# 29.5 Deg. Angle Tool For Lathe



## RJSakowski

A 29.5 degree angle is most likely the most used angle set on the compound on a lathe.  The Grizzly G0602 lathe has a difficult to read dial with 2-1/2 degree graduations.  My solution was to make a gage that would provide easy and accurate setting of this important angle.  
I made mine from a piece of 2" x 2" x 1/4" 6061 aluminum angle that I had in my scrap bin. I used my CNC to mill the piece but could have just as easily made it with a rotary table or by setting my milling vice at a 29.5 degree angle to the y axis.  I roughed out the piece on a band saw and finished the milling with a 1/2" end mill. The entire project was an easy few hours
Because I was using some scrap for the piece, my version is not exactly to the drawing.  Additionally, it works for the 0602 but the maker should check that the dimensions fit his or her particular lathe and make adjustments accordingly.
Enjoy!


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## Ken_Shea

That is a good idea RJ, it a pain setting exactly the 29.5.


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## T Bredehoft

It's more work, but I set up my  compound close to 30°, set an indicator to register movement of the saddle and another to measure movement of the compound in the Y coordinate.  For .050 in X it should read .0246 in Y.  Once you've achieved these readings, you KNOW it's right. The marks on my Clausing/Atlas are off by 1 1/2 marks, more or less.

Oh. Sine 29.5° = 0.49242.  0.49242/20 = .0246.

Tom


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## Ulma Doctor

Great Stuff!
i always rounded off to 30*and use a small 30*60*90* triangle gage to set it.
it seemed a lot simpler albeit less than correct.
the function is fine for the class of fit i'm accustomed to.
the error is small on my lathe(s) in reference to the triangle.

thanks for sharing!


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## RJSakowski

Ken_Shea said:


> That is a good idea RJ, it a pain setting exactly the 29.5.


With the CNC, I started at an offset from the apex of the triangle I set that at 0,0 and ran G1 X-6 Y-3.3946. then X0 Y0.  Then I moved to X-.1 and set to 0.  I repeated until I had cleaned up the edge to my satisfaction.  The actual location of the apex is not critical.
If using a rotary table set your vice up with the jaws parallel to the x axis.  I use and edge finder but a test indicator will work as well.  Note the reading on the rotary table and rotate 29.5 degrees from there to cut the angle.
If you don't have either of those options, use a sine bar to set the vice.  The block stack for a 5" sine bar is 2.462". If you don't hahe a sine bar, a 30-60-90 drafting triangle with a shim at the 30 degree vertex will give you the required 29.5 degrees.  The shim is 8.73 thousandths for every inch of separation between the two contact points.
There isn't anything really sacred about the 29.5 degree angle.  Its intent is to shave a small amount of the left hand side of the thread as you advance the cut.  The South Bend book "How to Run a Lathe" recommends a 29 degree angle.


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## randyc

Holy cow !  Some of you guys are even more obsessive/compulsive than me and that's impressive !  29-1/2 degrees is a time-worn standard but it's really not all that critical.  At least I haven't found it to be - cranking the compound around so that my aged eyes detect that the angle is somewhere slightly less than 30 degrees seems to be satisfactory.

If the cutting tool shaves the flank of the thread, doesn't chatter and produces a nice finish, the exact angle doesn't matter.  For example, this particular reference from "Machinery's Handbook" suggests 29 degrees (the extra half degree was left by the wayside - SACRILEGE):

http://www.kanabco.com/vms/eng_mhandbook/eng_mhandbook_06.html

Here’s an illustration that I snatched from the internet.





Note that the lower left illustration suggests that compound angle can be adjusted over a fairly wide range provided that it is less than 30 degrees.  The object is to lessen the stress on tool/work, cutting NOT like a forming tool, that must remove ALL material from both thread flanks.

The better alternative, as we know, is to remove most of the material from the leading edge while just shaving the training edge.  Cutting pressure is reduced and surface finish consequently improved (no chattering).

The angle of the compound – within reasonable limits and always less than 30 degrees – can be adjusted to the point that chatter starts to occur given a reasonable DOC (usually less than .015) then backed off slightly to achieve satisfactory results.

Just my experience, of course -


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## RJSakowski

Randy, I believe I said that in the last post.  However, with my G0602 anyway, the dial has 2-1/2 degree graduations and is buried where it is difficult for me to read.  On top of that, it has an offset as well.  Being able to loosen the bolts, slide the gage in and retighten is worth the hour or so spent machining the gage.  
Interesting that the title on the lower left illustration says "15 to 29-1/2 Degrees Infeed Angle" while the illustration says 1 -3 degrees.


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## RVJimD

RJ, Could you show me a picture of where/how you use this on your 602?  I have the VFD version the that lathe and would like an easy way to set it for threading.  I know exactly what you mean about hard to see/read the dial on the compound.

