# Got a new lathe!



## calipsoii (Jun 14, 2014)

After staying out of here for a good number of years, I feel like this is the subforum that has captured my interest the most lately, so maybe it's time to make a post!

I guess a bit of an introduction is in order: my name's Mike. I've been slowly inching my way into metalworking for the last year or so. My skills are still very basic so I've just been absorbing as much as I can from the skilled machinists who frequent this subforum. I'm in IT so this is quite a departure from what I do to earn a living. I have a bit of machining education, though just through night classes (not pursuing an apprenticeship).

I've spent the last year standing in front of this little guy. With no power feed, a minimum 550 RPM spindle speed, and a 3lb chuck, it's been a good little learner lathe. I've gotten quite good at smoothly turning the handwheels. 






My projects have been getting more ambitious lately though and the Taig hasn't really been keeping up. I've found it really frustrating to work on due to its small size, lack of power and inability to power feed. The thought of continuing to work on it was really depressing me, so I started looking around at alternatives. I'd have loved to get a PM1236 - the CPF'ers here who own one speak highly of its features for the price. Unfortunately it's not really a good fit for my house or where we're at in life right now.

In the end I wound up purchasing an import lathe from a retailer in town. I looked at a lot of used Southbend and tool room lathes, but our family is kicking things into high gear and I'd be lying to myself if I thought I had time to rebuild an old lathe. It'd probably wind up sitting unused. The best fit for now is a cheap(ish) machine with retailer support in town, and something small enough to fit in my tiny garage.

The Taig before I tore apart the workbench I lovingly constructed for it:





What I replaced it with:





The toolchest was recommended on a gun-turners forum by a number of people with benchtop lathes. It's from Costco and is surprisingly sturdy! It came with rolling casters but I replaced them with hockey pucks. 





The lathe is a Craftex 10x22. It's a house brand and is sold by a dozen different retailers under a dozen different names. So long as you keep the price in mind, it offers a good mix of features! It's also a heck of a lot larger than my last one - here's the entire Taig sitting on the cross-slide. 





Every exposed inch of it was covered in packing grease. Every unexposed inch was covered in casting sand. Every oil reservoir was full of something resembling black maple syrup. It took me 4 weeks of evenings & weekends to strip it down to the nuts and bolts, clean it, oil it and reassemble it. I learned a lot about how it works and I tweaked a lot of things to make it run smoother. I'm not in any rush to repeat the experience. :laughing:





My first project on it will be replacing the turret toolpost with an AXA QCTP. It's an Aloris clone and needs bored out before it will fit onto the existing compound slide. Gonna chuck it up in the 4-jaw and enlarge the hole a little.





That's about all I have for now! I have a lot of learning and practicing to do so I'll update this thread once in a while with my progress.  Cheers!


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## timbo114 (Jun 14, 2014)

Very nice set up - QCTP is 100% the way to go, it's the only type we use @ the raw carbide tooling plant where I work.
We've probably got 1000 of them.
If I had space for a lathe like yours .... I'd be making $$$ instead of spending it all.


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## MRsDNF (Jun 15, 2014)

What a nice upgrade. Your little lathe looks intriguing. I dont remember seeing anything like it before. I'm really looking forward to see what you create on the new beast. Have you anything in mind?


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## gt40 (Jun 15, 2014)

Congratulations! Always nice to see a new lathe...


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## precisionworks (Jun 15, 2014)

calipsoii said:


> Every exposed inch of it was covered in packing grease. Every unexposed inch was covered in casting sand. Every oil reservoir was full of something resembling black maple syrup. It took me 4 weeks of evenings & weekends to strip it down to the nuts and bolts, clean it, oil it and reassemble it.



And I thought only mine came with those options :nana:

Nice upgrade, you can do a lot of work on that size machine. First job is to go to the bank & get a loan to purchase tooling :devil:


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## calipsoii (Jun 15, 2014)

MRsDNF said:


> Your little lathe looks intriguing. I dont remember seeing anything like it before. Have you anything in mind?



