Posts Tagged Improvements
After dismantling the tailstock to apply the tweaks, it was grossly out of alignment, as seen from the top:
Seen from the side, the tailstock center is way too high:
No surprises there.
The object of the game is to make the tailstock bore collinear with the spindle bore in all four degrees of freedom:
- Yaw angle
- Pitch angle
The first step is to match those two points, then measure the angular error.
Loosen the (new!) screws holding the tailstock top & bottom castings together:
I set them snug enough to prevent casual motion and loose enough to allow adjustment with gentle taps from a plastic hammer. Tapping the top casting forward lined up the dead centers horizontally, leaving only the vertical alignment.
Then I clamped the tailstock’s bottom casting to the lathe bed:
Loosening the screws a bit more let me tilt the top casting to the left and slide a brass shim between the two castings, adding just a little more height to the left side to move the tailstock center downward.
This could do any or all of:
- Correct a pre-existing pitch angle so everything is fine again
- Pitch the tailstock ram axis out of line with respect to the spindle axis
- Confuse the issue
I started with a 6 mil = 0.15 mm shim that didn’t quite do enough and a 16 mil = 0.4 mm shim was a bit too much. Pinching a brass shimstock snippet between the centers show how they match front-back and don’t match up-down, with the tailstock center now too low:
Some back-and-forth fiddling showed a 10 mil = 0.25 mm sheet came out about right:
With the two linear degrees of freedom accounted for, measure the yaw angle by comparing the position of the tailstock ram’s far end:
With its near end:
Note: measure the offset by sliding the tailstock along the ways, not by retracting the ram. Reassuringly, the ram slides out parallel to its axis.
Measure the pitch angle, similarly:
As it turns out, the far end of the ram is 5 mils down and front from its base near the tailstock. Over 1.5 inches of travel, 5 mils works out to 0.19°.
Although it’s a small angle, the huge Jacob chuck supplied with the lathe puts a typical drill 125 mm from where you see the tailstock dead center’s tip. In round numbers, the drill point will be 16 mils low-and-front, about 25 mils radially off-center, which agrees reasonably well with what I actually see:
Because I don’t do much turning between centers, I retinkered the alignment to put a point held in the drill chuck on center. Deep hole drilling won’t work quite right, because the ram extends along those 0.19° angles, but it’s Good Enough for now. It’ll be much easier to correct the yaw misalignment than the height mismatch.
Those of you who read image metadata surely noticed the pix aren’t in ascending temporal order. Verily, this was an iterative process, with pix happening all along the way.
Filling the mini-lathe’s tailstock ways with epoxy made it slide easily and lock firmly. Some upcoming projects urged me to perform The Canonical Mini-Lathe Tailstock Upgrades, as shown nearly everywhere on the Intertubes and detailed in various HSM articles.
For unknown reasons, the screw clamping the tailstock’s top and bottom castings together threads into the top casting from below:
Although it’s faintly possible you could adjust it by reaching up from below the bed, it’s easier to just drill out the threads for a clearance fit around a 5 mm SHCS:
The drill went through the tailstock so easily I think the hole had been capped with body filler, which would eliminate the need for a bottoming tap.
Then build a square nut from a slice of 7/16 inch square stock:
… and be done with it:
If the tailstock ever needs more adjustment range, I can knock those corners down a bit.
The screw clamps the castings vertically, with a second screw under the tailstock ram handwheel forcing the top and bottom not-quite dovetails together horizontally. I replaced both with 5 mm socket head cap screws:
Tightening a cup-end SHCS against the square not-a-dovetail tends to shift the upper casting; the original screw had a narrow pin end to reduce the torque. Having brass rod close at hand, this seemed easier than machining the screw:
The little tip comes from using a square-ended cutoff tool. Purists will dress the tool at a slight angle to cut off one side first. Of course, which way one dresses it depends on whether you want the remaining stub on the stock or the cut-off part. Sooo, I still have a square tool.
The tailstock has a cam lock handle clamping a square-ish plate against the bottom of the bed ways. Unfortunately, the manufacturer cut the plate with a dull shear, producing two beveled edges:
Flipping it over dramatically improved the clamping action, although I must eventually scrape the paint and grunge off the bottom of the ways. While I had it off, I turned a small aluminum bushing to replace the pair of washers:
The plate hangs lower toward the rear because the clamping bolt isn’t in the middle. The tailstock originally had a mighty spring holding it level, but the spring tended to snag against the front side of the bed, so I removed it.
The lever handle actuating the tailstock cam lock had no stops and rotated freely counterclockwise when loosened. The tailstock casting had enough meat for a 5 mm threaded brass insert in a useful location, so I drilled a suitable hole:
The vacuum hose slurped up the cast iron dust, which is a Very Good Idea.
Butter up the insert with JB Kwik epoxy, slide into the hole, wipe off most of the excess, then pause to admire the result:
The lever stopper won’t win any design awards, even though it’s a dramatic usability improvement:
The finger-tight nut serves to lock the SHCS in place against the lever’s impact. I conjured a small bumper around the head from a rubber foot intended to fit under a random box of electronics.
