Cylinder boring without a cylinder borer.

[Frank S]

We had a ford inline 300 I wanted to rebuild for a guy's rat rod, the shop I used since I didn't have the equipment to do it my self. had to shave .008" off the deck #2&#3 bores were .010" off center in the opposite directions Took a while to figure that one out the only thing we could determine was the engine had previously bored to .030" Ordinarily the block would have been scrap in my book but the guy wanted to go max overbore and a 4.375" stroker crank I think he wound up with somewhere in the neighborhood of 336 to 338 CI range Not a high rev'er but had torque for days

[satx]

the MT5 boring bar is snugged in with a draw bar?

[hemmjo]

This thread is of special interest to me. I joined this list initially as I was, still am, in the process of rebuilding an obsolete jet ski engine. It has been pushed aside many times due to other, more pressing issues, but I am always on the look out for ideas to help me complete the project. As you mention Tony, there is no one around here that wants to mess with boring this engine. So I am going do it myself. I have thought about and discussed here on a couple of threads about just honing it to size. But I think I am going to have to re-sleeve the cylinder, so the honing is not really a very good idea. The engine is a 2 cylinder 2 cycle. Both cylinders are in the same jug, so spinning the jug on my lathe is not possible. Bore and stroke are 83 mm x 71mm.

I am wondering if my lathe is up to the task of doing this in similar fashion? I have an 11" Powermatic/Logan. I am wondering about the stiffness of my spindle. The spindle is smaller than most 11" lathes. The through hole is just large enough to get 1" round stock through it if there are no chips in it. The taper is some proprietary thing in the range of #4 morse, but the taper does not match and it is about 1/2 the length of a standard Morse taper. The spindle nose is 1 1/2 x 8 thread. I am sure the internal taper not up to the task.

I am wondering, assuming that I have the skills to actually make the adapter, do you think the spindle is stout enough to attempt to make a similar boring set up using the external threaded part of the spindle nose? Possible I can make the set up stiffer, using the tail stock as Toolmaker mentioned?

Thanks for your input.

John

[satx]

I am wondering about the stiffness of my spindle.
John

preface: I have no idea what I'm talking about

If your spindle really is of suspect stiffness, can't you just bore the cylinders by sneaking up on the target diameter with light cuts?

Do you have a steady rest?

how would one measure deflection of, eg 1" round rod in the chuck, deflection at the point where the cutting tool would be?

[tonyfoale]

the MT5 boring bar is snugged in with a draw bar?

yes, of course.

[tonyfoale]

I am wondering if my lathe is up to the task of doing this in similar fashion? .......I am sure the internal taper not up to the task.

...... do you think the spindle is stout enough to attempt to make a similar boring set up using the external threaded part of the spindle nose? Possible I can make the set up stiffer, using the tail stock as Toolmaker mentioned?

John,
I think that you are pushing the envelope with a lathe of that size. Apart from the rigidity of the spindle, is your cross-slide large and stiff enough to mount the cylinder block on? Although back in a previous life I did similar jobs on a Myford 7.
As I was reading your post, I was going to suggest using the threaded nose as the support but you were already there as shown in your last paragraph. Even with that I think that you would still need to use the tail stock with a centre for added support. That means that you need to incorporate another method for adjusting the depth of cut.
Good luck with it, to do a good job it will take a lot of time, patience and care with that lathe, but that is no reason not to try.

[Toolmaker51]

I'll have to edit more material in evening; but this is a perfect example of building up tooling to accomplish a specific task. The order is sort of important, but not critical, just logical.
This also answers ralphxyz thinking #3MT too small. Use the spindle threads.
a] an indicating setup to measure odd spindle taper. There a few; Morse, Jarno, Brown & Sharpe and a sh_ _load of proprietor specials. Who cares, we're making our own!
b] offset center to produce it on what will become a boring bar
or
a] establish dimensions of thread
b] procure means to cut ID thread what will become a boring bar.
c] plate fixturing cylinder block in 3 correct planes; even without enough cross travel. Knowing accurate distance between centers needed here. Prepare torque plate at same time.
d] boring bar with that spindle taper or thread and center drilled opposite end. It'll need means of adjustment. We'll get to that.
e] known piston diameters minus hone allowance and correct measuring instrument.

