Author Topic: Building a New Lathe  (Read 152753 times)

Offline PekkaNF

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Re: Building a New Lathe
« Reply #225 on: May 08, 2015, 04:44:11 AM »
Not sure what you mean Pekka.  No matter what shape the flutes, the screw can only make its own shape in another solid. A different shape flute relief will affect the ease of cut, only.

Commercial taps have radiussed relief cuts mainly to reduce notch sensitivity I believe, so the tap will break less easily.

You are right. I was too tired when I was thinkking of this...like helix angle + side clearances and projections. Like gear cutter.

Any change of a separate how-to-thread with a little text and few picures on how you did that tap. I am specially interested on case hardening. There used to be many chemicals awailable here, but most seems to be either forbiten on unobntanium for hobbyist.

Pekka

Offline Will_D

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Re: Building a New Lathe
« Reply #226 on: May 08, 2015, 05:14:15 AM »
Will, In this case I need to tap the casting.
My idea was more along the lines of:

Take a silicon rubber mould off of the thread.

Fill this with investment, remove silicon. Use the male invetsment as a core for the cast bronze.

Or similar using a lost wax master of the leadscrew.

Only trouble may be shrinkage!
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Offline vtsteam

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Re: Building a New Lathe
« Reply #227 on: May 08, 2015, 03:51:11 PM »
Thanks Abraham, Pekka, Will!  :beer: :beer: :beer:

Pekka, I used Kasenit to case harden the tap. I have a can of it bought a dozen years ago. I don't know if it's still available. Lookups on the net aren't showing it other than providing references to alternative products, or case hardening discussions.

Will, I meant I had to tap a hole in the carriage casting itself, rather than produce a separate leadscrew nut for the carriage. That's why I needed a tap.

Your method seems to imply making a new small part (like a leaadscrew nut), and so it's definitely possible to core a thread in that kind of thing. The Gingery lathe I built has such a casting -- the split nut.
I love it when a Plan B comes together!
Steve
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Offline S. Heslop

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Re: Building a New Lathe
« Reply #228 on: May 08, 2015, 05:50:20 PM »
Last week I was looking up the prices of acme/ trapezoidal taps and got a fright. I then proceeded to try find information on making taps and found nothing but garbage. So this stuff is very much appreciated!

Offline vtsteam

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Re: Building a New Lathe
« Reply #229 on: May 08, 2015, 07:28:25 PM »
Simon, Pekka, there's a lot of reference online to homemade case hardening compounds. I haven't tried any of them because I already had Kasenit, though I'm very interested in simple materials.

It's hard to sift through all the claims and counterclaims, and I don't want to experiment with the ferro or ferri cyanides based on various sometimes opposing opinions.

And those recipes calling for many hours packed in bone, hoof, horn or leather (and there is disagreement about which is best) sealed in stainless boxes at yellow heat isn't practical for me.

It would be nice to have a tested way of case hardening even light depth that was both safe and quick, and involved available materials. I think Andrew, you once mentioned something along those lines -- can't remember.....

The other way to make a tap is to start with hardenable material like drill rod, then turn the thread, mill the flutes, and harden and temper.
I love it when a Plan B comes together!
Steve
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Offline Jonfb64

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Re: Building a New Lathe
« Reply #230 on: May 09, 2015, 02:54:36 AM »
Yesterday while at the Harrogate model show I bought a tin of case hardening compound, the ingredients are as follows

Sodium chloride
Potassium ferro cyanide
Charcoal
Calcium phosphate

I forgot to ask how to use the stuff  :Doh:

Steve that lathe is starting to look really good. Are you going to go for direct drive for the spindle and use a motor vfd  combination?

Jon

Offline DavidA

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Re: Building a New Lathe
« Reply #231 on: May 09, 2015, 06:51:13 AM »
VT,

The method we used at work to observe the depth of hardness with steel samples was to grind and polish the piece (say a section cut through a case hardened bar) Then immerse it in NItrol.  A mix of Nitric and Hydrochloric acid.
You could then see the depth to which it had been hardened.

