muffler Tapping

Tapping thin material can be a challenge. Here's a few tips on power tapping for a new nozzle.

    To get the best smoke performance from your nozzle,  proper placement is critical.  Drilling and tapping a new smoke port in the proper location to direct the nozzle spray across the exhaust port window opening is often needed.  Nozzles are designed with depth and rotational adjustability to fine tune your smoke fluid spray location.  I suggest running your smoke nozzle in an open air test to get an idea of the spray angle either with water or smoke fluid.  This will aid you in determining placement for your new smoke port to be drilled and tapped.  

    Hold your workpiece in a vice wrapped in a towel. Mark your location, and then lightly use a center punch on your mark so your drill bit won't skid around. Use a new drill bit and position on the mark you just made. Start the drill slowly with light pressure to start your hole. Not much more than a turn or two of the drill bit. Stop and verify that you are still on your mark. Reset your position and with the drill at mid to moderate speed use light pressure to begin drilling. Chips should be thin wire-like. When you feel the tip begin to break through – keep the speed up, but reduce pressure to almost none. The drill should not grab, snag or plunge. If done right you will hardly tell that you broke through. This will yield a nice round accurate hole.

   For tapping I prefer power tapping versus hand tapping. Practice manipulating the forward / reverse on your drill so you can change directions by feel without looking or moving the drill around. Chuck your tap firmly and lubricate the tip of the tap with a drop or two of tapping fluid. Position the drill  above the hole slightly and start the drill at about the same drilling speed. Practice coming up to speed quickly then stop. Reverse direction and come up to the same speed in reverse. Try to do this in one in one fluid motion holding the tip of the tap in the same spot. Practice a couple times and drop it into the hole. Don’t force it or help it. It will feel pretty fast. When through about 10 turns, reverse the drill and smoothly pull out at the same rate it wants to outfeed using that same smooth motion. If you practice on some thin scrap first you will get the feel for it.  Once tapped, remember to thoroughly wash and dry your  muffler to remove metal chips before installing your nozzle.  

   Keep in mind this technique is for a thin wall thru hole and not a blind hole or deep tapped hole. There are other power tapping techniques for those scenarios. Hand tapping a thin material will usually lead to a sloppy hole due to the fact that the tap handle will be off axis when you manipulate the handle in your hand. I would also not recommend a drill press for this as you tend to loose the feel for the upward and downward pressure in the quill and will more than likely tear the threads out of the hole or you may break the tap.