Jim


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## darkzero

Nice, I like that. I use a dedicated preset bevel square but I think I'm going to have to make something similar. Thanks for sharing.


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## RVJimD

Will,

Thanks for the photo!  It was late last nite when I saw the angle and my brain wasn't showing me a good picture of how it was used!  

Jim


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## RJSakowski

RVJimD said:


> RJ, Could you show me a picture of where/how you use this on your 602?  I have the VFD version the that lathe and would like an easy way to set it for threading.  I know exactly what you mean about hard to see/read the dial on the compound.
> 
> Jim


Jim, The vertical side mates to the left hand vertical surface of the cross slide.  The vertical edge of the triangle mates to the left hand vertical edge of the compound base.  I have a beefed up compound clamp, the corner of which is visible as a vertical surface above the cross slide and below the 90 degree angle on the triangle. It is slightly inset from the slide so I am referencing the slide and not the clamp.

Bob


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## RVJimD

Bob,

That helps!  I also like your "hole covers" in the follow rest holes.  I should do that, I just have the bolts from the rest in there and they get in the way when trying to brush chips away.

Thanks

Jim


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## RJSakowski

RVJimD said:


> Bob,
> 
> That helps!  I also like your "hole covers" in the follow rest holes.  I should do that, I just have the bolts from the rest in there and they get in the way when trying to brush chips away.
> 
> Thanks
> 
> Jim


The bolts were leftovers from one of the Grizzly installs I did.  I would have preferred a flatter head  on them but that was an easy fix.


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## T Bredehoft

I've revised my "need" for accuracy.  Anything less than 30° is good.


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## Ken_Shea

T Bredehoft said:


> I've revised my "need" for accuracy



Agreed, used to do the same thing with the mill DRO that reads four places, the time spent chasing that last digit was almost always a waste of time, so is chasing that 29.5º using a Chinese protractor  I do like RJ's method though, no chasing just set it. On my lathe, once set, I scribed mating lines on the compound base and rotating part with the degrees on it, makes it pretty quick to set when needed also. The mating lines can be put anywhere easy to see since it is just a reference.


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## RJSakowski

I guess I do chase the tenths around on my DRO.  I know that I am not machining to the accuracy indicated but I do so for two reasons.  One is that the total accuracy is made up of a number of different components, the DRO reading is one.  

It is kind of like sighting a rifle.  My hand isn't that steady so do I have to be sighted in to an eighth of an inch?  If I am off two inches to the right, my groups should cluster about that offset which increases the probability that I will miss my intended target.  It costs me little in time to make that final adjustment so I do it.  

The second reason is when I am running manually, I read the dimensions from my drawing and set the DRO to match.  I usually use ordinate dimensioning and set my DRO origin to match.  In my advancing years, my poor brain does not always function as well as it should so having a DRO reading exactly match the the drawing value is a mental check for me that I am doing what I intended to do.  I use four decimal place on the drawings for the same reason.  Note that these are for my personal use and not intended to communicate any implied accuracy to others.  For me, the cost is minimal and the benefit is significant.  

Disclaimer: I am not running a for profit machining business and I am retired so I am not concerned with a little extra time spent.  I probably also suffer from OCD as well.


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## Ken_Shea

I'll end up in the area of four places but no more chasing the precise digit, I still have to fight not chasing though


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## T Bredehoft

" I am retired so I am not concerned with a little extra time spent. I probably also suffer from OCD as well."

I probably should have written the above, myself.


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## randyc

RJSakowski said:


> Randy, I believe I said that in the last post.  However, with my G0602 anyway, the dial has 2-1/2 degree graduations and is buried where it is difficult for me to read.  On top of that, it has an offset as well.  Being able to loosen the bolts, slide the gage in and retighten is worth the hour or so spent machining the gage.
> Interesting that the title on the lower left illustration says "15 to 29-1/2 Degrees Infeed Angle" while the illustration says 1 -3 degrees.



Bob, I noted that angular difference too but just assumed that he was illustrating that his cutting tool was set within 1 to 3 degrees of 30 degrees _in that specific example_, not that he was suggesting that it was the total allowable angular variation.  Perhaps if he'd drawn the angles to depict the full movement from 15 to 29.5 degrees, the sketch would have been cluttered and confusing ?

Yes you did note that the 29.5 degree angle wasn't cut into stone tablets - I've posted your statement below in case anyone missed it in the first reading.  My point was not to contradict anything that you (or anyone) said specifically but to illustrate how some sacred cows don't have to be taken seriously and just how widely the compound angle can change while producing perfectly acceptable threads.



RJSakowski said:


> ...There isn't anything really sacred about the 29.5 degree angle.  Its intent is to shave a small amount of the left hand side of the thread as you advance the cut.  The South Bend book "How to Run a Lathe" recommends a 29 degree angle.


