Open Column Launch Engine from Kit

[zeeprogrammer]

You can just sneak up on the final bore size. Last couple of passes cutting just squeak <0.001 should get you a nice clean and round hole. Match the piston to fit.

Hi Bob. I must admit I'm thinking about it. I'm supposed to sand it to get rid of the reamer marks and then work the piston to fit anyway. Let's see what tomorrow brings.

Thanks.

 

[vlmarshall]

Hahaha, yeah, I figured as much. ;D

Bore it out like Foozer said!



-Vernon

 

[vlmarshall]

Hmmm, I'm one post too late. ;D

 

[zeeprogrammer]

While I think about what I'm going to do about reaming the cylinder (I ordered a reamer by the way)...I thought I could at least work on the mill and finish the crankshaft.

To finish it I needed to mill a flat for the rotary valve's setscrew, a flat at an angle for the flywheel's setscrew, and a hole for the pin that attaches to the piston rod.

To find the spot where the flat went, I moved the end mill up to the shoulder with a piece of paper in between. When the paper was pulled out of my hand...I stopped and then backed up the required distance. (All per instructions - but that's going to require a bit more practice.)

The flat for the valve's setscrew...

Now for the flat for the flywheel...the instructions called it a 'whistle slot'. I needed an angle plate. For those of you who remember...I tried making one as my first milling project...the result being two very neat holes in the table and no angle plate. A handy ever present reminder to double/triple check. In any case, the angle plate would have been too thick. So I used an old drafting triangle. Probably the first time I've used it in 40 years! (High school drafting class.)

I was careful to take out backlash and ease down but all of a sudden the head dropped a goodly amount even while I was holding onto the fine crank feel. I'll go back later and investigate further.

So now it was time to put the hole in for the pin. I don't have vise jaws with a groove so I thought I'd use a V block. Problem 1: the shaft was too small. Solution: Put a small square piece of aluminum behind it to hold. Problem 2: The hole is supposed to be lined up with the flat but I can't see the flat. Solution: Do the best I can. Problem 3: No space below the vise for the shaft to stick through. Solution: Let it stick up...small hole right? Light touch right? It would be here that a knowledgeable one would slap my forehead.

Made a light touch with a center drill. Sure enough. The thing wobbled like crazy. Revisit problem 3. Experimenting showed that if I moved the vise out far enough then a space opened up for the shaft. The next pic shows the final set up. (The parallels are there to hold the V blocks up.) This also helped problem 2. I could put a parallel against the flat and eyeball it square to the vise. (Close enough.)

So centered drilled, drilled, and reamed. Cleaned up the part...not real happy with the finish.

So let's see if the pin can be pressed in. Oh yeah. Easily. Slides right through and onto the floor. Instructions said I would be lucky if I could press it in. Is this lucky? Well it did mention using Loctite. Should be okay.

Now...about that reamer...

 

[mklotz]

Carl,

Take a look at your picture with the plastic triangle. Downward forces from the endmill are going to try to push that triangle to the left and make it "squirt out" from under the part. You need something immovable behind the left edge of the triangle to keep that from happening.

There's nothing intrinsically wrong with using the plastic triangle except that it's not very durable. Over the years, I've made many small (shorter than vise jaws) aluminum triangles (each carefully engraved with its angle) that drop into the vise and back up against a vise stop to prevent the "squirt out" problem.

Alternatively, you can consider buying a set of commercial angle blocks, e.g.,

http://www.use-enco.com/CGI/INSRIT?PMAKA=630-4258&PMPXNO=945262&PARTPG=INLMK3

or

http://www.use-enco.com/CGI/INSRIT?PMAKA=422-3382&PMPXNO=7911574&PARTPG=INLMK3

or get a sine bar,

http://www.use-enco.com/CGI/INSRIT?PMAKA=637-7551&PMPXNO=2902858&PARTPG=INLMK3

and make some sizing blocks for various angles. [Don't let anybody tell you that you need gage blocks yet.]

Re: sloppy fit of pin in hole...

Did you check that the pin was the same size as the reamer? Stock material can be slightly off nominal size. Did you drill the hole smaller than the reamer size?

I hate to keep recommending more tools but maybe you want to consider an over and under reamer set? (Have we discussed those before?]

Loctiting the pin in the hole is perfectly acceptable. That part of the engine won't be getting very hot, even if run under steam, so you don't have to worry about the Loctite breaking down.

