# Threading on a PM1127 lathe - turning instead of threading



## Pcmaker (May 16, 2019)

Does anyone have a Precision Matthews PM1127 lathe and has been threading with it? I put it on threading leadscrew, going from right to left. I've tried on A, B, C, speeds. It turns the workpiece instead of threading. I tried different depths of cut from .001 to .010.

I used a carbide threading insert.

I did not mess with the threading gears. I just left it as it was when I received the lathe. I'm just trying out threading and don't care what thread pitch.


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## higgite (May 16, 2019)

Pcmaker said:


> I did not mess with the threading gears. I just left it as it was when I received the lathe. I'm just trying out threading and don't care what thread pitch.


You have to mess with the change gears. There's a helpful chart of gear combinations on the gear cover and on page 27 in the manual.

Tom


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## markba633csi (May 16, 2019)

If the factory setting is a fine feed it will look like turning instead of threading.  Set the gears for a coarse feed/thread and make some scratch passes to check the pitch. Try threading some aluminum first to get familiar- cutting steel threads takes a number of passes and can try your patience at first
Change gear lathes take a bit of getting used to  Your geartrain is a hybrid, semi quick-change gears.
Use the slowest speed initially to cut threads


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## Canus (May 16, 2019)

Have you read your manual?


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## epanzella (May 16, 2019)

Pick a thread, look it up on the chart and thread it. You won't learn anything by just flipping the lever to "thread".


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## Pcmaker (May 16, 2019)

The diagram is so confusing and the manual does not even explain how to read it. There's L1, L2, etc.. but doesn't show what "H" means.


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## royesses (May 16, 2019)

Pcmaker
              I don't own a PM , but just trying to help. I looked at the manual and The reference I saw is for L and H being the speed pulleys. Could this be what is confusing? It looks like some threads require changing the belt on those pulleys. I agree it is confusing. This is what I am talking about:



Roy


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## ddickey (May 16, 2019)

Looks to me that H is a gear.
Yeah H must be a gear.
Are there any gears marked H?


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## Pcmaker (May 16, 2019)

I didn't see any H gears, but I'll look again. All the gears I've seen are numbered.

Here's a screenshot from the .pdf manual I downloaded from the site, which is a lot better than the paper manual it came with.









royesses said:


> Pcmaker
> I don't own a PM , but just trying to help. I looked at the manual and The reference I saw is for L and H being the speed pulleys. Could this be what is confusing? It looks like some threads require changing the belt on those pulleys. I agree it is confusing. This is what I am talking about:
> View attachment 294727
> 
> ...



I don't see any "L"s on the diagram, so I'm not sure if "H" is referring to the high/low speed or not.


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## ddickey (May 16, 2019)

No I was wrong. L looks like a position. The arrow pointing to L, is that a dual gear like the other, one gear on top of another?


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## ddickey (May 16, 2019)

My old lathe was like that. One gear of the pair never got changed. I bet that's what it is.


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## ttabbal (May 16, 2019)

L is the leadscrew. H represents spacers, you should have 2 in the tool box that came with the lathe. Let's say you want 12 TPI. 

On the leadscrew you have a spacer, then the 80 gear. 

The next spot up is a stack with 50 and 75. With the 50 meshed with the 80 on the leadscrew. 

At the top, we have a spacer and a 55. The 55 meshes with the 75 and the spindle. The vertical lines show which gears need to be meshed together. 

Get those set up properly, set the gearbox to B, set the thread mode, set the direction. Make sure you use the half nut control, not the power feed. 

It's not too bad once you see how it works works, but yes, the chart can be confusing. Always take a scratch pass and verify with a pitch gauge. Particularly if you have a thread on a part you spent a lot of time on.


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## epanzella (May 16, 2019)

I think H might be a spacer.  Look at 8tpi. Power transmission is 60-70 then 60-65. At the top row only Z2 (60T)  is being used on the right and to the left in the Z1 position  is H. In the bottom row, or L position, only the 65T gear on the right is used and on the left is H. It seems to me H is a spacer that positions a gear on the inside or outside and is not used in power transmission.


