# Havin Trouble Cutting Threads Correctly



## Ray73 (Aug 5, 2015)

After figuring out how to set up the change gears on my 8x14 HF/LatheMaster lathe I want to learn to cut threads and have been practicing but my threads aren't a nice v shape like they should be. I am using a 60 degree HSS tool that I ground and have tried it with a store bought carbide 60 degree tool as well.  My threads always "point to the right of the chuck" is the only way I know how to explain it. I am going by the videos and articles that I have read. I have my compound set to 30 degrees like I see done in the videos and have lined up my tool with a fish tail gauge. I am using the compound slide to advance in a couple thousandths after each pass and I always engage the half nuts on the same number. I'm cutting 20 tp 
	

		
			
		

		
	



	

		
			
		

		
	
 i and that seems to come out correct but they just aren't shaped right. Could it be that my compound is different and needs to be set to something other than 30? I did try 29 once but it didn't really make any difference. I have attached a pic and maybe someone will see this and be able to tell right off what I am doing wrong. Maybe someone even has this same lathe and can give some tips on threading with this particular lathe. Thanks in advance!


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## T Bredehoft (Aug 5, 2015)

Perhaps you should set your compound to 60º?  The compound needs to be 30º off square with the work, not 30º off parallel with it.


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## pdentrem (Aug 5, 2015)

Some lathes are marked opposite like Tom has suggested. 60 instead of 30. I posted apicture awhile back showing a easy way to set the top slide using a drawing triangle.
Pierre


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## Handy4563 (Aug 5, 2015)

Looks like to me the thread cutting bit is not 90 degrees to the shaft you are threading.  I have cut lots of threads on my lathe, but if the cuter is off the threads will look off to one side.


Sent from my Venue8 3840 using Tapatalk


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## RJSakowski (Aug 5, 2015)

Your problem is with how you align the threading tool.  After you set your compound to the desired angle, you need to adjust the alignment of the threading tool.  The tool must be set so the angle of each face to the  spindle axis (work) is the same.  This is normally done with a fishtail gauge, also called a 60 deg. center gauge or threading gauge, (a little gauge with 60 deg. Vee cut into the end).  The threading tool is adjusted so it matches the vee when the other end of the gauge is contacting the work.

Bob


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## RJSakowski (Aug 5, 2015)

Here is a Starrett center gauge.  
	

		
			
		

		
	




Bob


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## Doubleeboy (Aug 5, 2015)

You might also simplify your life a bit and set tool square with work using fishtail gauge like others mentioned and then use crossfeed to control depth of cut.  On threads as fine as you are cutting the cross feed method works fine.  Lot easier to cut threads when you take the compound out of the equation. 

michael


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## Ray73 (Aug 5, 2015)

RJSakowski said:


> Your problem is with how you align the threading tool.  After you set your compound to the desired angle, you need to adjust the alignment of the threading tool.  The tool must be set so the angle of each face to the  spindle axis (work) is the same.  This is normally done with a fishtail gauge, also called a 60 deg. center gauge or threading gauge, (a little gauge with 60 deg. Vee cut into the end).  The threading tool is adjusted so it matches the vee when the other end of the gauge is contacting the work.
> 
> Bob


Thanks for the reply. As I mentioned in my post I have lined up the tool using the fish tail gauge. maybe it is the angle of the compound. I will try a different angle.


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## Ray73 (Aug 5, 2015)

Doubleeboy said:


> You might also simplify your life a bit and set tool square with work using fishtail gauge like others mentioned and then use crossfeed to control depth of cut.  On threads as fine as you are cutting the cross feed method works fine.  Lot easier to cut threads when you take the compound out of the equation.
> 
> michael





T Bredehoft said:


> Perhaps you should set your compound to 60º?  The compound needs to be 30º off square with the work, not 30º off parallel with it.


My compound only goes up to 40. I'll have to take a look at the angle and see which way I need to go with it.


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## Ray73 (Aug 5, 2015)

RJSakowski said:


> Your problem is with how you align the threading tool.  After you set your compound to the desired angle, you need to adjust the alignment of the threading tool.  The tool must be set so the angle of each face to the  spindle axis (work) is the same.  This is normally done with a fishtail gauge, also called a 60 deg. center gauge or threading gauge, (a little gauge with 60 deg. Vee cut into the end).  The threading tool is adjusted so it matches the vee when the other end of the gauge is contacting the work.
> 
> Bob


Yes, I mentioned in my post that I used a fish tail gauge to align the tool. I think I'm doing that the correct way. I did it in the way that I see in most of the videos I have watched. It must be in the angle of  the compound. mine was set to 30 but others have mentioned it may need to be 60 on my lathe. My lathe stops at 40 though so I guess its just a matter of measuring without the numbered plate.


