Author Topic: Building a New Lathe  (Read 130160 times)

Offline vtsteam

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Re: Building a New Lathe
« Reply #475 on: June 11, 2018, 09:44:33 PM »
And finally, boring the headstock!  :ddb:

Uhhh....this is going to take awhile.......


I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #476 on: June 12, 2018, 02:25:17 PM »
Verrry slow going. I have to re-sharpen the HSS bit every pass. Unfortunately, I have to enlarge the diameter by 0.5", just for a clearance bore. I'm probably only cutting .010" per pass.

The recesses for the bearings are larger than the clearance bore. The are not full depth, however, so they should go more easily.

Also, I'm still at an interrupted cut stage, and there are undoubtedly sand inclusions in the cast skin in the bore. Once that's all gone, and the interrupted cut is over with, I hope the bit will stay sharp longer and things will go more quickly.
I love it when a Plan B comes together!
Steve
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Offline NormanV

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Re: Building a New Lathe
« Reply #477 on: June 12, 2018, 05:26:04 PM »
I am confused by your problems. When I bored the tailstock of my lathe, similar setup, I was hand cranking it and had no problems with tool sharpness. I was particularly surprised as I was machining the split collet (steel) at the same pass and found it a bit tight. When I examined it afterwards I found that the collet had managed to move between each pass of the cutter but fortunately on the last pass it all seemed to be ok. I can't show a photo as everything is packed up for an imminent house move.

Offline vtsteam

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Re: Building a New Lathe
« Reply #478 on: June 12, 2018, 10:38:30 PM »
Norman, BIG difference between cast aluminum and cast Zamac, or even steel and cast iron. I too found boring the aluminum headstock and tailstock castings for my Gingery lathe a piece of cake, by comparison.  They were also a lot smaller radii than this one where I'm boring a clearance hole over 2" in diameter, not to mention the even larger recesses for roller bearings. That alone means more much more metal to take off than a tailstock, and I have a full half inch to go on the through bore -- not a close bore to start.

Both metals were sand castings, and I can't exactly explain why if the holes had been the same size this one would be so  different in cutting ease than the other, but the fact remains, they are.

One noticeable difference to aluminum I've found is that the tool grind angles have to be much sharper with Zamac because it is both slippery and very very tough, and the necessarily fine edge needed to cut it doesn't last well. Zamac machines beautifully, but not necessarily easily, and I'm working with a home concocted Z-12, not commercial quality. Filing and hacksawing also are noticeably more difficult than with sand cast aluminum, and those dull quickly as well, on the same types of jobs I would do with aluminum.

This particular casting really wants a carbide tool with sharp angles and top relief, but I don't have anything suitable that I can use with this boring bar. So it's slow going with HSS. And frequent re-sharpening. I do think that when the skin is fully removed from the bore (it was quite irregular and there are still patches of as-cast skin) that I won't have to sharpen as frequently.

No problem, really, Norman,, I'm patient, and I'll get there. I hand scraped the ways over several days, and I don't see that it's a big deal to take it slow boring either. All part of the game...

I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Building a New Lathe
« Reply #479 on: June 13, 2018, 01:38:34 AM »
Steve, could you possibly have remaining sand inclusions in the skin that are dulling your tip?
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #480 on: June 13, 2018, 08:08:43 AM »
Definitely Andrew, what I was trying to say., last two posts The bore was dirty and irregular shaped if you go back to my original casting photos, necessarily -- it was a difficult casting to get everything right.

Because the bore is irregular and has hollows, I can't just get rid of the entire skin in one cleans swipe -- it will take removing another quarter inch of material to get completely rid of it. One small patch will dull HSS instantly.

But I also do think that this Zamak 12 is really recalcitrant anyway, by nature. You can get a good surface finish with carbide, but it's really tough on ordinary tools -- noticeably so on hacksaw blades and files. And chisels -- I did try chiseling off some of the flash. Nothing like as easy as even mild steel. I'd far rather hacksaw a 1/2" thick slab of steel, than the same size slab of Zamak. I think it's the combination of slipperiness, with high tensile strength, yet relatively soft qualities. It's both sticky and slick, and nothing less than a perfect edged tool tends to plow it to the side rather than chip it off. Or just slide over the cut. It is nothing like brass -- though you would think it's similar. The last thing you'd want is to stone back the inside edge of a drill. Cutting tool angles have to be more acute not to just ride over the cut.
« Last Edit: June 13, 2018, 08:52:08 AM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #481 on: June 13, 2018, 04:53:56 PM »
I was curious to see how much skin was left, so I decided to pull the bearing cap off and have a look. Quite a lot, since there were hollows in the core impression. 

