HELP- HARBOR FREIGHT 8X12 LATHE ADVICE

[sunnyday]

I got this home, cleaned it up and I was pleasantly suprised to see it had auto feed feature which I wasnt aware of .

Anyways, the instruction manual for this thing is awful . Can anyone help me with the following questions :

1. I dont understand the pulley/ v belt rpm explanations

2. I am totally lost on the change gears and threading explanations

3. The lathe came with 2 sets of 3 jaw chucks . The 1st set seems to be for smaller metal stock and the 2nd set is for larger metal stock . The 2nd set will not align up properly in the headstock chuck assembly . I see the jaws are stamped with the numbers :

1

2

3

but I dont see any numbers stamped on the headstock chuck to match up to the jaws.


and finally , is there any way to bore out the hole thru center to 1 " or larger diameter or does anyone sell a whole new headstock assembly with a 1 " or larger thru hole ?


I called harbor freight customer service and they werent any help at all .

[Freddy Warbird]

Originally Posted by sunnyday Anyways, the instruction manual for this thing is awful .

Ya, the instruction manual is not very newbie friendly. It is written for experienced operators.

Can anyone help me with the following questions :

I've been reading around, and I think i've figured some of it out, but I don't have my machine yet to verify anything, only pictures from other machine to go by.

1. I dont understand the pulley/ v belt rpm explanations

Still lookng into this. But, I do know that you want the tension pulley to ride on the backside, or outside of the belt at all times, and NOT on the inside, or "V" part of the belt. This would cause excessive, and premature failure of the belt. On a side note, I think its a good idea to check the tooth motor belt as well to make sure it rides center.

2. I am totally lost on the change gears and threading explanations

From the looks of the gear selection chart, its broken up in five segments. The very top left hand corner box is a visual representation of the center to center distance between thread, or the pitch.

Starting at the top left hand corner of the chart, and reading straight across, 8,9,10,11,12,14, those respesent the pitches.

Again, starting at the top left hand corner of the chart, and reading straight down vertically, the B-E-D-f represent the gear shafts that the change gears flow, or mesh.

So, say we want to cut 8 TPI. We follow vertically down the "8" column. The "B" shaft, or the top change gear shaft would take an 80T gear. I think the top gear shaft that "B" is on, meshes with the main spindle. The middle shaft would house two gears, the "D" gear and the "E" gear which would be an 75T, and a 40T. The "E" gear would mesh with the top "B" gear. The gears "E" & "D" on the middle shaft, would be splined together some how to turn as one to transfer to "F". The "D" gear or 75T gear, would mesh with "F". The "F" gear, represented with forward, and reverse arrows, indicates the carriage screw shaft. Basically we are following the mechanical link from the main spiindle all the way down to the carriage screw, so that the carriage advances only so many rotations as the main spindle pre revolution. That's how I am reading it. Someone correct me if I'm wrong.

At the very bottom left hand corner of some charts, such as the Lathemaster 8x14, it displays all the gears, and their respected locations depending on standard, or metric, and TPI. The bottom right hand corner of the chart confuses me.

3. The lathe came with 2 sets of 3 jaw chucks . The 1st set seems to be for smaller metal stock and the 2nd set is for larger metal stock . The 2nd set will not align up properly in the headstock chuck assembly . I see the jaws are stamped with the numbers : 1 2 3 but I dont see any numbers stamped on the headstock chuck to match up to the jaws.

Its a good idea, before one diassembles the chuck, to punch mark the jaws to the chuck body, but that seems to be moot now. Take a really careful look at the chuck. There may be numbers, or punch marks somewhere on the thing. If not, your going to have to figure out the hard way until they center once again.

and finally , is there any way to bore out the hole thru center to 1 " or larger diameter or does anyone sell a whole new headstock assembly with a 1 " or larger thru hole ?

I don't know the answer to that question. As far as I know, the spindle can only handle up to a certain dia.

I called harbor freight customer service and they werent any help at all .

They just sell the stuff LOL..

[blades]

Not too difficult for the trained eye to determine the jaw order: look at each jaw. The first tooth that engages the scroll when you put it in the slot will be spaced differently on each jaw. The jaw with the start tooth closest to the inside clamping surface of the jaw goes in first. Then advance the scroll around to the second slot, and put the middle jaw in. Then advance the scroll again to the 3rd slot, and put the remaining jaw in. This jaw should have the start tooth the farthest from the inside grip surface of the jaw.
If none of this makes any sense, just line up all 3 jaws with the teeth facing upward, and you will see the difference.

