chopped bolsters

[crockett]

I'm still trying to learn about folding knife construction pre-1840. Sort of running into a lot of dead ends and most of what I "think" I know is "suppos'n". A lot of folders had a liner and bolster that were forged from a single piece of steel. Okay on that. As one gets closer to 1840 the practice of a flat liner and a separate bolster came into use. When I was a kid I tore apart a pocket knife to see how they made it, there was a little rivet from the bolster sticking through a hole in the liner. The bolster was not soldered on to the liner- that got going in the early 1900s and even then wasn't common.
My problem is how the "rivet" was attached to the bolster? Integral (seems like a massive job to make a bolster with an integral post (rivet). Staked? Brazed on? I asked a "Knife Expert" on another site and he said they were "chopped" but wouldn't tell me what "chopped" means.
Hoping someone may know. All help appreciated.
Right now I'm having a lot of "learning" in trying to reproduce pre-1840 spring back folders. The craftsmen at the time were turning them out pretty fast: using forging, tilt hammers, stamps, punches. It's taking me forever.

 

[M. De Land]

I don't know either but when you find out I would like to know as well.
I'm not even fully up to speed on the terms you use and how they apply to a folding knife,can you provide some pictures and examples?

 

[crockett]

I'm sort of challenged on posting photos but I'm using Levine's Knife Guide and the Sheffield Knife Book. Originally to forge out flat liners and then attach front (shoulder) and rear (cap, heel) bolsters was a lot of work and not common. When manufacturing methods improved to include metal stamping and sheet metal at low prices, then the older method of forging out the liner with integral bolsters started to wane and the "applied" bolster method became ever more common. I saw a U-tube on Sheffield pocket knives, the guy was soldering the bolsters on to the liners and BL told me that was more of a 1900's thing, it wasn't done in the 1800's. In the 1800's there was a stub on the inside of the bolster that when through a hole in the liner and then was peen hammered fast. The front bolster would also have the blade rivet so that was two anchor points. The rear bolster would have the rearward pin holding the spring (anchor rivet) so that plus the stub was two anchor points on the rear bolster.
BUT....when I asked about how this stub was attached to the bolster, good old BL simply said they were "chopped" and said no more. I asked around and was told they were integral, the bolsters were made that way. I don't believe that because the whole deal was bolsters stamped out of sheet metal. The stub had to be soldered, brazed, or staked to the inside of the bolster. My problem is if I drill a hole on the inside of the bolster and then solder a stub- is that PC? and...the hole would have to be very shallow. I'm thinking a brass pin was likely brazed but it would have to match the location of the hole in the liner. To be honest, I have no idea how they did it but given the costs of the knives, it had to be rather easy and inexpensive.

 

[44-henry]

In die work chopping is sometimes used to refer to a shearing operation, or any separating process that does not require chip removal. I know that it also can refer to a type of defect in die work.

One thing to keep in mind when trying to understand 19th century manufacturing is that approaching it with 21st century reasoning doesn't always work. While you might reason that if something was sold cheaply during this period it must have been quick and easy to manufacture, you may not always be right. Cheap is a relative term to begin with, but if you are going to use it consider that in comparison today labor was cheap. Many items of this period were very labor intensive to produce and would be cost prohibitive to produce that way today. Also, consider that there was a great deal of specialization that occurred than, there might have been just one person making these bolsters and he might have produced dozens, perhaps hundreds in one day. A task that to us would seem near impossible may have been to such a worker a fairly simple process and there was likely very specialized tooling available to make the job even easier.

I wouldn't rule out the possibility that these bolsters were made in a two piece forging die that could have formed the rivet and shape of the bolster. The term chopped might have implied that slugs of steel of the appropriate size were sheared "or chopped" from a bar prior to being formed in such a die, i.e. "chopped and forged". Drop forging was not all that uncommon a process even in smaller shops and would have been quite advanced in larger factories of the period.