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## mikey (May 16, 2019)

I would just add to the excellent explanation above that you need to space the gears apart from each other by about 0.0030". Easiest way to do this is to slip a piece of paper between the meshing gears, tighten them in place and rotate the gears to remove the paper. This prevents binding of the gears and possible damage.


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## darkzero (May 16, 2019)

mikey said:


> I would just add to the excellent explanation above that you need to space the gears apart from each other by about 0.0030". Easiest way to do this is to slip a piece of paper between the meshing gears, tighten them in place and rotate the gears to remove the paper. This prevents binding of the gears and possible damage.



I'm sure using a piece of paper is a pretty common trick in general & is what I do also. After all I learned this when I was 14 as that's what did for my RC cars (back then RC cars had to be fully assembled down to the differentials, no RTRs like today). When I first setup change gears on a lathe I used paper without even thinking about it. Thinking about it now, what do people normally do, just eyeball? Well just eyeball & feel is perefectly fine too I suppose if you know what you are doing.


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## yendor (May 16, 2019)

I'm somewhat familiar with Change Gears as I have an Atlas 10F with change gears ( I also have a QCGB 42 but that a different story)
and I could be all wet - and if you ask my wife she'll agree.
BUT...
I'm 99.9% sure the gear train is almost all double gears that fit together.

X is the Shaft the gears mount on.

If you look at the Picture Z1 / Z2 -( Z1) is a bold line as if you can see it's outline so it would be on the outside on top of the Z2 gear.
Z3 / Z4 - the (Z3) Gear is shown with a fine/lighter line as if it is behind the Z4 gear on the inside.

I would guess that "L" is the leadscrew shaft and is identified with a gear and a specific number of teeth.

If you follow the columns in the chart the for the .07/mm pitch it would be:
Top Shaft:
Z1 - Outside Gear 45 teeth
Z2- Inside Gear 75 teeth

Lower Shaft:
Z4 - Outside Gear 80 teeth
Z3 - Inside Gear 20 Teeth

Gear on Lead Screw Shaft - 85 Teeth

The "H" I'm not sure But my guess would be the BELT Position but I would have to pull down and read the full manual.

Good luck.


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## darkzero (May 16, 2019)

I agree with ttabbal that H must be a spacer & L means leadscrew. I don't have this lathe but my lathe is the same way, I have a spacer for the gear that drives the leadscrew that I need to reorient for metric threading. My chart doesn't show a letter or anything, it's just blank where the spacer needs to be.

I was trying to think of a word like that starts with the H sound in Chinese but couldn't find one. I came to the conclusion that whoever wrote the manual must have a heavy accent & decided to name it Hempty.


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## higgite (May 17, 2019)

H stands for "Hey! A spacer goes here!"

Tom


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## epanzella (May 17, 2019)

I don't see how "H" could be belt position.  Changing the speed of the spindle doesn't affect the pitch or feed. The only way a belt could affect pitch is if it was inserted into the gear train but slippage would make it impossible to synchronize the spindle with the leadscrew.


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## markba633csi (May 17, 2019)

H probably stands for "holder" as in placeholder
Could also mean hellish
I notice two slightly different charts for inch threads- did the mfg offer an inch or metric machine and PM only sells the inch version?


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## Pcmaker (May 17, 2019)

I don't undertand why none of this is in the manual


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## darkzero (May 17, 2019)

Pcmaker said:


> I don't undertand why none of this is in the manual



The manual that usually comes with an asian import machine is a basic generic manual from the CM. Distributors like PM & Grizzly rewrite the manual. Use the PM manual & forget the CM's manual.


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## markba633csi (May 17, 2019)

I guess the reasoning is if you are capable enough to use machine tools then you can figure things out without detailed manuals.  Also, it's a fact that people generally don't read manuals anyway.  Cost probably is a factor too
Not making excuses for poorly written manuals, just sayin'


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## Pcmaker (May 17, 2019)

I just tried it. I was trying to do 1.25mm but the gears don't seem right. Used a spacer for "H"

Also, the inserts are such a pain to get out and put on. 