So I got out a Dremel and chucked up a carbide burr, and went at all the grainy looking areas I could find. When I put the cap back and resumed boring, I noticed a definite cutting improvement. I'm still sharpening the bit frequently,  but not as much, and the cuts are a little deeper and more consistent, end to end.

Next improvement I'm contemplating is making a new 3/4" boring bar to replace the 5/8" one I started with. There wasn't clearance for anything bigger to start, but now that the bore is much larger I can move up in size. A larger bar will mean I have to also bore the pulley to fit it, but I judge there's enough hub to do that.

3/4" would be the limit for hardware store pulleys though.

Getting there.....
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Building a New Lathe
« Reply #482 on: June 13, 2018, 04:58:36 PM »
Can you not re-arrange so that the pulley is at one end, and just turn down the bar to suit the pulley bore ?
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #483 on: June 13, 2018, 05:55:29 PM »
I could. The pulley is located at  the very end of the bar, now -- just a tiny bit ahead of the 60 degree tapered end that fits the center drilled hole in the tailstock ram blank. So yes, Andrew that would be do-able. Might take you up on that idea.  :nrocks:
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Building a New Lathe
« Reply #484 on: June 14, 2018, 12:38:18 PM »
. . . .no charge . . . . :lol:
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #485 on: June 14, 2018, 02:32:14 PM »
Before I did make a new bar, I decided to cut down one of my 1/4" indexable turning tools (from a cheap set that I've never found replacement inserts for) to 1-1/2" long, and put it into the boring arbor.

Man what a difference! It really chews through the sand cast Zamak. Not a pretty cut, but I can take .030 off the diameter in a single pass, no sharpening, at twice the RPM and a decent feed. I was starting to get down about all the sharpening I needed with the HSS. Well, this is a job for carbide only. Obviously the insert and angles aren't ideal for a clean cut, but at least the end is in sight for this clearance bore. Phew!
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #486 on: June 15, 2018, 06:11:20 PM »
As I get closer to finished bore size, the extension of the tool bit has increased to the point where it's moving slightly despite the set screw. So today I hunted up an old piece of cast aluminum sprue, and turned and milled up a little boring head for my arbor, just a 0.1" smaller than the present bore.

This should make the next few cuts out to finished size a lot easier, and though it presently fits the 5/8" arbor, I can open it out for a 3/4" arbor later -- which will be necessary for doing the bearing recesses.

By starting with 5/8" I'm able to keep the tool bit a little longer inside the shell for better support, until the bore is larger and I can switch to a longer tool. And this time the tool is held by two set screws, so I don't think movement will be a problem... at least for awhile.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #487 on: June 15, 2018, 10:32:10 PM »
It's working very well, much deeper cuts but necessarily slow feed. Otherwise the driven pulley slips. Since I can't fit a carbide tool in the small space, it also means I'm back to HSS, and frequent sharpening. But progress.  :dremel:

This is probably unecessary at this point -- the spindle is about one and a quarter in diameter, and I'm nearing 2" on the clearance bore. But I had it in mind to make it to 2.125" and I haven't given up on that....for no apparent reason.
I love it when a Plan B comes together!
Steve
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Offline Homebrewer

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Re: Building a New Lathe
« Reply #488 on: June 15, 2018, 11:37:17 PM »
So, it looks sort of like you're using a fly cutter like tool, mounted on a mandrel.

I have been watching this thread with great interest because if I ever get out of this apartment and into a house, I plan to go through the Gingery book and build a lathe similar to yours.  Following your thread has both given me ideas as well as validated some others that I'd give consideration.

Sent from my SM-G950U using Tapatalk


Offline vtsteam

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Re: Building a New Lathe
« Reply #489 on: June 16, 2018, 12:38:03 PM »
Thanks very much Homebrewer. :beer:

Yes, I've made a few similar over the years -- the first was back 13 years ago when I was adding a milling attachment to the Gingery lathe -- I didn't have a milling machine then, so the fly cutter with an arbor mount, instead of the usual stub, was used to level a new milling and boring table:

https://madmodder.net/index.php/topic,8191.msg88064.html#msg88064

I personally think building a Gingery lathe is the best possible kind of machinist self-education, because you're really starting from scratch, and you are forced to use historical methods, hand work and ingenuity to get to the finished product. Buying a lathe is fun because you can get started right away, but it kind of short circuits that education. Turning and threading are all a lathe can teach you -- at least out of the box. There are probably fifty more things you learn building one from scratch.

