Author Topic: Building a New Lathe  (Read 161474 times)

Offline vtsteam

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Re: Building a New Lathe
« Reply #300 on: June 14, 2015, 03:59:06 PM »
Heh, you did get me going Andrew -- the idea that it would "fizz" away like a big battery if wet didn't uhhhhh hold water, so in humorous spirit then back at ya, don't sweat it! :lol:

As you know  brass IS zinc and copper combined, and gets wet without fizzing away, and likely won't mind keeping company with zinc as much as some other metals it's routinely mounted on.
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 #301 on: June 14, 2015, 04:22:34 PM »
Anyway, it looks very nice! Sort of maritime!

Regards, Matthew

Thanks Matt!  :beer:

That reminded me of a marine steam engine I have -- over 60 years old -- of brass and aluminum construction. Between steam and water, it definitely was wet for a lot of its useful life, and since it was built in Baltimore, might even have seen salt water. It's a beauty and proud posession, in very good shape, and still runs:

« Last Edit: July 11, 2017, 03:19:17 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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RobWilson

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Re: Building a New Lathe
« Reply #302 on: June 14, 2015, 04:38:15 PM »
That's a Canny wee engine you have there Steve  :thumbup:

Lathes looks like its coming on a treat  :clap: :clap: :clap: :clap:

Rob

Offline vtsteam

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Re: Building a New Lathe
« Reply #303 on: June 14, 2015, 04:59:30 PM »
Thanks Rob!  :beer: :beer: It's a pretty good sized engine, Rob, bigger than it looks in the picture -- one of two that I bought about ten years ago at a model engineering show at the Precision Museum in Windsor, VT. Very similar engines are mentioned in an old Model Engineer, built by Arthur M. Balling of Balimore (issue 3308), and I'm certain this one was built by him. The seller did mention Baltimore, also. You can see the raw sand casting in some areas --n he built a big series of these as experiments to test out different valve gear.

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 #304 on: June 14, 2015, 11:02:20 PM »
Tonight I spent a couple hours out in the workshop, and made the halfnut detent arm and spring, and filed grooves on the halfnut rim to accept them. I shaped everything until I liked the feel of the snaps, both engaged and disengaged.

I found I had a little play in the half nut engagement with the leadscrew, yielding backlash, because it wasn't quite thick enough to contact the back of the apron, by .024", measured with a feeler gauge. It was cocking slightly with a change in direction. It is supposed to bear against the apron, so I made up a shim washer that thickness, and then there was no more play at all. The backlash disappeared.

Everything was a little stiff, so I chucked an electric drill onto the tailstock end of the leadscrew and moved the carriage end to end 20 times times to wear the halfnut in a little. Then I checked again the position of the engagement detent to adjust if necessary, but it was fine. The carriage moves smoothly now, the halfnut stays engaged, and clears when disengaged.

I moved the carriage near each end in turn and adjusted the leadscrew bearings up or down to eliminate any bow when engageing the half nut. I haven't drilled for the bearing mounting bolts yet, but they now are both correct in height and clamped, ready for drilling. I might slot them anyway so they can be adjusted up or down if needed.
I love it when a Plan B comes together!
Steve
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Online awemawson

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Re: Building a New Lathe
« Reply #305 on: June 15, 2015, 02:44:01 AM »
Steve I'd be tempted to slot them and when I was sure that the adjustment was spot on, drill and ream for a roll pin.
Andrew Mawson
East Sussex

RobWilson

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Re: Building a New Lathe
« Reply #306 on: June 15, 2015, 04:37:53 AM »
Thanks Rob!  :beer: :beer: It's a pretty good sized engine, Rob, bigger than it looks in the picture -- one of two that I bought about ten years ago at a model engineering show at the Precision Museum in Windsor, VT. Very similar engines are mentioned in an old Model Engineer, built by Arthur M. Balling of Balimore (issue 3308), and I'm certain this one was built by him. The seller did mention Baltimore, also. You can see the raw sand casting in some areas --n he built a big series of these as experiments to test out different valve gear.

