Boring bar

O

oogenshire

Registered
Registered
Joined
Jul 22, 2022
Messages
75
i want to bore out a piece of aluminum tube thats 1.5" od. just clean it up and get it to a nominal slip fit on the inside. i want to make a boring bar, have 1.5" 4130 stock, what would the minimum thickness i would be able to turn it down to to be solid at 9 to 10 inches long? using a bxa qctp so i will have to mill the end to lock into a bxa toolholder
thanks for the input!
 
Seems like a waste of 4140 1.5" bar! Got anything in the 3/4" range? I've bored 8" deep in Aluminum with a 3/4" bar. You can hold the smaller bar in a regular tool holder.
 
no ive got some mild steel but figured i need the hc rigidity for it, the only tool steels ive been able to get is drops from local machine shops
 
oogenshire said:
the only tool steels ive been able to get is drops from local machine shops
Click to expand...
The online sellers of metals stock a huge selection of metals, including tool steels. I bought a few rounds of O1 a long time ago. It doesn't take a lot for most tooling. O1 has been fairly easy to harden and temper. I just use a magnet to tell when and a can of any oil that gets in the way to swish the tool around in. Your wife's oven works for tempering, when she isn't looking. There are guides that use color for flame tempering. SS foils or wrap the tool in soft iron wire and borax paste for preventing oxidation. Clickspring demonstrates the borax method.
Use enough oil so it doesn't reach the flash point!
 
oogenshire said:
no ive got some mild steel but figured i need the hc rigidity for it, the only tool steels ive been able to get is drops from local machine shops
Click to expand...
There's no practical difference in rigidity amongst all the steels. Hardness, toughness, yes, but not rigidity. Use mild steel, save the 4140 for something else.
 
The resistance to bending (rigidity) is proportional to the bar's dimensions and the Young's Modulus of the material. All steels are within 2.5% or so of the same Young's Modulus, be it high speed steel, tool steel or hot rolled A36. If you want the stiffest boring bar that is practical, use tungsten carbide - but that is pricey. If sticking with steel, all steels have effectively equivalent rigidity (for the same bar dimensions), so use the cheap stuff! Save your good stuff for an application that needs it.
 
oogenshire said:
no ive got some mild steel but figured i need the hc rigidity for it, the only tool steels ive been able to get is drops from local machine shops
Click to expand...
There is no difference in rigidity between soft and hard steel, it comes down to modulus of elasticity, there is negligible difference between alloy or carbon steel, my reference is "Tool Steel Simplified", by the Carpenter steel Co.
 
ok i did not know that about the modulus of the material, ill recheck what i have for stock on hand appreciate it.
 
You must log in or register to reply here.
Back
Top