The Hammer

One of the first projects I decided on when I bought my lathe was a brass hammer.  There were several reasons for this choice.  First, a hammer has a fairly simple profile and seemed apt for a first project.  Second, I gave me the opportunity to learn/improve several different skills in one project.  Third, I wanted something fairly small but interesting to send to a friend.  The project ended up being easy and very rewarding since at the end I had a useful tool.  I ended up making two of them, one to keep and one for myself.

I started out by drawing a general design in Google Sketchup.  I didn’t really care about exact measurements or tolerances so I just threw something together.  It looks like this.

The next step was buying some brass for the head and some stainless steel for the handle.  I found out that Amazon has a huge selection of metals in bar, sheet, round or just about any other shape you want, in every alloy imaginable.  Great place to look for metal if you want it quickly and don’t feel like digging through scrap yards looking for useful material.  I bought a 12″ chunk of 1-1/4″ brass and cut off two 3″ chunks with my band saw.  After that, it was a simple thing to face turn on end flat and then turn the outside a few thousands to get it nice and shiny and round.  I cut three grooves in the end with a grooving tool and put a very slight chamfer on the corner with a chamfer tool.  I then flipped the stock around to work on the taper end.  Chris from Sector 67 gave me a tip on chucking finished work without marring the surface.  You can wrap a single piece of construction paper around the end where the chucks will bite.  I did this, tapping the seam, and it worked perfectly.  Once I had it chucked I spent a significant amount of time making sure it was perfectly centered and level since I would be turning this end to try and match the other end.  On hindsight, I didn’t need to do this since I was going to be cutting a taper on it but at the time I didn’t think it through all the way.  After turning the cross-slide to 10 degrees, I started cutting the first (biggest) taper.  Once I got it down to where I wanted it, I simply kept cutting but stopped about 1/4 of the way up the outer taper.  I repeated this until the final taper was the right size.  I just estimated the depth and length of each taper and it turned out fine.  I put a slight chamfer on the small end as well.  You can see in the first picture, on the first head I turned the spacing was a bit off.  I fixed this on the second head.

Neither one is perfect but I’m still happy with them.  I call the taper a Devo Taper, I’m taking credit for that term since I haven’t seen it used before.  Next step was the handle.  I was originally going to go with a 12″ handle so I cut a piece of stainless and chucked it up.  The stainless rod I used is 3/8″ and I cut a course 3/8″-16 thread on it.  I found the gear setup for cutting 16tpi threads, put them on the machine, jumped into it head first and made a few mistakes.  The first mistake was using a grooving tool instead of a threading tool.  I’m still learning on things like tool geometries and stuff so I’ll chalk this one up to a learning experience.  I also was originally trying to cut the threads too deep per pass.  After I totally failed with the first attempt, I cut about an 1.5″ off the piece and went and read up on cutting threads.  On the second attempt, I first used a cutoff bar to cut 1/8″ of thread relief on the bar where I wanted the threads to end.  This gives the cutting tool some clearance while cutting the threads.  I then found my ACTUAL 60 degree cutting tool and centered that in the tool holder.  The trick to cutting threads on a lathe is watching the thread dial indicator and starting the auto-feed on the appropriate number.  The threaded rod on the auto-feed has 16tpi and since that is what I was cutting, it didn’t matter what number I started on as long as I always started on the same number.  This ensures that each time I cut a pass, the carriage is riding on the same thread of the screw and the tool cuts on the same path.  I started out with a 1 thousandth pass just to see what would happen.  It put a faint spiral on the piece.  When the tool hits the thread relief, you stop the auto feed, back the tool out two full turns (50 thousandths per turn or 1 tenth of an inch), move the carriage back to the starting position, move the tool back in two turns and then set your new depth.  I put another thousandth on and cut again.  This put a nice groove on the piece which is what I was looking for.  After that, it was just 2-3 thousandths per pass, lots of cutting oil and repeat until the threads are the proper depth.  Since I wasn’t sure what the proper depth was supposed to be, I just tested a 3/8″-16 nut several times until it felt right.  All in all, I think it turned out great for my first try.

After that, all that was left was to put the knurling on the handle.  I have a large scissor-style knurling wheel that mounts into a quick-change tool holder.  When knurling, slow feed seems to be the way to go so I set the gears back to the stock settings.  I think this feeds around 0.0004″ per revolution.  I chucked the threaded end of the work just past the threads and then used a center drill to prepare the work for a live center.  The live center sits in the tail stock and supports the opposite end of the work so it doesn’t flex while you’re working on it.  Once this was done, I tried to line up the two wheels on the knurling tool directly above and below the work centered as best as possible.  I got it as good as I could and then tightened down the wheels until they they started biting into the work.  Applied lots of cutting oil and then turned it a few times by hand just to see how the pattern looked.  It looked great so I fired up the lathe to about 150 rpm and engaged the auto-feed.  It was real slow going but turned out looking great.  Once it got as far as I wanted the knurling, I backed off the disengaged the autofeed, loosened the wheels, backed off the tool and moved the carriage back to the start.  I lined it back up on center.  I tightened the wheels slightly and turned the work by hand.  The wheels slipped into the grooves that were cut on the first pass and I tightened the wheels to what I estimated as twice the cutting depth.  I made a second pass to finish up.  Once done, I ran a diamond file over the knurling to clean up any sharp edges.  It turned out great.

After that it was a simple matter to drill a hole in the head of the hammer, thread it and then screw the rod in.  I offset the hole slightly towards the big end as close to the center of gravity as I could get it to keep the weight right.  They both turned out great.  The first one is mine and the second I sent to a friend.

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