In my job it was vital that I only used the original metal as samples, so I had to ensure there was no case hardening left.

Dave.

Online awemawson

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Re: Building a New Lathe
« Reply #232 on: May 09, 2015, 07:05:05 AM »
In WW11 British Prisoners of War used to successfully case harden mild steel to make wire cutters from nothing more complicated than sugar and a spirit lamp. They were distilling hooche and used the resultant neat alcohol on a cotton wad wick, blowing through the flame with a tube rolled from tin plate cut from 'Klim Tins' (dried milk tins).

The steel was heated to a bright red in the improvised blow lamp, then dipped in sugar which carbonised and formed a crust. It was then reheated for several minutes for the carbon to penetrate the surface to get a decent depth of case, then plunged into water. This made a glass hard case and the remnants of the carbonised sugar flaked off.

It just shows that if the needs must ..... simple processes get results !
Andrew Mawson
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Offline NormanV

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Re: Building a New Lathe
« Reply #233 on: May 09, 2015, 09:39:38 AM »
I tried to case harden some steel using sugar, I'd never heard of anyone else using it. Sugar is carbon rich so I thought that there might be a chance that it would work but it didn't for me. The reheating might be the answer, I will try it.

Offline vtsteam

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Re: Building a New Lathe
« Reply #234 on: May 09, 2015, 10:16:00 AM »
Thanks guys. I think this is an interesting enough subject to many of us that I'm going to start a separate Mod-Up, with the purpose of finding and trying useful DIY case hardening materials and methods. No prizes (other than possibly useful information) and I don't think it makes sense to have a vote or winner, but just for fun experimenting, with maybe some benefit from the results.

Also disproving any myths, answering arguments over what works and doesn't, and what is better or worse. My guess is that we'll find that method is at least as important as ingredients. Give me a few minutes to set that up......


Okay, here it is:

http://madmodder.net/index.php?topic=10681
« Last Edit: May 09, 2015, 10:53:40 AM by vtsteam »
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Offline Manxmodder

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Re: Building a New Lathe
« Reply #235 on: May 09, 2015, 02:06:49 PM »
I tried to case harden some steel using sugar, I'd never heard of anyone else using it. Sugar is carbon rich so I thought that there might be a chance that it would work but it didn't for me. The reheating might be the answer, I will try it.

Norman,sugar does work quite well. No matter what the carbon rich source is the reheat/heat soak phase is important as it allows time for the carbonising layer to penetrate to a greater depth and build in thickness.

For convenience I do use Kasenit compound fairly frequently,but other carbon sources like charcoal and soot will also work. I have also seen steel hardened with a sooty carburising flame from an oxy-acetylene torch......OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline vtsteam

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Re: Building a New Lathe
« Reply #236 on: May 11, 2015, 06:05:40 PM »
Cross slide casting. That was a tough one, too. Parting line was part way up the sides so false cope again, and that long thin extension way up in the cope. Messed up the draw twice and had to remake it. I should have made it a loose piece, but didn't. The crucible was absolutely brim full, but I managed without a spill. I thought it might pour short because I had a big riser to fill. Definitely thought I might be doing this one over.... but it poured perfect to the top with no leftover for ingots, and the casting came out fine. So no complaints here! On we go....



« Last Edit: July 11, 2017, 03:48:40 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline Joe d

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Re: Building a New Lathe
« Reply #237 on: May 11, 2015, 06:21:22 PM »
Well. that one came out looking good.  Like the one before it.  And the one before that....

think you've got this casting stuff down, Steve :bow: :bow:

Joe

Offline vtsteam

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Re: Building a New Lathe
« Reply #238 on: May 12, 2015, 05:03:50 PM »
Thank you kindly Joe!  :beer:

I miled the top and the slides and rails on the bottom of the cross slide casting. And here's the ball handle I'll be using, which I cast earlier in brass. I didn't set a core in it, so the core print was cast, too, since the pattern had prints. I'll just saw it off and drill.