The Taig is a really nice lathe! It's made in the US and has excellent fit and finish. For small things like model engines or watchmaking it is amazing. The issue was really when I was trying to use it to drill a 1/2" hole in 4" of stock and it simply couldn't cope. There's only so much rigidity you can get out of a lathe light enough to carry with 1 hand. I'm still using it for very basic milling - it does an excellent job at that.

As for projects, I have a few things I've been thinking of for some time that I'd like to try. Being able to cut single-point threads has been on my wishlist for ages so I'm excited to work on my threading.



precisionworks said:


> And I thought only mine came with those options :nana:
> 
> Nice upgrade, you can do a lot of work on that size machine. First job is to go to the bank & get a loan to purchase tooling :devil:



Interesting you mention the tooling! When I was looking at the Taig, I spent a lot of time lurking on the machinist forums and read that same message over and over and over. When I finally got the Taig I had this picture in my mind that I needed to buy huge amounts of tooling if I wanted to be a capable machinist. So I went and purchased lots of stuff - too much! Things I thought I would need, things that looked handy, things I saw others using. Most of it is sitting unused in a box... it was an expensive lesson. From that point onwards I've only purchased things as I need them for a job. A drill here, some lubricant there, etc. For the Craftex I had a good idea which tools it required that I was lacking and I budgeted them into the purchase price. 

When I bought the Taig I did treat myself a bit though. For any equipment that wasn't limited _just _to the Taig (things I saw myself using for many years) I splurged and got good quality stuff.

I absolutely love these. Using them is a pleasure every time.





For the cutting tools, I looked up what size tooling the PM1236 could use and bought the absolute largest tools that the Taig would accept. Some of them look comically huge when mounted on the Taig. They're a bit small on the Craftex but I've tested most of them out on some brass and they all work well. They're made by AR Warner in the US and accept indexable HSS/carbide inserts. They have a good weight in the hand and I'm glad I spent more up front and can re-use them with this machine.


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## harro (Jun 15, 2014)

> I absolutely love these. Using them is a pleasure every time.



Pretty much anything with the letters ' Mitutoyo ' in its name is going to be good stuff


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## precisionworks (Jun 16, 2014)

+1

Can't go wrong with either Mitu or Starrett.


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## gadget_lover (Jun 16, 2014)

You will enjoy that new lathe. Being able to reduce a bar from 1 inch diameter to .75 in a matter of minutes is neat stuff.  


Don't beat yourself up with threading. Lots of folks here can help explain the basics. 

Daniel


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## calipsoii (Jun 16, 2014)

There are 3 individuals who put out Youtube videos saying that they switched the turret toolpost with a QCTP, but not a single one of them documented the process. I always find this the most frustrating thing - share the knowledge people! :scowl: I'm going to add a quick post to this thread in the hopes that any future lathe purchasers will find it and get a general idea what worked for me.


* Adding an AXA Quick-Change Tool Post (QCTP) to a Craftex CX700 10x22 Lathe*

* You do this entirely at your own risk. Measure 10x and cut once. *

The CX700 has a very annoying shoulder at the base of the threaded toolpost stud. All the aftermarket AXA toolposts I looked at cannot fit over this shoulder. You can have a machine shop remove the shoulder from your compound slide, or you can modify the toolpost to try to accomodate it. I chose the latter since if I bugger it up, a new toolpost is a cheaper replacement. Plus it lets you undo the mod and re-mount the old toolpost.





Disassemble the toolpost. I'm using this one and I purchased this guy to make life easier (otherwise you need to build it yourself).





Center the hole in the bottom the best you can in the 4-jaw chuck. Protect the workpiece from the jaws using business cards.





Measure the shoulder diameter and bore the toolpost hole out a tiny bit bigger than that.





Check that it fits snug.





