How to Make Copper Cap Boppers
James C. Keffer
1. Copper plumbing caps, sizes 1/2" to 2"* (available at most major hardware stores).
2. Wood for handles, sandpaper in 80, 100 and 220 grit for handles
3. Wood finish - polyurethane (my preference) shellac, or varnish for handles. Keeps wood from shrinking reducing the chance that the cap will loosen
4. Hardened lead. (Wheel weight lead is harder than pure lead - adding antimony, zinc or tin increases hardness). Hard lead resists deforming and helps keep the bopper end round and uniform.
5. Epoxy - Loctite Heavy Duty Professional Grade (available at most major hardware
6. Sandpaper (80 grit) or Sandblaster and sand for inside of copper caps
7. Acetone and paper towels for epoxy cleanup
1. Doming punch set or doming anvils.
a. Example of doming anvils (homemade)
i. 1/2" and 3/4" round bar with rounded ends
ii. Hitch balls rounded to size, 1-1/2" and 2"
iii. Ball peen hammer 1" (1-1/4" not shown)
2. Hammers for doming, ball peen or auto body hammers
3. Wood lathe or carving tools for handle
4. Pot to melt lead in, burner with which to melt lead (propane torch, propane burner or a
gas stove will work)
5. Mixing cup and stirrer for epoxy
6. Clamps for holding caps to handles while epoxy dries
7. Paint brushes for applying wood finish
Tools and Materials:
First, start by doming the copper caps.
The objective is to get the copper cap as round and smooth as possible. The more round the
cap is the better control you'll have in striking flakes. You want to be able to strike the rock
with a single point of the bopper end as shown below.
Next clean the inside of the cap with sandpaper or a small sandblaster (I use either a small
cabinet sandblaster or an inexpensive siphon sandblaster).
Siphon sandblaster ($20):
Level the cap and secure (I use a vice and bubble level).
Then melt some lead and pour into the cap. Leveling the cap helps to balance the weight
distribution of the lead creating a more consistent bopper.
Be sure and only fill the cap up to the end of the dome. This serves two purposes, it allows
sufficient area on the handle and inside the cap for the epoxy to adhere and also places the
weight forward making the bopper more efficient at delivering the energy to the platform on
Caps filled with lead just to top of dome:
Let the cap/lead cool. There is a high degree of probability that the lead will not adhere to
the copper, particularly if using hard head. I find the easiest way to secure the lead to the cap
is with epoxy applied when attaching the cap.
Other means of securing the lead involve 'tinning' the cap with solder prior to pouring the
lead. This doesn't work as well with hard lead containing either zinc or antimony (the two most
common alloys used to harden lead).
Another technique is to 'punch' the lead. Place the cap on a sandbag or similar surface and,
using a blunt punch (or carriage bolt), hammer the lead to where is swells within the cap
thereby creating a tight fit. Again, this also doesn't work as well with hard lead. Since epoxy secures the lead to the cap and the hardened lead doesn't deform, I prefer to use harder lead and epoxy.
Roughen up the interior of the cap with sandpaper or sandblasting one more time to take off
any residue or glazing cause by the hot lead. This will help insure the epoxy has the best
opportunity to create a strong bond.
Making a handle can either be very simple or quite elaborate. Handle styles are a matter of
personal preference but most are usually 3-5 inches in length and made of hard wood. Oak, walnut, maple, alder, fir or any other wood that does not contain oils (such as teak which does not take glue well) will work for a handle.
A wood lathe allows for fast and easy turning of custom-fit handles. A variety of shapes,
sizes and styles can be created relatively quickly. Alternatively, carving/whittling can
achieve the same end although with considerably more work. The simplest and fastest way
to make a handle is to start with a wood dowel and whittle one end to fit the cap snugly.
Turning a handle on a wood lathe:
Checking the fit - a handle that allows the cap to fit flush is more comfortable to use. The
caps should fit snug but not too tight to allow enough area for the epoxy to form a strong
Checking the fit:
Attaching the Cap to the Handle
Mix a good two-part epoxy according to the directions. Use only enough epoxy for the
number of caps you can attached in the curing time specified by the epoxy instructions.
Liberally coat the inside of the cap (if using the epoxy to secure the lead, coat the entire
inside of the cap and then place back the lead). Also apply epoxy to the end of the handle
where the cap will be attached. Place the cap on the end of the handle and twist back-and-
forth several times to even disperse the epoxy. Clamp firmly and clean up excess epoxy with
paper towels and acetone. NOTE: for boppers larger than 1-1/2, epoxy alone is not
sufficient to hold the cap securely to the handle. I use two 1" copper rivets but nails will
Clamping the cap:
2" boppers with caps pinned with copper rivets;
Once the epoxy sets, sand the handle and apply a good wood sealer/finish. I use Birchwood-
Casey Tru-Oil, a shellac based wood finish make for gunstocks. Regular shellac or polyurathane finishes work as well. Sealing the wood helps prevent the wood from expanding or shrinking with changes in humidity, one cause of caps becoming loose.
One the finish is dry you have a bopper!
Drying Boppers (a drying block helps!):
The Finished Boppers (Walnut and Maple)
All that is require to maintain the boppers is to occasionally re-seal the handles with your finish of choice.
When a copper cap wears through - and if you use it a lot - it will, you can remove the cap from
the handle by applying medium-high heat (I use a standard size propane torch). The epoxy will
soften and, using gloves, you can usually twist the cap off. I simply form a new cap of the same
size, put it in a vice, level it, set the old cap on top and melt the lead out with a propane torch.
This insures that you have just the right amount of hardened lead in the new cap. Leveling the
new cap prior to pouring in the lead is critical to assure the best balance. Once the cap is cool to
the touch you can re-attach in with epoxy. Removing some of the old epoxy first using some
coarse sandpaper should provide an adequate bond.
I've only had a handful of caps come loose in over 500 boppers I've made. None of the caps
have come completely off and those that came loose had to be heated in order to remove them.
Once removed, I just re-glued with epoxy none have come loose since.
From what I've observed the primary reasons for caps becoming loose:
1. Inadequate epoxy coverage. Solution - use extra epoxy and twist the cap several times to
disperse the epoxy evenly.
2. Too smooth surface on cap/handle. Solution - roughen the inside of the cap with sandpaper
(better still, sandblast the interior of the cap- I do) and roughen the part of the handle that goes
into the cap. Clean with denatured alcohol.
3. Wood shrinkage - wood shrinks or expands with humidity. Solution - seal the handle with
wood sealer, shellac, lacquer or polyurethane.
4. Too much lead in the cap resulting in insufficient glue surface area. Solution - fill the cap just to the top of the domed area.
5. Too tight of a fit between cap and handle, not enough glue area - solution - make sure the gap
between cap and handle is large enough for adequate gluing - not too loose but not tight. Clamp
and let set for 12-24 hours - regardless of the 'advertised' set time.