 

[zeeprogrammer]

Hi Marv,

Yes I was bothered about using the triangle. I tightened down pretty good...but still.

Thanks for the links. Not sure they would work...1/4" thick is thicker than the crankshaft.

I have a sine bar...but to be honest...I didn't want to move the vice for this one cut. What I should have done is wait until all the other parts are done that needed the vice and then moved it.

No I hadn't checked the diameter of the pin. Should have. I did drill under 1/64 before reaming.

I just measured...the pin is 0.125. the reamer also 0.125. So I don't think it was intended to be a tight fit despite what the instructions said. Looking at the drawing, the hole tolerance is -0.000/+0.002. That also seems to indicate a 'loose' fit or the pin is supposed to be bigger than 0.125.

Would it be better to have reamed at 0.124? I do have a set of over/under and have the 0.124. Could I have pressed the pin in with 0.001? Then, had I measured the pin I would have been good.

I don't know enough about press fits and what tolerances are required. Could temperature have figured in and caused the metal to expand/shrink?

I haven't measured the hole...don't really know how I'd get an accurate measurement.

Thanks Marv.

 

[vlmarshall]

...I was careful to take out backlash and ease down but all of a sudden the head dropped a goodly amount even while I was holding onto the fine crank feel. I'll go back later and investigate further.

Ugh, I've had a mill do that, with a sticking gib, and too much play in the leadnut. I worked my way around it by moving off the part, down past the backlash, and then back up to height.
Time consuming, but it's better than having the endmill suck the head down into the part I'm trying not to ruin.

...So let's see if the pin can be pressed in. Oh yeah. Easily. Slides right through and onto the floor. Instructions said I would be lucky if I could press it in. Is this lucky? Well it did mention using Loctite. Should be okay.

Ha, don't you hate that. .002" clearance is no press fit, and it's not your fault, nor the fault of temperature change.
A one thou press-fit is good in aluminum, I'd press it in with a vise.
Maybe they meant -.002"/ +.000" , but I'm just guessing.

Have you learned the ball-bearing trick yet? Set a ball on the hole and tap it with a hammer. You'll close up the hole a bit and the pin will fit 'better'. I'd still Loctite this one, though.


All of you people working on more complex projects are making me envious.

 

[mklotz]

Lots of questions... I've interleaved my answers

Yes I was bothered about using the triangle. I tightened down pretty good...but still.

***But you're tightening on the crankshaft, not the triangle.

Thanks for the links. Not sure they would work...1/4" thick is thicker than the crankshaft.

***That's what pusher blocks are for. Eventually you'll have a whole box full in every conceivable size. It's what mistakes become when they transmogrify into tools.

I have a sine bar...but to be honest...I didn't want to move the vice for this one cut. What I should have done is wait until all the other parts are done that needed the vice and then moved it.

***I apologize. My vise is big enough that I can simply drop the (2.5") sine bar into it.

No I hadn't checked the diameter of the pin. Should have. I did drill under 1/64 before reaming.

***Good onya. You're not forgetting what you learned previously.

I just measured...the pin is 0.125. the reamer also 0.125. So I don't think it was intended to be a tight fit despite what the instructions said. Looking at the drawing, the hole tolerance is -0.000/+0.002. That also seems to indicate a 'loose' fit or the pin is supposed to be bigger than 0.125.

***Dumb tolerancing if they want a press fit. 0.125 -0.001/+0.000 would have made more sense. It's not that big a deal. Loctite is your (and my) friend. Type 609 is called, IIRC, "press fit assist" and is the best thing since sliced bread.

Would it be better to have reamed at 0.124? I do have a set of over/under and have the 0.124. Could I have pressed the pin in with 0.001? Then, had I measured the pin I would have been good.

***A thousandth is a bit on the large side for 0.125" but, with the assistance of a brass BFH, it would be possible.

I don't know enough about press fits and what tolerances are required. Could temperature have figured in and caused the metal to expand/shrink?

***A good tool for novices trying to deal with all the possible types of fits is my program, surprisingly named FITS. It isn't as thorough as MH but it works well for our less demanding work and is infinitely easier to use.

I haven't measured the hole...don't really know how I'd get an accurate measurement.

***Holes that small are usually measured with pin gages.

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=616-8126&PMPXNO=950065

This is a specialized tool and you'll be happy to hear that you don't need to buy it yet. I'm simply showing you what I'm talking about with the URL.

On that note, I'm not a salesman for ENCO. It's just convenient to use their (or MSC's) on-line catalogue to dredge up a picture to show you what I'm talking about. No endorsement of the product shown is implied or intended.