[sunnyday]

got the jaws figured out...

still dont have a clue about the change gears and threading...LOL...damn chinese manuals.

[Freddy Warbird]

Originally Posted by blades Not too difficult for the trained eye to determine the jaw order: look at each jaw. The first tooth that engages the scroll when you put it in the slot will be spaced differently on each jaw. The jaw with the start tooth closest to the inside clamping surface of the jaw goes in first. Then advance the scroll around to the second slot, and put the middle jaw in. Then advance the scroll again to the 3rd slot, and put the remaining jaw in. This jaw should have the start tooth the farthest from the inside grip surface of the jaw. If none of this makes any sense, just line up all 3 jaws with the teeth facing upward, and you will see the difference.

That makes sense. Good for reference thanks.

[blades]

Originally Posted by sunnyday got the jaws figured out... still dont have a clue about the change gears and threading...LOL...damn chinese manuals.

I'm sure others have a TON more experience than I do regarding the change gears, but basically you have this hand-full of gears with numbers on them, which represent teeth count. Certain combonations of these gears will produce the appropriate feed-rate with regards to the chuck rotation, which will produce the desired thread pitch (threads per inch). All you really need is some sort of reference table that shows the gears you need to produce your thread.
I doubt the HF manual does a very good job explaining this. I haven't even looked at my manual since I'm doing a CNC conversion anyway.

[Zap]

I've been using my 8x for a few months now and can offer a little advice.

The "auto feed" is actually for threading. You set it up to go so many threads over so much distance by changing the gear ratios. Engaging the feed starts the cutter moving at the right speed in relation to the spindle RPM to match the threads. The chart on the cover tells you what number of teeth gear to use in each position for each thread. Basically just stack each gear in the same position as the numbers on the chart shows. Each number on the chart corresponds to a matching gear that has a number stamped on it showing how many teeth it has. Make sure there is a little play between each gear. To tight on meshing the gears will wear them down fast. I don't even engage the gears to the spindle unless I am threading. They are very noisy and you can hear them self destructing at high speeds. Before you engage the gears, check to make sure you can turn them completely around by hand. If they bind up at any point then they are to tight. It takes a little messing around to get it just right. I also don't use power for threading. I use a hand crank and just take it easy so I don't screw anything up. It is too easy to run the carriage into the chuck by accident while under power. Not likely to happen if you turn it by hand.

Yes, the idler pulley rides on the back side of the belt and simply gives it some tension. It does not need to be real tight, just take up the slack so it wont slip. I only need to mess with the idler on a couple speeds on my machine. The belt is tight enough on the others. The cog belt needs to be pretty tight tho or it jumps teeth at start up and that is very hard on the belt. If it is too loose you will hear a loud grinding sound when you turn the machine on as it jumps a few teeth getting up to speed.

For the 3 high speeds the V belt goes directly from the motor to the spindle. For the 3 low speeds it goes from the motor, via cog belt, to the reducer pulley, then the V belt from the reducer pulley to the spindle. Larger motor pulley means higher spindle RPM. Larger spindle pulley means lower spindle RPM.

My chuck has the numbers stamped inside the jaw openings. Open the jaws up wide and you should see them under there. The extra set of jaws are for gripping around the end of large parts.

You can probably open up the thru hole on the chuck a little but you will still be limited by the thru hole on the spindle. Don't mess with the spindle because you will screw up the MT3 taper and possibly weaken the shaft beyond repair. Also... completely tear down the chuck and take careful measurements before trying to bore it out. There are 3 screws holding the back cover of the chuck and they will be damaged if you go to far and you will ruin your chuck. On my chuck those screws are in the way of making it a 1" bore. It would be real easy to go to far and hit the scroll as well. The gain in bore size is not really worth the effort when there are other ways to handle the job.

A few other, and better, options are to... Simply get a bigger chuck but you will still be limited by the spindle bore and you will need an adapter plate... Use a steady or follower rest... Use a live or dead center. Or even a combination of all 3 depending on what you are working on. The idea here is to minimize deflection and chatter while working on long parts and to keep the end from whipping around uncontrolled which will rip it out of the chuck and possibly kill yourself or anyone else standing around.

