How do you thread on the HF 8 X12 ?

[sunnyday]

Can anyone show me a video or clearly expalin the process of changing the gears on the 8x12 for threading ?

The instruction manual and pictures are useless to a newbie like me.

[ToddK]

I agree, the directions for threading completely suck. Changing the gears is fairly straight forward, there are only two big lessons that I learned. The gears ride on studs that are mounted onto an arm. When putting on the two nuts that hold the gears to the stud, remember that the gears will turn, but the nuts won't, so you need to be careful to not have the nuts contact the gears. I tighten the nut closest to the gear into the other nut, to ensure there is some clearance. The other huge point that I initially missed is that the arm that holds the three sets of gears can pivot by loosening a screw down at the bottom of the arm. By swinging the arm left or right, you can get the appropriate engagement and spacing to the two gears above the arm. Make sure you retighten the screw after adjusting the arm, and leave a little bit of clearance to the two upper gears, so that nothing binds. Other than that, it really is as straightforward as it looks. -Todd.

[TroyO]

I had the same problem.... it's not all that easy to figure out, LOL.

Have you seen a generic video on threading and have you gotten the concept of the leadscrew turning in relation to the headstock rotation? You really need to get that to figure out the rest.

I only mention it because, never having actually used a lathe for threading before I got the 8x12 I was missing some of the basic concepts and had a dickens of a time undestanding the process.

These video's are nice.... it's not the same machine (By any stretch!) but it covers the concepts pretty well... and the price is good. (Free)
http://techtv.mit.edu/videos/134-machine-shop-9

Here's another site that may help... at least to get the idea of the mechanics.
http://www.fignoggle.com/machines/8x...tLeadGears.htm

Anyway.. overall you are trying to get the leadscrew to move the cariage some certain distance per turn of the headstock. How far the cariage moves per turn is what determines the thread pitch.

To change that ratio, you select and interchange various gears in the geartrain on the lathe.

One thing that took me a while (because the manual sucks buttermilk) is that the geartrain is mostly mounted on an "Arm" that holds gears the label calls B C D E and F. That gear arm has a screw on the bottom that you can loosen and rotate the whole thing either closer to, or further away from the headstock gear.

In addition, the gear shafts that hold BCDE in place can be loosened so that the shafts can be slid along the arm to accomodate different gear sizes. You should have gotten a tool that has a square socket in the end of a T handle. (Be carefull.. the shafts are soft and easy to strip) That loosens/tightens the gear shafts. Also note, there are lube points in the ends of the gear shafts....give them a squirt.

F is the final gear that hooks all the other gears to the leadscrew. A is the first gear next to the headstock and usually isn't changed. Mostly you are working with BCDE (and sometimes F).

There's another gear on a bolt that you screw in to reverse the cut... IE, for left hand threads.

I hope that helps, instead of making it more confusing, LOL.

[TroyO]

This may help....

Pic 1 shows the gear locations... at least I think it's right, LOL.

Pic 2 shows a gearing chart...

To talk it through...
Follow the chart from left to right, then down

(18 TPI)
First row:
First spot is blank... that means put in a spacer gear. (One that is too small to touch any other gears but fills in the space on the shaft.)

Next spot is 70, so put in a 70 tooth gear. Notice the line down below the 70? That means it touches that gear... that's where the power goes through.

Second row:
First spot gets a 60. The line tells you it's sending power to the 45 tooth at the botton.

Second spot gets an 80, which gets power from the 70 tooth gear above it.

3rd row:
First spot gets a 45
Second spot is just a spacer. (But not a gear.. last row actually has a round spacer... I think the manual calls it a banjo or something.)

[sunnyday]

Troy, why are your alphabet letters out of order on your picture ?

man, this is confusing for my brain .

But pictures and photos do help and If anyone can put up some actual photos of the gear train , and correct banjo gears pertaining to a certain TPI , im sure I will get it.


the way the lathe came from the factory, it already had gears in there..are those gears ONLY for cutting and facing ?

In other words, if a person changes out the gears that are installed from the factory, for another set of banjo gears for threading, do you have to always take those threading gears back out, and install the stock gears again to go back to facing and turning ?

[TroyO]

They are "out of order" on the pics because they are out of order on the lathe.... it doesn't make a whole bunch of sense to me either but I'm pretty sure that's how they have them labeled.

You can't use the gear drive for facing (that I know of anyway) only for turning... it will move the whole caraige left or right but not in and out.

The stock gears are set for turning oprations... basically the same idea except the ratio is very high.... so it moves the cariage just a tiny bit for 20-30 turns of the headstock. Think super-extra fine threads... so fine it's essentially smooth.

You don't have to put the turning gears back in unless you want to use the power feed for smooth cuts. I usually don't bother unless it's a long smooth turning cut. (Like a cylinder or tube) For most stuff, I just hand feed it and it's smooth enough.

[Freddy Warbird]

TroyO;662174

First spot is blank... that means put in a spacer gear. (One that is too small to touch any other gears but fills in the space on the shaft.) Second spot is just a spacer. (But not a gear.. last row actually has a round spacer... I think the manual calls it a banjo or something.)

I was wondering about that. Good info. Thanks. Reading 8x12 related threads are certainly preparing me for less confusion, and better understanding of how to adjust this machine.

[Freddy Warbird]

Something looks different on TroyO's lathe from the pic in post #4. Is that a variable speed mod?

[sunnyday]

Thanks troy...you have been a big help..

I think im ready to try it...

so the top 2 shafts that hold banjo gears, may also have to use small spacer gears...but the bottom shaft will always use a spacer instead of a gear spacer ?

also, it seems like the bottom shaft has a screw or bolt that holds on the gear, unlike the top 2 shafts that use 2 nuts on each shaft to hold the gears.

the instruction manual to this lathe is a freaking abomination from hell.

I assume if I want to make a bolt that has 1/2" -20 tpi , then i need to use a piece of round metal stock that is 1/2" round ?

oh, and for normal threads, i guess the lathe button needs to be turned on to the R position and not the L position ?

[TroyO]

Freddy.. yep, it's a variable speed mod... some more about it in this thread:
http://www.cnczone.com/forums/showthread.php?t=87683

Sunnyday... yes. The bottom shaft will always use a spacer.. at least as far I've run in to. It's kind of the final step, so having two gears on there wouldn't help.

Correct.. the bottom shaft has a screw and washer to hold the gears on. That bottom gear is directly connected to the leadscrew.

As far as the lathe direction... well, usually it would be R and run in the normal fashion. To cut left handed threads you change the gearing to run the other way, not the lathe direction. (That's what that gear mounted to a bolt does for you.)

Not to add confusion there has been some discussion about threading upside down though, where the bit is mounted upside down and the lathe run "backwards". It's also good for "parting off".. any operation where there's a lot of force on the bit. (The idea beaing that the force is pulling the bits up and away from the lathe. That will pull out any slack and flex in the system insuring the bits don't "dig in") But you don't really need that to get started... try it the "normal" way first, LOL. It also means you can cut right hand threads so that the caraige moves AWAY from the headstock during the cut.