 

[zeeprogrammer]

Ugh, I've had a mill do that, with a sticking gib, and too much play in the leadnut. I worked my way around it by moving off the part, down past the backlash, and then back up to height.

Ah...thanks Vernon...I think that's what I was doing wrong...I thought being high enough and cranking down to height would take out play...I'll 'play' with that.

Have you learned the ball-bearing trick yet? Set a ball on the hole and tap it with a hammer. You'll close up the hole a bit and the pin will fit 'better'.

No I hadn't heard about that. What if the hole is already chamfered? Oh...and the part is steel, not aluminum. I guess it would still work but require a heftier blow?

Thanks Vernon.

 

[Foozer]

I just measured...the pin is 0.125. the reamer also 0.125. So I don't think it was intended to be a tight fit despite what the instructions said. Looking at the drawing, the hole tolerance is -0.000/+0.002. That also seems to indicate a 'loose' fit or the pin is supposed to be bigger than 0.125.

I've drilled/reamed too many thousands of holes 0.187-0.190 to remember. Always a 0.187 reamer would end up at 0.188, close enough to. . . If I needed a hole to be on 0.187 I'd take the reamer and run the cutting edges against a piece of steel for a sec or two. This dulled it down enough so that the hole would be closer to the 0.187 size. Now on occasion some smart alec would pull out the electronic measure to the Nth decimal, reporting the hole at 0.1868, but thats another story. If you have the 0.001 undersized reamer go with that. The 0.124 reamer new and sharp probably leaves a 0.1245 to 0.125 hole. Pin will fit nice and snug. You can press a pin in with 0.001 undersized hole, heck drop the pin in the freezer for a while and the piece with the hole in the over at 250 degrees and they probably will slip together with ease. Once it returns to room temp you'll have the dickens of a time getting them apart. liquid nitrogen is great for this, but alas not recommended for home use

 

[zeeprogrammer]

***But you're tightening on the crankshaft, not the triangle.

Yes. It's what I meant. My hope was enough pressure so it wouldn't move...I could have just as well taken out the triangle. But I believe I understand your point.

My sine bar is 3.75"...but regardless...any pics showing a sine bar inside a vise?

***Good onya. You're not forgetting what you learned previously.

Try not to with you watching ;D

***Holes that small are usually measured with pin gages.

Well that was wierd. My company used to have a machine shop. They were throwing things out so some of the guys collected the stuff and hid it in a lab. Once in a while I troll through just to look.

Just yesterday I was looking at a box of pin gages wondering what in the world they were for. I didn't know they were called that either.

(They have a beautiful height gauge I've placed dibs on if they ever toss it. They also have a surface block that's at least 2.5' by 4' by 8" or so.)

Thanks Marv.

Hi Bob. Yes I have noticed that most of my holes seem to be a tad larger than expected. I hadn't thought about drilling smaller and sneaking up on it. Thanks.

 

[mklotz]

Yes. It's what I meant. My hope was enough pressure so it wouldn't move...I could have just as well taken out the triangle. But I believe I understand your point.

If you could have taken it out, then it's not supplying any support to the part. In addition to establishing the angle, it should support the part against the cutting forces.

I bring this up now because, although you got away with it this time, you may not be so lucky next time and the part will move while you're cutting on it. Backing up the triangle so it can't squirt out will prevent that from happening.

I don't have any pictures but imagine the sine bar sitting in the vise parallel to the jaws with its roller feet sitting on the "floor" of the vise - the flat horizontal part below the jaws. The part lies on the sine bar which is blocked up to get the correct angle. If the width of the sine bar is greater than the width of the part, the movable jaw can't close on the part so a pusher block is used between the movable jaw and the part.

It looks from your pictures that you're using a toolmaker's vise rather than a conventional milling vise. It's likely that the toolmaker's vise is too narrow to do what I'm describing so don't get overly involved with what I wrote.

Pin (sometimes called plug) gages are useful little critters. Did you know that they can be used in triplets to measure holes larger than the largest pin in the set? Take a look at the text file that accompanies my PLUG program.

 

[Seanol]

Zee,
Maybe you know this but the v block can be turned around to the other, smaller v. It still might be too big but it should get you closer.

Hope that helps,
Sean

 

[zeeprogrammer]

Hi Marv,

I did a little search...precious little on 'pusher blocks'...but came across this in the forum...

http://www.homemodelenginemachinist.com/index.php?topic=2585.0

It had some of your posts...pusher block being different sizes of 1-2-3 blocks? Still having a little trouble visualizing things. Does this work...?

