# Threading Tools Keep Breaking



## armytbone (Feb 24, 2016)

I've been tinkering with my new G4000 for a month now. Some decent success turning W1 to a set taper and finishing it smoothly. I decided to try threading as my next learning project. 

I'm trying to turn 1/2 inch rod to have an end with one inch of 8mm-1.5. This will fit the tool post turret bolt to hold my tool post secure. 

I had a 1/2 inch carbide tipped bit and also a 5/16 Grizzly carbide, a McMaster-Carr indexable carbide insert bit, and a McM-C carbide bit. All had 60 degree points for threading. 

First I tried on W1 tool steel. All of the bits chipped. 

Then I tried on cheap hardware store steel rod which I knew was softer, thinking maybe I shouldn't turn tool steel. 

My inserts broke and the point under the insert, on the tool, chipped. 







I made sure the tips were on center, using a dead center as a reference. I only advanced the tool .005 per pass. Spindle speed was slow. 

Seeing as I'm a newbie, what is happening? Why are my bits being eaten by even hardware store rod, considering I have turned tapers using bit from the same makers and they were fine?

Thanks for the advice. 


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## coffmajt (Feb 24, 2016)

What kind of cutting oil did you use ?  What degree did you have your cross compound set to?  29.5 is what you need. Also I have learned to back out after each pass with the compound feed with it set on a zero then advance it back to the zero before advancing the cross compound by .002 to .003. You may need a little faster spindle speed as well.  Hope this helps. Jack


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## Karl_T (Feb 24, 2016)

You are going to be WAY better off learning to thread with HSS...

Carbide chips easily, you already know that. it just doesn't work well with the very low speeds for manual lathe threading.

Carbide threading tools work GREAT on my Hardinge CHNC lathe at 1000 RPM.

Karl


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## T Bredehoft (Feb 24, 2016)

Not that it will keep your tools from chipping ( yeah, go with HSS) you might find it easier with an inch sticking out of the chuck and forget the live center. Under no circumstances (until you find out you know better) take a depth of cut of more than .005 on one side. .002 or .003 is really enough until you're really comfortable with threading.


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## Mork (Feb 24, 2016)

I'm fairly new to machining but i have successfully cut thread probably 10 times (not counting a couple of mishaps). First off, those are not threading tools you are using. Threading tools have a very sharp point. Threading requires quite a few passes and the amount you take off needs to be very slight on the final few passes. the compound has to be set to 29.5 degrees and the tool dead square and on center. Basically you only use the compound to move the tool in with each new pass so you are only cutting one side of the cutter. 

Here's a very good two part video:


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## Billh50 (Feb 24, 2016)

As the others have stated, the tools you show are not for threading. Threading tools have a very very slight radius if any at all. I myself do not set my compound at 29.5 degrees. Some people, myself included, will just set the tool at 90 degrees to part and feed in with the cross slide. The cut depth should be very small and last couple only .001 - .002 deep.
High Speed tools do much better on the smaller lathes than carbide. Also if you are only threading 1 inch of the bar then move it closer to the chuck with no center. You will get much more rigidity that way.


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## Mork (Feb 24, 2016)

Wow...  I tried going straight in and it didn't work well at all. It cut rough and was difficult to control on the final passes. Maybe with a larger more solid lathe it would work better but my results were not good.


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## Wreck™Wreck (Feb 24, 2016)

WAY to much nose radius on the tools shown, none appear to be threading tools.
Threading 1018 mild steel stock is dodgy at best, small wonder that you destroyed a few tools.


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## Tozguy (Feb 24, 2016)

Same thing happened to me when starting. Chipped a bunch of carbide tools before switching to HSS.
Once my confidence was up and I tried carbide again at higher speeds it was better. But it is still too easy to chip a carbide for my liking.
Since brazed carbide tools need sharpening too there is really no way to avoid learning to grind tools yourself. As already said those are not threading tools. Spend the time to practice tool grinding and use sharp tools.  
Threading next to a live centre is not rigid enough for what you are doing. A dead centre is better but cutting close to the chuck is best. Locking the cross slide and compound for the cut might help if the gibs are not broken in and set snug.
Hang in there, your eureka moment is coming!


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## wawoodman (Feb 24, 2016)

You might want to pick up some 12L14. Very nice on a lathe.

And like everyone else has said, HSS, and take it easy!


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## T Bredehoft (Feb 24, 2016)

As others have said, you haven't used any threading tools. the included angle on  a threading tool is 60º, the left hand and triangle tools are included angle 120º, twice the angle  you need.