The best way to find out would be to get your hands on an original knife of this style and study it. Best if it is a piece in need of restoration so that you can justify taking it apart to inspect it.

 

[crockett]

Well, as I said, when I was a kid I took apart an old pocket knife, the front bolster had this stub that went through a hole in the liner. The blade and blade rivet had been removed by now. I knocked on the stub to free it from the liner so all I had left was the front bolster with stub. As best as I can recall (many years ago) the stub and bolster were all the same metal and looked to be all of one piece. The bolster was held to the liner with this one stub plus the blade rivet. When I knocked the stub through the hole in the liner it just fell freely away.
Well, I have much to learn.

 

[Elnathan]

Crockett,

I've seen a tutorial on making a Mediterranean-style folder with applied brass bolsters, copied from an original, and it just used a couple pins/rivets to hold everything together.

Are you sure they had integral pins? What kind of knives are you talking about, exactly?
Looking at some pictures of 18th century English knives with integral steel bolsters, it looks like they just have a pin for the blade to hinge on and two rivets, one in the center-bottom and one in the tail to hold the spring in and keep the whole thing together, plus a couple small pins to keep the scales in.

 

[LRB]

My best thought would be a tight press fit, maybe only for symmetrical alignment with the opposite side, and not for any real holding power, other than to provide a little bit of shear strength. Any other method, in my mind, would be a time consuming process, unless one used a mill or mill type arrangement of a bit cutting a flat face that had a hole in the center in order to leave a post at completion of the operation. This could possibly be done on a preformed casting as just a clean and true procedure I would think. What is the possibility that the stub was all the way through, and peened so well, possibly by machine power, that you could not see the joint on the surface?

 

[crockett]

Wick- my thinking is similar to yours. The applied type didn't really become popular until after manufacturing methods could turn out inexpensive sheet metal/bar and metal stamping could punch out bolsters and liners. The idea of cutting away on the inside of a bolster to leave a stub just doesn't seem like the way it would be done. The soldering I'm told by BL didn't get going until the early 1900's and wasn't considered the work of better craftsmen.
And, I tried soldering on prior efforts, if the liner is thin the cool rate between the part against the bolster and against air is different and I got some warping. NOT GOOD.
On the method of the pin all the way through the bolster and peened so good it is invisible, maybe, I just don't know. It would sure hold the bolster in place.
Right now I am thinking the stub must have been staked or brazed on. On the staking, as I understand you drive the stub into a hole and then tap/dimple around the stub to force the surrounding metal tight against it. As you said, the main attribute was shear or to stop rotation and the blade rivet- peened, must have kept the bolster tight against the liner.
BTW, to any following this thread- I've heard various names used for parts but generally the blade rivet is self explanatory. The spring has a pin midpoint and another pin at the rear. What I've read called the midpoint pin or rivet the balance rivet and the rear pin or rivet the anchor rivet. This anchor rivet is usually through the spring but I've seen a photo or two of a very straight spring and then the anchor rivet underneath the rear of the straight spring.
Sometimes the balance rivet was no wider than the spring and liner thickness, it was flush to the outside of the liner and when the scales were put on the scales covered the balance rivet. I've also seen the blade and anchor rivets in iron while the shoulder and heel bolsters were brass but that was very rare, on all others the pins aren't visible so the same as the bolsters (Brass or nickel silver).
And finally, BL has the "Art of the Cutler" a 3 volume work in French published 1776 on every aspect of setting up a cutlery shop and making knives. If you ask nice I think he can somehow get you a translation in English. BL is plenty smart with a Harvard Degree, just have to treat him gentle. :grin: I've got to try and get the English version, would probably explain a lot.