The center bushing now stands too tall. It's sitting on the shoulder while the toolpost is sitting on the slide.





The center bushing simply would not part off on the lathe, nor in my small bandsaw. The only thing that worked for me was a hacksaw.





Chuck the bushing up in the lathe and face it off a bit to remove any slant imparted by the hacksaw. And ignore the fact that I didn't fully face it, it was getting late and I was tired (School of Good Enough :devil





There is a threaded nut at the very top of the toolpost. It tightens down on the bushing you just sawed. You need to transfer the force through the bushing and into the toolpost housing. To do this, you need to build an adapter that will spread the forces down around the shoulder, tightening the toolpost housing to the cross-slide. Otherwise your toolpost will twist and turn in place no matter how tight you make the top nut.










Re-assemble it and test that the toolpost tightens to the compound slide. Enjoy!


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## gadget_lover (Jun 17, 2014)

I have the same tool post on my 9x20 lathe. It's nice and solid. The extra tool holders are easy to get and pretty cheap.

Good work on the write-up too.



Daniel


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## KC2IXE (Jun 18, 2014)

Well, their .0001 test indicators aren't the best - Go Brown and Sharpe (aka Bestest aka Compaq)


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## precisionworks (Jun 18, 2014)

KC2IXE said:


> Well, their .0001 test indicators aren't the best - Go Brown and Sharpe (aka Bestest aka Compaq)


Totally agree, most of the the Rolls Royce dial test are those made by TESA Group in Switzerland. Brands are:

TesaTest 
Brown & Sharpe 
Interapid 
Compaq 

The other best quality brand is Girod-Tast made in Switzerland by B.G. Instruments S.A.

My collection includes two Interapid's and one each of the other brands. Also an Alina, made by Compaq until the mid-1960's. Mine has an extended measuring tip, 40 mm long & is the berries for measuring runout way up inside a flashlight bore when setting up. Parts are no longer available so I try to treat it gently. Huge range on the Alina, .080" with a telltale hand showing where it's at. Single directional only so a switch must be flipped to reverse. I never reverse so that doesn't matter.






That said there's nothing wrong with Mitu. I've owned their dti's in the past & they worked well. Long Island Indicator (the best place for instrument repair IMO) says this:



> *Mitutoyo:
> 
> *New models, completely redesigned, are manufactured in Japan. Some models are available with optically scannable serial numbers on the dial face. The weaknesses of older models have been corrected but in an effort at cost saving, these new models have weaknesses of their own. The new "pocket" models 513-512 and 513-518 are a major improvement in design and construction over the old models and can be recommended. The other models don't compare with their European counterparts. The newer slanted dials which mimic the Swiss Interapid indicator have one significant difference: they are accurate when the contact point is used at an angle of 0°. This could be a source of confusion—and error—in a shop which uses both brands.



A brand comparison of both new & older indicators at http://www.longislandindicator.com/p37.html


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## calipsoii (Jun 20, 2014)

A little update: 

I've had ~9 hours after work this week to tinker with the new lathe. To say I was frustrated with it would be an understatement! At first, it seemed like everything I did it wanted to fight me. Chatter, squealing and crappy finishes (usually all of them at the same time. Drilling was horrible, parting off was impossible.

I spent the week making tiny adjustments though, and this evening was very pleasurable! A lot of it was changing the habits I picked up while using the Taig. 

Reducing speed and increasing feed while grooving/parting eliminated the squawking. There's a sweet spot you can feel when you turn the handwheel and the chip just starts peeling off in a nice sheet. 
Increasing speed and taking deeper cuts while facing/turning vastly improved the finish. 
The gibs were a bit wonky and playing with them helped a lot. 
The compound slide seems happiest when it's sitting in the middle of its slideways - I had it hanging too far back sometimes. 
Rotating the threading tool holder to the correct position and cutting with the cutting edge sure did make a difference.  
My go-to drills were old and beat up and buying a new one instantly improved drilling. 
 Spent a couple hours this evening working on a project I've wanted to do for a while. It was a good chance to practice external threading. I think the next practice piece I'll run the tool over them one more time to clean them up. I believe there are also threading files you can purchase and run over the threads to straighten them out a bit?