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## Andre (Feb 24, 2016)

Rough out single pointing then clean up with a die. When threading mild steel I get it close then finish it with a file to have some hope of a decent surface finish.


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## TOOLMASTER (Feb 24, 2016)

this is why I only use taps and dies unless I realllllllllly have to do threading


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## kvt (Feb 24, 2016)

My first couple of tries with a carbide it broke like yours.   I found that you have to back them off before reversing each time or it will chip.  Light cuts, on mine.  I have cut a few threads since getting mine, some look better than others.  Plenty of cutting fluid, helps, and even with the tail supported it seemed to give,  thus I put it as close to he chuck as possible to thread.   HSS is also good.   Keep trying and you can get it.


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## armytbone (Feb 24, 2016)

And this is why I joined the forum. Thank you!! Many good things to learn. I need a threading tool. I need a threading setup on the compound. I should go shallower per pass. At least it's an affordable mistake and a good investment in learning! 


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## Wreck™Wreck (Feb 24, 2016)

T Bredehoft said:


> As others have said, you haven't used any threading tools. the included angle on  a threading tool is 60º, the left hand and triangle tools are included angle 120º, twice the angle  you need.


There you would be wrong, an equalateral trianglular insert has an included angle of of 60° by definition, however the relief angle on a tool may make a fine OD turning tool yet impossible to thread with depending on the lead.


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## T Bredehoft (Feb 24, 2016)

Wreck™Wreck said:


> an equalateral trianglular insert has an included angle of of 60° by definition



My error, Wreck, you're absolutely right.  I guess it's been too long since I had to think like that.


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## Paul in OKC (Feb 24, 2016)

If you haven't heard it yet, the inserts are not threading inserts.  Looks like two of the three brazed on carbides might have been. Like Wreck said, the angle on the inserts is correct being a 60* included angle, but not relieved for threading. Most threading tools have about an .008 radius max. For that small of a diameter, my guess is you are going way to slow. Carbide does not like to cut slow. Best to start with a HSS blank and grind it for threading. Did you use any cutting oil?


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## dave2176 (Feb 24, 2016)

I love single point threading and have only used carbide. Make sure your tool height is exactly centered. You can set your compound to 29.5* off perpendicular to the spindle if you like but I rarely do that anymore. I just use the cross slide for adjusting depth of cut most often. I don't see anything in your photo that wouldbe a good threading bit, turning yes but not threading. Here's a picture of what I use.  Sorry it's not the best quality,  the camera on my tablet is nothing to write home about.


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## derf (Feb 25, 2016)

Looks to me that you have too much flex in your tool post/tool holder. Typically things start out fine but as you get towards the last pass, the tool will grab and go under center, causing a chipped cutter. I can tell you if you are using a QCTP, a wedge type has a big advantage over a piston type.


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## epanzella (Feb 25, 2016)

Like others have said, those are only turning tools. Being a beginner on a light lathe you're only stacking the deck against yourself using carbide. Carbide won't tolerate a lack of rigidity and it  also doesn't like it when you stop the spindle before backing off the cutter. Get yourself a fishtail gauge and grind some HSS threading tools. I grind most tools freehand but my threading cutters are ground on a disc sander with a miter gauge. I use a piston type QCTP and feed with the Xslide. You might also check your setting for that thread you're cutting. That pitch looks a mile faster than a 1.5mm pitch to me.


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## Fabrickator (Feb 25, 2016)

I use HSS threading tools, .002-.003 cuts, flood cut with Tap Magic oil, use lower than higher speeds so I won't crash on a shoulder.  Keep it as close to the chuck as possible, I use a center when I can.  Proper support is very important.  I make a cut and stop. back out a couple thousand (DROs) and then reverse back to the start. I never use the threading guide and instead leave the feed engaged until it's done. When I started out, I actually "taped" it engaged, so I wouldn't forget (by habit) and disengage it.


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## Paul in OKC (Feb 25, 2016)

If you need to stop the spindle before backing the tool out, try cutting a relief groove where the thread ends. That way you can stop the spindle and the tool wont be engaged in the material. That will help stop the breakage as well. If you can't cut a groove, practice pulling the tool out at the end before shutting off the spindle. Disengage and pull out at the same time. Kinda like rubbing your head and patting your tummy, but it works!