Arrh , I do remember you mentioning the engine find now. Looks a well made engine  :thumbup:


Rob

Offline vtsteam

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Re: Building a New Lathe
« Reply #307 on: June 21, 2015, 03:50:38 PM »
The headstock pattern has taken a lot more time than I thought to plan out and build -- it's a pretty simple shape, by the end, but getting there took it through all kinds of contortions! There a deceptive number of requirements since I'm working from an existing spindle and bearings, and bed, and I wanted to use a greensand core instead of making coreboxes. and placing cores. Plus I wanted to add a full length bearing cap, The headstock rides inside the ways, rather than outside. Then adding draft, machining allowance, etc. Yet keeping it within the melting capacity of my furnace. All kinds of things fighting each other....

Anyway, here is the headstock base pattern, with, I hope, everything I wanted together and sized right with allowances. It will need 3 new flasks, and I might have to make a bigger crucible. But those things are handy to have, so i don't mind.that part. The bearing cap pattern is started, but not done yet.

« Last Edit: July 11, 2017, 03:20:18 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline mattinker

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Re: Building a New Lathe
« Reply #308 on: June 21, 2015, 06:12:31 PM »
It's surprising how the apparently simple patterns can be very complicated!

Regards, Matthew

Offline RussellT

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Re: Building a New Lathe
« Reply #309 on: June 22, 2015, 04:03:04 AM »
Hi Steve

That looks very solid.  :clap:

Where is the drive going to be?   :scratch:  I'd assumed that since you were using bearing caps to make the spindle removable there would be a belt between the bearings - and that making the spindle easy to remove would make belt changes simple.  It doesn't look like that's your plan - unless you're going for underdrive.

Russell



Common sense is unfortunately not as common as its name suggests.

Offline vtsteam

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Re: Building a New Lathe
« Reply #310 on: June 22, 2015, 07:38:10 AM »
Very true, Matt!

Russell, drive is at the aft end -- variable speed DC motor. I split the bearing housing for reasons other than belt changes:

Quote
It  would be nice to be able to remove the spindle assembly without having to use a puller. It would also mean I could do the casting in two parts, and more easily fit a heavy casting pour in the crucible capacity I have.....

...Another helpful aspect if I can split it is that I can probably use the same boring bar and setting to bore both bearing recesses at front and back without changing anything. Each recess has an inside lip, and the boring bar can't make it through that, but if the cap was removed the tool bit could face up, slide through to the other side, and then replace the cap, and bore the other recess.

I would definitely prefer to do it that way than remove the boring bar from the boring jig setup, or move the tool bit in and out to cut both recesses.

I might also make up more than one spindle for this lathe down the road. I'm not too enthusiastic about the design of the  7x14 mini-lathe spindle. I made several swappable spindles for the Gingery lathe.
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 #311 on: June 22, 2015, 08:04:21 AM »
This is the bottom view. That is going to be a difficult greensand core to preserve. I'm going to have to cope down for the 4 projections you see here. The flask has 3 parts -- the center part is exactly as tall as the pattern.

The bearing journal area will also be pretty interesting to try to mould with all the other stuff going on -- two part sprue, etc. and probably several rolls. Though i keep thinking it through, I haven't got it completely thought out yet. I expect the first time molding will just be a practice run to reveal what I should have done, and I'll have to start over. Lets hope it isn't more than three times! Working outside the sand dries out if you take too long to get something molded, and then you get drop outs and sand in the casting. This baby is going to be heavy to roll, and carry, too. Should be interesting!

« Last Edit: July 11, 2017, 03:20:58 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline mattinker

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Re: Building a New Lathe
« Reply #312 on: June 22, 2015, 08:24:13 AM »
Why don't you want to make it with a core? Your pattern is almost a core-box in it's self. For difficult "green sand" cores (petrobond in my case!) I've found nails or short pieces of small section re-bar usefull.

The best of luck with it, regards, Matthew.

Offline vtsteam

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Re: Building a New Lathe
« Reply #313 on: June 22, 2015, 09:53:15 AM »
Well Matt I don't particularly like making hard cores if i don't have to -- they are more additional work than making the pattern and part itself, and consume more materials. There are more things that can go wrong with the casting as a result. Off gassing, too hard a core, too soft, misplaced, softened in greensand by delay.

