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New to me Central machinery 8 x 12

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Samot

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#1
I picked up a used 8 x 12 Central Machinery lathe.
Tag says 07 model ...
Guy i bought it from said he only made watch or clock parts or something ......
machine is not wore....
it's not scratched or dinged up it just look like it's been sitting in a basement for a long time paint looks like it's new.
Most of the tools are still in the plastic so fella didnt do much with the lil thing....
This is my first mini lathe...
I've been Machining for 20 years....
So the machining aspect is not my issue...
I've got the lathe setup on the table that I made and I'm now going over it with my ol trusty interapid test indicator.....
I put a dowel in the 3 jaw Chuck and I can get about .003 run out which I understand or am I'm hearing this is typical , normal or in tolerance...
I need it better !!!!
so I took the chuck apart today deburred ,cleaned it up, took a stone to it and just made it slick as could be.....
reinstalled and I'm still .oo3 out of round not to mention out about the same horizontal in 4inches or so toward chuck...
I guess the confusing part is when the chuck was off I put the test indicator on the adapter and swung it and I can't get a half thousandth of variance anywhere....
Bearings maybe ?
I've been reading post after post after post and videos on YouTube and all kinds of stuff on this lathe and I figured I would start my own post to get some insight I plan on doing quite a bit of threading with the lathe as soon as I can figure out how to engage the half nut :) and change the change gears I'm use to a big mazak I don't think I've ever changed, change gears before ? :)
:)
Any input would be greatly appreciated
Thank you
 

Bob Korves

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#2
The .003" runout is the nature of the 3 jaw chuck. The scroll that the jaws follow to loosen and tighten the jaws is not a precision device. It also wears differentially with use, can get damaged in portions of it, and will often give different results with different diameter work. With a different diameter part in the chuck, it might be right on or twice as far out, impossible to guess with confidence. Still, if you chuck up something and turn it, it will be round and without runout where it has been cut. All that is just the nature of the beast.
 

darkzero

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#3
You could always make your chuck a "tap-tru", that way you can dial in the runout whenever you need. But you'll need access to another lathe to do it assuming you have the stock chuck that bolts directly to the spindle. Take 5-10 thou off the register on the chuck so that it's oversized to the boss on the spindle. If you have a bigger chuck with an adapter you wonxt need another lathe, skim the boss on the adapter so it smaller than the register on the chuck. Then when you want to dial in a part, loosen the mounting bolts so that they are just snug, tap the chuck where needed.

I used to have one of these lathes. I had fun with it in the short time I had. I ended up giving it to my lil brother. Here's mine:

http://www.hobby-machinist.com/threads/my-hf-8x14-mini-lathe-mods.11048/
 

Samot

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#4
Thanks for the response guys.
I guess im trying to wrap my head around how the spindle can be within a half tho but the chuck has runout and taper ?
Again this is the first "mini" lathe ive touched so bare with me here.....
Im also not hip to the terminology and name of all the components of the mini lathe
I have access to another lathe and could chuck up my chuck and turn a couple tho off the mounting area and then dial it in upon install ....
Is that the best option ?
Ive gotta get it better than .003
Ill settle for .001 :)
The Runout is consistent no matter what diameter material is in the chuck...
@darkzero ... i had allready read your post on your 8x12
Nice work and advice ....
Honestly. Im considering the "tap-tru" method .
Like i say the runout is consistent regardles of part size.
I started with an 9in section of a 1in ejector pin now down to a 3/8 dowl i use to use to square up blocks on Blanchard..
Uhg.......
Would one of the after market chucks run truer?
Heck i just thought of putting the other jawz on and indicating az they are still in the wax paper maybe they arent damaged.
Is there a "precision" scroll available?
I just never ran a machine starting out un true...
So its got me spinnin in circles trying to figure out the "cause" .
If the spindle was out id understand...
But its not....
Ill be back :)
 

Bob Korves

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#6
Try measuring runout at different distances from the chuck with the same work piece in the chuck and see what you get. Something at least 4" long...
 

darkzero

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#7
The proper way to fix this is to regrind the chuck jaws. But if the fit of your chuck on the spindle is loose there's no point in doing this. The tap-tru method is easier & will give you the adjustability whenever you need. On a lathe this size you'll never have to worry about the chuck getting knocked out of true.

