First Build - EZ Engine

[Rayanth]

I first started this hobby, in a sense, several years ago when I discovered somewhere the plans for the Edwards Radial 5... and through a number of searches stumbled upon HMEM. Until very recently, the extent of my hobby had been simply downloading all of the free plans I could find, and modeling them in CAD (Namely, AutoDesk Inventor) to see how they worked. While modeling, I always kept a mind to "how would I machine this" and tried to learn the best I could by reading countless build logs by the masters of the hobby.

In June 2012 I purchased a Grizzly 7x12 lathe, at the recommendations of others I went with the lathe first as I did not have funds for both lathe and mill, and I was informed the lathe would be the better choice (I am mostly familiar with mills, from high school shop fifteen years ago). Due to moving and work and getting married and various other things, I had to put the hobby on hiatus shortly after buying the lathe, but this winter I put the 'new' shop together and started trying to figure out how to use the spinny thing to make round things to exacting tolerances.

In June when I bought the lathe, I settled on the 'EZ Engine' plans (also found on HMEM at the time) because it could be done almost entirely on the lathe, and with some fancy footwork the non-lathe parts could probably also be done on a lathe with care. I am now comfortable enough with the lathe to give this guy a try.

The first part I chose to make, which I determined would probably be the easiest, was the Piston. This consists of two different diameters, and a flat spot for the "connecting rod" to screw in. The flat spot has a #4-40 hole tapped into it. The bore is 0.500" and I had 0.500" brass barstock. I didn't like the surface finish of this stock, though, so right off the bat I started making changes to the plans. I would turn the diameter down to the next smallest drill size, 0.484" and go from there. This will surely have repercussions later, but I'll cross that bridge when I see it.



After turning the two diameters, my next task was to create the flat spot. I had just used the cutoff tool to face the end to the right length, so I angled the QCTP slightly and used the edge of the cutoff tool to mark the centerline (obviously with the lathe turned off).



Since I have no mill to speak of, and could not immediately remember where to find my files (and who wants to file away THAT much material?) I chucked a 320 grit sanding drum to my Dremel and went to town... This seemed to be going great, but in the long run was less than ideal... The image does little to show just how not-flat that cut really is. 



Thinking about the best way to fix this, I settled on files. But hadn't I just commented that I had no idea where my files were? I planned on picking up a set tomorrow, but... that means no more shop time and I'd barely been out there half an hour    ... but that box over in the corner looks my 1:32 scale F-15 Model Work-in-Progress... and that's where I last used my files... so that would be the LEAST likely place to find them, let's look... hey, my files! 



That got it much smoother, and relatively flat. there's still a bit of an indentation to it but it will serve its purpose well.

Some 320 grit followed by some 600 grit, gets the flat spot looking a bit better :



Followed by a buffing wheel on the Dremel with some buffing compound to give the whole piece a beautiful shine... OK not quite as immaculate as I've seen from others here, but I think I forgot to 600-grit the round parts, and only did the flat spot. 



I then used the trick from others to set my cutoff tool perpendicular by pressing the QCTP to the face of the 3-jaw, and cut off the part. I had to remove the blade to do this, and I guess that set it to no longer centered properly, so I got a little bit of a nib...



And fixed that up by chucking it back up and facing off that end (which was .004" too long anyway)

I'm fairly pleased with the end result, but wish I could have handled the flat spot better. With just a lathe and files, I can't see what else I could have done... I can think of a dozen ways to get it perfect on a mill. oh well, for my very first 'production' part, I will call it a success!!

Just gotta decide what part to make next.

-- Rayanth

[b.lindsey]

Looks like you are off to  fine start there Rayanth. I'll be watching along with many I am sure. That first engine is a special one and I think you picked a winner to start with!!

Bill

[peatoluser]

Ah! the joys of filing. My most used tools. nothing wrong with the part or using files to get there. I do find that brass prefers new files. Once they start going blunt , they'll cut mild steel OK but not so good on brass. As for the pip from parting off....well it's small compared to some of the ones I get! Sometimes the blade is at the right hight but the 'little diameter' left is too weak to support  the part, and it will climb over the parting tool and break off. Try grinding the tip of the blade at an angle to the lathe axis so it just leaves a small cone on the stock.
good luck with build. looking forward to it

peter

[steamer]

Great Start Rayanth!  the toughest part is starting!

Dave

[tel]

Yep, that's a good looking part. Don't worry about the pip - you'll always get that on the free end of parting off

[Mosey]

Great beginning! Keep up the good work.

As for the pip, a little more concentration on what you're doing and it will vanish, as it should. Isn't that what this is about?