I think all it took was getting used to how this machine behaves compared to my old one. Looking forward to continuing to practice on it. :thumbsup:


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## benchrest (Jun 21, 2014)

Awesome write up. Subscribed and will take notes. Keep up the good work calipsoii :twothumbs


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## MRsDNF (Jun 21, 2014)

What type of threading tools are you using?


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## calipsoii (Jun 21, 2014)

MRsDNF said:


> What type of threading tools are you using?



This one. It was a stupid mistake, but I didn't realize that the holder should be oriented as it appears in the picture: with its cutting insert mounted on the side. I had it flipped 90 degrees so that the insert was laying flat across the top. My internal threader specifically says 'laydown' but the external one didn't say 'side-cutting' so I assumed you somehow cut with it mounted on top. You can imagine the kind of mess that was making!


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## precisionworks (Jun 21, 2014)

calipsoii said:


> ... It was a stupid mistake, ...


If you can't see a bone & you aren't gushing blood it isn't so bad 

Insert type thread tools are either stand up or lay down, both having advantages & disadvantages. Some machinists like to grind their own 60° HSS thread tools & that isn't hard to do. HSS tools run at half the speed of carbide tools but can be useful when surface speed is low as it often is on small parts in brass. Coated carbide inserts may work better because of the reduction in BUE (built up edge).



> Spent a couple hours this evening working on a project I've wanted to do for a while.


That's a great job on the shroud & you may want to consider selling them. Lots of E-series parts are difficult to obtain & the one you made would easily sell for $25 or a bit more. Considering set up time your first shroud probably earned you all of $2.50/hour LOL.

That part reminds me of the first SF light I bored. Fixture building took something around 40 hours for the first workable fixture, now I can knock one out in 60-90 minutes. You'll figure out how to build parts in less time as you do the same part over & over. 



> threading files you can purchase and run over the threads to straighten them out a bit?


Thread Restoring Files are designed only to restore damaged external threads. 

To get a smooth finish try flooding the work & the tool tip with the correct lube - Hercules sulfur-lard based cutting oils are the best I've used & other machinists also report good results. What happens in sticky materials like brass (and to a lesser degree in aluminum 6061) is call slip-stick. The tool slips along for a while & then sticks, rips out some material, slips some more, sticks again, etc. Correct lube eliminates some of this:

FROM THE HERCULES WEBSITE http://www.herchem.net/Products/oil_lubricants.html



> Application specific lubricants for both manual and machine metal working operations. Used for sawing, drilling, turning or thread cutting with all types of metals. These are superior quality cutting oils formulated to produce consistent results under all weather conditions. Hercules Cutting Oils contain activated sulfur to provide anti-weld properties, reduce friction and prevent excessive heat generation, thus minimizing material expansion resulting in ill-fitting joints. The high film strength of Hercules Cutting Oils maintains a continuous contact of the lubricant with the work assuring quick, accurate and high quality cuts with minimal tool wear. Lubricants contain no nitrosamine forming compounds or chlorinated oils.
> 
> Clear Cutting Oil
> A blend of high quality mineral oils with sulfur base. Used for cutting clean, unbroken threads during manual or low rpm threading machine operations on small sizes of steel and brass pipe. Also applicable for hacksawing and light drilling. Will not stain copper or brass materials.
> ...



If you were running a high speed screw machine or a CNC machining center the Dark Cutting Oil is perfect. For manual machining the Clear Cutting Oil is best & it allows a good view of the tool point - critical when disengaging the half nuts at the end of the cut.

Google Hercules 40-110 (1 pt. container) for about $8, quarts (40-115) about $12.

