1/4 scale Porsche 917 180 degree V12 Build

[crueby]

Thats a lot done! Great setup, lots of th8ngs to check and triple check, I  bet. For that kind of setup, the parallelism of the boring bar to the ways to the cross slide to the workpiece to... probably  some other things too!   

[steamer]

Thats a lot done! Great setup, lots of th8ngs to check and triple check, I  bet. For that kind of setup, the parallelism of the boring bar to the ways to the cross slide to the workpiece to... probably  some other things too!   

As long as the boring bars relation to the ways doesn't change while you're boring, the hole will be straight.

To be PARALLEL!   Well that requires the part to be set parallel   Helps when the machine is aligned already 

[crueby]

Thats a lot done! Great setup, lots of th8ngs to check and triple check, I  bet. For that kind of setup, the parallelism of the boring bar to the ways to the cross slide to the workpiece to... probably  some other things too!   

As long as the boring bars relation to the ways doesn't change while you're boring, the hole will be straight.

To be PARALLEL!   Well that requires the part to be set parallel   Helps when the machine is aligned already 

Oh, right, the bar stays still, well, spinning, while the part moves! I forgot that part!      This k8nd of boring is something I  never tried, neat stuff.   

[steamer]

Thats a lot done! Great setup, lots of th8ngs to check and triple check, I  bet. For that kind of setup, the parallelism of the boring bar to the ways to the cross slide to the workpiece to... probably  some other things too!   

As long as the boring bars relation to the ways doesn't change while you're boring, the hole will be straight.

To be PARALLEL!   Well that requires the part to be set parallel   Helps when the machine is aligned already 

Oh, right, the bar stays still, well, spinning, while the part moves! I forgot that part!      This k8nd of boring is something I  never tried, neat stuff.   

with long deep holes, its sometimes the only way.

Dave

[Roger B]

That is definitely a challenging set up however it looks like you have thought it through well. I'm looking forward to the result     

[jcge]

Fingers crossed for you with this operation Dave. You've clearly put a lot of thought into the setup, and I hear you about the pucker emoticon when its time to machine the bore and open it up for the reveal!
If not too late, suggest a test cut with the the actual cutting tool to ensure you get the surface finish that you're happy with.
Best of luck!
John

[steamer]

Thanks for dropping in John and Roger.   I do plan on putting a sacrificial test plate on the front of this for sizing purposes, and to get comfortable with speed and feed...

Dave
 

[Art K]

Dave, I just got caught up with your build. Wow, making lots of progress. I have to admit I couldn't attempt this on my lathe as the only points to mount such a machining fixture are under the tool post. Plus I'm not sure I'm up to the job. Great job! I don't usually feel the need for the clenching emoticon I think I would like to have it handy.
Art

[steamer]

Dave, I just got caught up with your build. Wow, making lots of progress. I have to admit I couldn't attempt this on my lathe as the only points to mount such a machining fixture are under the tool post. Plus I'm not sure I'm up to the job. Great job! I don't usually feel the need for the clenching emoticon I think I would like to have it handy.
Art

Thanks Art.   If I can get through this step successfully, I will be well on my way I think.   This and the crankshaft are the big hurdles I think.

[steamer]

OK   Last weekend, I spent some time trying to nail down center distance and size.   Not in the lathe, but with 1/4 plate and the mill.    What I was really after was as made center distance.   It was an eye opener!  I was also trying to work on how I will be measuring the bores which I also think I was successful doing.

Theoretical center distance is 1.09375.  ( 27.78 mm)   Great!   But here's what I found.  They clashed badly there, like not go together clash badly.  I made 3 more test plates with the mill, opening out the center distance each time by .005" and checking again....   The best "mesh" of the center drive gears, which include the crankshaft, output shaft and fan/ignition shaft was more like 1.105" (28.06mm)    0.011" difference!

Errors in the gears?   Probably   These are shop cut gears, and pitch diameter will vary, but I was surprised by how much!