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## chips&more

Nice work on your project. But this subject gets pounded to death on angle this and angle that. And I’m still gonna say, ”I go straight in with the cross slide only”. And I’ve been doing it that way for about 40 years now. Look at all that time I have save not messing around with the compound angle adjusting. And my threads look great. And my lead does not change so I can do trick things to the end of the thread too. And threading up to a shoulder is easier because your tool does not creep to the left. Try it, you might like it…Good Luck, Dave.


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## Baithog

Just some confusion in my old brain, but up there in the LL picture - If you use a standard 60deg. ground tool and set the compound at 27 or 26, or something like the picture title says, wouldn't you screw up the angle being cut on the left side of the tool, too? Half a degree is a wash, but several degrees starts to make a lopsided thread. Wouldn't it be better to have a tool ground with clearance on the trailing side. You guys with fancy carbide threading tools would have a hard time doing that, but those of us with more modest means and HSS threading tools can grind whatever angle we want... And I have done that by mistake


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## randyc

chips&more said:


> Nice work on your project. But this subject gets pounded to death on angle this and angle that. And I’m still gonna say, ”I go straight in with the cross slide only”. And I’ve been doing it that way for about 40 years now. Look at all that time I have save not messing around with the compound angle adjusting. And my threads look great. And my lead does not change so I can do trick things to the end of the thread too. And threading up to a shoulder is easier because your tool does not creep to the left. Try it, you might like it…Good Luck, Dave.



While personally, I use the angled compound to cut threads, I imagine a lot of people use the cross-slide, like Dave does.  As an example, I have an old book that came with my Sheldon EXL-56B that's similar to the South Bend book.  BUT there is no mention at all of angling the compound when cutting screw threads.  In fact, quite the contrary.

On the Sheldon, there is a little gizmo attached to the cross-slide that looks like this:




This arrangement is used for cutting threads in production.  The stop that is mounted to the carriage is rotated up so that it is over the threaded rod and between the two sets of lock nuts and locked into position.  The lock nuts are adjusted so that cross slide travel is limited to the thread major and minor diameters (by cutting a trial thread presumably).

It's a PITA to describe how to set up and use this tool but at no time does the operator have to look at any dial and make any adjustment other than feeding the cross-slide a fraction of a turn.  I've never used this feature so I can't attest as to how quickly threads can be produced with it.

The point of this post is to note that Dave's technique may be used far more often than the rest of us think.  And obviously with success


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## randyc

Baithog said:


> ....Wouldn't it be better to have a tool ground with clearance on the trailing side. You guys with fancy carbide threading tools would have a hard time doing that, but those of us with more modest means and HSS threading tools can grind whatever angle we want... And I have done that by mistake



You could do that but then the compound would have to be set at exactly thirty degrees because the rear flank of the thread would be produced by the compound infeed, not the shape of the cutter.  Also, to produce a good finish, the infeed would have to be very, very small which would take a l-o-n-g time to produce a screw thread.


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## RJSakowski

I would think that the  ability to go straight in without chatter will depend to a great extent how rigid the lathe is.  For a small lathe, making the cut from both sides  can be a problem.  At least it was for me.
The bottom line is whatever works is OK.  As has been pointed out, there are many ways to skin the cat.  From my personal experience, my threads are much nicer using the 29.5 feed angle.


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## randyc

RJSakowski said:


> I would think that the  ability to go straight in without chatter will depend to a great extent how rigid the lathe is.  For a small lathe, making the cut from both sides  can be a problem.  At least it was for me.
> The bottom line is whatever works is OK.  As has been pointed out, there are many ways to skin the cat.  From my personal experience, my threads are much nicer using the 29.5 feed angle.



That is the main thing, the chattering problem, and the reason that I also use the compound technique on my two small lathes.  I've tried feeding with the cross-slide but I have to run the spindle in back gear to keep the chatter down - it's a slow process and sometimes the finish is less than optimal.

FWIW - and this is not based on a lot of testing - I think that I get better thread finish when I run the spindle faster.


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## JR49

Baithog said:


> Just some confusion in my old brain, but up there in the LL picture - If you use a standard 60deg. ground tool and set the compound at 27 or 26, or something like the picture title says, wouldn't you screw up the angle being cut on the left side of the tool, too? Half a degree is a wash, but several degrees starts to make a lopsided thread. Wouldn't it be better to have a tool ground with clearance on the trailing side. You guys with fancy carbide threading tools would have a hard time doing that, but those of us with more modest means and HSS threading tools can grind whatever angle we want... And I have done that by mistake


Baithog,  I think what's  confusing you is that you're assuming that when the compound  gets angled to 29.5 deg., that will alter the angle of the tool bit.  That is not the case.  You set the compound to 29.5 deg. first.   THEN, you turn your tool post so that the threading tool bit is perfectly perpendicular to the work. Then as you advance the compound to take successive cuts into the thread, the tool remains perpendicular (at a right angle) to the work being threaded. Hope this helps,  JR49


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## RJSakowski

Ulma Doctor said:


> Great Stuff!
> i always rounded off to 30*and use a small 30*60*90* triangle gage to set it.
> it seemed a lot simpler albeit less than correct.
> the function is fine for the class of fit i'm accustomed to.
> the error is small on my lathe(s) in reference to the triangle.
> 
> thanks for sharing!