Then you'll want to examine your setup. Keep tool overhang to a minimum, use tailstock support if possible, etc. Brass turns & threads to a glass like finish when all the parameters are right.


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## calipsoii (Jun 22, 2014)

Awesome tips, thanks Barry! I'll pick up some of the Hercules cutting lubricant next time I'm placing online orders. 

It might be a couple weeks before I'm able to do anything at the lathe anyways. I touched the bottom of a hole I was boring today and the brass grabbed my boring bar. On the little Taig it might not have been a big deal, but this machine doesn't really mess around when things get stuck.


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## precisionworks (Jun 22, 2014)

Ouch! That's an expensive way to learn.

Since there's no DRO you'll want to figure out a way to manually depth stop the tool point. The easiest way is with a stop block clamped to the forward way. My lathe came with a micro adjustable stop:






It's just as quick & accurate to use a mag back dial indicator or a MightMag with indicator. For whatever reason the mag back indicators are my first choice. Even when you get a DRO installed the mechanincal stop or dial indicator is useful. This thread from the UK based Model Engineer shows some shop built designs: http://www.model-engineer.co.uk/forums/postings.asp?th=67207


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## calipsoii (Jul 7, 2014)

The new boring bar arrived and I was very careful this evening not to break it. Easy to do considering how nervous I was after the last accident! The force of the previous impact actually broke a few other things than the boring bar, namely a handful of bolts that had the threads ripped right off them. oo:






I spent some time this evening practicing internal threading but not getting very far. Twice during the threading process I heard/saw the threading dial skip a thread on the leadscrew. It's very frustrating as the very next pass has heavy chatter and noise while the previous passes were quite quiet.

The threading dial is one of those pivoting ones that you push against the leadscrew and tighten down with a socket-head screw:










The skipping happened twice: once during a cut and once while moving the carriage with the handwheel. I'm not really sure how to prevent it other than mashing the stupid thing in place and cranking it tight. I'm quite certain that the skipping caused the bad thread cuts though, so I just need to find a way to prevent it from happening...


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## precisionworks (Jul 8, 2014)

calipsoii said:


> ... I'm not really sure how to prevent it other than mashing the stupid thing in place and cranking it tight. I'm quite certain that the skipping caused the bad thread cuts though, so I just need to find a way to prevent it from happening...



On short threads (most of what I do) the threading dial stays in the drawer. Finish a pass, step on the foot brake & kill the motor power, _[FONT=&quot]leave the half nuts engaged[/FONT]_, back the carriage up to the start, reset tool depth, repeat until done. You'll need a small relief cut to land the tool but it's not hard to do at 100 rpm.

Takes a few seconds more time this way but you'll never have to worry about missing the pickup point. The important thing is stepping on the foot brake & killing motor power but that isn't a difficult skill to learn. It does cause more wear on the half nuts, twice as much to be exact, & that might be an issue if cutting threads 24-7-365. If you cut only a dozen or two threads weekly you'll likely never see the difference.


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## calipsoii (Jul 8, 2014)

Hmm, good suggestion Barry. The lathe is too small for a foot brake unfortunately - the smallest I've seen one on is a 12x36 (this is a benchtop 10x22). The manual recommends your procedure for cutting metric threads and it simply says to kill the power using the shut-off switch, so maybe I'll try that. At 100RPM everything stops moving _fairly_ quickly so it might be good enough even without the brake. Will let you know - I'd certainly rather spend a bit of extra time and be guaranteed to get it right rather than having a skipping dial (that's beyond my control) screwing up the workpiece I just spent an hour on.


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## mddolson (Jul 8, 2014)

Love your setup. I'm envious.
I have a Craftex 3 in 1 with 3" chuck. But I'd never expect anything better than 0.001" precision on it.

Mike D


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## Jakefreese (Jul 9, 2014)

New lathe is always a good thing! I am still getting things lined up to haul my new to me monarch 18x60 engine lathe home. Pushing 5 tons....