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## TC0853 (Feb 25, 2016)

A lot of good ideas here. In my mind use HSS. Just grind your own tools and save a buck or two. Until you get the hang of it stay in close to the Chuck and don't have the tools sticking out too far from the toolpost either. This is just me, but I set the compound straight in, and no more than 3 or 4 thou per side. If you're close in to the Chuck you can lose the live center too, it's just in the way. If you're into learning, there's a guy down in Phoenix called Swarfrat, he's got some nice instructional videos he puts out, and he's easy to understand. I had already learned to thread when I bought his videos but you could probably do well with at least buying the one on cutting v form threads. He'll have you setting the compound at 29.5 but that's your call. Once you've cut your first decent threads you'll say "I can do this, piece of cake".it is too, just stick with it and get your tools ground up good and you'll be counting threads in your sleep. After you've mastered the thread dial,  get used to leaving the half nut engaged and backing the motor up because you'll need to know that to metric thread.


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## mmcmdl (Feb 25, 2016)

Not mentioned on here either . If threading up to a shoulder gives you the chills , machine an undercut to the root diameter and chamfer it 45 degrees . Turn your tool upside down and thread away from that shoulder IN REVERSE !! Nice little trick on ID threads .


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## BGHansen (Feb 25, 2016)

I primarily thread with a carbide insert tool from Shars (picture below).  I bought inserts off eBay from a number of sellers, usually get them for about $3 each.  I, like most others, set my compound to 29.5 deg.  That way you are cutting on one edge and just dusting off the other.  I take around 0.003 per pass and use cutting oil liberally.  What the heck, bought a gallon of Rigid non-stinky oil for under $20 which will last me a lifetime of threading. 

If I'm threading up to a shoulder, do an undercut to the root diameter for pucker factor.  You need some relief anyhow if you need to nut or whatever you're threading into to bottom out on the shoulder.  If I'm cutting metric threads, I can't disengage the half-nuts.  Just shut the lathe off early and turn the chuck by hand.  I've used the 3-wire method to check for depth, but find a thread micrometer to be much less cumbersome.  I get at least 2 feet of threading in stainless before the tip of the insert starts to go.

I also will thread with HSS, but am getting lazy in my old age and go for the inserts in general.  Pretty cheap and have worked well for me.

Bruce


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## CluelessNewB (Feb 25, 2016)

There are also HSS insert tools available from Arthur Warner  http://www.arwarnerco.com/


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## LEM (Feb 25, 2016)

Watch the video by Tubalcain.  I did and cut perfect threads the first time.  I used Carbide and turned as slow as machine would go.  I have done 1/2 and 1 1/4 threads on both steel and aluminum.  It takes me maybe a dozen or more passes but then I am such a neophyte that I am super cautious.


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## royesses (Feb 25, 2016)

I've been using the Arthur R. Warner HSS tools. I love them. You can re-sharpen the inserts and they work great on mini lathes. The center cutting 60° tool in the 5 piece set specifically states it can be used to cut threads. While expensive compared to the import tools, they are superior. I also enjoy supporting a family owned U.S company. I get mine from LMS, but they are the same price on the A.R. Warner web store.

Just my uninformed non-real machinist opinion of course.
Roy


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## Tozguy (Feb 26, 2016)

BGHansen said:


> If I'm threading up to a shoulder, do an undercut to the root diameter for pucker factor.  You need some relief anyhow if you need to nut or whatever you're threading into to bottom out on the shoulder.  If I'm cutting metric threads, I can't disengage the half-nuts.  Just shut the lathe off early and turn the chuck by hand.  I've used the 3-wire method to check for depth, but find a thread micrometer to be much less cumbersome.  I get at least 2 feet of threading in stainless before the tip of the insert starts to go.
> 
> Bruce
> 
> View attachment 123191



Cutting metric threads without disengaging the half nuts was a lot more fun after installing a crank on the back end of the spindle. Now I do the whole job by hand, no power and no tight sphincter.


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## BGHansen (Feb 26, 2016)

royesses said:


> I've been using the Arthur R. Warner HSS tools. I love them. You can re-sharpen the inserts and they work great on mini lathes. The center cutting 60° tool in the 5 piece set specifically states it can be used to cut threads. While expensive compared to the import tools, they are superior. I also enjoy supporting a family owned U.S company. I get mine from LMS, but they are the same price on the A.R. Warner web store.
> 
> Just my uninformed non-real machinist opinion of course.
> Roy


Good point on supporting a U.S. company.  I work at the GM plant in Lansing, MI; Lansing Grand River where Cadillac CTS, ATS and Chevy Camaros are built.  We would appreciate the rest of the country considering our products when they are new car shopping.  It is a global economy; our transmissions come from France, wire harnesses from South America, many other parts from Mexico, Canada, China and Korea.  Regardless, about 1500 Americans putting them all together.

