Right and Wrong way to "drill out" a full tang

[EdCaffreyMS]

I see images all over the internet of full tang knives being constructed with a bazillion holes drilled in the tangs. I have never been able to wrap my head around the logic of it. I dear friend recently posted a pic, and I stole it to illustrate my point. (Because I only drill TWO, usually 7/16" or 1/2" holes in a full tang, and those holes are always drilled in a place that leaves the largest "web"/support material possible.)

When a bunch of holes are drilled in a full tang, I can only assume that people think the are "lightening" the knife/tang, but they take no consideration in how much they are weaken the tang. In the instance of this photo, look closely at the break.... and think about just how little material was left to support the tang after the holes were drilled. Then think about how that particular area of a knife is exactly where it usually incurs the most stress..... bad juju!

 

[J. Doyle]

I've never really done the hole drilling thing for lightening.

I never could believe that it really makes much difference in the big picture. Seems like a lot of extra work, wear on tooling and potential issues to offset the small amount of weight those holes actually remove.

I could be way off base; but I have a fair amount of experience with pinewood derby cars where weight matters a lot and it amazes me how much material removal or addition is required to change the weight just a tiny bit.

I just can't see a few holes in a tang making much difference in feel/performance in the grand scheme of things.

 

[Smallshop]

Fortunately on larger longer bladed knifes you usually WANT the weight in the tang as balance is really more important than over all weight. I played and played with fullers on my Bowie model until I could get it to balance. i even thought about weighting the pommel area to get it there. a balanced knife feels "quicker" than a lighter unbalanced knife...imo. but I'm getting away from the point of this post...

Ed's point of making generous webs between lightening or gluing holes is on point. I do think plate quench or air quench is more forgiving with stress risers than oil quench? But if you want those beautiful looking differentially hardened blades you certainly need to mindful of web thickness for stress.

I like some small holes for glue (on one offs). otherwise I mill pockets thru the blade. On smaller knives I don't worry as much about balance so gluing is the key there for me. Holes are merely a glue latch for me.....and are usually under 1/8" dia.

 

[EdCaffreyMS]

I just can't see a few holes in a tang making much difference in feel/performance in the grand scheme of things.

Sure, I doubt the average knife user would be able to discern any difference if just drilling a couple of larger hole in an un-tapered tang.
However, based on my experiences, when you combine a couple of larger holes in a full tang, and then taper the tang, there is a very noticeable difference as compared to the same knife with a non-tapered tang, and the holes. The larger the knife/tang the more noticeable the difference.

In situations where there are no mechanical fasteners used on a full tang, I believe that a couple of larger holes provide for a virtual "epoxy rivet" between the scales. I always run a small hollow down the center of a full tang to create a "channel" that gives a bit more room for "epoxy".

This all comes to mind because just a couple of weeks ago, a local guy stopped by the shop with a "custom" full tang knife, that had no mechanical fasteners, and the right scale had popped off.... wish I'd taken a picture, but imagine a full tang, flat and clean as a granite surface plate, with a scale of some weird synthetic material that I've never seen glued to it.... and the clamped so hard it squishes all the glue out.

Anyway, he wanted me to "fix" it, and I told him he needed to go see the maker....who lives a few hours away, but he kept insisting that he wanted me to repair it. When he wouldn't settle for my rule of not repairing another makers knife....... I quoted him my hourly rate for repair work, plus materials..... that was the end of that.

 

[J. Doyle]

I agree with you Ed. Even your first post. Tapering the tang (with or without holes) is, IMO, a better and more useful way to adjust balance.

I liked your original post. If I was inclined to use lightening holes, it would definitely be the method you described.

The Swiss cheese approach seems like it creates more problems than it solves.

 

[tkroenlein]

Seems like I saw a stress riser diagram somewhere that was illustrated showing how the strain traveled around a hole, and at what point it significantly decreased strength. Short version is you want at least 2/3 of your material intact.

 

[chrisstaniar]

Yeah, the amount of material removed is insignificant. You could take the pile of leftover shavings, weigh it, and it wouldn't amount to much. I don't bother with it, I'd rather have the material remain and not risk a failure.