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## precisionworks (Jul 10, 2014)

Jakefreese said:


> ... monarch 18x60 engine lathe ...



Without photos it didn't happen :nana:


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## Jakefreese (Jul 10, 2014)

I'll get some pictures while we're loading it! There is a 10ee local to me that I wish I could get but the wife didn't like the idea of dropping more money on machine tools.


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## precisionworks (Jul 11, 2014)

Jakefreese said:


> ... There is a 10ee local to me ...


The 10EE & the Hardinge HLV-H are the finest small machines ever built & both are 12x20. Spindle runout on the 10EE is 40 millionths standard or 30 millionths optional & the Hardinge is similar. A new 10EE runs a bit under $100k & a new HLV-H is about 1/3 less. Both weigh over 3000# so getting one loaded onto your trailer & unloaded at the destination takes planning (as in forklift or tow truck). 

If you have some time look at the history on Tony's site: http://www.lathes.co.uk/monarch/page2.html


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## Jakefreese (Jul 11, 2014)

I have seen that monarch page. Lots of cool info, I don't think there are any other lathes that have a following like the 10ee has. I know someone that is getting there 10ee refurbished at monarch and the new ones are north of 140k now. I'll eventually get my hands on one! The big ole engine lathe will get the job done for now!


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## toastystuff (Jul 13, 2014)

Wanna bore out my v11r ti+ and tcr10 ti to accept bigger batteries?


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## calipsoii (Jul 15, 2014)

toastystuff said:


> Wanna bore out my v11r ti+ and tcr10 ti to accept bigger batteries?



Sorry toastystuff I'm the wrong person to ask for that.



precisionworks said:


> On short threads (most of what I do) the threading dial stays in the drawer. Finish a pass, step on the foot brake & kill the motor power, _leave the half nuts engaged_, back the carriage up to the start, reset tool depth, repeat until done. You'll need a small relief cut to land the tool but it's not hard to do at 100 rpm.



Had a few chances to try this method out this evening:

1st attempt I forgot I was working inside the piece and accidentally turned the cross-slide dial the wrong way while cutting the relief, gouging a huge ring and scrapping the piece. 
2nd attempt the threads had this odd 'intersection' in them halfway through. Beginning of thread was fine and end was fine, but part-way through it's like they overlapped. The chatter got pretty bad so I think the tool jumped. After that I pulled the workpiece into the jaws more and got rid of some tool overhang and tightened some gibs and things had less chatter. 
3rd attempt I cut the best internal threads I've done yet... a few sizes too small. It was late and I misread the blueprint and bored the hole too small before cutting. 

Overall a productive night full of lots of learning and stupid mistakes. 

2nd attempt:





3rd attempt:


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## MRsDNF (Jul 17, 2014)

Nice effort on the last one. It does not matter how long you have been machining occasionally we all still slip up, just not as often, touch wood.


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## precisionworks (Jul 17, 2014)

calipsoii said:


> 1st attempt I forgot I was working inside the piece and accidentally turned the cross-slide dial the wrong way while cutting the relief, gouging a huge ring and scrapping the piece.



Internal is like working with a mirror but you're catching on fast. 



> I pulled the workpiece into the jaws more and got rid of some tool overhang and tightened some gibs and things had less chatter.


The small details are really important - 

Minimum tool overhang (or minimum threading tool projection if you prefer) 
Part rigidly secured - this may be a chuck (3/4/6 jaw etc.), a collet running in a collet chuck or sometimes inside the headstock taper, a dedicated boring fixture, etc. Most of my flashlight boring is done with the body held by a Delrin bushing machined for a size on size fit. Surefire L1 shown below is typical:






The thick walls of the bushing allow good tightening without distorting the thin aluminum tube. 
Sharp/fresh tip on the threading tool. It may be hard to see that the tip is dull or chipped unless a magnifier is used. 
Tip height set .010" (.25mm) above center to avoid rubbing the bottom of the tool. 
Cutting tip & part flooded with lubricant (TapMagic is great but any lube is better than none. The lube helps avoid stick-slip than leaves a rough finish). 
Gentle depth of cut. 

