield, 90 ksi tensile.

https://www.aedmotorsport.com/asset...el-1020-126-dom-round-tube-specifications.pdf

https://www.aedmotorsport.com/assets/uploads/resources/4130-Round-Tube.pdf

Heat treat the 4130 to 35 Rc and you get a lot of strength benefit. This link shows 138 ksi yield and 161 ksi tensile, but it's a different section (solid bar vs. thick wall tube):

MatWeb - The Online Materials Information Resource
 
thats actually interesting. why do they then make cages from chrome moly?

In NASCAR 4130 is not allowed. Mild steel only. In practice they use 1020/26 DOM and have it centerless ground to get down to the minimum (.090) rulebook wall thickness to save weight.
 
Light weight and strength

Nope, sorry, all steels weigh the same.

Un-heat-treated (condition N, sort of process annealed) 4130 in diameters below 2" and wall below .095 isn't significantly stronger than 1020/26 DOM. Its ductility is lower than DOM and its weld zone is subject to mass-quench so you have to postheat. Unless you are going to heat treat the finished weldment it's not worth it.
 
I guess I should have explained it better. They use a thinner wall when using chrome moly compared mild steel. Trying to remember chrome moly can be .083 wall and mild steel has it be .118 or .130 so it lighter. This is for drag racing cages.
 
thats actually interesting. why do they then make cages from chrome moly?

It's partially tradition for open wheel cars (sprint cars, midgets). It is also somewhat stronger, so if you're chasing ounces (and actually doing the enigneering, which most don't), you can make a structure a bit lighter for the same strength. The tradeoff is you give up stiffness by using lighter tubes. Also, the quality control of 4130 tends to be better...there are only a handful of mills that make it. I can specify American or German tube and it will come from 1 of 3 manufacturers (Plymouth, Webco, or Bentler).

I guess I should have explained it better. They use a thinner wall when using chrome moly compared mild steel. Trying to remember chrome moly can be .083 wall and mild steel has it be .118 or .130 so it lighter. This is for drag racing cages.

The drag racing rules are written for the difference between 4130 and welded seam (ERW) mild steel tubing. Most of that is 1010, so you're looking at 32 KSI yield, 45 KSI ultimate tensile. Big difference between that and 4130. If you could find 1020 ERW, it's 38 KSI yield. Cold work in the drawing process for DOM nearly doubles the strength of the material.
 
Hi most places making cage kits or like myself that made my own use Dom tube because it's consisted thickness + or - .005 compared to E welded that can be much higher and not pass the thickness test to get the car tagged. Lots of company's also sell chrome moly kits but it has to be Tig welded and should be stress relieved after welding. I have 2 drag cars both are mild steel Dom tube and are likely about 300 pounds more than a chrome moly car but I am good with that for my class if racing.
 








 
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