Tomorrow I'll start on the bottom slide retainers, gib and gib screws. I have meetings from 12:30 on until 6:00 so not sure how much I'll be able to get done.

« Last Edit: July 11, 2017, 03:49:11 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline tom osselton

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Re: Building a New Lathe
« Reply #239 on: May 12, 2015, 05:13:02 PM »
Another good one! I haven't done any casting yet this year and still haven't tryed a false cope. I use a homemade 5 1/2 "square steel crucible 9" deep  for aluminum so its a little harder not to have enough metal. I use the clay graphite so far for brass and will hopefully give cast iron a go.

Offline vtsteam

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Re: Building a New Lathe
« Reply #240 on: May 12, 2015, 07:16:10 PM »
Tom what kind of furnace for the iron? I do remember your first aluminum castings were perfect.  :thumbup:

The cross slide is an inch thick and weighs 10 lbs and the metal for that, the heavy sprue and riser truly filled the crucible. It was cast in Zamak again. I decided to use that for anything that has linear slide on this lathe, since it has really nice bearing qualities on steel.

I've been using a clay graphite crucible for the zinc alloy, a new one I bought, originally advertised for iron, but others of the type deteriorated quickly for that purpose so I had shelved this one, new. It is is fine at lower temperatiures for zinc however, and is in perfect shape after three pours.

For small brass crucible so far, I use a small cast iron plumber's pot lined with fireclay and sand mix.

Looking forward to seeing more of your casting! :beer:
« Last Edit: May 12, 2015, 09:12:04 PM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline Meldonmech

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Re: Building a New Lathe
« Reply #241 on: May 13, 2015, 12:28:30 PM »

  Steve, they are fine castings, I have only used a loose piece on a pattern once, but it was quite successful. The brass handle has come out well, did you make a pattern or use a modified original with the hole plugged?  I have now relined my furnace with 1600 degree C refractory, and am building up to a brass melt, just need a crucible. I did have a nice cast iron plumbers pot, but accidentally melted it during an aluminium melt. At least it proves the heat is there. I have quite an amount of scrap brass which is chromium plated, have you ever removed this from any of your scrap, if so how?

                                                                   Cheers David

Offline Andrew Wildman

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Re: Building a New Lathe
« Reply #242 on: May 13, 2015, 01:04:03 PM »
not much to add - other than to say that I am enjoying the build.  One of the most practical and well thought out home built lathes I have seen.

Like the use of the Zamac material.  Looks like it could be very useful for a number of different applications. :beer:

Offline vtsteam

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Re: Building a New Lathe
« Reply #243 on: May 13, 2015, 04:36:57 PM »

  Steve, they are fine castings, I have only used a loose piece on a pattern once, but it was quite successful. The brass handle has come out well, did you make a pattern or use a modified original with the hole plugged?


I made a wooden pattern, David, quite a long time ago -- might have even been the first casting I did (aluminum version) for the Gingery lathe 14 years ago. Normally the core is a piece of steel rod, blacked with soot of a candle so it can be knocked out of the casting to leave a perfect fitting hole.



Quote
I have now relined my furnace with 1600 degree C refractory, and am building up to a brass melt, just need a crucible. I did have a nice cast iron plumbers pot, but accidentally melted it during an aluminium melt.


WOW! that was hot!

Quote
At least it proves the heat is there.

I guess so!

Quote
I have quite an amount of scrap brass which is chromium plated, have you ever removed this from any of your scrap, if so how?

David, I've never removed it from brass. I have removed it from pot metal (diecast zinc) simply by melting the zinc out. Chromium has a pretty high melting point, and zinc quite a low one, so it wasn't difficult to separate the two on a small scale. The diecast metal puddled out of the plating which remained as a thin skin and was separated out with a slotted spoon.

