Line Boring Model Bearings

[briankenyn]

Hi all,

I would appreciate some help in setting up and aligning a line boring arrangement on the cross-slide of my 8x14 HF Lathe. I should mention that I have two 1/4 20 mounting holes drilled into the cross-slide to mount my Atlas Milling Attachment.
Other than that, I'm clueless about how to proceed.

Thanks in advance and regards,
Brian

 

[radfordc]

I saw some pictures once of how to do it...wish I could find them again. Basically, you mount a boring bar between the spindle and the tailstock so that it is aligned perfectly with the ways. Then mount your crankcase on the carrage so that it is aligned perfectly with the boring bar. Set the depth of the cutter accurately and run the carrage so that the cutter cuts all the bearing holes to the same size.

Charlie

 

[GWRdriver]

Brian,
Just out of curiosity, how many journals do you have to bore through, what diameter, into what material, and how long with the required table/carriage travel be? Is there a place or surface on the frame/crankcase to mill witness marks or flats so if necessary the frame/crankcase can be re-indicated in parallel to the bore? It would help if we knew what engine you are building.

You should be aware (if you aren't already - we can't tell how much you know) the way you align something perfectly square, perpindicular, or parallel to something else is to use a DTI (dial test indicator) also known as a clock gauge in Britain and even an inexpensive DTI will give you indications of a higher order than your lathe and milling attachment are capable of. In England many lathes for the amatuer come equipped with slotted cross-slides for doing exactly the job you want to do. Them Brits are a lucky lot.

 

[briankenyn]

GW & Charlie- I have two .375 x 1.125 x 1.000 journals of aluminum with bronze bushings pressed in to accomodate a .312 shaft. The journals will be spaced 1.625 on a aluminum base and I have already stack drilled the bearings to .250 in the DP. Due to the small shaft diameter, I didn't plan to use the tailstock [which I might have to rethink]- I thought that I would drill to within a 64th and ream them. I use a decent Enco X-Y DP table with adjustable .100 dials and good hole spotting procedures, and am getting somewhat more accurate in hole alignment. Can you please explain the milling of witness marks and their significance? - I'm tool knowledgeable but a retired banker by trade. I have a DI but don't really know what to indicate first. I thought of chucking a .250 rod in the lathe and finding some way to clamp the base to the cross-slide- Including stopping everything and attempting to mill a small T-slot table add-on.
The engine is a simple single cylinder, single acting, poppet valve affair designed in the '40s by CW Woodson. Its an interesting little design with an unusual .750 bore and .625 stroke.

 

[GWRdriver]

Brian,
Are you building the Little Husky engine? If so I think I may have a better way for you to bore the journals and witnesses won't come into play although I'll explain a bit more about those later.

 

[briankenyn]

GW,
That's the one, and I didn't know that it had much fanfare!

Brian

 

[GWRdriver]

Brian,
I Googled CW Woodson steam engine and the Little Husky was the design that popped up most frequently so I made an informed guess.

As for the simpler journal boring alternative I mentioned, I've thought about it and I don't know if this one will be simpler for you (or your machine) or not, but I'll describe it. Are you familiar with using an angle plate attached to your faceplate? The engine bed and journal assembly would be bolted to the angle plate and squared with the the axis and aligned with the lathe center line. Then you just bore it through with a small conventional boring bar. A picture is really worth a 1000 words and this is the best I could do on short notice but it gives you the general idea. A simple angle plate can be made of rolled steel angle with the bolting faces finished square in your lathe. And to go along with their slotted cross-slide tables the Brits have the very handy Keats Angle Plate, one of which I wish I had.

 

[briankenyn]

Many thanks, Harry; I might have produced a facsimile drawing by say...December, but not in one day. I have a couple of faceplates but questioned my ability to adequately square the engine base plate, but that does seem to be the logical answer for my lathe. I won't know 'til I try.
As an aside, CW Woodson was a commercial artist with a lifelong interest in metalworking. I picked up his trail in late '30's home shop articles and he designed several very nice engines which appeared in Popular Science and Popular Mechanics over a 30 yr period- the models show up from time to time.

Once again, thank you for your kind efforts,
regards,
Brian

 

[briankenyn]

Hi Harry,
I just noticed something in your drawing that I take to be a counter-weight mounted on the faceplate. Am I right?

Thanks,
Brian

 

[GWRdriver]

CW Woodson . . . he designed several very nice engines which appeared in Popular Science and Popular Mechanics over a 30 yr period

Brian,
You're very welcome and you'll be interested to know that much of that material is now available on Google Books. I found the complete construction articles for your engine.

And yes that is a counterweight and those are usually needed to prevent things shaking about, but not always. It kind of depends upon the job, how much weight needs to be counterbalanced, what the rpm is, etc. For a small diameter bore the rpm should be appropriately high so a counterweight will be needed.

 

[briankenyn]

Hi All,

A month ago I was obsessing over an engine line-boring problem, and Harry was kind enough to redirect my efforts to a more feasible approach. As anyone will see from the attached photos, my setup less-elegantly approximated Harry’s excellent CAD drawing, which is in this string. The boring bar solution worked for me because of the relatively small distance between the journal blocks [~2.0”], and previously having made a boring bar that was up to the task.
I took some care in locating the journal blocks on the engine base, and used a DI to square the base to the lathe axis. I originally thought to press in the bushings first and then bore to the .312 shaft diameter. In fact that was exactly what I did the first time, which was why I was doing it again. Rethinking the process, by simply boring the much larger holes in the aluminum journal blocks to the approximate OD of the bushings, I could use a stiffer, longer boring bar. Then, turning and boring the bushings on the lathe from one piece of bronze rod allowed me to cut each of them to size and press them in with the reasonable expectation that they would be in alignment. In practice, that was approximately the case: the shaft jammed halfway through the second bushing and I had to lap it to allow the shaft to pass completely through.
Because of the length of the boring bar, I limited my initial cuts to no more than .010. My final cut was of the order of .001 or so at about 1,000rpm. The photos don’t show a faceplate counterweight for balancing the load. I had to make one up for this job, sized 2.0” Dia x 1.0”, to keep the lathe from jumping off the bench. Not having a capable band saw, I rough cut the blank with a carbide angle cutter from a discarded, cast iron exercise weight. I have read some comments about spotty quality in some weights, but mine was a 20lb rectangle and very decent material to machine, relatively speaking.
A word of interest: I used a small Arbor Press for seating the bushings, which despite my efforts to tighten it up, still had some side-play in the ram. I realize now that I might have ensured far better initial bushing alignment by turning down the first .062 length of each bushing to achieve a tight slip fit into the journal block, then pressing the bushing home. I might also have paid closer attention to the orientation of each bushing to the other during the parting process [as I had originally intended], and pressed them in to the journal blocks in sequence.

Regards,
Brian