Time Fuse Cutter

WARNING AND DISCLAIMER:  If you are underage, then consult with your parents or guardians before attempting any of this.  You are on your own - I'm not responsible for your actions or harm you may bring to others because of your actions.  Making the items described below  can result in injury or death to you or people in your vicinity. Some things mentioned here may be illegal to make in your city, county, state, or country so check the laws that apply to you before you attempt anything described here. These notes are not complete on purpose. If you are reading them and new to pyrotechnics, then you are making a mistake. Stop now - this page is not for you. Get a beginning book on fireworks (see Skylighter or American Fireworks News (very quick shipping)  for a start) and read up. You can't make any of this work without more information so read up or join a club or ask someone to help you.

 

This is a note on how to build a relatively inexpensive time fuse cutter that makes very accurate and very repeatable cuts. It is also simple to build.  The cost, assuming a new cutter, is about $35 (2010 prices).  Be sure to read through this whole page before starting the project.  There are several additions at the end that might save you time or effort.

The above is the finished item.  Cute, eh?

Here are most of the pieces you need to make it. All brass fittings are from Menard's but can be had from about any plumbing supply.  They are 1/8" brass pipe fittings. You need:

1 1/8" MIP nipple 2" long - Watts Part Number A-717
2 1/8" MIP nipples Close (no length - all thread) - PN A-715
2 1/8" FIP pipe tees - PN A-704
1 1/8" FIP pipe cap (get two... I always ruin one)
Some 10/24 all-thread (or 1/4:20 all-thread) about 3" long
Tap for the all-thread (either 10/24 or 1/4:20)
Tap for the cutter (1/4: 20)
13/64 bit to make the tap holes for the 1/4
5/32 bit to make tap holes for 10/24 if you use that
1/4 bit
Drill
Sears Handi-Cut (long blade - 3 7/8") - note: the short blade cutter can be made to work - see the end of this page for howto.
A few nuts and washers for the all-thread
1 3/4 1/4" shallow headed cap screw (or any  1/4" machine screw that is 1 3/4 long)

 

First unscrew the anvil screw on the Handi-Cut. This is a metric screw so I replaced it
with a 1/4" screw. 

 

Drilling out the hole with a 13/64 bit and then one side of the holder with a 1/4" bit

 

You will need to tap only one side and make the other size a full 1/4".  Alternatively, just drill the thing
out to 1/4" and use a nut on the other side of the 1/4" screw.

Now drill out and tap the 1/8" cap for 10/24 all-thread (or 1/4" all thread if you
feel lucky and can hit the center of the cap... it ain't easy so you might want to use
10/24) 

 

Centering the hole in the cap as best you can, drill her out and tap her 


Assemble the pieces that you've made and tighten them. Tighten the short nipple as tight as you can.
Don't worry about messing up the threads since you will trim it back. Use Vice Grips or a vice.

 

 

Trim back the nipple so it just sticks out from the T that it is screwed into. It is also helpful to file the threads flat
on the part that rests against the anvil of the cutters as seen in the second picture.  Alternatively, you can turn down the nipple as seen in the third picture. Do one of the three... or nothing. ;-}  The idea is to get the fuse as close to the anvil as possible so any cutting will be supported and result in a straight shearing of the fuse with no damage to the powder train. Be sure to leave a little space between the nipple and the blade so you can fetch the fuse out of the tube.  Sometimes I have to use tweezers but most of the time it will shake out.

Here is why you put that nipple on the end of the T and up against the cutter - it makes a snug collar for the time fuse. Test your time fuse with the setup - you may have to bore out the collar a bit.  I have seen time fuse diameters vary from .223 to .255.

Finally, screw the bottom T onto the Handi-Cut, the all-thread into the cap and the cap onto the long nipple and you are done. It helps to file a mark on the nut on the back of the fuse holder so you can easily count the turns.

The lip of the nipple that you cut back should just rest on the anvil. You can also NOT cut the nipple and just file the bottom flat so it fits on the anvil itself and when a fuse is in it as described a few pictures above this, the fuse is almost resting on the anvil.  This guarantees the fuse won't bend down and spoil your cut. You might have to build up the screw mount with a couple of washers so the fuse holder fits correctly. You want the fuse to be as close to the anvil as it will go. 

You can also swing the holder back so the fuse is cut near the back of the jaws - some may find that easier to use. Watch out for that sharp blade!

Late additions and updates:  

The long nipple (the 2" MIP Nipple) has a square edge, it helps to chamfer the inside of the nipple so it is rounded or ramped.  That way the time fuse will slip through it easily.  The easy way to chamfer it is to use a cone grinder from a Dremel or a power drill and just grind the square edge away.  You can use something like the picture above:

In use, the distance between where the fuse is cut and the brass tube that steadies the fuse is somewhat small and makes fuse removal a bit tedious at times.  Life is easier if you file a slot in the top brass T so you can urge the fuse out of the contraption with your finger nail.

 

Here is an alternative way of mounting the device. Use the rear lower bolt hole, drill it out to 1/4" and put a longer bolt and nut on it. This is slightly easier than drilling the anvil bolt out. David Gustafsen suggested this on Passfire.

 

Here are a couple of questions asked about this on Passfire:

 

Q1: So Danny, if I'm reading this correctly, one could use 10x32 for a fine thread pitch/control?


A1: Yes, you could use (and I recommend you DO use) 10x24 or 10x32. The main reason is that the 1/8" pipe is just slightly larger than 1/4" I.D. The 10x24 or 10x32 allows you some leeway. If you use 1/4" all-thread, it might jam on you unless you set it up perfectly when you tapped the cap.

As far as pitch of the threads, it doesn't quite matter whether you use 20, 24, 28, or 32 pitch threads. One turn with 20 is 1/20th of an inch. If you wanted finer then turn it 1/2 turn (1/40th of an inch). Any finer than that and I doubt your time fuse is capable of knowing the difference. The accuracy is the same with whatever pitch you use so you don't lose much by going with standard threads. Of course, you need to remember what threads you used so you can get the cuts right.


Q2: How hard is it to get the fuse back out?


A2: If you mount the fuse holder on the front of the cutter, it is easy enough to grab it with your fingers without coming back with a bloody stub. My (new) cutter cuts better in the back of the jaws so I rotated the holder to the back - see picture above. However, there is only a little leeway for the fingers. Nicely, the crack pipe setup still works fairly well. The fuse holder is loose enough that you can just shake it and the fuse will usually fall out else you will need to use tweezers.  UPDATE: See the late additions above. A slot cut in the top T makes it much easier to remove any sticky fuses.