I believe chromium vapor is hazardous, so one wouldn't want to melt that, but as I say, the difference in melting temp was great. I don't know about brass and how much leeway there is for the chrome. Might be do-able but you'd have to study up on temps and exercise more care. If your furnace melted a cast iron pot during an aluminum melt it sounds like you have a monster burner -- might be a consideration.
« Last Edit: July 11, 2017, 03:49:48 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 #244 on: May 13, 2015, 04:40:37 PM »
Thanks kindly Anrew W. !!  :beer:
I love it when a Plan B comes together!
Steve
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Offline tom osselton

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Re: Building a New Lathe
« Reply #245 on: May 13, 2015, 05:33:35 PM »
Tom what kind of furnace for the iron? I do remember your first aluminum castings were perfect. 

I will try it with my forced air, propane/fiberwool furnace so it will be interesting to see if the blower will give enough air its ok with brass plus there is always the shopvac as backup.
I have to admit I have had good luck with my casting so far mostly using dad's patterns or 3d printed ones. I have been increasing my woodworking tools to get more into patternmaking and should get a better pair of gloves for the higher heat.

Offline vtsteam

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Re: Building a New Lathe
« Reply #246 on: May 13, 2015, 09:26:50 PM »
Well, let us see how it goes with iron when you get to it. It was quite a learning curve for me. I haven't cast iron yet this year as conditions are not yet right -- first too wet in the spring, now too dry -- the whole state is presently under an outdoor burning ban.

It's funny, I started out this project thinking I was going to do most of the major pieces by fabrication in steel, but have ended up casting all but the bed.

I might just switch back to steel in doing the headstock. It's not a sliding component, except for initially boring the bearing recesses, and I'm running low on zamak. I don't favor aluminum here -- steel will give me more rigidity and mass in the same thicknesses, and I definitely want that in the headstock. Cast Iron is still not do-able for the above fire reasons. So steel might be the best choice.

Zamak has worked well for castings, but is difficult to work with -- especially with hand tools. Filing practically doesn't work -- it is both hard and slippery, and a file tends to skid across the surface, and won't bite in. It clogs grinding wheels, unlike iron or steel.

I would NOT recommend zamak castings to anyone building a first lathe like the Gingery. Or anyone who didn't own a milling machine to work it. I think aluminum is ideal for the Gingery lathe (except fof the half nut, which should be zinc alloy for wear resistance and bearing qualities). Dave Gingery suggested either alloy would work, but I think zinc alloy would be torture for a beginner with only a set of files and a homemade scraper. I doubt the lathe would be finished after a difficult start.
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Steve
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Offline mattinker

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Re: Building a New Lathe
« Reply #247 on: May 14, 2015, 05:41:01 AM »
Steve,
I would NOT recommend zamak castings to anyone building a first lathe like the Gingery. Or anyone who didn't own a milling machine to work it. I think aluminum is ideal for the Gingery lathe (except fof the half nut, which should be zinc alloy for wear resistance and bearing qualities). Dave Gingery suggested either alloy would work, but I think zinc alloy would be torture for a beginner with only a set of files and a homemade scraper. I doubt the lathe would be finished after a difficult start.

I f I remember correctly, you are using ZA2? Zamak comes in several varieties, I made ZA12, which has 10% more Al (by weight) in it, which should be easier to file etc. I have never made ZA2 so I cant compare!

Regards, Matthew

Offline vtsteam

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Re: Building a New Lathe
« Reply #248 on: May 14, 2015, 07:45:07 AM »
That could be a difference Matt, haven't tried ZA-12. I chose ZA-2 for a different project and its good bearing qualities, Maybe what makes it a good bearing (wear resistance, slipperiness) is what makes it challenging to file. I'll have to try za-12. Have used ZA-3 as well.
I love it when a Plan B comes together!
Steve
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Offline Brass_Machine

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Re: Building a New Lathe
« Reply #249 on: May 14, 2015, 02:33:12 PM »
...

Tomorrow I'll start on the bottom slide retainers, gib and gib screws. I have meetings from 12:30 on until 6:00 so not sure how much I'll be able to get done.

...

Sounds like the type of days I have... we work for the same company?  :lol:
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