Now that I had the design and a cut list I needed to build four
different jigs to cut and assemble the pieces.
Rather than show a completed picture and say, “I built the jigs.” then
let it go from there I had planned on spending a little time going through the jig building process. The jigs are important since if they are not right the piece won’t be either. However, as you can see this post is titled The Jigs Part I which
means there will be a Part II. As I developed the jigs the build process got
a bit more complicated than I thought and the information grew. It finally got to a point where I needed to
break the material into two posts. So
this post covers the jigs that get mounted to the lathe.
The process starts by making some drawings to get the design
down and figure out what I need in the way of materials. Three of the jigs get mounted on the lathe.
The first and easiest is an indexing wheel. It along with the second jig is used to
accurately set the individual segments every 30 degrees and to offset the
adjacent layer by 15 degrees. I printed
out a paper copy of an indexing wheel made for a 12 segment design, glued it to
a piece of thin plywood cut it out on the bandsaw and sanded the edges smooth.
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Index Wheel Drawing and Paper Glued to Plywood & Cut Out |
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1. The alignment guide made out of clear plastic.
2. A plywood backer to support plastic.
3. The top crosspiece that goes across the lathe
ways to which the alignment guide and its backer are screwed to.
4. A spacer that goes between the ways to keep the
jig square to the spindle axis and hold it a fixed distance away from the lathe
headstock.
5. A clamping bolt that when tightened holds the
jig in place.
6. The bottom crosspiece which goes below the ways
that the clamping bolt is threaded into.
Only a couple of pieces need to be cut and located carefully. The top of the alignment guide needs to be
right at the centerline of the spindle.
You want the line on the index wheel to be parallel with the top of the
alignment guide. If the alignment guide
top is above or below center then it will never be in correct registration.
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Alignment Jig & Index Wheel in place |
The other piece is the spacer that goes between the lathe
ways. To keep the jig square it needs to be moveable but not a sloppy fit. I spaced
mine the thickness of a playing card (about .01”) less than the ways spacing. The piece in the photo is long enough for
both this jig and the next one.
Its length needs to be cut so when it butts against the
headstock it holds the plastic alignment guide about 1/16” out from the index
wheel. Lastly, the spacer and top
crosspiece are fastened together at 90 degrees.
To make the clamping bolt knob here is the process I go
through. I start with a template to
layout the shape, bandsaw it close, finish shaping on the disk sander, cut a
square mortise for the carriage bolt lugs, drill a hole for the threaded shaft
of the bolt, round the edges, sand smooth and finish.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguR0HyUQRnMNmUHjL37oY6wLe69Se_2e6BNXikfc86J7I1oUsIUu6epbwkXMhRQ1sx0GwEBEL0SZrrMTtrCDCKwOrBBVGVm94DLZ8mpaIvo87yISs_xtQ3boyBWy6jDGKBtTrpUipsPsk/s200/0212_DSC9192.jpg)
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1. Threading an insert on a threaded rod and holding
it in place with a jamb nut
2. Mounting that assembly in a drill press
3. Use the spindle feed handles to start the insert
and put some pressure on it.
4. Turn the drill press chuck by hand to run the insert
in to the desired depth.
One thing, just don’t turn the drill press on to run the
insert in. If you do it will be
thrilling but not the kind of thrill you really want.
The last jig that gets mounted to the lathe is the Gluing Jig. It makes sure the
segment is set parallel to the layer center line and that it is at the correct
distance from the layer center point. While
the actual size of the jig is not critical I made it large enough to be rigid
when clamped in place. My base ended up
being 12 ½” x 14”. As with the last jig
there are a few things that are important such as keeping the pieces square and
plumb with the lathe ways.
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Gluing Jig |
However, the location of the aluminum angle at the top is
the one item to really pay attention to.
The top corner and its horizontal cut edge needs to be right on the
centerline of the spindle because that is your reference point for setting the
outside edge of the segment. If it is
off then so will your layer diameter which impacts the gap size and the size of
that little glue joint which holds everything together. The long part of the angle needs to line up
with the center line across the face plate.
If it’s out of parallel with the ways, too high or too low then the
segments will be twisted when you look down on the ring.
This completes the jigs necessary to accurately locate and
glue the individual segments in place.
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Completed Jigs Ready to Use |
Next up – The Jigs Part II
Great illustration and descriptions Dave. As an engineer, I appreciate precision in design, description and construction. As a turner, I appreciate your work. Thanks
ReplyDeleteGlad you are getting something out of the blog. I have enjoyed making the projects and posting them so as others try these projects they may have an easier time of it than me.
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