 

[opaul]

If the holes were drilled to lighten the blade or for epoxy bridges? I remember seeing a post by an experienced knife maker that suggest at least 1/8” of steel between
holes and edges. I typically do not drill numerous small holes (I think I did in the beginning- not sure why). Now I drill one or two larger holes to balance the knife. I haven’t tried tapering tangs yet. What I have started doing more often is grinding a fuller in the tang. Does that do anything? It does allow for more epoxy. It continues the steel bridge so it most likely is the more structural option.

 

[Sean Jones]

I've been guilty of drilling a lot of holes in the tang. I was thinking mostly for the epoxy to get through. However it sounds like a lot of holes aren't necessary. I'll keep that in mind for future knives.

 

[Smallshop]

If the holes were drilled to lighten the blade or for epoxy bridges? I remember seeing a post by an experienced knife maker that suggest at least 1/8” of steel between
holes and edges. I typically do not drill numerous small holes (I think I did in the beginning- not sure why). Now I drill one or two larger holes to balance the knife. I haven’t tried tapering tangs yet. What I have started doing more often is grinding a fuller in the tang. Does that do anything? It does allow for more epoxy. It continues the steel bridge so it most likely is the more structural option.

I think anything that disrupts that shear plane helps. Holes, fullers, etc., on the chance that scales were over clamped a bit...all the added depth of glue will help.

 

[John Wilson]

I did the swiss cheese thing early on because i had a pisspot drill press and stepping up 4 drills per hole was a pain. It was easier to drill 500 quarter inch holes.

I drill three 1/2” holes now to lighten the tang. On a chef knife it does matter and you can feel the difference in balance. Those holes don’t seem like they’d make a difference when you hold a raw blank, but by the time the blade is ground the blade weighs less than half of what it did as a blank. The steel removed for those holes is an appreciable percentage of the final weight. Three 1/2” holes is about half the area of the tang covered by the handle scales. Half the area is half the weight.

The thing to remember on a chef knife is that the handle is as much a counterweight to the blade as it is something to hold onto. How the knife balances has a lot to do with how it acts and performs.

On a hunting or utility knife the balance isn’t critical and the holes account for less percentage of the total weight, but lighter is still better in most instances, imo.

 

[Boatbuilder]

I've never really done the hole drilling thing for lightening.

I never could believe that it really makes much difference in the big picture. Seems like a lot of extra work, wear on tooling and potential issues to offset the small amount of weight those holes actually remove.

I could be way off base; but I have a fair amount of experience with pinewood derby cars where weight matters a lot and it amazes me how much material removal or addition is required to change the weight just a tiny bit.

I just can't see a few holes in a tang making much difference in feel/performance in the grand scheme of things.

I want to keep this knife as light as possible because its the knife I use for cleaning fish every day during the summer. I usually spend anywhere from 1 hour to 4 hours depending on the day and if anyone there to help. The knife gets real heavy after cleaning tuna for 4 hours straight. LOL. Wish I had that problem every day.
Jim

 

[Randy Lucius]

I drill holes in tangs because when I started that’s what I saw people doing. Monkey see monkey do. It was explained to me that it helps lighten the knife but the main advantage I see is it allows the epoxy to serve as internal pins. Also with the holes it reduces surface area making it easier to flatten the tang for scale fit up. I have a knife on my bench that just has the holes drilled for the pins. I’m gonna finish it without the extra holes and see how it goes.

 

[J. Doyle]

I want to keep this knife as light as possible because its the knife I use for cleaning fish every day during the summer. I usually spend anywhere from 1 hour to 4 hours depending on the day and if anyone there to help. The knife gets real heavy after cleaning tuna for 4 hours straight. LOL. Wish I had that problem every day.
Jim

Hi Jim. I can understand the reasoning in your case for sure. I have a nice large chef's knife that I made for me....to use at dinner time for like 20 or 30 minutes. It has things that *I* like. But if I was a professional chef using it 8 hours a day, every day, I'd probably make some changes. So I can see your point.

I like the second way you attempted the lightening holes much better than the first. I personally probably still prefer other methods for weight reduction and balance but there is nothing wrong with your second approach and I don't have issue with it.