Pushing the lever leftward to the stop lets the tailstock slide freely and pushing it to the right clamps the tailstock to the bed. The cam’s limited rotation keeps the plate close enough to the underside of the bed to prevent it from tipping left-to-right as the tailstock slides, so it no longer snags.
While I had the tailstock up on jackstands, this is what the ram thrust bearing looks like:
The flange over on the left bears against the steel disk on the right, with no real thrust bearing to be seen. A dab of grease improved its disposition.
Now, to realign the thing …
So now we know a chrome-plated steel rod will survive 16 years in a bathroom drain, at least if you’re willing to coddle the fool thing far more than seems reasonable.
I eased a slug of epoxy into the brass tube to seal the wet end. Given how little use the stopper gets, I hope it lasts forever …
Having used a nail for far too long, this is a definite step up for my machinist vises:
The vise knob has a hole just barely passing a length of 3.4 mm = 9/64 inch mild steel rod from the Small Box o’ Cutoffs.
While I was at it, I made a handle for the parallel jaw clamps:
Those knobs pass a 3.0 mm = 1/8 inch rod, similarly sourced. Inexplicably, one clamp expected no more than a 7/64 inch rod; a brief introduction to Mr Drill Press persuaded it concerning the error of its ways.
I should have made the handles distinctively different, because they’ll get mixed up in the box of vises & clamps. Next time, fer shure!
The Tommy Bar handles use the same solid model as the Sherline Tommy Bars, with hole diameters as noted. Cyan PETG is definitely easier on the eye than red PLA, although it does fade into the background clutter around here.
Mary doesn’t like wearing the wrap-around-her-head earpieces found on sunglasses these days under her bicycle helmet, so I must trim them to fit:
Perhaps I won’t need an old pair to prepare the next set: a scant four inches from the hinge.
We have, as you might expect, a Favorite Cheese Slicer of no particular provenance. Being made of cheap pot metal, it left black smudges wherever it went and, decades ago, I coated it with bright red rubbery grip material. Recently, the coating became lumpy and peeling off the loose sections revealed a definite problem:
Vigorous scrubbing with a foam sanding block and a Scotchbrite pad, interspersed with rotary wire brushing, removed the corrosion and left a slightly pitted metal frame. Protip: scrub under water and wire-brush with a vacuum hose to keep the dust under control.
A pair of 6-32 screws, nuts, and brass sleeves, with two oil dots protecting the frame threads, provided hand grips while I wiped it down with denatured alcohol and coated it with XTC-3D epoxy:
Turns out the mixing stick worked quite well to cover the entire thing, as the epoxy does a great job of leveling itself. I suppose wasting a tiny brush would be more professional, but …
It quietly dripped excess epoxy into a strategically placed trash can for about ten minutes. I wiped off the final drip before the epoxy solidified, leaving a smooth layer over the end of the handle:
It’s back in service and works as well as ever, with a handle now smooth to the touch. I suppose I could have tinted the epoxy to hide the metal, but we regard those corrosion pits as beausage.
The instruction sheet says XTC-3D isn’t the most transparent epoxy they make and, indeed, the layer left in the mixing pan came out more hazy than I expected:
They point out the haze doesn’t matter for thin surface coatings, which is certainly true.
Thirteen years after the original repair on the left side and eight years after I fixed the drawer slide on the right side, this happened:
The general idea is to wrap a new bracket around the old bracket, because trying to remove the old one will probably cause more damage:
A pair of screws hold the new bracket to the shelf support:
Those two screws must support the entire weight of the drawer, which is exactly what broke the original all-plastic frame and slide.
The epoxy chip and transparent plastic sheet in the first picture spaced the old aluminum bracket away from the shelf support and reduced the space beyond the new bracket enough to require drilling access holes. Fortunately, they’re hidden inside the support frame, so nobody will ever know.
The shelf support is a huge floppy rectangle, so I clamped it to the bench vise while drilling the holes:
The new bracket is on the right, with a sheet of white acrylic spacing it away from the shelf support by exactly the same distance as the angled aluminum snippet replacing the failed epoxy & plastic on the broken part:
The two holes in the middle of the aluminum parts show that I used exactly the same angle brackets as raw material. It’ll be a sad day when I eventually use the last of those brackets.
Putting the parts together, with double-stick tape holding all the parts in place, shows how they fit:
And then it just snapped into place. I didn’t bother pretending solvent glue would help anything, nor did I apply any epoxy, so this whole thing hangs from those two 4-40 screws. On the other paw, their steel beats the original white plastic.
I devoutly hope to never rebuild the actual drawer slide, but these dimensions may help somebody else out of a jam:
The vertical “40” dimension refers to the available space from the bottom of the white plastic part to the top of the shelf support frame; the new bracket is a tad shorter than that.
The plastic parts in that refrigerator have been a complete disappointment: were it not for my relentless repair jones, we’d likely be on our third or fourth refrigerator by now. Oddly, the cooling parts continue to chug along (*), without more than the occasional loud noise in the middle of the night.
We’re definitely doing our part to reduce our waste stream.
(*) The most recent freezer fan hasn’t failed yet!