First Build - EZ Engine

[mklotz]

Addendum to above... You may also want to look at...

http://www.modelenginemaker.com/index.php/topic,303.new.html#new

[Rayanth]

Thanks for the input Marv, It more or less confirmed I was doing things the right way =) Unfortunately I can't really make something like that with what I have on hand just yet... but it confirmed my method would work.

Upon further inspection of the plans, I decided that the bore in the cylinder does not necessarily have to be offset. I can see why it is, and why it is probably good for a beginner to have to deal with it that way, but I can redesign around it to not be offset, I believe. That said, I left my square stock nicely centered, and proceeded to try out my keyless dill chuck in the tailstock. The cylinder bore is 1.375" deep, and with the drill chuck installed in my tailstock I only have about 1/2 - 3/4" travel before i max out the ram.

I'm stuck on this operation. I'd like to do it on the lathe, but I can't think of a way to get that much travel without drilling to the extent, then moving the tailstock in further, then drilling further. But this leads to a second problem - how do I know my hole depth if I keep moving the tailstock? For that matter, my DI is only 0-1" so I need to come up with a way of actually measuring 1.375" depth for a hole....

I *could* do this on my drill press, but measuring depth of hole there is also an issue, and I have no method of clamping the drill press vice down, there's a chance it will move on me.

Yes, the hole has been center drilled. (at least I think it's the center... too late I realized I never verified my tailstock was properly centered... that'll be high on the to-do list once I've got this part removed from the chuck)

-- Rayanth

[black85vette]

Measure the drill bit and put some tape on it.   Drill down to the tape and stop.   Tail stock and DI aren't needed for this one since precision is not needed.   Just don't drill through the back of the cylinder.   But if you do, just glue a brass disk over the hole and call it the head cover.  DAMHIK.   

[Rayanth]

Measure the drill bit and put some tape on it.   Drill down to the tape and stop.   Tail stock and DI aren't needed for this one since precision is not needed.   Just don't drill through the back of the cylinder.   But if you do, just glue a brass disk over the hole and call it the head cover.  DAMHIK.   

... I do the tape trick all the time at work, why didn't I think about doing it here? 

So then I can just drill as deep as the tailstock will let me, shut off the lathe, move the tailstock in further, drill some more...fun times!   

-- Rayanth

[mklotz]

Rick is right about it not mattering.

However, as a matter of intellectual interest if it did matter, here's an approach to consider...

Drill the hole to some convenient depth <1.375, say about 1".  Measure the hole depth; let's call this depth 'D'.  Retract the TS ram as far as possible and move the TS forward until the drill bottoms out in the hole.  Set the DI to measure ram extension and zero it.  Drill until the DI reads a value of 1.375 - D.

[Rayanth]

Finally got another round in the shop, and might head out again a little later tonight, depending. Today was continuation (and almost completion) of the Cylinder.

My last shop time had the part centered in the 4-jaw, and a center drill start on the end where a hole would be drilled 1.375" deep (in theory). With my rather large drill keyless drill chuck mounted in my tailstock, I don't quite have 1.375" of travel with the tailstock ram. There were two ways around this - I could drill the hole on my drill press, which I don't trust (it's secondhand and I really haven't used it at all) or I could make a mark of some sort and drill the hole in 2-3 stages, moving the tailstock in between.

My solution was to use the top slide, which is set to 0degrees with a machinist's square. I would tape a sort of ramstop to the top slide, zero out the DRO with that stop touching the drill chuck, then move the top slide the required distance. When the drill chuck hit the ram stop again, it would have drilled to the right depth. I eyeballed the point of the drill at about 0.1" deeper than the full diameter, so I added that much to the required travel. This shows that setup with a piece of scrap double-sided-taped to the topslide DRO as the ram stop:



Note also that the drill is already brought to the 'surface' of the hole by use of a .0015" feeler gauge covering the hole, once the tip hit the gauge, the gauge was removed and it was considered at 0 depth. With this all ready to go, I flipped the switch, the chuck gave 1/4 turn and thunked right into the top slide  this is the first time i've ever turned on power without checking for freedom of movement. Learned that lesson quickly! I was able to just back off the compound to get clearance, without changing any of my settings.

During the process of drilling the hole, I overloaded the lathe's motor twice. I was running at slow RPM's under high speed mode, so I suspect I simply didn't have the torque for drilling such a large hole straight up. This is a 15/32" drill bit, with no pilot. I will in the future step it up in a few stages just like I do at work... I switched the lathe to low gear and about the same RPM, and it didn't 'crash' again.  The other problem I ran into was that the entrance to my hole is tapered. 15/32 = .46875 and the piston is .484 but slides into the entrance of the hole a short ways. I think the drill bit was just sticking too far out and didn't have enough support from flexing, causing it to 'wobble' from the perspective of the part. I do still need to ream it up, though.



It was now time to drill the mounting holes and the air passage hole, and for this I simply had to use the drill press. I could have spent the several hours needed to figure out how to mount the part in the 4-jaw with the necessary offsets, but it just wasn't worth the hassle!

the two mounting holes are drilled a little further from the end than the drawing calls for. This has a 'stupid' reason but it really doesn't make a difference. The problem was that I chucked up the part to face the solid end, as it still had the hacksaw surface to it. When I did this I knew I had about a tenth of an inch extra material, but to get the ACTUAL amount would require facing it square, then taking it out, measuring, and putting it back in. I didn't feel like re-centering it, so I just accepted the extra material on the far end where it makes no difference.

Turns out the drill press is pretty straight. It has a bit of a wobble when first biting the material, though. This is the two .128" holes for #4-40 fasteners :



And the air passage hole, which is also at .1285, and I now realize it was supposed to be 0.125, but... close enough for government work. And I should know, I used to be in the Air Force 



That was a bit shiney to show it, but the picture was also taken after 320 grit was applied

And then some 600 :



This shows the piston inserted until it bottoms out in the taper. It's not far, maybe 0.25" or so, and in the long run it shouldn't affect operation too badly. Also after a buff with the dremel:



This shows the shine a little better....



It's no mirror, but I decided not to hold myself to "perfectionist" standards on this first attempt. There will probably be one more attempt at this engine after I have a mill, I have ideas for changing the design to be a bit more aesthetically pleasing.

I need to obtain a reamer in the appropriate range for this, maybe even two... or I might just measure the end of the taper and get a reamer that size so I can clean it up, and remake the piston.

Not sure what to do next... hmm.
-- Rayanth

[steamer]

Coming along nicely Rayanth!

Dave

[mklotz]

I eyeballed the point of the drill at about 0.1" deeper than the full diameter

For future reference, given a standard, 118 deg point drill, the allowance for the point is 0.3 times the diameter. 

[Don1966]

Looking good, keep it coming Rayanth. Looks like you have figured a way to overcome your limitations with your tail stock drilling.

Don

[Rayanth]

I eyeballed the point of the drill at about 0.1" deeper than the full diameter

For future reference, given a standard, 118 deg point drill, the allowance for the point is 0.3 times the diameter.

Yeah it works out to 0.145, not 0.1.. but I think I drilled too deep anyway, so no biggie =)

-- Rayanth

Er, wait... no, the full size hole will be .145, this was one step undersized... so just a hair less.

[Rayanth]

Looking good, keep it coming Rayanth. Looks like you have figured a way to overcome your limitations with your tail stock drilling.

Don

Yup! It's called "Buy a Mill" 

Seriously, though, I'm trying to work out a way to get that Grizzly G0720R I was talking about in another thread, hopefully in about a week and a half. Unfortunately I start school in a week, so that'll significantly reduce my play-time.

-- Rayanth