Anyone know what the picture means on the top of the threading chart? And why are there metric and inches sections under both metric and inches?


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## Pcmaker (May 17, 2019)

I got this email reply:



> Hello,
> 
> The H is a spacer, thats it.
> 
> ...


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## darkzero (May 17, 2019)

Yes but it seems there is an inconsistency on the chart from the manual. Does it also look like this on the chart on your lathe?


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## Pcmaker (May 17, 2019)

I don't get what those "I"s are supposed to be


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## darkzero (May 17, 2019)

Those lines indicate which gears mesh (drive) together. If you look at the rest of the chart it's consistent as well as the spacer & gear position for the leadscrew, all except the ones I pointed out.


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## Pcmaker (May 17, 2019)

This is what's on the lathe itself. What's the top box for? If the middle is metric, the bottom box is inches, what's the top?


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## darkzero (May 17, 2019)

Pcmaker said:


> I just tried it. I was trying to do 1.25mm but the gears don't seem right. Used a spacer for "H"
> 
> Also, the inserts are such a pain to get out and put on.
> 
> Anyone know what the picture means on the top of the threading chart? And why are there metric and inches sections under both metric and inches?



Ok, since it seems you are still having trouble getting 1.25mm pitch I'll take a stab at it.






Edit: See next post.

Looking at the 2 diagrams I circled in blue, to get 1.25mm pitch.....

40T is at the very top which I assume is a gear off the spindle that can not be changed.

Standing in front of the lathe looking at the change gears, Z1 & Z2, 60T would be on the inside (right side closest to the headstock) & a spacer would be on the outside (left side).

Z4 & Z3, 80T would be on the inside & 50T would be on the outside. There's a line inbetween Z2 & Z3 so that would mean the 60T & 80T gears mesh together.

Finally for the leadscrew drive, another spacer used on the inside & another 60T gear on the outside that would mesh with Z4 which would be the 50T gear.

Lever on position A.


However what doesn't make sense to me is on the right side of the chart it shows a different gear setup for 1.25 also using position A. So if the above gear combo doesn't give you a 1.25mm pitch, then try the following configuration.


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## darkzero (May 17, 2019)

Pcmaker said:


> This is what's on the lathe itself. What's the top box for? If the middle is metric, the bottom box is inches, what's the top?



Ok, that's better, I'd follow the chart on your lathe instead of the manual. As I said above I don't understand why there are 2 gear combos with the same lever position for 1.25mm pitch in the manual.

In my post above, follow the gear combo in the second pic as that's what matches the chart on your lathe.

The top section is for feed rate in inches (used for roughing & finishing passes). When you hear IPR (inch per revolution of the spindle), that's what that is. The first 3 lines are feed rates for the carriage. The next 3 lines are feed rates for the cross slide.



So starting from the top for 1.25mm...

60T on the inside/right side, spacer on the outside/left side.
63T on the inside, 50T on the outside. 63T meshes with the 60T.
Spacer on the inside, 80T on the outside. 80T meshes with the 50T.
Lever on position A.


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## epanzella (May 17, 2019)

These charts seem messed up to me. Look in post 24 where you can see all 6 boxes. Look at the bottow 2 boxes left and right. The QC gear positions change left and right for B & C with the different gears combos. Then look at the A position. It stays the same left to right yet the same gear combinations that change B & C are NOT changing A. That seems impossible.


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## ttabbal (May 17, 2019)

The manual has, I think, a set for metric leadscrew. Use the inch side, PM only sells inch leadscrew models. It matches the one on the lathe. 

The top chart is for feed rates. It shows the rates for longitudinal and cross feed. 

The gear setup for threading looks weird compared to how it came. 

For metric threads, remember that you can't disengage the half nuts once you start or use the thread dial. (there are a few ways, but for just starting out, it's just easier). 

For the sleeves, yeah, mine were a bit tight. I took a file to them. You only want to take off just under a thou. I believe it was an "X" drill bit I ran through it as well. Mostly to clean up burs from filing.  

If you do that, don't take much off. You want them snug, slop in the gears would be bad.