I don't mind cylindrical baked cores, since I can make and bake them easily in split pipe shells that I already have. But building complex highly finished core boxes (if they can be avoided by design) and baking cores feels to me like a delay. Production has different needs than I do, and hard cores can be made by the dozen (or hundred) to ease casting there. I'm impatient, and I cast practically everything one-off (unless I mess up!) so I design patterns for greensand cores where possible.

Besides I like a challenge in simplifying designs to use the minimum of materials and process complexity. This is a simple pattern, really. I may have a tricky time molding this piece because I don't do it every day, but I'm sure an old time sandcrab wouldn't think twice about assembling this mold. Who knows it may come out easier than I think -- will be casting today.....
I love it when a Plan B comes together!
Steve
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Online awemawson

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Re: Building a New Lathe
« Reply #314 on: June 22, 2015, 12:05:56 PM »
... do it Steve - just need some chaplet pegs to support it :

http://www.gsfoundry.co.uk/chaplets.html


Incidentally, talking of loose bits in patterns, how do you like this Perkins 2 cylinder digger engine casting where they have obviously screwed a plate on the pattern for variable information, giving perfect impressions of the screw heads  :lol:
Andrew Mawson
East Sussex

Offline NeoTech

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Re: Building a New Lathe
« Reply #315 on: June 22, 2015, 01:49:49 PM »
This is a brilliant thread Steve.. just awesome. =)

 :beer:
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline vtsteam

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Re: Building a New Lathe
« Reply #316 on: June 22, 2015, 02:48:19 PM »
Well here we go, I'll give you a blow by blow photo shoot of today's attempt.

I taped closed the rough journal -- a little trick I've used once or twice. The journal is way undersized for machining allowance, so not critical. I've done this before on smaller castings and it has worked well. Tape has zero effective thickness, and you can sort of shape the sand with it by pressing while molding to yield draft.

Well, better for something this big would have been to make 2 loose pieces to fit the journal sections, and included draft for the ends. But hadn't thought of it ahead of time, and like I say, the journals are undersized so not a big deal if the ends aren't perfect -- they are just added so I don't have to bore off so much metal, and to reduce the size of the crucible needed to fill this mold:

« Last Edit: July 11, 2017, 03:21:39 PM 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 #317 on: June 22, 2015, 02:57:15 PM »
Pattern in the middle one of the 3 flasks, a section of sprue -- flask and sprue are the same height as the pattern.

It was a beautiful day, but not for molding outdoors! Lots of sunshine and wind they dry out the sand fast and you have to work quickly, especially opening up 3 sections and with a hanging greensand core (the journals) and coping down. Not possible working fast and taking photos, but Madmodders deserve a looksee so we did the best we could under the circumstances!  :mmr:



« Last Edit: July 11, 2017, 03:22:05 PM 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 #318 on: June 22, 2015, 03:00:23 PM »
Ramming up:

« Last Edit: July 11, 2017, 03:22:29 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline Eugene

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Re: Building a New Lathe
« Reply #319 on: June 22, 2015, 03:02:37 PM »
Steve,

Just a plea ... if you do have to make a new crucible, could you give us a run down? I can see one on the horizon.

Eug

Offline vtsteam

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Re: Building a New Lathe
« Reply #320 on: June 22, 2015, 03:04:40 PM »
Rammed up and molding board rubbed in:

« Last Edit: July 11, 2017, 03:23:00 PM 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 #321 on: June 22, 2015, 03:10:15 PM »
Sure Eugene. Unfortunately, I didn't this pour...... more later....:beer:

Middle flask, first roll:


« Last Edit: July 11, 2017, 03:23:26 PM 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 #322 on: June 22, 2015, 03:13:51 PM »
Coped down to pattern and cleaned up:

« Last Edit: July 11, 2017, 03:23:46 PM 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 #323 on: June 22, 2015, 03:18:29 PM »
Dusted with parting, drag set in place ready for filliing:

« Last Edit: July 11, 2017, 03:24:16 PM 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 #324 on: June 22, 2015, 03:23:45 PM »
Drag rammed up, molding board rubbed in, second roll.

I had to cope down here a little, too and clean up:

« Last Edit: July 11, 2017, 03:24:40 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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