Put sine bar parallel to vise jaws. One end on the floor, the other propped up with blocks/scrap to get the required angle. Maybe use a parallel on the floor if the sine bar doesn't straddle right? Place the part on top such that the fence at the bottom of the sine bar keeps it from sliding down. Use blocks (aka 1-2-3 or the like) on either side of the part, or maybe just one side, so that the vise can clamp and hold. When a downward force is applied, the fence helps to keep the forces on the sine bar straight down...no squirting. Is that right?

You mentioned a 2.5" sine bar. Mine is too. I didn't realize the measure is between the centers of the rolls. I tried setting up so I could take a pic...the sine bar takes so much room it doesn't look like I can fit pusher blocks in sufficiently for the vise to hold.

I'm thinking I should use the angle plates but that still leaves the question of downward forces and their 'squirting' out. Probably a stop?

Interesting you mentioned the vise. I've never really been happy with it. Part of a 'starters set' from LMS. I've been considering getting a different one. In fact...I see from my instructions for the engine that a sine vise is used. Oh goodie.

That's been one downside of this 'beginners kit'. You'd think it would be such that someone could have success making an engine with few tools. Instead it seems to be designed such that you need every tool in the catalogs. At one point I'll be using the rotary table and facing the question I had earlier...lack of z room. I'm okay with it...whatever disappointments I'm having...are learning experiences. But a lot of people need some periodic successes to keep going. Or...the cost will put people off...again, I'm okay with this because I know I'm in it for the long run and will eventually need this stuff anyway.

Well...enough yak yak. Surprised people read all this anyway.

Thanks again Marv.

Sean...thanks. I did use the smaller v and it was still too big. Better that than too small I suppose ;D [Edit: Was reviewing the earlier pictures and realized Sean was right. I was using the bigger v. At least, it looks that way. It hadn't started that way but somehow when I went from my first attempt to the one shown in the pic...I got it turned around.]

 

[Maryak]

Zee,

Not everyone is a brave as you when they start out machining. Hence the starters kit is just that. More power to you for having the guts to avago and your willingness to ask lots of questions. :bow: :bow: :bow:

Best Regards
Bob

 

[zeeprogrammer]

Thanks Bob. I appreciate it. (Some of the trembling is beginning to subside. :big

The cylinder is still in the lathe. The race...work with the mill until the reamer arrives or let the forces to turn take over and take out the cylinder? Again...having still a 1/16 to bore...I can probably take the cylinder out. But anyway...

Doing the piston rod...

Trimmed the edges...1.780 by 0.250. Two parallels below...one to hold the part and one side of the top parallel and one to hold the other side of the top parallel. The orange bit you see is a bit of foam I cut from a halloween decoration. (I'm hoping the kids don't remember we had that. ;D)

Now for the hole that pins to the crankshaft. Used the edge finder (recently learned) to center side to side and then move in from the end...

Center drilled, drilled and reamed (0.125)...

Flipped the part over. The vise is square to the table, so used the edge finder again from the end to get to the desired spot.

[Edit: That was poor practice. As mentioned in a later post (thanks Marv) I should have had a scrap of metal under the part that I could have drilled into. For one thing...the part would have had more support rather than hanging in the wind...but more importantly...I could have moved directly from one hole to the next and this would have been much more accurate.]

Center drilled, drilled and reamed (0.063). Then put the part in my bench vise and used a file to round the ends. I had considered using a rotary table...but I'll have an opportunity to learn that when I finish the rotary valve.

Now how exciting is that? Trimmed four sides and drilled two holes. woo hoo.

I have to put two bends in the piston rod using the bench vise. At first I thought I would wait to polish until after bending...but I thought that would make it harder. So I'll go ahead and polish now. I'll use some soft material between the part and the vise jaws when I bend...any cleanup should be minimal.

Now the only operations left with the vise is drilling some holes (more excitement!). I don't need the accuracy of the vise being square so I can remove it and prepare for the rotary table. Oops waiting on tools for that too...a slitting saw and arbor. Stuck. Well maybe I'd better get some work done around the house before I get caught. :big:

 

[mklotz]

Carl,

New vise? That's not the same one as in the previous pictures.