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## jcp (May 17, 2019)

ttabbal has it right.....use the chart on the lathe......its riveted to the lathe for a reason...can't misplace it or get on the wrong page of the manual.
Top chart..cross feed and longitudinal feed in inches.


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## Pcmaker (May 18, 2019)

I think I figured out the gears, but now the issue is the washers. Trying to figure out how to how to keep the right side of the gears from grinding on the banjo and to keep the gears from "wobbling." That one is probably a washer issue, too.


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## ttabbal (May 18, 2019)

If the gears are wobbling or scraping, they are installed incorrectly. 

There are 2 washers for each gear stack. Large ID goes first on the axle. The small ID goes on last. Once the axle is tightened, there should be no play in the gear stack, other than being able to rotate.


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## murraym (May 18, 2019)

Pcmaker said:


> This is what's on the lathe itself. What's the top box for? If the middle is metric, the bottom box is inches, what's the top?


I believe the box indicates feed rates for the feed screw instead of the lead screw in thousandths.


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## murraym (May 18, 2019)

I would try to put a spacer and a 60T gear on the Z1/Z2 spindle with the 60T gear meshing with the 40T gear. The Z3/Z4 spindle gets a 63/50T gear with the 63T gear meshing with the 60T gear on the Z1/Z2 spindle. The L spindle gets a spacer and an 80T gear with the 80T gear meshing with the 50T gear on the Z3/Z4 spindle. Also, You would need to be in the A position.


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## epanzella (May 18, 2019)

the top box is feed in inches/revolution. Look at the little drawing on the left. The first one show a lathe tool cutting longitudinally and refers to the first three rows.  The second drawing is a lathe tool facing a shaft (crossfeed) and refers to the next three rows. You use the feed lever for these and the power goes thru the gears in the apron to slow it down way more than the thread settings. Lottsa good stuff in the apron!


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## higgite (May 18, 2019)

We're repeating ourselves. I said, we're repeating ourselves. 

Tom


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## Pcmaker (May 18, 2019)

I shoulda spent $400 more and gotten the 12x28, which has a quick change gear box


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## mikey (May 18, 2019)

Your lathe will cut more threads than the typical QCGB lathe will. You just have to learn to use it properly. 

Go buy the book, Gears and Gear Cutting for Home Machinists, by Ivan Law. It will educate you on how gear trains work and make it clearer how to work with your change gears.


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## Pcmaker (May 18, 2019)

I think I got it to work, just need to tweak it a little bit. The gears are making more noise than it used to. I need to space them out with a piece of paper, like someone here recommended. I'm thinking of getting a .003 feeler gauge and cut it so it can fit between the gears and use that instead from now on.


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## mikey (May 18, 2019)

Pcmaker said:


> I'm thinking of getting a .003 feeler gauge and cut it so it can fit between the gears and use that instead from now on.



You cannot do this with a feeler gauge. The paper goes between the gear teeth of the two gears you are trying to mesh. It spaces the two gears by 0.003" so they fully engage but do not rub or bind against each other.


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## ttabbal (May 18, 2019)

They will be little louder, but not too much. Put paper in the teeth while meshing them together, rotate them to remove the paper. Nothing to it. Make sure you put a little oil on them as well.


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## Pcmaker (May 18, 2019)

I need to make new nuts that hold the gears in place. The ones it came with needs a special tool to loosen/tighten and the set screw is a flat screw instead of an allen


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## mikey (May 18, 2019)

mikey said:


> Go buy the book, Gears and Gear Cutting for Home Machinists, by Ivan Law. It will educate you on how gear trains work and make it clearer how to work with your change gears.



Sorry, I meant to point you to a different book, Screw Cutting in the Lathe, by Martin Cleeve.


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## higgite (May 18, 2019)

Pcmaker said:


> ...... The gears are making more noise than it used to. I need to space them out with a piece of paper, like someone here recommended........


Gears that are meshed too tightly together are noisy. Take a piece of heavy notebook paper or similar and squash it between gears as you mesh the gear teeth together. Then tighten the nuts/bolts/whatever secures the gears in place and rotate the gear train to feed the paper out. Watch this video from 4:20 to 4:55.





