Author Topic: Building a New Lathe  (Read 152664 times)

Offline vtsteam

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Re: Building a New Lathe
« Reply #450 on: June 05, 2018, 09:52:45 AM »
Okay, back to doing things. First we cut out a couple of pieces of scrap galvanized steel sheet:

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 #451 on: June 05, 2018, 09:55:37 AM »
Then clamp them together over the lathe bed near the tailstock, and contacting both the side and bottom of the boring bar. The tab at the bottom should be tight to the front way edge. Apply a few drops of super-glue to the mating sheet edges.

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 #452 on: June 05, 2018, 10:07:11 AM »
And we now have a gauge for setting the other end of the bar. This is a variation on the Gingery lathe boring gauge -- that one is a single piece gauge, and is cut to the desired center height of the lathe minus half the boring bar diameter.

In my case I had an existing tailstock of presently unknown center height that I want to match in boring the headstock, so I used a two piece gauge fabricated against the existing lathe components. No measurements involved. And it should be possible to set the other end of the boring bar to exactly the same height using this gauge, which I will keep as a permanent tool for this lathe.

Oh, also, it gives me the actual center height, by calculation. Not that I will use it to set the boring bar -- a gauge is far more accurate -- exact, in fact.

But for information purposes, the gauge measures 4.210" in height where the boring bar touches it, and the boring bar measures 0.622" in diameter there, so taking half that we get 0.311". Adding 4.210", we get 4.521" true center height. So we're on target for a 9" swing lathe - plus a whisker.  :med:

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 #453 on: June 05, 2018, 10:21:43 AM »
Very neat trick Steve  :thumbup:

How did you ensure that the sheets were perpendicular to the lathe ways?
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #454 on: June 05, 2018, 10:24:40 AM »
Wiggle 'em.

Just like calipers.

Feel for it. Feel the force, Luke.  :zap:
I love it when a Plan B comes together!
Steve
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Offline ddmckee54

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Re: Building a New Lathe
« Reply #455 on: June 05, 2018, 03:52:34 PM »
Cool, you built your own version of a telescoping gage.

Don
Too many irons, not enough fire.

Offline vtsteam

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Re: Building a New Lathe
« Reply #456 on: June 05, 2018, 09:53:29 PM »
Hi Don, pattern fitting, which is what this really is, is a prehistoric method. I wouldn't mind a set of telescopic gauges, though.

Today I dug out of the depths of my tiny shop my treadmill motor and DC controller -- a "Cycletrol 150." Both bought used 3 years ago on Ebay. Both subjected to way too much moisture. I had my doubts they would work.

After finding a schematic and manual online, I tried for hours to get that motor to turn, but no luck. There were 8 DIP switches, 3 potentiometers on board and lots of screw terminals with inputs and jumpers. Nothing worked. The schematic called for a 5K ohm external pot, for the speed control, and I had squirreled away a linear I had bought for this purpose from Radio Shack before it closed. That's how old all this stuff is.

(Cyclotrol Model 15303 Manual attached below)

One obvious problem was that the red "Brake" LED was always on. I tried everything, and was about to give up, when I tried just disconnecting the 5K pot altogether. Suddenly the motor ran. I tested the pot -- it was fine, double checked my jumper wires...they were fine. Finally I tried the only other pot I could find in my electronic junk box, a 1 megohm type. Oddly enough, it worked -- after a fashion. The motor would start, and I had some control over speed.

I started to play with the onboard trim pots -- one adjusted the minimum motor speed, and one adjusted the maximum. With these I was able to adjust a full range of RPM for the speed pot. So all was working finally. Only spent all day on it! No further work on the lathe

But I really don't understand why the 5K pot the mfr. called for didn't work, while a 1 megohm pot did. I mean how could it be that far off??? I substituted back the 5K ohm pot, and the same problem returned. I even found a 10K pot in an unused piece of computer gear, pulled that out, tried it with the speed controller and again, no go.

Well, I guess I ought to just be happy it works finally. It's just a puzzle to me. But onward with the lathe.



I love it when a Plan B comes together!
Steve
www.sredmond.com

eskoilola

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Re: Building a New Lathe
« Reply #457 on: June 06, 2018, 10:44:52 AM »
....
But I really don't understand why the 5K pot the mfr. called for didn't work, while a 1 megohm pot did. I mean how could it be that far off??? I substituted back the 5K ohm pot, and the same problem returned. I even found a 10K pot in an unused piece of computer gear, pulled that out, tried it with the speed controller and again, no go.
 ....

From experience I would say that the impedance on pin 9 (SP1) is way too high. When placing a high impedance potentiometer the voltage on pin 9 does not drop. But when the potentiometer is the specified 5K then the voltage suddenly drops. The brake light might be a part of this syndrome - it is my assumption that the light will go on when the voltage on pin 9 is lower than a given limit.