Mosey

[black85vette]

Good start.   When I got started and couldn't yet justify a mill I got one of these:

http://www.littlemachineshop.com/products/product_view.php?ProductID=1956&category=

It was not perfect but helped a lot on small parts.  Had to make a mount for it, but heck that is part of the hobby; use tools to make parts for more tools.   Repeat over and over.   There are plans for a mounting block on one of the tabs on that page.

Tip; usually I do the cylinder first and then turn the piston.  It is easier (for me at least) to make small adjustments on a round piece than one that I have to drill or bore.   I leave the piston in the chuck and test fit the cylinder onto it.  It is better to leave a part mounted in the chuck and do as much work as possible before you remove it.   The least number of times you re-mount or re-clamp a part the better.

[Don1966]

Hi Rayanth, glad to see you getting a good start. I will be following along with you. There is plenty ways to do things and you must find what works for you. Good luck on your first engine and I look forward to more progress.

Don

[mklotz]

A jeweler's saw is an inexpensive and very useful tool for many jobs.  With one you could have removed the bulk of the stock from the flat, then finish filed to size.  The less filing you have to do, the higher the probability that you'll do it well (not to say you didn't do this job well-just generalizing).

Also, let me reiterate Rick's advice:  Always fit the piston to the bore, not vice versa.  The exact size of the bore/piston pair is generally immaterial.  You've got some leeway in which to do the fitting.

[Rayanth]

Thanks all for the feedback! 

Rick/Marv : I realized after I had started machining the piston that I should fit it to the bore. I think I can rectify this by drilling the bore undersized and then opening it up slowly with a boring bar while fit checking with the piston.... we'll see how that goes. If all else fails, I can make another piston.

black85vette: I have been looking at that attachment but was skeptical of its uses... it seems to be limited to such tiny pieces. Still, I suppose jigs can be made to let it hold specific larger pieces. I nabbed the Jose Rodriguez video from LMS also, and he shows the usage of a similar milling attachment and I can see how that would be a great way to get some of the basic milling operations done, and am now more actively considering purchasing one.

Today I will attempt either the cylinder with its offset bore, or the valve... but from the feedback, the valve also should probably be machined after the valve body's bore is cut so I can check fit the valve's OD, so I may have to hold off on that... I guess this means taking a stab at figuring out how to offset square stock in a 4-jaw. Be prepared to laugh at me 

-- Rayanth

[black85vette]

... I guess this means taking a stab at figuring out how to offset square stock in a 4-jaw. Be prepared to laugh at me 

Don't wait until you are into an operation to ask for help.   I still hit spots where I just ask;   "How the heck do I do this??"   You will get suggestions, pictures, web links and other help.   Better to go into something new with some ideas than to just figure it out. 

About the cylinder; it is less work to get a clean smooth cylinder using a chucking reamer than a boring bar.   At .5 inch you would be using a smaller boring bar that will have some flex to it.  For a project like this just drill 1/32 or 1/64 under then run a chucking reamer at slow speed with lots of oil.   Pull it out frequently, like every 1/8" to clean off the swarf.

[Mosey]

I've been thinking about the little pip when turning. This is from another beginner, so take for what it is worth. The pip, means that your tool height is not exactly at the center of your workpiece height. This is an important thing to be able to do when turning, and later when parting it becomes more critical. This is a basic skill you want to have.
Now I'll shut up and sit back for more skilled members to elaborate.
Mosey

[b.lindsey]

I would disagree somewhat though being off center can be an issue also.  Depending on the material....thinking of softer metals like aluminum and brass...once you get down to that last .020 or .030", even if you are dead on center, the weight of the material about to be cut off can stress or fatigue the small bit of material left in the cut. Since the part is free to move, relative to the stock piece in the chuck, the break will more likely leave the pip on the cut off part. 

Bill

[Rayanth]

sort of along the lines of what i was thinking, Bill. The cut was very clean, and when I followed through after the breakoff there was no measurable pip left on the chucked part, which means I was pretty much dead on center. It didn't make sense after I thought about it, that the blade would be in a different spot just by removing it from the toolholder... it was the same blade in the same toolholder at the same settings, it should not have changed its height. The blade's tip is fairly flat to the work, I will consider angling it so it has a point on the side away from the chuck, so it is more likely to cut cleanly.

My concept for off-setting the square stock in a 4-jaw is to use a Dial Indicator pointed at the centerline of the back side of the stock, and rotate the stock until all four sides show the same offset - namely, it's centered. Then pick an axis and offset it the required amount to bore the hole.

-- Rayanth

[mklotz]

My concept for off-setting the square stock in a 4-jaw is to use a Dial Indicator pointed at the centerline of the back side of the stock, and rotate the stock until all four sides show the same offset - namely, it's centered. Then pick an axis and offset it the required amount to bore the hole.

