Author Topic: My introduction  (Read 4755 times)

Offline Jonitus

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My introduction
« on: May 05, 2010, 12:11:45 PM »
Good morning.  Long time lurker that has decided to become a member.  I've enjoyed looking over the threads on these forums and gleaning what info I can.  There are some very talented folks here.

I've recently acquired a 7x12 mini lathe and hope to be able to use it in my hobby pursuit.  I build replica sci-fi props.  You can see a few of them at http://workshop.judgesabersmith.com

With any luck in getting the lathe tuned in and running right, I hope to be able to start making some of my own parts to specification rather than accepting what I can buy from stores or find in scrap piles to use in my builds.  I'm trying to sort out a chuck that doesn't run true, excessive backlash in the cross slide, compound and carriage and also the handwheels not turning smoothly.  It'll be a project getting the lathe up and running before I can begin making parts on it.

Not much else to tell right now.  I'm going to dig through some of the threads on here and see what else I can find to look at.

Offline Brass_Machine

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Re: My introduction
« Reply #1 on: May 05, 2010, 12:50:33 PM »
Hi Jon,

Welcome to the collective :borg:!

Interesting stuff building sci/fi props. I have a bunch of pictures/plans/etc saved to build a lightsaber one of these days.

You should consider posting up a running project log as you get your lathe to spec. I am sure there is a bunch of people on here that can help you get through the tough stuff. It may even help a few in your situation as well.

Looking forward to your posts.

Eric
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Offline sorveltaja

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Re: My introduction
« Reply #2 on: May 05, 2010, 02:14:32 PM »
Jonitus, I guess, that cross-slide backlash is quite a common problem on used lathes. For example, my lathe has a horrible cross-slide backlash, but during the years, I've got used to it, so it's not a problem.

What comes to that chuck problem, I can't help, but if my memory serves, there is a thread about that subject either on this forum, or on HMEM.

Offline Jonitus

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Re: My introduction
« Reply #3 on: May 05, 2010, 02:58:42 PM »
(un)fortunately, the lathe is brand new, which is why the excessive backlash kind of upsets me.  I cleaned the lathe thoroughly, but I am thinking perhaps I should have done a better job and torn it down more.  I'm thinking of removing the carriage and cross slide tonight to make sure I have all the grit and grime removed.  I might take the opportunity to lap the gibs while I have it apart.

I may take the advice and start a project log of getting the lathe up and running and dialed in.

Offline Brass_Machine

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Re: My introduction
« Reply #4 on: May 05, 2010, 03:25:37 PM »
(un)fortunately, the lathe is brand new, which is why the excessive backlash kind of upsets me.  I cleaned the lathe thoroughly, but I am thinking perhaps I should have done a better job and torn it down more.  I'm thinking of removing the carriage and cross slide tonight to make sure I have all the grit and grime removed.  I might take the opportunity to lap the gibs while I have it apart.

I may take the advice and start a project log of getting the lathe up and running and dialed in.

The new Chinese lathes (and mills) unfortunately for the most part are "kits" that require feddling and tweaking to get to a point of reasonable accuracy. I think a project log (with pictures ofc) will help immensely with your goals. Many of us have been (or like me, are) where you are at now. I am gearing up to dissemble my lathe and get it to where I am happy. To that end, I will be replacing the bearings, etc...

Eric
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We're all mad here. I'm mad. You're mad.

Offline dsquire

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Re: My introduction
« Reply #5 on: May 05, 2010, 03:44:08 PM »
Jonitus

Welcome to MadModder Jonitus.  Looks like you have got a good start on your first project with getting the lathe sorted out. If you have any questions just ask. There is always someone around to answer or at least give an opinion. Which lathe do you have? Perhaps one of the chaps here have a similar lathe and can help out. I look forward to seeing some of your projects as they develop.  :D :)

Be safe, have fun and enjoy the forum.  :mmr:

Cheers  :beer:

Don
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'til your good is better,
and your better best

Offline Jonitus

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Re: My introduction
« Reply #6 on: May 05, 2010, 03:49:40 PM »
I completely forgot to mention which lathe I purchased.  Oops.  It's a Cummins (Tools Now) 7x12.  I went with that one for the price, as well as it coming with lots of accessories I would have had to buy separately if I went with another company.

Offline Bernd

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Re: My introduction
« Reply #7 on: May 05, 2010, 08:23:28 PM »
Welcome to the collective Jonitus.  :borg:

First let me say that the cross slide backlash is not something to worry that much about. I worked in a large machine shop enviroment and have run large production lathes. They had backlash in the crossslide also. It's something that is inherint in any feed type screw. You will always have backlash. If you don't, the screw will be hard to turn. If you need to make an adjustment on the cross slide you would bring the setting out past the backlash and then back in to the setting you wanted it to be at.

Ya, I know clear as mud, right?

Work on getting the chuck to run true first. That's more important in producing a good part.