 

[crockett]

This is just a follow up in case anyone cares... I finally got around to the staked pin idea. On a 1/8" thick brass bolster I drilled a 1/16" blind hole a little over 1/16" deep. I did not square or flatten the bottom of the hole and I beveled the end of the pin to match the angle of the drill bit (about 60 degrees). Even with a drill press the fit of the 1/16" brass rod into the 1/16" hole was sort of loose. I wasn't happy with that. I think a wire drill bit of slightly smaller diameter would be better. On the staples used for tenons on rifles- one reads about first "driving" the pin or staple into the hole and then staking it. On staking, I used a round needle file to dimple all around the pin (in the hole) I was SURPRISED how fast this tightened up everything. A couple of very light taps two times around the pin and I could not pull it out, very secure.
These dimples theoretically raise little craters around their dimple which could raise the bolster off the liner. Theoretically you ought to finish up the job with a flat ended punch to flatten the dimple craters. I didn't do this because the fit of bolster against liner seemed fine but it really should be done.
The reason I was dragging my feet on this is I intend to do some file work on the outside of the bolster and I was afraid if I file too deep in the wrong spot I might hit the blind hole and that would be unsightly. I finally settled on putting the blind hole in an area not to be filed.
On a plain bolster, this whole issue wouldn't even exist.
In any event, I think I have arrived at the pre-1840 way bolsters were attached to a liner. It makes sense since it is fast, easy, cheap- an apprentice in a cutlery shop could do it. Of course NEVER assume anything- I have no documentation. IAE- a blind hole, a staked pin, that pin through a hole in the liner and peen hammered. The single pin holds great and once the blade rivet is installed- the whole thing is very secure.

 

[crockett]

Well, if anyone cares I thought I'd up date. I went with staked rivets in blind holes. Here's what I did:
The bolsters were 1/8" thick but were thinned down a little to about .110. I "tack glued the bolster to the liner and then on the inside of the liner drilled a 1/16" hole (liner mild steel and bolster brass). As soon as I hit "yellow" flakes I stopped. I then knocked off the bolster and used a smaller #53 (Ace Hardware) drill with a diameter of .0595 and drilled about .070" deep. I then used 1/16" brass pin material for the rivet. This pin had the end tapered about 60 degrees to match the drill, blind hole. It was lightly tapped into the hole and the tapping alone made a fairly tight fit. A round needle file was then used as a staking tool. I lightly tapped dimples around the base of the pin to drive surrounding bolster material tight against the pin. A couple of minutes of this work produced a pin that was so tight I couldn't pull it out with moderate to heavy pulling holding the pin with needle nosed pliers.
Both front and back bolsters will have this rivet plus a larger 3/32 pin. In the front the 3/32 pin is through the tang on the blade. On the back the 3/32 pin is one of the two pins used to hold the spring. These larger pins go entirely through the bolsters and when peen hammered down they will also help hold the bolsters in place.
I stuck the bolster on to the liner, the 1/16" rivet going through the hole and then peen hammered and then filed and sanded smooth. There is a difference in color- a brass dot in a steel liner and I didn't consider this however as luck would have it, both the spring and the tang of the blade cover these areas so on the completed knife they won't be visible. If a knife was designed where these would be visible if you looked into the slot, then I'd used 1/16" nickel silver.
So that's how I did it. I have no documentation however I don't think the originals were brazed or soldered nor integral (due to cost and that the method wasn't popular until sheet metal became less expensive). I don't think these rivets went all the way through because on at least a few surviving originals a slight visibility ought to be seen on some bolsters- so- to the best of my knowledge staking in a blind hole was likely used and now I know it works very well, was easy to do, and could have been done in a small shop by an apprentice.
Remember- I have no documentation, I am myself trying to figure these things out.

 

[Mike_Todd]

Thanks for your willingness to share and taking the time to post your findings.

Right now, I'm knee deep into making Scagel style folders, but knives with bolsters and period folders is on my to do list.

I'd figured solid bolsters were soldered to the liners and that's how I was thinking of doing it. Sheet metal bolsters were/ are a mystery to me. You've given me a lot of food for thought.

 

[LRB]

For 18th c., the bolsters and liner are one piece, and most often iron.