[NCturner]

Hey All...
I've had my HF 8x12 for a couple of years now, and find it both hardy and accurate; waay beyond what it's price point would suggest!
One of the things I dreaded most when I first got the machine was changing gears for threading. I've found that the easiest way to do all this and get it right the first time without cussing is to make a transmission stand.
Basically, it's just a chunk of whatever material you have laying around, turned down to two different diameters.
The base size doesn't matter, it can be as big or small as you want, as long as it's at least about 2" or so diameter, and an inch or better tall for finger access when you drop an axle nut...
The middle diameter is the same size as the hole in your transmission frame, where the leadscrew drive boss fits through, and just as long as the frame itself is thick.
the third (smallest) diameter is the same as the I.D. of the gears, minus a couple of thousandths, and as long as a pair of gears is thick, or slightly longer.
This allows you to take the entire transmission off the lathe and set up your gearing on the bench, and have everything in place and tight before slipping it back on the leadscrew stub.
To remove the transmission, unscrew the washer from the end of the leadscrew, loosen the pinch bolt at the bottom of the trans frame, and tug outward on the entire frame. Now take it over to the clean, wide open section of the bench where you have placed your transmission stand, and drop it right down on there! it may take a wiggle or two, but if you've made your stand right it'll drop right down on there, and you can rotate your gears exactly as they were on the lathe itself!
To set it up, remove both pairs of nuts from each axle shaft, remove gears and washers, and loosen both axles from their square nuts, but do not remove; just loose enough to slide.
Now, starting with the bottom gear (the one that drives the leadscrew) and it's spacer, put those on the transmission stand in whichever order they need to be (look at the chart on the lathe for gear selection and position).
Find the correct set of gears for the next axle, and set them one by one on the axle with a washer in between, sliding it up or down the transmission slot as need be to get the mesh proper (I like to rotate a strip of paper in between the meshing gears while tightening; this gives about .004" of slack, plenty for oil). Tighten the axle to it's square nut, then install the retainer nuts and tighten.
Next, add the top pair of gears in whatever order they go in, adjust for mesh, tighten axle, add nuts, and finally....

Lift all that off the transmission stand, being careful not to drop the (now unsupported) leadscrew gear and spacer, and slip it all back on the lathe. Add end washer and snug up the pinch bolt and move the drive into mesh with the spindle gear, and get to cutting!
It actually takes less time to do it that it does to talk about it... It took all of five minutes to get these pictures taken, and the basement was dark and the lathe assembled when I started.

Oh! And those weird diagrams in the lower right corner that have you confused? Feed rates. .010 per revolution (roughing), and .005 per revolution (finishing). Sometimes i wish I could get down to .002 per rev or less, but .005 per rev will get you a very useable and consistent finish, given proper tool nose radius and setup, and .010 will hog plenty fast enough. Hope this helps!
NCt

[Freddy Warbird]

Originally Posted by NCturner Hey All... Oh! And those weird diagrams in the lower right corner that have you confused? Feed rates. .010 per revolution (roughing), and .005 per revolution (finishing). Sometimes i wish I could get down to .002 per rev or less, but .005 per rev will get you a very useable and consistent finish, given proper tool nose radius and setup, and .010 will hog plenty fast enough. Hope this helps!

Thanks for clarifying.


By the way, how, and what do you lube the main spindle bearings/bushings with?

[NCturner]

Nothing. It's my understanding that they're sealed, much like the front hub bearings on a front-drive car. Not having the transmission inside the headstock (or anything else besides the spindle, for that matter) makes sealed bearings a very attractive choice for a manufacturer. Hard to screw up sealed bearings.

[Freddy Warbird]

Well, I've cut my first test pieces with my new HF lathe. Works pretty good. I need to cut more stock to find out where the lathe has its sloppy areas. From this simple "O" ring type piston I just loosely made, it looks like it can machine parts ok. Need more time on it to find its personality, and limits. I did discover with the parting tool that the spindle will walk away if chips lock out the tool from cutting, and pressure is continued. One thing I learned quickly is the parting tool likes to go straight in with no stalling at a pretty good feed rate. The parting tool makes a good "O" ring groove.

Edit: Did all my aluminum cutting @ 1000rpm. Going to try 2000rpm next time. I tried two kinds of coolant 90W, and WD-40. The 90W is just to darn difficult to clean up but it does keep the rotating stock cooler than WD-40.

[NCturner]

Hey Freddie,
Glad to hear you're up and cutting! That's great! Aluminum does like to be turned pretty quickly compared to steel, but for safety in parting, I usually run about a quarter of the speed I'd run in turning. Breaking blades or having things fly out of the chuck ain't no fun... Besides, it's more accurate to part long and face the back to length.
This little lathe is actually pretty darned accurate for as cheap as it is. There's a writeup that's a few years old at annisquamgranite dot com about our beloved 8x12's, and it explains (or hypothesizes about) why ours is a unique machine in it's size class.
Congrats on your new lathe! Have fun!