Bruce


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## aliva (Feb 26, 2016)

This is one type of insert you need. there are other design's, check out Carbide Depot.com


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## BGHansen (Feb 26, 2016)

aliva said:


> View attachment 123211
> 
> 
> 
> ...


Secret decoder ring required for threading inserts.  The one in aliva's post is probably a 16 ER AG60.  The first two numbers are the insert size.  06 is 5/32", 08 is 3/16", 11 is 1/4", 16 is 3/8", 22 is 1/2" and 27 is 5/8".  The first letter will be E for external threading or I for internal threading.

The next letter is R for right hand threads, L for left hand.  The ending numbers are for the threads per inch/range of tpi.  A60 is 16-48 tpi.  AG60 is 8-48 tpi.  G60 is 8-14, N60 is 5-7.  If they end in "UN", the number ahead is the tpi (one thread size, no range).  For example, 16 ER14 UN is a 3/8" insert, external right hand thread at 14 tpi.  Metric inserts are similar; number followed by GM.  A 22 IR3.50 GM is a 1/2" insert, internal right hand thread at 3.5 mm pitch.

I mention it because I bought a set of ten 16 IR 14 UN's off eBay for around $22.  Got them and noticed the threading "V" was not as pronounced as the 16 IR AG60's I already had.  Many places sell them, best prices I've found are on eBay though you'll likely be getting them from China.

Bruce


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## Silverbullet (Feb 26, 2016)

This is one area where a turret lathe is superior , the die heads are adjustable and collapsible taps will out perform single point threading. Another problem with cutting threads is the pressure put on the tool and holder and cross slide makes them flex which is what will cause the chipping your getting. My Logan lathe hates single point threading I've done it and have watched the compound slide bend and flex at the beginning and ending of the cuts.


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## planeflyer21 (Feb 27, 2016)

BGHansen said:


> Secret decoder ring required for threading inserts.  The one in aliva's post is probably a 16 ER AG60.  The first two numbers are the insert size.  06 is 5/32", 08 is 3/16", 11 is 1/4", 16 is 3/8", 22 is 1/2" and 27 is 5/8".  The first letter will be E for external threading or I for internal threading.
> 
> The next letter is R for right hand threads, L for left hand.  The ending numbers are for the threads per inch/range of tpi.  A60 is 16-48 tpi.  AG60 is 8-48 tpi.  G60 is 8-14, N60 is 5-7.  If they end in "UN", the number ahead is the tpi (one thread size, no range).  For example, 16 ER14 UN is a 3/8" insert, external right hand thread at 14 tpi.  Metric inserts are similar; number followed by GM.  A 22 IR3.50 GM is a 1/2" insert, internal right hand thread at 3.5 mm pitch.
> 
> ...



I learn something on here very often but the vexing question of how inserts are titled has bugged me for years!

Thanks Bruce!


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## Chris Hamel (Feb 27, 2016)

I have done fine with the brazed on carbide bits.  A couple of things.  One - I grind a lot more relief on the bit from the way it comes from the factory.  I use a green silicon carbide wheel..  Second thing I have found is that when I get near the end of the operation, I will often repeat a pass without advancing the compound  it will still take off some metal  (guess my old South bend has that much flex in it).  Keep in mind that when you get near the end, you are only advancing a few thousandths


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## Tozguy (Feb 27, 2016)

Rigidity, deflection, and tool life/cost are reasons why I thread by feeding with the compound set at 29.5 deg. and this, even for fine pitched threads. It also gives me only one side of the tool to sharpen .
A narrow deep cut works better on my hobby lathe. A wide but shallow cut (as in plunge cutting) is an invitation to chatter. I don't like it when a clean up pass has a lot to clean up.

It is important when sneaking up on final thread dimensions that I can rely on getting what was dialled in. I am a fan of smooth and close fitting threads which doesn't happen when there is stuff going on that I don't control. So the lathe is set accordingly and worked well short of its cutting limits.