If You have a voltmeter, You could measure the voltage availble at pin 9 with the 5K pot and the 1M pot.

Since I do not have the schematic on hands I cannot give suggestions on where to seek for the fault.

For me that sounds a lot like a cold joint on emitter follower transistor collector.

The voltage in pin 9 should be really low impedance, probably something like 1-10 ohm. Now it is at least 100K or perhaps even more. The normal way to lower the impedance on a place like that is to use a simple emitter follower. I believe this is a last millennium device.

It is also possible that the voltage in the pin 9 is regulated with a beck then normal 78xx series regulator. Schematics would be really helpful and take the guess out of guesswork.  :coffee:

Edit: Actually - it could be a bad joint somewhere in the circuitry supplying voltage to pin 9. Check the joint along the trace starting from the pin 9 and see if there are any suspicious solder joints. A suspicious joint can be quite innocent looking. For example some through hole resistors can get a nice oxide layer inside the solder joint.

Another edit: Example of a really suspicious joint



Offline ddmckee54

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Re: Building a New Lathe
« Reply #458 on: June 06, 2018, 03:26:51 PM »
Vsteam:

I got an in-expensive set of telescoping gages off Ebay a couple of years ago.  The set is 6 gages and it's good for 5/8" to 6".  Best part is I didn't have to sell any body parts to afford to get it.

I wouldn't try to build a rocket engine or nuclear reactor with it, but for what I do it's good enough.

Don
Too many irons, not enough fire.

eskoilola

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Re: Building a New Lathe
« Reply #459 on: June 06, 2018, 04:05:19 PM »
Snap gages are quite fun to use. I bought mine well beaten Starrets two years ago. Those are still giving consistent measures.

I have to thank mr. Booth for inspiring me to use them. I actually spent one evening just measuring diverse tubes and trying to get consistent measures. Then I bored a few steel tubes and aimed to some imaginary dimension. For some funny reason I learned to do the actual snapping my eyes closed just listening to my fingers. At the end of the day I was actually able to get 5 very similar results in a row.

However, in this particular context I would also prefer using some sort of a jig. Using snap gages to measure the boring bar height would be horrific and trying to set it up horizontally next to impossible using the gages. I suppose that jig should also be used in the listen-to-your-fingers mode.

Offline vtsteam

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Re: Building a New Lathe
« Reply #460 on: June 06, 2018, 06:59:38 PM »
Thanks for the electrical troubleshooting info Eskoilola, I'll check that later tonight.

Thanks Don, I may get some as soon as I get everything else I need to get the lathe going.

I had to work today, so very little time for the lathe, except I did braze a bit of scrap 1/4" water pipe to the treamill motor's base to serve as a hinge when mounting it. I was afraid to arc weld it, in case the arc affected the motor's permanent magnets. Wasn't sure on that, but figured better safe than sorry. And I didn't want to overheat anything, since there is a plastic end cap and brush holders, so just a few blobs of braze and then a dunk. But it should hold.

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 #461 on: June 07, 2018, 02:45:35 AM »
You are brave Steve!

I'd have brazed that pipe to another bit of plate then bolted it to the motor foot.

 . . . But then I'm a coward
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Building a New Lathe
« Reply #462 on: June 07, 2018, 07:58:21 PM »
Hardly, Andrew, from what I've seen you take on!

After work today I welded together a U-shaped bracket out of 3/8" x 1-1/2" hot rolled steel to take the motor pivot. I made it extra long because the belt I have for the initial boring job is a bit too long. Even so, after welding I realized I wouldn't be able to bolt it to the lathe bed because it interferes with existing cross bolts. Instead I'll just temporarily bolt it vertically on the bench and I will have to bolt the lathe down as well.

I'll cut it shorter and measure for a new belt, once the boring is done, and move the motor bracket to the headstock end.

Only a couple more jobs left before boring -- attach the headstock to the carriage with a piece of angle Iron, and attach the left side boring bar support at the right position, checking with the gauge I made. The support was bolted together with slots for adjustment of the boring bar position.

Oh, one more thing....I think I'm going to add a "ram" to it -- basically just a bolt with a center-drilled head, which will screw into the support block. A stop nut will lock it. The boring bar end will ride in the bolt head, not in the block, as I have it now. I will be able to adjust and snug the bar that way, if needed.

Getting close to boring day -- probably the most important single event in this whole process, and the one that, when finished will turn this glorified dog's ladder into a lathe.
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 #463 on: June 08, 2018, 02:25:46 AM »
Hardly, Andrew, from what I've seen you take on!


And it's all starting again Steve :bugeye:

That Beaver CNC lathe is being picked up on Monday, all 6.25 tons of it. It may well not be delivered to me the same day as its coming as a 'part load'

Excellent progress with yours and good luck with the boring  :thumbup:
Andrew Mawson
East Sussex

Offline Neubert1975

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Re: Building a New Lathe
« Reply #464 on: June 08, 2018, 06:30:05 AM »
when finished will turn this glorified dog's ladder into a lathe.