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## higgite (Aug 5, 2015)

I think T Bredehoft and pdentrem nailed it. If you're using the built in protractor to set the compound angle, those usually measure degrees off of parallel with the ways. What you want is 29-30 degrees off the direction of cross slide travel, or 60-61 degrees off parallel to the ways. You may need one of these to set the angle with.

Tom


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## RJSakowski (Aug 5, 2015)

Yes, in looking at your photo again, if the compound is set at 60 degrees and you are advancing the feed with the compound, you will get a pattern like that.  If you look closely at the right hand side of the threads, you should be able to see a series of small steps, each step equal in length to the amount of feed you use for each pass. 

The compound should be set at 30 degrees or less. At 30 degrees you should be following the previous cut on the right hand side.  If you set slightly less than 30, you will make a fine cut on the right as you remove material from the left.  This is why many operators prefer to set the compound around 29 to 29-1/2 degrees.  Using the cross feed to advance the feed or running the compound at significantly smaller angle than 30 degrees can cause chatter when cutting the thread as you are cutting both sides of the thread at once.

Bob


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## RJSakowski (Aug 5, 2015)

higgite said:


> I think T Bredehoft and pdentrem nailed it. If you're using the built in protractor to set the compound angle, those usually measure degrees off of parallel with the ways. What you want is 29-30 degrees off the direction of cross slide travel, or 60-61 degrees off parallel to the ways. You may need one of these to set the angle with.
> 
> Tom


Or make one of these:
http://www.hobby-machinist.com/threads/29-5-deg-angle-tool-for-lathe.34541/


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## 65BAJA (Aug 5, 2015)

Could you post a pic of your set up from above the compound?


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## eeler1 (Aug 5, 2015)

+1 on the compound setting,  even on my 1950's Logan, you start perpendicular to the ways, so at 90 degrees.  To get to 29 degrees, you actually set the protractor based at 61 degrees.  If I were to set it to 30 degrees my threads would look like yours.


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## Handy4563 (Aug 5, 2015)

If you use the gauge correctly and the tool bit has a true 60 degree point and is 90 degrees to the the shaft you are threading, both sides will be even no mater what angle the compound is set at if you set and lock the compound first.  The picture of the thread setting tool shows 2 v notches on the edges.  You placed one flat edge against the shaft and place your threading tool bit point in the v facing the bit and aline the bit in the v.  If the sides of the bit fit in the v it will be 90 degrees to the shaft.  From your picture it would not be straight.  I would like to see a picture of your bit lined up this way.

Sent from my Venue8 3840 using Tapatalk


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## RJSakowski (Aug 5, 2015)

Handy4563 said:


> If you use the gauge correctly and the tool bit has a true 60 degree point and is 90 degrees to the the shaft you are threading, both sides will be even no mater what angle the compound is set at if you set and lock the compound first.  The picture of the thread setting tool shows 2 v notches on the edges.  You placed one flat edge against the shaft and place your threading tool bit point in the v facing the bit and aline the bit in the v.  If the sides of the bit fit in the v it will be 90 degrees to the shaft.  From your picture it would not be straight.  I would like to see a picture of your bit lined up this way.
> 
> Sent from my Venue8 3840 using Tapatalk


That was my original assumption as well, but a closer look at the OP's thread shows a 90 deg. or close angle between the two sides of the thread.  This would happen if the compound were set at 60 degrees.  The right side of the tool will cut a taper, 30 degrees to the spindle axis or 60 degrees to the perpendicular.  The left side of the tool cuts the 30 degree angle for a total of 90 degrees included.

Were the compound angle set properly and the tool angle set wrong, the included angle would be 60 degrees. 

Bob


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## higgite (Aug 5, 2015)

Ray,

As already mentioned, an overhead pic of the compound/tool post/tool/work piece relationship that gave the results pictured in your opening post sure would eliminate a lot of guessing.

