Author Topic: mini lathe mods and accessories  (Read 10301 times)

ja2on

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mini lathe mods and accessories
« on: April 19, 2009, 08:04:48 AM »
great page with (mainly) mini lathe projects mods and accessories

for example
Ball turning tool
Norman style QCTP
Leadscrew handwheel

http://www.toolsandmods.com/ralph-patterson.html

Offline Stilldrillin

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Re: mini lathe mods and accessories
« Reply #1 on: April 19, 2009, 12:36:51 PM »
Not seen that one before......  :scratch:

Thanks Jason!  :thumbup:

David D
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Offline Brass_Machine

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Re: mini lathe mods and accessories
« Reply #2 on: April 19, 2009, 01:15:40 PM »
Me either. Downloaded them all. Thanks for the link.

Eric
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Offline PTsideshow

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Re: mini lathe mods and accessories
« Reply #3 on: April 22, 2009, 08:54:09 AM »
very cool thanks
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Offline sbwhart

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Re: mini lathe mods and accessories
« Reply #4 on: April 22, 2009, 09:00:42 AM »
Some good designs there Jason

Thanks for posting

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Offline raynerd

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Re: mini lathe mods and accessories
« Reply #5 on: May 04, 2009, 05:41:08 PM »
Hi, thanks for posting this link ja2on. I had come across the download for the carriage stop on another site and I am in the process of trying to make one. I am pleased to see all these designs to have a go at...! The leadscrew handwheel looks excellent and so does the carriage auto stop - clever little trip design to cut out the autofeed and disengage the half-nuts.

Just curious about the Arbor extension - what is this used for, clearly it extends the arbor but I`m not sure what that is and what it allows you to do. The text, diagrams and pictures don`t really explain - can anyone tell me its purpose?

Chris

Offline John Hill

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Re: mini lathe mods and accessories
« Reply #6 on: May 04, 2009, 06:48:43 PM »
I am not sure I understand the auto stop, especially while disengaging the half nuts.  It seems to very slowly raise the handle which I thought would have been quite undesirable compared to some spring device to flick it up. 
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Offline Darren

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Re: mini lathe mods and accessories
« Reply #7 on: May 05, 2009, 02:43:27 AM »
Slow, fast, doesn't really matter,

It's where that counts  :thumbup:
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Offline raynerd

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Re: mini lathe mods and accessories
« Reply #8 on: May 05, 2009, 03:16:54 AM »
John - are you saying it won`t be accurate enough? Surely as long as it raises the lever and disengages the halfnuts it won`t matter how slow it does it, provided it is correctly positioned!


bogstandard

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Re: mini lathe mods and accessories
« Reply #9 on: May 05, 2009, 03:26:02 AM »
John is correct.

If you slowly disengage a thread, as the two sliding faces start to disengage, there can be longtitudinal movement along the faces because of the angle, and thus miscutting of the thread. If a square drive thread was used there would be no problems.

So really, the disengagement should be as fast as possible, hence usually a latch and spring is used to carry out the job.


John

Offline Darren

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Re: mini lathe mods and accessories
« Reply #10 on: May 05, 2009, 03:38:15 AM »
This is in ref to a mini lathe that has a square drive thread....so as you say should give no problems if it is a slower disengage.

But I can see your point if a normal thread is used for a leadscrew, do any lathes use this type of thread on the leadscrew?
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Offline John Hill

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Re: mini lathe mods and accessories
« Reply #11 on: May 05, 2009, 04:41:16 AM »
Guys, my discomfort regarding the slowly disengaging lead screw is as the nut halves begins to move away there is less bearing surface to carry the load and this slowly decreases until the half nuts eventually  'pop' out of engagement.  I feel this will damage the half nuts by rounding the surface and eventually (maybe when the lathe is 100 years old, maybe sooner) the threads of the half nuts will be so rounded they wont stay in engagement.

Just my tuppence.
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Offline Darren

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Re: mini lathe mods and accessories
« Reply #12 on: May 05, 2009, 04:46:48 AM »
That's a valid point John H...well pointed out... :thumbup:
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bogstandard

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Re: mini lathe mods and accessories
« Reply #13 on: May 05, 2009, 05:39:09 AM »
Darren,

You will find that most leadscrew threads are in fact trapezoidal (acme shaped) rather than square, so what I was saying about the angles relates to those as well. As they are just like normal angled threads, but with the pointy bit cut off the top.

Also what John states about wear is a very valid point.


John


Offline Darren

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Re: mini lathe mods and accessories
« Reply #14 on: May 05, 2009, 05:44:43 AM »
I didn't realise acme was trapezoidal, thanks for pointing that out

I'll shut up now..... :)
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bogstandard

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Re: mini lathe mods and accessories
« Reply #15 on: May 05, 2009, 05:49:23 AM »
Not getting at you Darren, just giving a bit of freebie instruction whilst attempting to explaining a problem. :lol:


Bogs