Now that's the bad news.   The good news is there more than enough material in the bores that I can shift the position that much and get the mesh where I want it without too much bother   At that point they mesh well, so I'm happy with that.

i purchased 2 bore gages and 2 bore standards for this project ( used on ebay) and I can report that the big one works wonderfully!   I love being able to measure size to .0001" compared to a standard ring gage.   It's nice to check against my mikes as well.

[Vixen]

Hello Dave,

I am sure the problem of gear size is partially due to the simplistic approach we model engineers have to take regarding our gear cutting. If we were gear cutters by trade, we would be properly equipped with dedicated machinery and have a lifetime of experience and know all the tricks in the book, to get a pair of gears spot on.

At least you now know exactly what you have and the good news is you can shift the positions and get the mesh where you want it, without too much bother.

Like the two bore gages and standards, where is the green with envy icon when you want it.

Cheers

Mike

[steamer]

Hello Dave,

I am sure the problem of gear size is partially due to the simplistic approach we model engineers have to take regarding our gear cutting. If we were gear cutters by trade, we would be properly equipped with dedicated machinery and have a lifetime of experience and know all the tricks in the book, to get a pair of gears spot on.

At least you now know exactly what you have and the good news is you can shift the positions and get the mesh where you want it, without too much bother.

Like the two bore gages and standards, where is the green with envy icon when you want it.

Cheers

Mike

If you're patient, and pay attention to the various outlets  ( ebay   Marketplace)   Deals are available.  99.7% of my shop is second hand in some way shape or form.

[steamer]

OK   I think we do this today and tomorrow....stay tuned!

[steamer]

Well   3 steps forward and 2 back....

I got the block set up on the lathe and started to bore it.    But I ran into a problem......ME!

I left .040" material when I roughed out the block....but captain dumb dumb didn't think that would be 0.080 on diameter!    I was OK on the main bore...the boring bar JUST fit, but I can't get the 1/2" diameter boring bars in the roughed out 15mm bores at all!.....hmmmm

OK   so I'll start by opening the crankshaft bore, 32mm finished diameter out to about 30mm...    I found the next problem!
I can't get chips out of the block very well  Like NOT at ALL!    I end up recutting chips and it's a problem.   So my boring bar is basically too big in diameter.
So I made a 0.020 pass on the bore, and split the case  and clean out the case, reassemble the case and make another cut

OK   so the intent with all of this was to bore all the bores in one set up so that they're parallel and consistent.
Breaking the case open is not serving that very well, as I can't evacuate the chips.   I have 0.040 worth of material to come out of the 32m  crankshaft bore, so I'll leave that for now

but what's worse is I can't get into the bores of the 15mm bores at all until I open them up past 1/2" diameter.   They need to be opened up.   
OK  So I put a 1/2" long shank end mill into the lathe and bored these holes as deep as I could.  I then put a long shank 1/2 inch drill in the lathe and bored through.

I know this does not do well for locational accuracy, but the material has to come out.

So now Im at this state... I"m sitting Wondering what I should do.    So much for game plans right?

OK   

Plan 1
I think I need to make up a boring bar that is slightly smaller in diameter and 9" long.    with this I'll "worry" out the 15mm bores to say 14mm and then put my between centers bar in and take out the remainder.

Plan 2
pick up a 14mm diameter long shank end mill and long shank drill and open the bores to 14 mm  and finish with the between centers boring bar to 15mm.     I like this solution the best, as it's simple, and apparently effective.   I don't like long drills as then tend to wonder around though.

either way, I don't feel confident that I cant hold super tight tolerances with the bar alone as I can't get the chips out.   That said, I think I'll need to make up some laps to finish the bores to the tolerance I want. 

I'm going to buy some tooling and then mentally chew on this overnight, and see how it looks in the morning.

I have the mains at about 30mm and the 15mm at about 13mm currently. 

Going in the right direction, just trying not to screw it up.

Dave 

[Fj45]

 Hi Dave,
 Just a thought, could you bore under size for the cylinders and vacuum chips out there?