You found out what doesn't work & that's a valuable lesson :devil: You'll be cutting perfect threads in no time.


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## calipsoii (Jul 18, 2014)

Finished the part last night on the first try. As you've mentioned Barry, by not doing all the things that don't work, it goes a lot smoother. :laughing:











Still need to practice threading a bit. Even last night I am having an issue where the first 3-4 threading passes are very noisy and choppy. It's only on 5+ passes (threads 60% complete) that suddenly the chatter disappears and there's a nice hissing as it cuts. I have a feeling it has to do with the increased amount of material on the cutting edge. I'm using this tool, and it's not until the cutting edge is loaded up with ~0.028 of material that the action gets smooth and the chip comes off in a nice curl. 

Can't tuck the tool any further into the holder and the piece only has ~0.2" hanging out of jaws. Assuming a 0.038 DOC I increased the infeed as follows:

0.001 scratch cut 
0.010 
0.020 
0.025 (chatter disappears in 2nd half of threads) 
0.030 (chatter disappears entirely) 
0.034 
0.037 
0.037 (spring pass) 
0.038 (cross-feed only, no compound feed) 
 I wonder if it might also be the thin walls of the material? I'm working with 1" round bar and the threads being cut are 15/16x20. Maybe they're ringing? I'll try to pick up some 1 1/4" to see if it does the same thing...


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## gadget_lover (Jul 18, 2014)

I wonder if you are getting rubbing on the sides of the inserts? I've used those triangular inserts for inside threading and find they need a bit of side relief. 


BTW, there is a nice formula for determining how deep you should go for each pass. Interestingly, their example shows a depth of .037 so it would be about the same.

http://www.sandvik.coromant.com/en-...g/formulas_and_definitions/pages/default.aspx

According to that formula, you are pretty close to the "proper" infeed. They show:

Pass 1 .009
Pass 2 .008 (more)
Pass 3 .006 .
Pass 4 .006 .
Pass 5 .004 . 
Pass 6 .004 (more)


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## calipsoii (Jul 27, 2014)

I've switched back over to working on my primary project and I've been having some good success.

I machined the driver pill which includes a lot of threads. They look pretty good to my eye:





But unfortunately they don't fit in the prototype host I had already built some time ago:





The threads in the prototype were made with a 3/4x16 thread tap. Since it's a tap and comes from the factory ready to cut within tolerance, I have to assume that the tapped threads are the accurate ones and the ones I cut are inaccurate.

Tons of reading has told me that the formula for determining compound infeed when using the 29.5 deg modified setup is:

0.708 / TPI 
 So plugging in my values:

0.708 / 16 = 0.04425" 
 This is the exact amount of infeed I used when cutting the pill threads. I don't have a thread mic or 3-wires (I plan to pick one up eventually) so I cannot say what their finished pitch diameter is. They definitely will not fit into the tapped hole though. I started experimenting, and at 0.048 compound infeed the resulting threads screw into the tapped hole just beautifully. They also have a much smaller flat on the crest of each thread. 

I wonder if any of you guys have any idea why the 0.708 constant produces threads that are too large? I've triple-checked and the slide is set at ~29 degrees. There's no backlash in the screws. Cutting tool is new and sharp. Lots of cutting lubricant. Several spring passes and a 0.001" cross-slide infeed at the end.

I can start using 0.750 / TPI as my new calculation (as one guy on a machining forum suggested) but if I can identify the root issue and fix it I'll bet I have a much easier time down the road.


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## precisionworks (Jul 28, 2014)

29.5° isn't a set-in-stone number, any angle from 26° to 29.5° works wells (but changes the trig calculation). 



