Cin-D LOU EyeLids2
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Fig.14 - This is a new setup to drill holes at an X & Y location to a 0.001" resolution. Start by loading the sewing needle into the drill chuck. The tip of this needle is just used to zero positions and does not physically contact the stock. We will use the back/left edge of the fixed jaw on the vise as the [X=0.000, Y=0.000] coordinate location. This fixed vice jaw will be the 'reference edge' and it is an important concept for precision work. The X table and Y saddle are dialed-in to this point and edge by visibly viewing the needle tip. Note there is some backlash in the drives, so the zero is set by approaching in the +X and +Y directions.
Fig.15 - The X-feed (table left/right) handwheel includes a numbered dial. The scale goes from 0 to 200. One revolution of the handwheel moves the X-axis 0.200". Each tick mark on the numbered dial corresponds to 0.001" of travel. Five full rotations of the handwheel corresponds to 1.000" of travel. The numbered dial is fixed with a thumbscrew (not visible in this view). Loosen the thumbscrew to revolve just the dial to set the 0.000" position at the current handwheel/table location.
Fig.16 - The Y-feed (saddle forward/backward) handwheel has a similar numbered dial. The scale goes from 0 to 200 and works the same as on the X-axis. Loosen its thumbscrew to revolve just the dial to set the 0.000" position at the current handwheel/saddle location.
Fig.17 - Dial calipers are used to check the height/width of the brass strip is indeed 0.450". We want to put two 0.250" diameter holes in the center of this 0.450" height. We are going to move the spindle from the [0,0] position against the vice fixed jaw to be 0.225" away and the holes will be 'on-center' within the 0.450" stock.
Fig.18 - Now the X and Y handwheels are turned measured amounts to move the table and saddle to locate the X/Y center for the drilled hole. The tip of the needle shows the 0.225" Y-position better than the rough pencil mark. Note the X-position is a bit more than the 0.225" dimension because the end is still a bandsaw-cut, rough edge to be finish trimmed later.
Note we are using a new parallel under the stock. This parallel is 0.500" thick, which is a bit more then the 0.450" part. Therefore, a shim of the 0.065" brass stock is used between the moving vice jaw and the stock so the vice is firmly clamping the stock and not just the parallel. Some caution is advised in such cases. You always want to be sure you have a rigid setup for whatever cut you want to make.
Fig.19 - Now the spindle is in the exact desired X/Y position. We remove the needle and insert the center drill tool. The center drill is short and stubby, making it very rigid. It will 'spot' the hole center better than the drill. A drill without a starting center hole will tend to walk across the part and be off-center by several thousandths of an inch.
All eight parts are individually clamped in succession to center drill the same hole in all parts. Each part is placed in the setup such that its end is flush (or 'registered') with the zero face (left side) edge of the vice.
Fig.20 - After center drilling all parts, the center drill is replaced with the twist drill and all eight parts are drilled through in succession. Since the holes will be reamed to an exact 0.025", the drill used is slightly undersized, 15/64" diameter rather than 1/4" diameter. A 1/4" diameter drill will actually produce a hole that is not 'exactly' round and is several thousandths oversize.
Fig.21 - As an afterthought, all parts were taken back to the bandsaw to hand-cut a quick notch in the same upper-right corner of each part. This is to identify that unique corner as the zero reference. Without this notch, the parts are interchangeable top to bottom which can introduce slight inaccuracies in later steps. The notch allows future setups to be consistent, always a good idea.
Fig.22 - Now it is time to manually remove the burr left around the bottom side of the drilled holes. Run the deburring tool around the hole to produce a nice chamfer on both the top and bottom surfaces. A flat file is also lightly drawn across the top and bottom of the part to dress the small burrs around the part perimeter and leave a slight chamfer there also.
Fig.23 - Back on the mill, now with the reamer in the chuck. The spindle is still in the same X/Y position as before. Each part is located to the same reference so the holes still line up.
Fig.24 - Manually deburr and chamfer the holes left by the reamer. An X-axto knife with a #11 blade works well with this brass material to leave a small clean chamfer around the hole.Text
Fig.25 - Back on the mill, the X-position is zeroed at the current location on-center for the first hole.
Fig.26 - The X-axis is moved the exact distance to the center of what will be the second hole. The Y-axis is not moved, leaving the hole to remain in the center of the part in the Y-direction. This reversed view is taken from the back side of the mill looking forward.Text
Fig.27 - The same sequence of hole operations from before are now repeated at the second hole location; center drill, twist drill, deburr & chamfer; ream, and finish deburr.
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