And what a nice ladder/lathe it will be :clap:

Offline vtsteam

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Re: Building a New Lathe
« Reply #465 on: June 09, 2018, 04:04:04 PM »
Thanks Andrew, Neubert!  :beer:

I'm back to retirement as of today, so on with the show....

I just realized I also needed a ball handle for the leadscrew to traverse the headstock over the boring bar. So, I found some old propane valves that I'd removed from tanks used for other purposes (like building the tiny furnace). Popped them into a crucible and put it in the tiny furnace.

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 #466 on: June 09, 2018, 04:10:43 PM »
It surprised me how quickly the valves melted -- I barely had time to ram up a mold. This is with a purely atmospheric propane burner I built -- quite small actually. I did augment the draft with a length of stovepipe perched on top of the furnace lid.

The melt wasn't quite behaving right -- a little pasty, by the time I was ready to pour, so I guessed I'd lost some zinc in the long time it took me to make up the mold.. I decided to drop in a couple of the thin frozen zinc spills from prior pours-- less than an ounce I would guess. And yes the melt became nice and fluid soon after. I skimmed and poured.

Here's the result when I separated the flask. Besides the ball handle, I also cast a locking lever for the tailstock ram. and a very small oil dipper that it also takes. That last one didn't quite fill with brass -- you can see the impression of the post at the end is not quite filled.

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 #467 on: June 09, 2018, 04:15:18 PM »
Here they are liberated from the sprue, and rough cleaned. I'll probably just drill the oil dipper, and add a bit of brazing rod for its post. Surprisingly easy to cast some useful bits in brass today. Very pleased!

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 #468 on: June 10, 2018, 10:02:28 PM »
Today I drilled the ball screw to fit the leadscrew, and added a set screw. The carriage ran a little tight at first, but I had not tightened the screws adequately on an aluminum bed extension that serves as an attachment point and heat sink for a stepper motor -- should I decide to go with the electronic leadscrew I worked up a couple years ago. Anyway, the extension also carries the left side leadscrew bearing, and it turned out that the extension was rocking slightly and throwing the bearing out of line.

What was really needed was countersinking its attachment bolts, and fully tapping the corresponding blind bed holes -- which had never been fully bottom tapped. Once this was accomplished, the extension could be firmly bolted in place, and the leadscrew and new ball handle drove the carriage sweetly along the full length of the lathe.

Next to receive attention was the headstock. It also bound, about halfway along the ways. It slides on the inside edges of the two way pieces, while the carriage rides on the outside. I finally traced the binding to the fact that the headstock's retaining plate was contacting a slight high spot on the heavy steel bed bearers.

To solve that, I milled the retaining plate on the binding side about 0.030" narrower so it wouldn't contact the bed rails, just the ways. The headstock then slid sweetly along the full length of the lathe.

Finally I drilled a couple holes in short length of angle iron to attach the headstock to the carriage. Then transfer punched those locations and drilled and tapped the two moving parts. Finally the carriage and headstock are connected, and the leadscrew now drives the headstock down the ways. No binding, and the ball handle moves everything easily. I adjusted the two gib screws under the headstock, and hit them with some Loctite.

All that's left to do before boring is attach the left side boring bar support, fasten down the lathe and the motor bracket, connect the speed controller, and ......go.
« Last Edit: June 10, 2018, 10:45:01 PM by vtsteam »
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline vtsteam

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Re: Building a New Lathe
« Reply #469 on: June 11, 2018, 09:34:37 AM »
The cross slide has been removed, and the headstock has been screwed to the carriage temporarily with a bit of angle iron.

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 #470 on: June 11, 2018, 10:01:44 AM »
Steve, when do you sleep?

Offline vtsteam

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Re: Building a New Lathe
« Reply #471 on: June 11, 2018, 10:31:37 AM »
Heh, Norman, any time someone turns on a television, during company meetings while employed, when dragged to any recent movie involving male superheros or Johnnie Depp, while visiting friends for dinner if the conversation turns to Apple products, cell phone plans, or health issues, etc.  :)
I love it when a Plan B comes together!
Steve
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Offline krv3000

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Re: Building a New Lathe
« Reply #472 on: June 11, 2018, 05:56:34 PM »
 :D brill


Offline vtsteam

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Re: Building a New Lathe
« Reply #473 on: June 11, 2018, 09:41:23 PM »
Thanks Bob!  :beer:

For an adjustable pivot, I faced off a bolt and center drilled it. Tapped the support block and added the bolt. The boring arbor fits there, and I can take up the slack with the bolt. The nut is for locking it.

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 #474 on: June 11, 2018, 09:42:39 PM »
Setting up the bar with the gauge made previously:


I love it when a Plan B comes together!
Steve
www.sredmond.com