If you look at the specs from quality chuck manufacturers, you'll see that the guaranteed runout on plain back scroll chucks is usually .002". For the average inexpensive generic China plain back scroll chucks they don't guarantee better than .003" runout. So what you are getting is normal. Some people have been lucky & have got much better runout but that's just the luck of the draw.
 

Samot

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#8
I greatly appreciate the responses.
I have used an 8 in ejector pin as well as a 4in 3/8 dowel pin I get the same run out in side the chuck as I do at the end of the part.
Today I need to get into" dad mode" we have a Treehouse to work on :)
Most likely won't be able to mess with the Lathe for a couple days.... Mondayish :)
but I will be back on here as soon as I can....
also while I'm thinking of it , the dial for threading is not turning?
Is there some special way I'm supposed to engage dial for threading?
I just noticed the early this morning ...
Shaft is turning but the gear to the thread dial isn't engaged to the shaft...
Bear with me ,never ran lathe like this one ....
I'm sure it's something simple that I'm overlooking...
of course
 

Dave Paine

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#9
Does "Shaft is turning" refer to the leadscrew or the shaft in the threading dial?

If it means the leadscrew, then the threading dial needs to be rotated so its gear engages. Normally a bolt on which the threading dial pivots needs to be loosened.

If it means the shaft in the threading dial, then a pin between the shaft and the gear in the threading dial may be broken or a set screw is loose.

This is the threading dial for my Southbend Heavy 10. You can see the set screw on the right of the gear.

Southbend_threading_dial_cleaned_3490.jpg

Picture or two would help us to better understand the situation.
 

darkzero

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#10
the dial for threading is not turning?
Is there some special way I'm supposed to engage dial for threading?
First look behind it at the bottom, check if the gear for the threading dial is meshing with the leadscrew. If not, simply loosen the SHCS on the side of the threading dial block to pivot it to make contact with the leadscrew. I like to pivot mine out the way so it's disengaged when I'm not using it. No sense if having it spin all the time, reduce wear & tear, it doesn't use ball bearings.

Like any gear you don't want it to mesh too tight. If you are unsure of how much to mesh, stick a piece of paper in between, that should be enough gap.

If it is meshing with the leadscrew, then the SHCS that mounts the gear to the shaft of the threading dial is probably loose. There's no key as it really doesn't need one, it's just held on tight by the screw.
 

Robert LaLonde

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#11
I picked up a used 8 x 12 Central Machinery lathe.
Tag says 07 model ...
Guy i bought it from said he only made watch or clock parts or something ......
machine is not wore....
it's not scratched or dinged up it just look like it's been sitting in a basement for a long time paint looks like it's new.
Most of the tools are still in the plastic so fella didnt do much with the lil thing....
This is my first mini lathe...
I've been Machining for 20 years....
So the machining aspect is not my issue...
I've got the lathe setup on the table that I made and I'm now going over it with my ol trusty interapid test indicator.....
I put a dowel in the 3 jaw Chuck and I can get about .003 run out which I understand or am I'm hearing this is typical , normal or in tolerance...
I need it better !!!!
That is pretty normal for an inexpensive 3 jaw in general HF or otherwise. pull the chuck and indicate the inside the spindle bore. I bet its around .0005 - .001. My 8.5x18 barely moves the needle on my Last Word indicator. I use it for small stuff so I set it up with a 3C adapter and a 3C closer. Its under .001 all day long. If that's not good enough make an adator plate for a 4 jaw or for a pull back chuck.
so I took the chuck apart today deburred ,cleaned it up, took a stone to it and just made it slick as could be.....
reinstalled and I'm still .oo3 out of round
Could be the boss for the chuck was not cut in place. It could also be the chuck is off that much. Might also check it with different size gage pins just to see. Not only do inexpensive scroll chucks tend to be off they tend to be off by different amounts at different diameters. Again, go with a collet adapter, collet chuck, or 4 jaw if you want better.
not to mention out about the same horizontal in 4inches or so toward chuck.
That may be easier to fix. The head stock is just bolted to the bed , and the bottom is pretty rough. Could jus tbe a burr or chip in there. If not its dead easy to shim.
I guess the confusing part is when the chuck was off I put the test indicator on the adapter and swung it and I can't get a half thousandth of variance anywhere....
Well that pretty much confirms it. Its just a cheap 3 jaw scroll chuck then. .005 isn't uncommon. .003 is pretty good.
Bearings maybe ?
I don't think so. You might be able to feel .003 slop in a spindle by shaking it. They are just a grease lubed bearing though. Unless its different from the 7x10.
I've been reading post after post after post and videos on YouTube and all kinds of stuff on this lathe and I figured I would start my own post to get some insight I plan on doing quite a bit of threading with the lathe as soon as I can figure out how to engage the half nut :) and change the change gears I'm use to a big mazak I don't think I've ever changed, change gears before ? :)
:)
Any input would be greatly appreciated
Thank you
You are so going to miss your QC Gear Box. LOL. The half nut and engages the drive screw for both threading and turning. It does not have its own threading drive like bigger lathes often do. You are going to be swapping gears all the time. I suggest that one of the first things you make for it are long shoulder bolts with knurled thumb heads to make taking the cover off to change gears easier and faster. To go from turning to threading... yep. Change gears. MANUALLY.