Tom


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## Pcmaker (May 19, 2019)

Got these odd nuts that push the gears in. They have a slotted set screw that locks it in place. Thinking of making regular bolts with allen set screws to replace them


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## ttabbal (May 19, 2019)

Those are to adjust the stack height, once set you shouldn't need to mess with them. Removing and installing the gears is done with the square drive on the end of the axle. The lathe came with a T-handle driver for them.


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## Pcmaker (May 20, 2019)

I'm trying to figure out why the top gear wobbles. If I tighten the nut to keep it straight, it seizes the gear because it's being sandwiched between the spacer and the washer on the other side.


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## epanzella (May 20, 2019)

The nut should tighten up against a shoulder on the shaft before the gear is pinched. You may need to remove a washer.


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## ttabbal (May 20, 2019)

Adjust the "odd nuts" to allow movement without getting too loose. Make sure the washers are on the right sides as well.


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## Pcmaker (May 21, 2019)

My threads aren't going on the same place. The manual says if you're doing metric, to not use the threading dial. I have it set at 1.25 pitch

I take off .002 at a time. I thread from right to left, I turn off the emergency stop, I back out the cutter, then turn on the machine, then turn the directional from left to right. Then I hit the emergency stop, then turn on the machine, move the directional back to right to left, then it cuts on a different area.

Not sure what I'm doing wrong. It says to keep the half nut engaged at all times when you're doing metric threads and I've done just that. It keeps cutting on a different area when I come back for the second cut, which is also at .002 depth of cut.

*edit*

Redid the gears to where I'm cutting 24 TPI. I'm still trying to figure out how to use the threading dial. Not sure how it works.


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## epanzella (May 21, 2019)

You're reversing the motor electrically to back up to the start of the thread, right? Don't shift any gears or you'll lose the indexing between the spindle and the lead screw.


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## ttabbal (May 21, 2019)

Yeah, don't use the direction shifter. Use the motor reverse switch. 

For the TPI thread, even pitch threads can use any number on the thread dial. 

Set position and cut depth with the machine running. 

Wait for the thread dial to come to the right number, engage the half nuts. 

Disengage when you are ready, move the carriage to the start and do it again till you get to the right depth. 

There are tons of YouTube videos that demonstrate the process and it's basically the same on every lathe. Consider Joe Pieczynski's away from the chuck video as well.


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## Pcmaker (May 21, 2019)

I never tried with Forward/Reverse motor switch. I was using the leadscrew directional lever.


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## dpb (May 21, 2019)

That won’t work.  You have to use the motor direction.  Do not take it out of gear, or change gears, until the thread is finished.


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## royesses (May 21, 2019)

On my mini I lock the half nut and cut the thread. I stop the motor at the end of the thread. Next I put the forward/reverse switch into reverse then back out the cross slide. Then start the motor and let it reverse until I get past the thread start by a quarter inch or so. Stop the motor, put the forward/reverse switch into forward position then adjust the crosslide back to its zero position and set the depth of cut then start cutting the thread again. Repeat the procedure until the thread cut to depth.

Roy


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## Pcmaker (May 21, 2019)

Ok, that worked! Now I just gotta figure out how to make the gears less noisy.

The threads came out at an angle, though. I need to turn the QCTP a bit more.


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## jbobb1 (May 21, 2019)

Get yourself a fish tail.



			https://www.mscdirect.com/product/details/86413879?fromRR=Y


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## RWanke (May 22, 2019)

Pcmaker said:


> This is what's on the lathe itself. What's the top box for? If the middle is metric, the bottom box is inches, what's the top?



 I'm just guessing but It could be feed rates for regular turning. ????


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## Pcmaker (May 22, 2019)

Do I even need to use the threading dial? I've been just using the forward/stop/reverse sequence and no issues


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## markba633csi (May 22, 2019)

You can't use the threading dial for metric threads. You can use it for inch threads, but you don't have to- it's optional
Mark


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## Pcmaker (May 22, 2019)

Ok, good. Because it's confusing to me. I guess the only reason to use the dial is to thread faster as in to disengage the half-nut at the end of the thread, so you can pull the carriage back quicker or if you lose your place if you accidentally disengaged the half-nut?