Of the two, considering a small lathe, choice of threaded will allow a size without a small neck joining a decent size bar diameter. Center drill the end for tailstock support. A center may be a little bearing diameter but is sort of zero clearance for endplay. Slow RPM and a decent feedrate can be experimental dialing things in. Order pistons afterward, unless you blow the whole thing, if you buy .010's and miss you are stuck without replacement sleeves.

Poster 'marksbug' offered good details on boring, especially cutting .004 under and bring diameter in by hone, to stop fissures in cast iron. #28 @ http://www.homemadetools.net/forum/c...-borer-55286-3

A suspended boring bar [line boring] is worth the extra preparation and building. Instead of attaining precise diameter control with an offset boring head, find or make a boring cartridge. Visualize a threaded boring bit crossway in a threaded bar. They have a re-usable dial with graduations for size control...time spent in tapering the bar itself could eliminate that as a source of harmonics that create chatter, lots of way lube [as in WET] and high speed tool bit...My bet; this is completely achievable.

I expect and hope a lot of other readers will ring in. It's why we're here, after all.
And hemmjo/ John "I am wondering, assuming that I have the skills to actually make ___________". Develop skills by using them. Some volume of readers here, use ability to interpret and visualize as the keystone of skill. It takes some confidence, sure; but understanding is a better foundation for confidence than diving in blind. Not far away in comparison to connect the dots.
It also means you'll pick up on what needs attention to get improved results, by the time you get 'to size' you'll be gung-ho for next opportunity.
You'll want good ID measuring tools. On stuff like this I often use two different methods of confirmation. Cheap insurance.

Limited cross travel......that's a problem. Not big as insufficient center height! Determine the exact distance and plan a subplate doweled for each bore. 4 capscrews one each corner, 2 dowels diagonally opposed near a corresponding screw. The sketch will make this clear, not to size not to scale.

[marksbug]

I too have a jet ski engine that has been shoved to the side( 500 wave runner) I did all the machine work long ago including boring&decking and mild port work,I did it all over 25 years ago...I threw away the ski 2 years ago after cutting it up with saw... yes you can bore it on the lathe if you set it up right.you need to leave about .004-.005" smaller then finished size for honing.some bore to size and them do a light hone, that does not last.also kills the engine, boring the cast liners fractures the iron about .004 deep and the pieces come off when running, thus the hone of min .004 is required to do it right. and dont forget to deburr ports after honing so the rings dont gram them... I guess I need to get rid of this yamaha 500 engine in a box Ill never need it and the kids are grown&gone.(as is the ski body). I did it on the same rottler boring machine as I did 632+ci promod race engines,offshore race engines and everything else.( including my 4 wheeler and yz 250 dirt bike) and honed on our sunnen ck 10 hone machine.decked on the strom vulcan 85b. if it chatters you may need to bore less and hone more...(after trying everything you can to stop the chatter.(speed, setup, bar size,even big rubber bands around the chuck&cylinder to try to keep chatter away....yes it can work. if you have a chip tray be sure to try to keep it from vibrating adding weight or what ever. many times chatter is a harmonic set up by something else on the machine reverbrating a small amount into a large amount of hair pulling chatter.(thus the humongus heavy securly mounted lathes instead of small portable lathes doing production work...

[Ralphxyz]

Now that is a substantial boring bar, I want one but #mt is my largest spindle.

Ralph

[marksbug]

also in the big skeem of things, many bores are nowhere neer where they are supposed to be....so if your boring a cylinder .030 and get it to bore the entire way down you have done about as good as many manufactures..... not saying get it good enough, but if you have to get it this way or that way, get it so the piston go's straight alined with the rod&crank.the pin will pivot it the other way without any issue. yes it does alter cam&ignition timing, but getting it done when there is no other way....it's better than walking ... we had BHJ bore true to use on big block gm race motors....some were way off.thats why they make the bore true so you can put it right. I have had to offset bore a wore out block so it would clear the max bore. no isues, but not a race motor either.