Tom


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## janvanruth (Aug 5, 2015)

a fine example of a buttress thread


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## Ray73 (Aug 5, 2015)

higgite said:


> I think T Bredehoft and pdentrem nailed it. If you're using the built in protractor to set the compound angle, those usually measure degrees off of parallel with the ways. What you want is 29-30 degrees off the direction of cross slide travel, or 60-61 degrees off parallel to the ways. You may need one of these to set the angle with.
> 
> Tom


Yes I used a protractor just now and my compound when set on 30 degrees is 30 degrees to the work piece sticking out of the chuck.


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## epanzella (Aug 5, 2015)

Just feed in with the cross slide. If the threads look good it clears everything but the angle of the compound.


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## RJSakowski (Aug 5, 2015)

Ray73 said:


> Yes I used a protractor just now and my compound when set on 30 degrees is 30 degrees to the work piece sticking out of the chuck.


I couldn't find your lathe on the HF site but the lathes that they show appear to have the compound feed parallel to the spindle axis when the dial reads "0".  If that is the case for your lathe, you need to set an angle of 60 deg.  Oftentimes, there is a secondary index mark that you use when the dial goes past the primary mark.  If not, use a 30/60/90 drafting triangle or protractor to set the 60 degree angle.  The angle isn't real critical as long as it is at least 60 deg. In a pinch, you can use the 60 deg. angle on the fishtail gauge.

Bob


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## MikeWi (Aug 5, 2015)

That looks exactly like what I did once.  It was because I was using a HSS threading tool that was about 3/8" square in a QCTP tool holder that had a V-groove in the bottom of the slot for holding round tools.  Since the tool wasn't the full width of the slot, one edge dropped into that groove and tilted the bit.  I had to put a piece of flat stock under it so it would sit correctly.


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## Ray73 (Aug 6, 2015)

RJSakowski said:


> I couldn't find your lathe on the HF site but the lathes that they show appear to have the compound feed parallel to the spindle axis when the dial reads "0".  If that is the case for your lathe, you need to set an angle of 60 deg.  Oftentimes, there is a secondary index mark that you use when the dial goes past the primary mark.  If not, use a 30/60/90 drafting triangle or protractor to set the 60 degree angle.  The angle isn't real critical as long as it is at least 60 deg. In a pinch, you can use the 60 deg. angle on the fishtail gauge.
> 
> Bob


You are correct. I set it to 60 using a protractor and it cuts threads very nicely. Thank you for your reply.


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## Ray73 (Aug 6, 2015)

I set the compound to 60 using a protractor because my lathe is numbered only to 40. It now cuts threads very nicely. Thanks to everyone for the reply's and advice. Now I'm on to practice some inside threading. Thanks again!

Ray


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## RJSakowski (Aug 6, 2015)

Ray73 said:


> I set the compound to 60 using a protractor because my lathe is numbered only to 40. It now cuts threads very nicely. Thanks to everyone for the reply's and advice. Now I'm on to practice some inside threading. Thanks again!
> 
> Ray


Glad that you have it sorted, Ray.  

Now that you are correctly set for cutting threads, you may want to consider scribing a second index mark on your compound, say opposite the 40 degree line, so you can easily go to the correct compound setting for cutting threads.  

Bob


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## BarnyardEngineering (Aug 6, 2015)

Before you move anything now, find that 30 degree mark on the compound and scribe a mark on the cross slide to correspond to it.


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## Bill Gruby (Aug 6, 2015)

I'm really going to throw a ringer in here. The angle of the compound rest only tells you where the cut will be generated from on the tool. If you use the recommended  29degrees you will cut on the side of the tool facing the chuck. With that said, ready guys, the angle is only to put less work on the tool. I cut threads from whatever angle the compound is at the time. You heard right, if it's set 90 degrees to the work you can cut good threads with it. You are just cutting with both sides of the tool. It won't hurt anything.

Being new at threading you should however stick to normal practice. You can experiment later.

"Billy G"


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## Handy4563 (Aug 6, 2015)

Billy is right if you have the bit set right to the shaft your turning threads on it will be a even v cut no matter what angle the compound is set to. The case we have been talking about shows that it was the bit not being set right do to the holder tipping it which would cause the thread we saw in the picture.

Sent from my Venue8 3840 using Tapatalk


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## Bill Gruby (Aug 6, 2015)

I have been waiting some 30  years to hear someone say that. Kudos to you Handy4563.