The next thing I suspect you will miss is having a power cross feed.

Probably one of the first things you should do to the carriage is build a set shims so you can tighten the screws down tight on the sandwich plates and have very little movement. Just enough so it still slides easily.

I have a 7x10 converted to 7x16. Very similar machine.
 

Robert LaLonde

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#12
P.S. It will single point thread, but make sure you always use the same engagement mark on the dial. For most jobs I prefer to use a die drive sleeve in the tail stock. That could be the third thing you make for it.

Or I suppose the first. It would make turning those shoulder bolt cover screws easier. LOL.
 

Samot

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#13
Man I appreciate it you guys have been a lot of help I think my back is broken from working on the tree house but I'm in here messing with this lathe now ....
Before i read these posts I found the socket head cap screw for the thread dial and it was loose I just tapped it with my palm and manually move the handle and it started turning I'll check gear mesh here in a second.....
You guys are a lot of help I appreciate it.
 

Samot

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#14
Bob la londe... ..
You are correct!!!! I am lost without quick change gear box... !!!
This gear "stuff" is french to me ....
I did chuck up a 12" x 1.625 dia piece of 7075 between centers ...
Just experimenting with speeds n feeds ...... damed if i didnt end up hand feeding the material...
This is probably gonna get some giggles but ive machined for a long time.
Started in a job shop on a Bridgeport mill like 20yrs ago ....
Got into tool and die ...
Used machines from Blanchard grinders to charmilles wire and plunge EDM ...
Last "job" i had was making parts for a large steel mill ....
I was married to a 6in lucas boring mill ..... got tired of watching the "big dogs" make all the money so i utilized a passion or hobby of mine and started prototyping a part at a buddys family ownd shop.
Qualified the first part sent some emails and received my first QTY order from a Vendor in the biz....
that was 2012 .....
Ive made a pile of different parts since..
My design my work....(well first part is my work) :)
I dont have to work for big dogs any mo... :)...
What ive run into is finding an open machine to tear setup down just to run a few ops on latest "idea" and end up taking 2 months to get a proto just to test !!
Ive got 3 sons so my evenings and weekends are no longer mine....
Hence the reason i picked up this little lathe .... hopefully i am able to get my protos ready in a week or quicker and move more parts .....
Shew...... that was alot...... :)

Back to the questions :)
Freakin gears....
My "Tub" gear is a 100 tooth .....
When tryin to get a decent finish my speed was fine but my feed was to fast
Rather than change the gears AGAIN i just hand fed....
Nice finish !!!
And part is true!
Less than .0003 runout and straight !
I guess what I'm asking is throw me some gear combinations I've got some charTs that I pinned up on the wall in front of the lathe.....
I still can't make heads or tails of this dang thing..
I will be cutting a lot of aluminum mostly .750 to 1.5 dia
Some 304 SS
Im using inserts on kenmetal holders ...
(Mostly)
I need to cut a 8x.075 thread ....
There's about 48 gear combinations I can find for that thread.....
Im not doing something righ.....
I'm pretty sure I've got, a, b c, d e and F the tub gear figured out.....
I don't care if you got to draw me a picture in crayon ....
For the Love of All That is Holy just tell me what gear to put where :)
That metric thread will be on some pretty soft mild Steel....
And which two gears am I needing to change too slow my feed when cutting aluminum and wanting nice finish ...
Let say 1.5 dia alum.....
high speed semi slow feed .... ?

