Author Topic: A simple lathe project  (Read 662 times)

Offline AdeV

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A simple lathe project
« on: December 18, 2020, 01:47:52 PM »
Back when I bought my lathe, over 10 years ago now (!), I recall reading this excerpt on the lathes.co.uk website about it:

Quote
However, Edgwick did provide one unusual and very handy fitting, a device that secured the top slide exactly parallel to the bed ways. Positioned to the left-hand front side of the slide the unit consisted of a hardened plunger that passed though accurate bushings in the base of the top slide and the cross slide. A swivelling latch was used to hold the plunger out of engagement but when, for boring or other parallel work, it was necessary to have the tool in alignment with the headstock spindle, the latch could be swung out and the plunger pressed down.

This plunger is missing on my lathe (and I'm sure it is on most Edgwick lathes these days). The swivelling latch is there, however. See exhibit A:





Since installing my DRO, I no longer have any useful vertical height here, above the swing-out latch. So a slightly different design to what I envisage the above is called for. After carefully measuring the bore in the carriage, and the bore in the top slide, a simple pin was turned out of some mystery steel:



Testing showed I'd managed to get pretty close with my dimensions (yay DRO!), it makes a satisfying "pop" when withdrawn from the hole  :thumbup:  Interestingly, the hole in the top slide was slightly out-of-round; I'm not sure if that indicates that a bushing (as described above) has gone missing, or just that it's taken some abuse. I chose to make the pin to the smaller diameter, on the basis it ought to fit.  Interestingly, when I went to first fit it, I found that the top slight was ever so slightly not dead nuts straight! So it works, then...

Here it is in its home:



I had to chuck it back up and reduce the top diameter a couple of times, to allow the swing clip to move over. I thought I had it perfect the second time, but the knurling increased the diameter enough that it wouldn't pass! Doh! However, the pin now fits perfectly & I can be at least moderately certain that my top slide is perfectly parallel to the carriage! More certain than I was before, anyway!



So there you have it. A couple of hours turning & fettling, and a nice useful addition (or, rather, re-creation of a missing part) for my lathe.

I'll probably lose it the first time I have to turn a taper  :lol:
Cheers!
Ade.
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Offline philf

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Re: A simple lathe project
« Reply #1 on: December 18, 2020, 02:14:51 PM »
Hi Ade,

Another job to go on my to-do list although it will have to be differently executed.

How do you use the scale on your topslide? Does it add (or subtract) from the Y scale?

Phil.
Phil Fern
Location: Marple, Cheshire

Offline mattinker

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Re: A simple lathe project
« Reply #2 on: December 18, 2020, 02:32:42 PM »
Hi there Ade,

I not only I didn't get the pin, but I didn't get the latch either!

On the maybe one day after I re-scrape the lathe list!

Cheers, Matthew

Offline AdeV

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Re: A simple lathe project
« Reply #3 on: December 18, 2020, 02:38:47 PM »
How do you use the scale on your topslide? Does it add (or subtract) from the Y scale?

Hi Phil,

At the moment, it's separate from the Z scale, I don't believe there's any way to link them in the DRO readout that I have. One day, when I get back to my DIY DRO (readout) project, I intend to have an option that both links them, but will also take an angle for the top slide scale such that when I move it, it'll tell me how much it's actually moved in both X & Z directions, as well as the movement on it's own axis. I haven't come up with a good name for that axis yet.... maybe "T"?


Matt - Doh! If you need me to get dimensions for the latch, I'm happy to do that. It's got a spring in it, somewhere, I think, to hold it in the closed or open position.
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline philf

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Re: A simple lathe project
« Reply #4 on: December 18, 2020, 02:45:57 PM »
How do you use the scale on your topslide? Does it add (or subtract) from the Y scale?
At the moment, it's separate from the Z scale, I don't believe there's any way to link them in the DRO readout that I have. One day, when I get back to my DIY DRO (readout) project........

Ade - Is that after you get your CNC lathe sorted. (Or had you hoped we'd forgotten about that?)

You'd ideally link another encoder which inputs the topslide angle - some interesting trigonometry.

Phil.
Phil Fern
Location: Marple, Cheshire

Offline mattinker

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Re: A simple lathe project
« Reply #5 on: December 19, 2020, 07:41:31 AM »



Matt - Doh! If you need me to get dimensions for the latch, I'm happy to do that. It's got a spring in it, somewhere, I think, to hold it in the closed or open position.

Thanks AdeV it won't be soon!