Boring head.

A note regarding the use of harder stronger materials for such things as boring bars; it makes no difference in ridgidity using alloy steels, hardened or not, all steels have very nearly the same modulus of elasticity; a full hardened alloy steel is no stiffer than soft mild steel. The only way to increase stiffness to the diameter (in this case). As an example, increasing a boring bar or arbor from 1" to 1-1/4" diameter increases its stiffness by a factor of 5.
The job shown is clearly not a job for a boring bar of the type shown. One writer suggested pinning the threads to prevent the head from threading off; this would be next to impossible, as the boring heads are quite hard, besides which, I would suspect that the threaded part would be inaccessable for drilling.
 
The threaded portion of the head and arbor is quite short. Only about 1/4"-3/8" worth of engagement. Drilling a hole and pinning it could quite possibly weaken the structure too. I ran the bit in reverse from the bottom up for this operation. I got the job done. I realize none of this is designed for this operation, especially with cheap tooling.
The alternative would have been to take the time and set up the rotary table. But I saw a short video Tom Lipton did where he did the same thing. Albiet, a MUCH better mill and boring head.
 
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Put a set screw in mine, no problem drilling or tapping the boring head. I do not intend to rely on the set screw however if it can be avoided. It is better to run the boring head CW with the right tools.

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Or, can you raise your work off the mill table with sufficient clearance, turn the boring bar 180-deg to how the picture is shown & cut from bottom to top in the conventional direction?
 
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Quote....full hardened alloy steel is no stiffer than soft mild steel .

I beg to differ... Pump shafting of the same size is much stiffer than
most other steels.
 
Quote....full hardened alloy steel is no stiffer than soft mild steel .

I beg to differ... Pump shafting of the same size is much stiffer than
most other steels.
You are quite mistaken; do some research on modulus of elasticity, I got it from "Tool Steel Simplified" and had it confirmed by a professional mechanical engineer. Increased modulus comes only with change in material, such as carbide. The modulus varies with alloys of steel by only a tiny insignificant amount.
 
I am one of those "professional mechanical engineers" and I would side with Ben. Hardened steel tools are nice, they don't get beat up as much, they would typically be professionally made, everything fitting nice and looking good - but they are not any stiffer. I have a number of mystery metal boring bars, that are not hardened and of magnetic material which will rust. They work fine.

Now a solid carbide bar - that's a game changer! It has a significantly higher modulus of elasticity, and you can really tell. It is crazy what you can tackle with a solid carbide bars. David
 
I am one of those "professional mechanical engineers" and I would side with Ben. Hardened steel tools are nice, they don't get beat up as much, they would typically be professionally made, everything fitting nice and looking good - but they are not any stiffer. I have a number of mystery metal boring bars, that are not hardened and of magnetic material which will rust. They work fine.

Now a solid carbide bar - that's a game changer! It has a significantly higher modulus of elasticity, and you can really tell. It is crazy what you can tackle with a solid carbide bars. David
I seem to remember that carbide has something like 3 or 5X the modulus, is that right? HSS or any steel boring bars are limited to about 5 times the diameter to overhang to work with effectiveness; carbide extends that limit greatly.
 
I agree on the modulus of elasticity for any steel, but lower strength steels will bend due to the lower yield strength. Hopefully your never reaching that point on a boring bar though.

Greg
 
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