where should i put the blade retention screw and how many do i need

[megajs]

im making a lightsaber for heavy dueling but im not sure what screw would be best for securing the blade or how many i need its a type 16 blade holder

[Silver Serpent]

Only one blade retention screw. If you use more than that, it's actually less secure.

I'm a fan of 8-32 threaded screws for blade retention. If you're going for heavy dueling, you may want to consider using a set screw. Thumbscrews are easier to use when removing the blade since they don't need a hex wrench, but I've had a couple thumbscrews bent from errant saber strikes. The set screws don't stick out so they won't get bent on you. You'll just need to carry your hex wrench with you when you want to put in or take out the blade.

Put the screw as close to the end as you can. On the thick part of BH 16 is a good spot.

[Weaver]

Curious about the retention screws. Can you explain why more screws will lessen the security of the hold? For that matter, what is the style of retention? Is there a matching hole in the blade, or does the screw simply "pinch" the blade against the inside of the emitter?

[MedicineMan]

Curious about the retention screws. Can you explain why more screws will lessen the security of the hold? For that matter, what is the style of retention? Is there a matching hole in the blade, or does the screw simply "pinch" the blade against the inside of the emitter?

The screw simply pinches the blade in.

[dgdve]

Ok Ill try to explain this and the science of the "why"

You want to use ONE blade retention screw because the blade is actually being held in place by the friction between the flat side of the blade (opposite the screw) and the blade holder's inner wall... (its a nice long patch poly C + aluminum gripping against each other).. so the pressure from the retention screw adds to this friction.

IF you use 2 blade retention screws (in opposite directions) it causes the blade to be centered and is actually only being held in place by the tips of the screws themselves (so a much much much much smaller amount of actual friction/contact/pressure is being applied)

You also want your blade retention screw to be higher (rather then lower) just as a rule so it grabs a nice chunk of blade (and isnt holding near the end of the blade)

I really hope this helps! BUT listen to SS (I always do) that advice is perfect and gets a clean look of the set screw..

[Weaver]

Good point about the elimination of blade vs wall friction. I have some other ideas which might make for a more secure fit, however (I've never been a friction-fit kind of guy).

-Rim. A single, double, or even triple ring of some material, or perhaps rings created by bowing out the blade's material during formation, would prevent the blade coming out, since the set screws would rest to the outer side of those rims.

-Retention Hole(s) In Blade: If blade holders were to become standardized as regards the depth at which the blade rests in the holder, retention screw holes could be drilled and tapped in the blade itself. You'd either have to break the Polycarbonate or bend the screw to get the blade out without removing the retention screws.

-Internal Friction Fit + Rim: Think of a hobby knife or Dremel tool. Inside the blade holder (perhaps with a removable shroud) there could be a threaded insert with collet. Once the blade is inserted the collet is screwed down, thus gripping the blade from all sides. Adding a flared rim to the very bottom of the blade itself would prevent slippage altogether.

This may be hunting rabbits with a machine gun, but I'd rather go overboard than see my blade flipping through the air at somebody's baby. Would these adjustments be feasible (or even possible) on the blades/emitters TCSS makes?

[ARKM]

You don't need to standardize anything to be able to drill and tap a hole in a polycarbonate blade to fit in your blade holder properly. Just put the blade all the way in, mount the saber in a vise and drill through the pre-existing blade retention hole (A drill press works best here). Then use a tap in the already tapped hole in the blade holder to continue those threads on through the blade iteself. Then use a longer blade retention screw so that is also goes into the blade.

Now here's where most people will chime in and say... "DON'T DO THAT! IT WEAKENS THE BLADE. BLAH BLAH BLAH!". However I have done it and have done it for blades that we're heavily dueled with almost every day for a solid three months and had not any problems other then some wear on the hole in the blade. I don't do it that way anymore because I don't duel anymore and because I make sabers for other people and they don't want holes in their blades... and because the "one blade retention screw pinning the blade in" method supposedly works fine (as many will attest to). In other words, try pinning the blade in via pressure with one screw first and see how that works out for you.

The other options you mentioned are not really feasible. You cannot order polycarbonate tubes with lips/protrusions on them. Also I doubt you can get a pre-made collet that would be suitable for a 1" O.D. polycarbonate blade and you would probably have a very hard time getting a machine shop to do the necessary work on a blade holde to make that system work.

[xl97]

he is an old pic posted, when this topic pops up every now & again..

how-it-works.jpg

[Weaver]

Thanks for the replies. Also, I do understand the concept of the friction-fit; was just trying to come up with some new ideas (that ended up not being so new...sorry about that).

I think part of what makes the friction-fit work is the snugness of the blade against the emitter walls. Putting a screw in that hole should slightly deform the polycarbonate if the material had room to move. It doesn't. As a result of the material wanting to change its shape, the surface of the blade would create pressure all along the interior of the emitter. It's sort of like blowing up a balloon inside a pipe: Good luck getting the balloon out.

And, if I'm wrong about that being the why of it, it was still a good theory.

[Jay-gon Jinn]

Thanks for the replies. Also, I do understand the concept of the friction-fit; was just trying to come up with some new ideas (that ended up not being so new...sorry about that).

I think part of what makes the friction-fit work is the snugness of the blade against the emitter walls. Putting a screw in that hole should slightly deform the polycarbonate if the material had room to move. It doesn't. As a result of the material wanting to change its shape, the surface of the blade would create pressure all along the interior of the emitter. It's sort of like blowing up a balloon inside a pipe: Good luck getting the balloon out.

And, if I'm wrong about that being the why of it, it was still a good theory.

That's exactly the right analogy as to why it works. People have been using this method for several years, and it all boils down to the old adage that "if ain't broke, don't fix it."

I personally have seen an internal collet clamp set up machined to fit 3/4" blades about 8 years ago, and while it was very cool to see a custom saber have a tool-less blade retention system, it was extremely expensive, as there were (at the time anyway) no off-the-shelf parts that would fit. Everything was custom machined by the machinist that made the sabers, and to have it done just for one saber is usually cost prohibitive.