For me, building that lathe led to many things, including wonderful employment opportunities, that I probably wouldn't have had otherwise. Also, it's incredibly rewarding to build it. In fact, no project I've ever built using that lathe equaled the thrill of building it in the first place.

You're on the right track if that appeals to you. I'll always be grateful to David Gingery for that little orange book I just happened to pick up one day.
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline awemawson

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Re: Building a New Lathe
« Reply #490 on: June 16, 2018, 12:57:21 PM »
Many many pre-war (I mean 1939-1945 war) models of engines etc were made with very basic tools, the lathe often being treadle driven, and the models were of a very high standard. When I was involved with the SM & EE  I was amazed at the workmanship of some of those early models in their collection.

To have a milling machine in a home workshop was unheard of, but vertical slides to mill on the lathe were not uncommon.

I agree Steve - making things with limited resources demands imagination and determination but it CAN be done  :thumbup:
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #491 on: June 16, 2018, 05:28:33 PM »
Done with the clearance hole. Now starting the bearing journals.

I believe these need to be 2.441" in old measurement. This is going a fair amount easier with only an inch to bore for depth. The arbor mount cutter is working very well. Glad the other is over with!  :Doh:





I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #492 on: June 17, 2018, 01:12:47 PM »
Getting closer to journal size, it was time to make a bore gauge. I found a scrap piece of aluminum 2.5" in diameter. The bearing measured (on my calipers) 2.4395". Not that they are accurate to a half thou, but I've been using it consistently, so parts should match.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #493 on: June 17, 2018, 01:18:17 PM »
I turned the gauge to 2.440" on one side and 2.430" on the other. Sorry I don't have any photos of turning, but if you're interested, John (Doubleboost) posted a fine video on youtube awhile back showing the process of bore gauge making (his ER32 lathe chuck video).

I'm adding an additional touch to suit my particular headstock boring setup here -- first drilling the gauge 3/4"

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #494 on: June 17, 2018, 01:20:49 PM »
Then I sawed a slot close to the finished diameter on my bandsaw. I probably could have left it there, but decided to clean up the slot on the mill:

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #495 on: June 17, 2018, 01:24:42 PM »
And here's he finished bore gauge. The slot allows me to drop it down over the boring arbor and test the bore without taking apart my setup. I was a little apprehensive putting a slot in the gauge, in case there were internal tensions that would change the OD's, but measuring after slotting (and letting the gauge cool) showed the diameters were still spot on.

So I stamped both sides of the gauge with their dimensions, and we're ready to continue boring the journals.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #496 on: June 18, 2018, 05:14:00 PM »
And after boring all morning, we have a bearing journal!  :ddb:

Phew....!!


I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #497 on: June 18, 2018, 05:17:17 PM »
The gauge worked perfectly in sneaking up on the final diameter. The final fit is nice and close, and I'm happy. Hope the other one comes out as well.



One of the things to remember is that this type of boring has no actual lathe adjustment or graduation at this stage in the construction. It's all a matter of moving the cutting bit out of the boring bar small amounts at a time and re-tightening the setscrews. So it feels like quite a victory to hit the diameter right on the money.
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Building a New Lathe
« Reply #498 on: June 18, 2018, 05:19:27 PM »
Excellent Steve - that must be quite a relief to complete this phase  :thumbup:
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #499 on: June 18, 2018, 06:29:32 PM »
Well, one more journal to go, but the first one done means the end is in sight.

For those who haven't tried this: a little spring in the boring arbor is helpful in getting the final diameter right. It never cuts to full depth on first pass. For instance, if I set the boring tool out 4 thousandths the first cut will be maybe 2 thou (4 for diameter), the second cut one thou more (2 on diam), and the third cut maybe a half (one thou on diam) , and so on, until you reach the chatter point. So if you play this right by advancing the tool just a little past final size you can ease right down to where you want it in very small steps without resetting the tool, testing each pass as you go with the homemade gauge. When it just fits, you're done.

Rigidity is a plus in a lathe, but you can work with a less than perfect setup to get the results you want. It just takes more time, and understanding. Since this is a one-off situation (the finished lathe will be a much more rigid boring platform) boring the headstock before it is fixed in place with a 24" long  boring bar is a little tedious, but certainly tolerable, considering this kind of setup won't be needed again.
I love it when a Plan B comes together!
Steve
www.sredmond.com