Tired
Brain dead ....
Tbanks again guys.
 

Robert LaLonde

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#15
Oh, and if its like my 7x10 its got a universal brush motor for the spindle, so very little low rpm torque even in low gear.
 

waynecuefix

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#16
You said "I've got the lathe setup on the table that I made and I'm now going over it with my ol trusty interapid test indicator.....
I put a dowel in the 3 jaw Chuck and I can get about .003 run out which I understand or am I'm hearing this is typical , normal or in tolerance...
I need it better !!!!"

I hope I am not misunderstanding what you are saying but I will try to help with my limited experience with the Central Machinery lathe. I have a 7 x 10 I have used for @ 5-6 years and it was never consistent with the centering of stock in the jaws usually 3-4 thousandths out. When needed I would shim between the jaws and the stock to center my work. Eventually I replaced the 3 jaw with the 4 jaw independent chuck for my lathe from Littlemachineshop.com and suddenly life became much better. It was important for me to center my work every time I chucked it up and so it was worth it to use a 4 jaw independent and take the time to gauge the work to adjust to exact center. If this aspect is not what you are talking about, sorry, I am just an amateur.
"When in doubt I go ahead and step in, they will understand I am a greenhorn"
 
Last edited:

Samot

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#17
Wayne
You are spot on.
I have looked at the 4 jaw from LMS ...
Ive never "liked" having to shim work piece ,(on lathe) so a 4 jaw maybe something i pick up soon ...
 

Chip Hacket

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#18
I bought the four jaw from LMS for my lathe of the same type. I'm certainly no expert either but I understand if one needs spot on use a 4 jaw or a collet. I also bought the ER32 collet chuck. As budget allows I'll be getting the collets.


Sent from my iPhone using Tapatalk
 

Robert LaLonde

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#19
When I actually turned threads on mine I always just looked up the gears from the chart in the manual. Then I'd take a scratch pass and check it with a thread gage. If you didn't get the manual with the lathe its no big deal. Since its a current model you can probably just download it directly from the main HF website. If the manual is not available there is something some folks do not know. HF has (or atleast had) and on=line database of manuals. Its not formally organized except for by directory and model group, but if you send an email to their support staff they can provide a direct link. If you look at the URL for your manual you can quickly figure out how their on-line database is organized.

ER 32 collet chuck? Now that sounds interesting. I am using 3C with a closer in both of my small HF lathes, but ER 32 will hold larger stock than 3C. I'll have to look into that.
 

Samot

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#20
Hey guys .....
Thought I would get back in here with some more questions :)
I ended up picking up a 44991 mill with rotary table, forward reverse setup .......
Guy was starting a biz making somethin and decided he wasn't gonna make any money ..... so he listed it for sale and I ended up with it .. for 4 C notes .... :)
The 2 machines have actually surprised me........
Fairly accurate.... Lil machines... I thought $400 was good for the mill...
Ok..... so I got tired of trying to calipar / and or scribe to next location.
So I ordered one model #5012 , 12" readout.....
https://littlemachineshop.com/products/product_view.php?ProductID=5012

NOT my first order from them ... but this one was little unexpected I guess I'll say.....
I know I can cut the flat bar that the slider rides on
But would rather not.....
I've decided to add a 2" piece of 7075 in place of the left side, little red table end ..... made of plastic ..... uhh....
The hardware I received is ..... well it's not user friendly...
Some there is TOO much of .....
Some not enuf ......
I don't have or maybe I dont Understand how the or what the slider reads off of ?
Any input or help would be great !!!!!!
Also ......
No "instructions" (not that I would use them anyway....)
Provided
I understand the basis behind it ....
As far as mounting and such.....
Oh ya....
I took x axis handle off an seen those open , dry as hell "bearings" please tell me there is better bearing available or I'll just get one from bearing place.....
Thanks again ....
 

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Samot

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#21
Aaaaaaaaand.........
I cannot get this DRO to read correctly....
Mounted, ready to rock n roll and it WILL NOT move from 0.000
I'm hoping it's something silly I'm over looking ....
NOT super excited at the moment ......
Any input would be appreciated.....
Ahhhhhhhhh..!!!!!!!!
 

unioncreek

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#22
[Have you tried switching the jaws to different locations on the chuck to see if the runout changes/

Bob
 
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