> ... unfortunately they (the threads) don't fit in the prototype host I had already built some time ago ...


For production machining (where all your parts have to hit an arbitrary standard) you'll want a thread gage, either a plug for ID or a ring for OD. For custom & one off jobs don't worry about the numbers too much, keep gradually increasing the depth until it fits the part. There are times you may have to touch a flat file to the thread crests to make the fit.



> threads in the prototype were made with a 3/4x16 thread tap. Since it's a tap and comes from the factory ready to cut within tolerance, I have to assume that the tapped threads are the accurate ones


Depends. A high accuracy tap (Class 3) will be closer to the Machinery's Handbook specs than a medium accuracy tap (Class 2). Some less expensive taps cut a sloppy Class 1 fit so the resulting thread may be all over the place & still gage correctly. 

When in doubt remember The Machinist's Mantra:


> Hammer to Fit, File to Finish, Paint to Match


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## calipsoii (Jul 28, 2014)

precisionworks said:


> Depends. A high accuracy tap (Class 3) will be closer to the Machinery's Handbook specs than a medium accuracy tap (Class 2). Some less expensive taps cut a sloppy Class 1 fit so the resulting thread may be all over the place & still gage correctly.



The tap is a pretty good one (Guhring 2B H3) and I've babied it so it's probably as close as I have to a proper size reference.







precisionworks said:


> For production machining (where all your parts have to hit an arbitrary standard) you'll want a thread gage, either a plug for ID or a ring for OD. For custom & one off jobs don't worry about the numbers too much, keep gradually increasing the depth until it fits the part. There are times you may have to touch a flat file to the thread crests to make the fit.



I'll probably cut quite a few of these threads before the project is done so I made a little tester to check fit. I first tapped the ring (with the above tap) then used the lathe to cut threads on the plug until it threads nicely into the ring. Not as good as a proper micrometer but it's a quick way to test that they're not oversize.







precisionworks said:


> When in doubt remember The Machinist's Mantra:
> 
> 
> 
> > Hammer to Fit, File to Finish, Paint to Match



That got a good laugh out of me this morning, thanks man.


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## BVH (Jul 28, 2014)

And if it STILL doesn't fit......Get a BIGGER hammer!


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## Jakefreese (Aug 24, 2014)

I'm hauling it home next weekend


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## precisionworks (Aug 24, 2014)

Nice ... looks like a pre WWII machine that was first powered by overhead lineshaft & later electrified. Any way to confirm the date of manufacture?


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## gadget_lover (Aug 24, 2014)

Looks nice Jake. Judging from the levers, that seems to be a 12 inch, right?


Dan


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## calipsoii (Aug 24, 2014)

Oh man Jake, that is a beautiful (and enormous) piece of equipment. And to think I complained bitterly about cleaning the cosmoline off my little one! You're going to need to post some pictures of your progress getting it all setup in its new home.

It's nowhere near the scale of your task, but I spent a few hours removing the chips from under mine and I already feel better. A clean workspace (be it for metalworking, electronics or cooking) always makes me happy.


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## Jakefreese (Aug 25, 2014)

precisionworks said:


> Nice ... looks like a pre WWII machine that was first powered by overhead lineshaft & later electrified. Any way to confirm the date of manufacture?


From the UK monarch web page it appears to be a pre ww2 AA. The original motor mounting hardware is on the back of the lathe where the motor originally was. I forgot to get a picture of the lot number, I don't know if the serial number was there also. I didn't move the steady rest to see if the other numbers were there. From some of my research it's looking like it is 4000-5200 lbs. I down loaded the book for it and it had the rigging recommendations for it also. 

The machine is very very clean and well cared for by the previous owner.


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## Jakefreese (Aug 25, 2014)

gadget_lover said:


> Looks nice Jake. Judging from the levers, that seems to be a 12 inch, right?
> 
> 
> Dan


it's a 17"


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