I've published this writeup I did for our club before but it's worth repeating for those who may have missed it.
      
            Centering Work in the Four Jaw Chuck

Probably every machinist has his own pet way of doing it.  My technique works
for me.  Take whatever is useful and modify as you see fit.

To easily center work in the 4J, you'll need to make yourself two tools.
First, make a dedicated holder of some sort so you can mount a dial indicator
(DI) on the tool post (or directly to the compound) with its axis
perpendicular to the spindle axis.  Adjust the DI so its plunger is vertically
aligned with the spindle axis.  An easy way to do this is to put a pointed tip
on the DI plunger and align the point to a dead center in the headstock.  The
idea is to make something that you can drop into place, already aligned, and
lock down in ten seconds or so.  Leave the DI permanently mounted to this
holder.  A cheap import DI (<$15) is fine since we'll be using this only for
comparative, not absolute, measurement.

While you could use a conventional adjustable magnetic DI holder, I strongly
recommend that you make a dedicated mount that is easily installed and removed.
A general maxim of machining is that you'll be much more likely to do something
'the right way' if setting up to do it is quick and simple.  If it isn't you're
much more likely to try some half-a$$ed setup that doesn't work and ends up
damaging the tool, the work, or, worst of all, you.

The second tool to make is a clone of your 4J chuck wrench.  We're going to be
adjusting two jaws at a time and it's infinitely easier to do if you can move
both jaws in and out in concert without having to swap the wrench from hole to
hole.  It's another example of the maxim I mentioned above.  The clone wrench
doesn't have to be anything fancy.  Machine a square tenon to match the
existing wrench on the end of some suitable stock, and drill for a press-fit
cross bar.  Use your existing wrench as a guide for dimensions.  I've found
that, if there's not a lot of room on the back side of the lathe, making the
clone somewhat shorter than the supplied wrench is a good idea.

Ok, now for the procedure.  Mount the work in the 4J and roughly center -
either by eye or by using the concentric circles scribed into the face of most
4Js.  Snug the jaws down so the work is held securely.  Turn the chuck so one
jaw is at the nine o'clock position as seen looking from the tailstock down
the spindle axis.  Use the cross-slide to bring the DI up against the work and
reading about the middle of its range (e.g., about 0.5" on a 1" DI).  Turn the
scale on the DI so its needle indicates zero.  Now swing the chuck through 180
degrees.  Unless you've got an impossibly good eye, the DI will now read
something other than zero.  (For an example, let's say it reads 0.038.)  Turn
the DI scale so the zero is halfway to this reading.  (Move the scale so the
needle points to 0.019.)

Now, insert both chuck wrenches and adjust the jaws so the DI needle points to
zero.  Swing the chuck 180 degrees and check the reading - it should be close
to zero.

[Aside:  If the part you're centering has the same dimension in both jaw axes
(i.e., it's not rectangular), the DI zero you established above will also be
the zero for adjusting the other two jaws below - another advantage of this
technique.]

Repeat this entire process for the two other jaws.  [What we're doing here is
treating the 4J as two two-jaw chucks.  We can do this because the jaw pairs
are orthogonal and, to first order, adjustments of one pair will have very
little effect on the setting of the other pair.]

If you've been careful, the total runout on the part should now be only a few
thou.  Depending on your esthetics and the part requirements, this may be good
enough.  If not, repeat the entire process until the runout meets your needs.
After centering, check to ensure that all the jaws are clamped down tightly.
It's easy to leave one loose.  If you have (left one loose), you may need to
rerun the centering procedure after you've tightened it.

With this procedure, you should be able to center something to +/-0.001" in
ten minutes on your first try.  With not much practice, you can get that
number down to one or two minutes.  Soon your three-jaw will be gathering
dust.

One of the most common uses of the 4J is for drilling/boring offset holes in
eccentrics (i.e. cam drivers for model engines).  In this case, you aren't
centering the stock itself (as we were above) but rather need to center the
location of the hole.

First centerdrill the location of the hole in the milling machine.  Mount the
stock in the 4J and roughly center this centerdrilled hole.  [A fast way to do
this is to use the pointy end of an edge finder held in the tailstock drill
chuck.]  Now you need a PUMP CENTER.  This is a longish rod (mine is ~10"
long).  At the tailstock end is a spring-loaded female center.  At the
headstock end is a rigid male center.  The male center goes in your
centerdrilled hole.  The female center is supported by a dead center in the
tailstock and the tailstock is adjusted to lightly compress the spring.  The
DI is made to bear on the rod near the male center.  Using the procedure
outlined above, adjust the jaws until the DI shows little or no runout.
Voila, the location of the offset hole is now centered.

[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