 "Billy G"


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## T Bredehoft (Aug 6, 2015)

" _no matter what angle the compound is set to._ "

If I set the compound to 45º and use it (the compound) to feet the tool it will NOT make a good thread. If you lock the feed on the compound and feed with the cross feed screw, then the angle of the compound is of no consequence. *The two statements should be made together. *


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## John Hasler (Aug 6, 2015)

Handy4563 said:


> Billy is right if you have the bit set right to the shaft your turning threads on it will be a even v cut no matter what angle the compound is set to.


If you are advancing the bit into the work with the cross-slide and not with the topslide.


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## Bill Gruby (Aug 6, 2015)

With all due respect, if the Top slide is perpendicular to the work piece and in line with the cross slide and the 60 degree cutting tool is set correctly you can advance the top Slide to make the cut. It is not common practice because of the work load on the tool but yes it can be done. The only problem that could arise is that of heat build up at the tool point. Any angle other than 90 degrees will require the cross slide to make the cut. I should have added that to my post. Nice catch John.

 "Billy G"


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## Jester966 (Aug 7, 2015)

"_I cut threads from whatever angle the compound is at the time_"

If you _feed with the cross slide_ then yes, the thread form will be good regardless of the compound angle (provided the tool is set correctly, perpendicular to the work) because you will be cutting equally with both sides of the tool.  The problem is a heavier work load and, depending on the rigidity of the machine and setup, potential for chatter.  If the threads cut nicely though, then this method works.

If you _feed with the compound slide_ and the compound is set to_ anything less than 30 degrees_ from perpendicular to the ways then your thread form will still be good as you will still be cutting with both sides of the tool.  If your compound is set to anything over 30 degrees, however, you will _not_ have a good thread form, as seen in the OP's photo.  You end up cutting with one side of the tool only and leave steps on the other side of the thread form.

29.5 degrees is recommended because it cuts primarily with only one edge, reducing load, but still cleans up the back side of the thread to leave a good finish.  Like anything else in the trade/hobby though, there are many ways to accomplish a task and if the end result is good, then use whatever method works for you.


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## chips&more (Aug 7, 2015)

I have been thread cutting on a lathe for about 50 years. And about 40 years of that has been cutting threads straight in with the cross slide. For me, I have no problems at all doing that way. I’m reading too much work load, chatter and whatever. Sorry, I have never had any problems like that and I would recommend anybody trying to thread on a lathe at least give the method a try. Where are the Mythbusters when you need them…Dave.


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## Bill Gruby (Aug 7, 2015)

Thank you Dave. You will find that most answering something like this have never cut threads any way other than the norm. They read  of the problems caused when they stray and let it go at that. Like you I have never had a problem. For you and people like you the Myth was broken some time ago. I was in a hurry one day many years ago and just cut the threads from where ever the top slide was set. From then on I did it from where ever the top slide was.

 "Billy G"


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## Jester966 (Aug 9, 2015)

"most answering something like this have never cut threads any way other than the norm."

I did not mean to imply that either way was right or wrong.  It's good to know and understand different methods of any operation.

I was taught 29.5 degrees and feed with the compound during my apprenticeship, but I actually do feed with the cross slide more often than not.  I have _never_ had any problems feeding with the cross slide on a full sized lathe, but my little 10" Atlas does not seem to like it.  I have really had to go back and re-learn the basics with this lightweight machine to get good results.

Definitely try both methods and do whatever works for you and your equipment.


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## Tozguy (Aug 9, 2015)

One of the reasons for feeding with the compound when set at 29.5 deg. is to sneak up on the final dimensions. Using the compound at this angle allows finer cuts than when using the cross slide.


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## Bill C. (Aug 9, 2015)

You should add a stop or a 0-1" travel indicator on end the cross-feed ways so it will always repeat to the zero point on the micro-dial.  I have done it both ways.  If in doubt use a die on the last pass, been there too, on thread diameters under a 3/4".  Bigger threads are easier to see how the cuts are looking.


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## Paul in OKC (Oct 3, 2015)

Late reply. Looks like the op got the problem figured out. As to using the compound or the cross slide, I almost never use the  compound. But as said above, equipment makes a huge difference. When I thread at work on a 'big' lathe, using the compound is rarely needed. At home I have an old 16" South Bend that prefers I use the compound. Also have a 7x14 mini lathe that I rarely thread on, but compound used as well. It does take less tool pressure.  The pitch of the thread makes a difference as well.  An 8 pitch is a pretty deep thread and best done with the compound on smaller machines.


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## epanzella (Oct 12, 2015)

It's been years since I threaded any other way but feeding straight in with my xslide. I use my compound so infrequently that I made a milling attachment out of it.


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