A pusher block is any piece of metal used to transmit the force from the movable jaw to the part in order to hold it in place. Imagine that you had a 1/8" part sitting atop a 1/4" thick parallel. As you tighten the vise, it tightens first on the parallel and not at all on the part. So you stick a small chunk of, say, 3/16" stock between the part and the movable jaw so the force of the movable jaw acts on the part before it hits the parallel. That small chunk is a pusher block.

Nice job on the connecting rod. Let me offer one bit of advice for the future. Generally, the only critical dimension on a connecting rod is the distance between the two holes. It's a bit more accurate to space the second hole directly from the first. I would have put a bit of scrap between the part and the parallel, drilled the first hole, then used the mill handwheels to move the required distance before drilling the second hole. This would guarantee that the holes were at the required spacing. The scrap underneath the part allows you to drill the part without drilling into the parallel. It almost certainly doesn't matter for your engine but keep the ideas in mind for future jobs where hole-to-hole spacing is important.

You don't need the rotary table to round over such a small part. Hand filing is perfectly adequate, as you discovered. Other approaches include using a belt sanding machine or a jig to rotate the part against a rotary file held in the mill...

http://www.schsm.com/html/marv_klotz_41.html

Bending stuff in the vise can be tricky. Is an offset bend required? (Maybe you can show a sketch of the bent part - that wouldn't violate copyright) If so, I've got a trick for doing that.

 

[zeeprogrammer]

New vise? That's not the same one as in the previous pictures.

A pusher block is any piece of metal used to transmit the force from the movable jaw to the part in order to hold it in place.

Generally, the only critical dimension on a connecting rod is the distance between the two holes. It's a bit more accurate to space the second hole directly from the first.The scrap underneath the part allows you to drill the part without drilling into the parallel.

or a jig to rotate the part against a rotary file held in the mill...

Bending stuff in the vise can be tricky. Is an offset bend required? (Maybe you can show a sketch of the bent part - that wouldn't violate copyright)

Hi Marv,

Same vise. Could be the photo angle or the V blocks makes it appear different. LMS calls it a 'heavy' milling vise.

Pusher block. In the pic with the V blocks and the crankshaft, I had a piece of square aluminum holding the crankshaft up to the V block. So I guess you'd call that a pusher block. Same for the parallel I used to hold the piston rod. More of a functional name then?

As for the two holes...had I thought about using scrap to drill into, I could have done just that, and moved from one hole to the next. Thanks for the tip...I didn't like having the part hanging in wind.

I had seen your jig in another thread some time ago...someday.

The offset bend is required according to the instructions/drawings. But I'm not convinced yet. I'm going to wait until I have the rest of the parts done and do some trial fitting. The instructions talk about using an 'angle finder'. Guess what I don't have. Also mentions a square and spacer shim. Two bends...from the side looks like
_____
\______

but the middle part is longer and the angle is much shallower. 0.06 from bottom of left end to bottom of right end. If/when I get there...I'll ask for that tip.

Thanks Marv.

 

[zeeprogrammer]

Poor practice should be pointed out.
I have edited the post describing the drilling of the two holes in the connecting rod.
I'd rather someone learn from my blunders than repeat my blunders.

Thanks.

Wish there wouldn't be more...but I never bet on myself.

 

[mklotz]

Carl,

You didn't need to edit your previous post but I appreciate you doing so - a karma point's worth of appreciation. You see, I have this vision of this thread being of great value to all the novices out there, most especially the lurkers, and touches like that just make it more useful.

I'm not sure what they mean by an "angle finder" but I don't think you need one to do a simple offset bend. Angle finder is sort of a generic name and could refer to any of a number of tools.

At any rate, the attached figure will show how I've done offset bends. Given the amount of offset required (the distance between the vise jaws in the figure), make two pusher blocks with a thickness equal to the required offset minus the stock thickness. Place them in the vise with the stock as shown, locating the ends of the pushers where the bends need to occur (if that matters - it may not). Hold everything together with cellophane tape if you haven't yet grown the obligatory machinish's third hand.

Once in place, simply crank the vise jaws closed and voila (not viola - a fat violin), your bend is made. Once removed from the vise, there may be a bit of spring back but that's easily dealt with fingers or parallel jaw pliers (another essential tool for this sort of work).

Obviously, this approach is meant for relatively thin parts that won't stress the vise. Don't try it with a piece of 1/4" steel.

What bothers me here is making the bend after so carefully spacing and drilling the holes. Obviously, the hole-to-hole dimension will change after the bend is made. But, not having seen the engine plans, maybe it won't matter.