Also, when threading, should you use the slowest speed when turning?


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## jbobb1 (May 22, 2019)

Pcmaker said:


> Also, when threading, should you use the slowest speed when turning?



That really depends on the tooling you're using, material your threading, and most of all right now, your reflexes.


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## darkzero (May 22, 2019)

You can use the threading dial/half nuts for metric threads with an imperial leadscrew (and vise versa, imperial threads with metric leadscrew), just have to keep track of where you disengaged.

https://www.hobby-machinist.com/threads/cutting-metric-threads.22504/#post-199388


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## Creativechipper (May 24, 2019)

This all sounds so familiar, I totally know the feeling of dealing with a change gear for the 1st time is intimidating. I took some pics and posted on this thread....








						Threading for beginners
					

Finally gathered up all the basic stuff to start threading, I think...   Threading wires, micrometer, thread pitch gauge (U.S) , fish tail gauge, and some tap and dies.   I have watched a lot of videos and read a lot of stuff but this is still a bit intimidating. Equations to figure out size and...




					www.hobby-machinist.com
				



Looks like you got it now, best of luck!!  
Check a couple videos, you will see a pattern or rhythm that is helpful to follow and know about before threading.


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## markba633csi (May 24, 2019)

Takes quite a few passes to cut steel threads- seems to take forever till the nut finally screws on.  Last few passes need to be light ones to give good surface finish to the threads
M


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## Pcmaker (May 24, 2019)

I was threading 1/2" stainless yesterday using 24 tpi. This takes patience. I was going .005 at a time and it took a long time. I would've been taking larger cuts if I was working with mild steel.

Should I be using cutting fluid when I'm using a carbide insert when threading? I hear carbide doesn't like cutting fluid.

I also ordered a center gauge today from Amazon.


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## Mitch Alsup (May 24, 2019)

markba633csi said:


> You can't use the threading dial for metric threads. You can use it for inch threads, but you don't have to- it's optional
> Mark



ABomb79 showed how to use the threading dials on a metric thread with inch lead screw a couple weeks ago.

As you near the end of the thread, you perform the usual fast turn of the cross slide dial to pull the tool from the work; and as fast as possible, turn the motor off.
Then reverse directions and when the threading dial reaches the correct number you re-engage the half nut; and let the carriage carry the tool past the start point.

I thought this was both clever and handy.


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## markba633csi (May 24, 2019)

For a beginner this may be a bit much to digest, but yes there are moves that allow using thread dial for metric


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## epanzella (May 25, 2019)

Pcmaker said:


> I was threading 1/2" stainless yesterday using 24 tpi. This takes patience. I was going .005 at a time and it took a long time. I would've been taking larger cuts if I was working with mild steel.
> 
> I also ordered a center gauge today from Amazon.


When you first start a thread you can use heavier cuts as only the very tip of the tool is engaged. As the cuts get deeper and the tool load increases you can reduce DOC.  You should really buy the book titled "How to Run a Lathe". Trying to learn all the ins and out of a lathe a post at a time is confusing at best.


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## Pcmaker (May 26, 2019)

On the feed rate chart, when it shows 0.0025 does it mean 0.0025 per revolution? I like using the auto feed and I'm getting rough finishes when I have the threading gears on. I want the feed rate to be very slow for a better finish. At least, I'm getting better finishes this way.


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## jbobb1 (May 26, 2019)

Yes, you are correct.


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## epanzella (May 26, 2019)

Pcmaker said:


> On the feed rate chart, when it shows 0.0025 does it mean 0.0025 per revolution? I like using the auto feed and I'm getting rough finishes when I have the threading gears on. I want the feed rate to be very slow for a better finish. At least, I'm getting better finishes this way.


Not threading gears, change gears. You use change gears for both threading and feeding. For threading the carriage is driven right off the leadscrew by the halfnuts. When you release the halfnuts and use the power feed lever it adds nother stage of gearing inside the apron that slows it down to feed speeds like .0025/revolution.


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