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## kennycrawford (Feb 27, 2016)

I am a relative newbie to machining too. I own the G4000 lathe and have threaded on it. On the small diameter you stated, 8mm, the fact that the larger bits you were using probably rubbed on the thread while it was cutting. It is because for threading you are cutting a spiral and you need to have clearance for the thread to pass safely as the tool moves down. I ran into this with the insert tooling bought with my lathe. I ruined a bunch of stuff before finding forums like this and Youtube to help me along. I hope I explained this clearly, I am guessing one of the other previous posts already mentioned this but I have no background in the machining trade and the terminology can still be foggy for me sometimes.

The G4000 lathe in itself is a project. Between the Pitkin donut , 4 bolt clamps, gib straightening, headstock aligning, extending the cross slide and putting bearings in the compound and crossslides, I have been busy learning how the machine operates. I can tell you that what is in my garage now works so much better than when I purchased it nearly 2 years ago it might as well be a different tool. Just my observation.


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## benmychree (Feb 27, 2016)

derf said:


> Looks to me that you have too much flex in your tool post/tool holder. Typically things start out fine but as you get towards the last pass, the tool will grab and go under center, causing a chipped cutter. I can tell you if you are using a QCTP, a wedge type has a big advantage over a piston type.


I have had both wedge and piston type tool holders, and there is really no difference in ridgidity between the two; I have accidently forgotten to lock the holder in, and even parted off that way with no chatter.  According to Aloris, the only reason for the wedge type is that it is more positionally accurate.  As to threading tools, I very much agree with the posters on this thread; use HSS, learn to grind them from scratch, or use the Aloris threading tool, which is form ground and only needs sharpening on the top.  For internal threading there is the HSS boring type tools with integral shanks or threaded on tips made by Bokum; they are also form relieved and sharpen on top, preserving the thread angle for the life of the tool; I have found many of them on E Bay, and they also make lead style and flat bottom boring tools that are a pleasure to use.  I take issue with the tiny cuts recommended in the posts; perhaps they are necessary for tiny machines, but they will tend to dull cutting tools more rapidly that deeper cuts, especially the first cuts can be deep, then ease up.  Also I see no mention of lubricants, which are quite necessary for threading steel; I use Tapfree for most all lathe work.


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## armytbone (Feb 27, 2016)

What a wealth of info. Thanks everyone for the replies! Just digesting all of the tips is a task unto itself. At first, the thought of angling a tool with a 60 degree tip made no sense. If I turned it 29.5 degrees, it would end up as a flat cutting surface parallel to the workpiece. That, in turn, wouldn't make any grooves! But then it clicked. As everyone stated, I didn't have the correct cutting tools. A correct tool that can be fed on the 29.5 degree angle set on the compound would allow the tool to cut on one side only, rather than feeding at 90 degrees and causing immense stress on the tip and both sides of the tip. It's no wonder that I broke a few! Alas, I will be ordering the correct tooling.

Which brings me to another concern -- the tool post. That four position turret tool post holds 1/2 inch bits a tiny bit low of center. I have a handful of feeler gauge fingers to be able to shim, but is there a good QCTP for the G4000 that would make for a good upgrade? Thanks for ideas.


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## timmeh (Feb 27, 2016)

Side(front/leading edge relief) clearance is your first issue, and applies to HSS as well, look up helix angle in threading literature.
Spindle speed is too slow for carbide tools.
As has been noted most of the tools you have shown are not "threading tools", there's one in there somewhere, even that probably has little or no clearance.


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## kennycrawford (Feb 28, 2016)

As far as a tool post goes I made my own from a kit I bought from Metal Lathe Accessories for the G4000. They say you can make all of it on the lathe, but a mill will be very beneficial for that project. I now have 4 lathes and have made the tool posts on all of them except the Taig. I bought the tool post for it from Little Machine shop. I have next tuesday off, if you would like I will take some pictures. Just realize I am very much still learning too.


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## Tozguy (Feb 28, 2016)

Please, just to be sure about your post, the tool is NOT set at 29.5 deg. to the work. The tool has to be set at 90 deg. (perpendicular) to the work usually with the help of a fishtail gauge. But FIRST set the compound to 29.5 deg. from perpendicular to the work. 

Re the QCTP, a Phase II set with an assortment of holders would be a good place to start. The swing of your lathe determines the size you need. Now that I have used a piston style one for a few years now it seems like the best money I have spent so far.


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## dave_r_1 (Feb 29, 2016)

This thread has some of the problems I had with my lathe for doing threads, along with how I dealt with them, along with pictures of the results.

http://www.hobby-machinist.com/threads/when-is-it-good-safe-to-engage-the-power-feed-lever.43754/


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