Bernd
Route of the Black Diamonds

Offline andyf

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Re: My introduction
« Reply #8 on: May 06, 2010, 03:42:45 AM »
Hi Jonitus,

I think some runout (often varying with different diameters of stock) is to be expected with a 3-jaw chuck, especially a budget one. There's one fix here:

 http://warhammer.mcc.virginia.edu/ty/7x10/vault/Lathes/7x10-7x12-Projects/SetTruBackplate/

Alternatively, if you feel up to it and have access to another lathe, the same effect can be achieved by slightly enlarging the register diameter on the back of the chuck. Then, before finally tightening up the securing nuts, tap it around with a rubber mallet until a dial indicator shows that the work is running true.

There are some good tips on mini-lathe alignment here:

http://www.gadgetbuilder.com/Lathe_Align.html

Andy

Sale, Cheshire
I've cut the end off it twice, but it's still too short

Offline spuddevans

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Re: My introduction
« Reply #9 on: May 06, 2010, 04:08:58 AM »
Hi and welcome to madmodder :wave:


Tim
Measure with a micrometer, mark with chalk, cut with an axe  -  MI0TME

Offline Jonitus

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Re: My introduction
« Reply #10 on: May 06, 2010, 09:21:03 AM »
I tore down the entire machine last night.  Nothing went untouched.  Every single moving part of the lathe got a thorough scrubbing with mineral spirits and a good wipe with clean rags.  As I began to put things back together, I lubricated what needed it with a good 10W30 and checked operations.  Here's some of the more interesting finds:

Virtually no fastener on the machine was tight.  As I disassembled the compound, cross slide and carriage, I noticed that all the fasteners were sloppy loose.  The plates on the underside of the carriage that hold it against the bedways were completely loose.  It took me about 45 minutes to adjust them just right, then shim the difference, then readjust.  Once done, I had to work the carriage onto the bedways, but it moves very smoothly and there is NO play.  It might be a bit tight, but new equipment always is until it gets some use.  Also adjusted the half-nuts so they engage/disengage the leadscrew properly.  For some reason, I didn't get a handle for the selector knob, so I'll have to make one...on my lathe...LOL.  I hate that I had to stack a bunch of small shims, so I'll keep eyes out for some thicker stock and redo the shimming of the carriage.

The cross slide was disassembled and cleaned.  Lots of grit and grime to get rid of.  Lapped the gib strip and the dovetails.  Reassembled and adjusted the gib screws just right.  No play in the cross slide.  Much less backlash.  Success.

The compound was a mess.  Disassemble and clean.  Again...lots of girt and grime.  Lapped the gib strip and dovetails.  Reassembled and adjusted the gib screws.  No play.  Much less backlash.

The chuck was taken off and disassembled.  I wanted to change the jaws anyhow, so I figured I might as well take it all apart while I could.  Gross.  Loaded with gunk and grime.  None of the fasteners on the cover plate were tight, nor were the bolts retaining the small gears.  I cleaned it all up and lubricated it.  Took my time reassembling, making sure of what jaw went where AND MARKING THE CHUCK.  I used a automatic hole punch to make a single indent for #1 jaw, 2 indents for #2 jaw, and 3 indents for #3 jaw.  Much better.  Still couldn't find an indexing mark on the faceplate to mount the chuck, so I'll have to test when my measuring equipment gets here.

I also ditched the splash pan.  It wobbled.  I can live with getting the surface of the workbench oily.  It'll give it character, right?

Long evening, but I have increased the fit and finish of the machine by orders of magnitude.  It is now much closer to being ready to be put to work.

As an aside, I wanted to throw this out here and see what some of our machinists thought of the idea.  The guy who looked over my shoulder as I was machining the apparatus for my master's research project had a neat tool he used to indicate parts in a 3-jaw chuck.  It was a steel bar milled to size to fit a standard tool holder, and had a roller bearing on the end of it.  He'd lightly chuck his workpiece and move this tool up to the work and you could see the piece come into alignment.  When it was running true, he'd tighten the chuck.  He could always get within about 0.001" of true with this little tool.  I'm thinking about making one or having one made.  Thoughts?

Offline Bernd

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Re: My introduction
« Reply #11 on: May 06, 2010, 09:33:40 AM »
Jonitus,

Great that you've had success on your lathe.

Would you please start a thread in the Machine Shop section so we can have a running thread there about your lathe fixes. Kind of keeps the Intro area from getting cluttered up. Thank you very much.

Bernd
Route of the Black Diamonds

Offline sorveltaja

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Re: My introduction
« Reply #12 on: May 06, 2010, 03:08:42 PM »
Jonitus, I'm with Bernd. Start a new thread at machine shop -section, and tell, what you have experienced, to get the lathe at working condition.

It would give newcomers(and also to others) valuable information :thumbup:.

Offline Jonitus

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Re: My introduction
« Reply #13 on: May 06, 2010, 03:10:11 PM »
Info from my last post was copied and pasted into a new thread in the Machine Shop section this morning.