Elmer's Kimble engine

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arnoldb:
This afternoon I clamped the covers and block together. The perspex cover is sandwiched between the brass cover and the block, and the masking tape on it helps a lot to keep things from moving:

Off to the drill press to drill the 1.6mm holes. With a small drill like this, I'm comfortable, yet very careful, to keep the workpiece firmly pressed down on top of the vise jaws with my left hand and operate the quill with my right. Because of the different layers in the sandwich, I peck-drilled the holes to keep swarf in them to the minimum while drilling:

When needing to move the clamp to a different position without letting things come apart, I just clamp the lot in a spot where the old and new clamp position wouldn't interfere. Sometimes I do that with another toolmaker's clamp or in this case I used my small milling vise:

Here I wanted to flip the clamp from the left to the right to be able to drill the holes on the side where the clamp was before changing.

Next off to the mill to get rid of excess stock on the covers:

Silly me... I'd put the studs and nuts on the top on the wrong side. That made milling excess stock off the top more difficult, as I'd originally planned to just remove the nut and stud on the alternative top parts to finish to size. The nut was too big to rotate, so I had to go around its back:

Next I turned up 1.6mm pins from some 4.3mm aluminium rod I have. The toolbit is set up to leave a very slight taper on the aluminium, and the entire thickness is turned down in one go. I used the small ER11 collet chuck, as it has a 4.5mm collet that can easily clamp down to 4.3mm - thus saving strain on my 5mm ER 25 collet:

The four completed pins/plugs. As you can probably see, I just used a side-cutter to clip them off at just over the approximate length needed. The two longer pins are to plug the holes right at the top of the engine top; they need to be long enough that their inside ends will be machined flush with the valve bore later on:

Here I installed one of the side plugs - a tiny dab of loctite on it, and hammer it into the hole with a small ball-peen hammer. I knocked it good and flat, so that the plug will properly fill the hole, and once the excess is filed off, the plug will be completely invisible:

The two top pins knocked in and then filed flush; as you can see, they "disappear":

Same with the pin on the side; just lightly cleaned up here:

There are still tool marks on the sides of the block; these will be removed later in the build.

At this point I called it a day, as a big thunderstorm with high winds broke. I'd left a lot of doors and windows open in the house, so I had to go and attend to a bit of mop-duty :D:

:beer:, Arnold

saw:
Nice build Arnold, I am very excited to see how this engine will come out :thumbup: :thumbup: :thumbup:

DaveH:
Coming along nicely Arnold.

Heat wave last week - floods this week :lol: :lol: :lol:

These weather excuses - a bit feeble mate :lol: :lol: :lol:

Nicely posted as usual though :clap: :clap: :clap:
:beer:
DaveH

arnoldb:
:beer: Thanks Benni - it's going a bit slow though...

Cheers Dave :beer:. :lol: I can add some more excuses... Corporate take-overs, incorporating new corporate logos on electronic stationery, updating mail server signatures and on and on, but those are boring; it's more fun to blame it on the weather :lol:

:coffee: A bit of a boring update today...

The cover plates were still sticking together after last weekend's work - this was a result of using some old gummy masking tape to protect the perspex cover, so I lightly clamped them together just to make sure they didn't come apart, then opened the holes to 2mm for clearance for M2 screws, and then countersunk all the holes - easy to do by getting one hole to the correct depth and setting the drill press depth stop:

I had a bit of chatter in the holes; after a careful check,I found that these holes are actually a bit small for the countersink I have and it can barely open them up, so I'll have to buy a smaller countersink at some point.

Next up, tapping the M2 holes in the engine block. My M2 taps are too short to tap the holes right through, so I had to tap the holes from both sides. I used my tapping guide to limit the depth to tap too to half of the engine block depth (Apologies for the out-of-focus photo :palm:):

Then I set about tapping all the holes. For aluminium I use methylated spirits (rubbing alcohol) as tapping fluid, so I poured some into a spray-can top to make life easier. The meths easily washes off any chips stuck to the tap, so it's easy; tap the hole; swash the tap in the meths and it gets both cleaned off and "lubricated" for the next hole:

The dark bits in the meths are chips that were washed from the tap.

Next a quick check, and as I thought, the shortest M2 screws I have are too long for the thin cover:

They are OK for the perspex cover though.

I've had to shorten M2 screws in the past, and it's a bit of a pain in the rear :palm:. Usually it was just one or two screws at a time so I'd fiddle along, but I was in no mood to fiddle ten of them... So I diverted and built a little tool :dremel:.
I just chucked up some 8mm hex brass, drilled it 5mm diameter (for M6 threading) 15mm deep, and followed the 5mm drill with a 2mm one another 4mm deeper. Then I tapped it M6, and parted the piece off 17mm long. On to the mill, and with a 2mm slot mill, I milled a slot to the center of the 2mm hole, and a perpendicular slot wide enough to allow a 2mm screw's head to pass through far enough from the end to leave the cone section left by the 5mm drill intact.

To my horror I discovered I'm out of 6mm silver steel to make the rest of the tool :bugeye:, so I used a cap screw with the head sawn off and the end section of the thread relieved to clear the last bits of thread in the brass bit:

I wouldn't recommend using the above tool under power on the lathe, as the screw will easily deflect into the slot while machining. I just used it chucked up in the lathe (with motor off) to saw off the excess length of the screws with a junior hacksaw with a fine blade:

It is convenient to have the tool in the lathe, as it's easy to clean up the cut face with a small file, and also file a slight taper around the cut face by rotating the chuck by hand. These screws are stainless steel, and just outside the size for my favourite electronics cutter, if they were within it's size I would just have clipped off the ends with it and cleaned off with the file.
Ideally, I should have "relieved" the seat for the screw in the brass bit to 90 degrees rather than using the 118 degree cone left by the drill bit - but that would have meant making up a d-bit reamer and I wasn't in the mood for faffing around with that today :coffee:.

The little tool works quite well. Slip a screw in, tighten up the brass section on the arbor, saw off the little screw, file the nose flat to remove the burr from sawing, file a slight taper around the end of the treads then loosen the brass nut with a hand under it to catch the screw as it falls out... It took me less than a minute per screw to get this lot shortened:

All the little screws in place - I need to make all the countersink holes about 0.1mm deeper though :palm::

And the perspex cover screwed on:

To compensate for the thickness of the masking tape that was on there, I countersunk the holes slightly deeper. Unfortunately, I over-compensated :loco: - these are slightly too deep.

Hopefully, I'll have more interesting progress to report tomorrow.

:beer:, Arnold

saw:
Nice done Arnold I like your thinking and your way to make some easy tools. I will copy your idea when I need it. Your buildings skill is something too take after. :clap: :clap: :clap:

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