Will this knife design be strong enough?

A

alexmin

Joined
Nov 16, 2005
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513
Will this knife be strong enough?
It's an integral made out of a solid piece of steel with a threaded(5/16-18) hole(3/4" deep) at the base.
Threaded rod will be a hidden tang?

I like to make integrals out of thick steel and 3/4" thick O-1 gets pretty expensive.


integral2-1.jpg

integral3-1.jpg
 
Cool idea mate. I think at those dimentions a stainless steel bolt would take a massive amount of stress to break. My only concern would be the blade unscrewing and I would not trust locktite over time. Maybe solder and high tensile bolt would be better. Yes I am making this up as I go. Good luck with it.

peter
 
I would not be so concerned about lateral strength, but if the knife is used with a chopping motion, it doesn't appear to have enough cross section to withstand the shock.
Could you add a stub tang and then weld an extension to it.

Fred
 
Fred, are you saying that you think his bolster will crack or that the 5/16 allthread will let go. If the piece is about 3/4 wide it would have 7/32 on each side of the threads in the bolster area. I would think that would be sufficent especially 3/4 deep. Would it help to submerge the blade and heat the bolster area up to about 600f to make it less prone to cracking.

I forged about the same thing out of a piece of damascus round stock and used 3/8 allthread, but a much shorter blade and it seams fine,
imviall
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Just my opinion but thats not something I'd call an integral, integrals are made for the purpose of being very strong for the simple reason they are a continuous piece of steel thru the handle. A true integral actually has the pommel area included in the same steel. I was always told just the bolster area included was called a 1/2 integral. With no continuous steel running thru the handle thats not even 1/2 integral.
Steel is the cheapest part of the knife, its the time, labor and equipment that runs the cost up.
That is an interesting idea though, but lets face it, another 4-4 1/2" inches of continuous steel behind the bolster wouldn't be that much more expensive and the knife wouldn't have any issues of strength. JMOP


Bill
 
B . Buxton said:
Steel is the cheapest part of the knife, its the time, labor and equipment that runs the cost up.
That is an interesting idea though, but lets face it, another 4-4 1/2" inches of continuous steel behind the bolster wouldn't be that much more expensive and the knife wouldn't have any issues of strength. JMOP
Bill
Click to expand...

Well. It's not just cost. It's also lot's of work to mill 4" long tang out of 3/4" thick steel.
 
First of all I would like to say that I don't know squat... but have you thought of using thinner steel and welding the bolsters on like Mr. Goddard shows in his book. It would reduce the cost and most likely the time, not to mention it looks awesome. Just a thought from a journeyman novice.
 
The sharp corner between the threaded piece and the bolster is a stress riser. It will be weakest here and have a tendency to break off at this place. I've done some hand drawing to show how I would remedy this. The integral bolster is large enough to allow for welding the 5/16"-18 theaded rod at the joint. I would do the following:
  1. Thread the rod into the end.
  2. Run a bead of weld around the circumference to join the threaded rod and the bolster.
  3. Run a second bead of weld that joins the bolster and the first bead of weld.
  4. Run a third bead of weld that joins the second bead of weld and the threaded rod. This third bead will also finish covering the first bead of weld also, tying it all in together.
  5. You can than belt sand and file a sweeping curved shape to the welds as in the last picture. This will be a much stronger joint. I
It still isn't as strong as a true integral, but much better than just loctite.
 
alexmin said:
Well. It's not just cost. It's also lot's of work to mill 4" long tang out of 3/4" thick steel.
Click to expand...

No, it's a lot of work to file a tang out of 3/4" steel. If you've got a mill, what's the problem?

This whole thing just seems counter intuitive to me. If you're trying to save work, then why are you trying to mill a knife from 3/4" thick steel in the first place? A conventionally made full tang knife with applied bolsters/guard would be easier, and still stronger than the shortcuts you're trying to come up with on this design, IMO.
 
ib2v4u said:
Fred, are you saying that you think his bolster will crack or that the 5/16 allthread will let go. If the piece is about 3/4 wide it would have 7/32 on each side of the threads in the bolster area. I would think that would be sufficent especially 3/4 deep. Would it help to submerge the blade and heat the bolster area up to about 600f to make it less prone to cracking.

I forged about the same thing out of a piece of damascus round stock and used 3/8 allthread, but a much shorter blade and it seams fine,
imviall
[/IMG]
Click to expand...

I would be a lot more comfortable with the 3/8 allthread.

Do you think a 5/16 allthread could withstand a 2x4 chopping competition?

I don't think milling 3/4 inch stock is a very efficient approach to making an integral blade.

Fred
 
OK
I can't stand it anymore. Alex I know you are looking for some advice here and so far you have mostly been scorned or at least your idea. I have seen swords used in battle that have had a crossection less than a 5/16" allthread bolt. I know exactly why you have conceived this idea, and it is well-conceived. I know my advice is only one among many, however I have made it my strength to know when to go with the crowd and when to stand alone.
Trust your own mind on this.
To all others, it is not my intent to offend, only not to see creativity beaten down.
Thanks,
Del
 
delbert ealy said:
OK
I can't stand it anymore. Alex I know you are looking for some advice here and so far you have mostly been scorned or at least your idea. I have seen swords used in battle that have had a crossection less than a 5/16" allthread bolt. I know exactly why you have conceived this idea, and it is well-conceived. I know my advice is only one among many, however I have made it my strength to know when to go with the crowd and when to stand alone.
Trust your own mind on this.
To all others, it is not my intent to offend, only not to see creativity beaten down.
Thanks,
Del
Click to expand...

Well said Del :thumbup:

Alex, in the design of this knife, using mild steel for the tang is the way to go, use fine thread as it is stronger connection than course thread. Mild steel will do a whole lot of bending before it will want to snap :eek:
 
Here is how I would approach your problem:

I would not use allthread. Instead, I would use 5/16" rod and tap 3/8" length of thread on the end.

Drill the hole for tapping the hole in the bolster to your planned 3/4 depth. Counterbore @ 5/16 and ream .001" over to within 3/8 of bottom of hole. Tap 5/16" hole to bottom with plug and then bottoming tap.

JBWeld into place. A weld bead would be better, but testing may show it's not necessary.

The rod will fit up into the bolster. There will then be no exposed threads to create a weak point.
 
if I were going to spend the money on an intergral I would add the handle to the design.
 
"Do or do not, there is no try."
Yoda

Either it's an integral or it's not. That design is nice but it's not an integral. I think it might be strong with a 3/4" deep hole for the rod but if you're gonna do this much work already why not mill out the handle.....................?

Just my 2 cents

Syn
 
Well it was just my opinion and it still is, I give/gave you credit for an interesting idea, but thats still not an integral, by claiming it as one I feel your taking credit away from people that make integrals as they are suppose to be made. Claim it to be something other then an integral and run with it, but again this is just my opinion. You are using a mill, the ones I've made are full integral and were done using a belt grinder, a band saw and some files, so the work issue doesn't mean much to me. Sorry if I might have rained on anyones parade, but the question was asked and I just gave my opinion, thats all.

Bill
 
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