Thanks for the like.

I believe that the rationale for the slightly less than 30 degrees is that you want to make a very light shaving cut on the right-hand side of the thread to clean it up.  From what has been said, the angle isn't critical.  

My G0602 protractor is not that accurate and the divisions are 2-1/2 degrees and hard to read so I would use a triangle or adjustable angle square as well. It was too difficult for my arthritic hands to try to juggle a square, a spacer, and the compound while clamping it down; hence the gage.

If I were using your method, I would set it to 30 degrees with the 30/60/90 triangle and bump it a little to be slightly under.  I used a 30/60/90 triangle to check the machining cut when I made the gage.


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## RJSakowski

Baithog said:


> Just some confusion in my old brain, but up there in the LL picture - If you use a standard 60deg. ground tool and set the compound at 27 or 26, or something like the picture title says, wouldn't you screw up the angle being cut on the left side of the tool, too? Half a degree is a wash, but several degrees starts to make a lopsided thread. Wouldn't it be better to have a tool ground with clearance on the trailing side. You guys with fancy carbide threading tools would have a hard time doing that, but those of us with more modest means and HSS threading tools can grind whatever angle we want... And I have done that by mistake


No you won't mess up the left side.  When you set you compound angle, you set the angle at which you advance the tool.  You then adjust the angle of your tool in your toolholder with the fishtail gage so the cutting bit is perpendicular to the thread axis.  As you advance the tool, the cut surfaces are always 60 degrees to the thread axis. The left side is making the bulk of the cut while the right side is making a very light cut, almost scraping.  Think of like cutting a double bevel.

If you ground your tool bit with clearance on the right side, the thread angle on the right side would be whatever you set the compound angle at.  Take it to the extreme and set the compound angle a zero.  You are now advancing the tool straight in.  The left side will give you a 60 degree bevel while the right side be perpendicular to the thread axis.

Sorry Baithog, Your post came up on top and I thought it was new.  I should have looked at the post date.  I also should have my morning coffee before reading or replying.


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## kingmt01

Nice tool. If you don't have nothing else to do why not make a tool that you can be proud of? Now if you notched a 60 in it to square the tool youd have a two in one.


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## The Liberal Arts Garage

Ulma Doctor said:


> Great Stuff!
> i always rounded off to 30*and use a small 30*60*90* triangle gage to set it.
> it seemed a lot simpler albeit less than correct.
> the function is fine for the class of fit i'm accustomed to.
> the error is small on my lathe(s) in reference to the triangle.
> 
> thanks for sharing!


.  If I remember correctly, the missing half
degree is there to concentrate the cutting action on the leading  edge.
If  I remember correctly, the cutter is to be set  at thirty degrees for the
last " polishing" pass. Please correct if I am misled.......BLJHB.


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## Round in circles

Is this off setting the cutting tool tip  to the axis needed if one uses a coolant to take the heat & friction out of the thread cutting ? 
IE.
When using indexable pre ground TC tips


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## Ken_Shea

David,
The compound would be set to the 29.5º and the tool holder 90º to the axis.
The compound set to 29.5º instead of 30º isn't terribly important on small threads but is helpful on deeper threads, some set it to 30º and feed straight in, mine is set to 29.5º and the compound is used for feeding for all threading.

I bet there are plenty of examples on YouTube showing the set up to clarify if needed.

Ken


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## Shadowdog500

That looks beautiful!!!!  

I'm no expert, but I wonder if an  angle block is really needed unless your compass is missing or way off. The big thing is making sure you are at exactly 30° or less.  29.5° gets you close without having to worry about going over 30° if the protractor on your compound isn't exact or too small to see.  Some use 29°, some use 29.5°, while some try to nail 30°, so it probably don't matter that much as long as you stay under 30°.  I use 29.5° and my last cut is always a small plunge cut.    

If I were going to make an angled gauge block to sweep with a indicator to set my compound I'm wondering it if would try to make it something like 29.9° since I'm checking it so accurately.

Chris


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## Ken_Shea

Once you are satisfied with your set angle put a scribe mark on the compound and the compound base in some conspicuous place, doesn't have to be in or on the degreed area, next time all you have to do is align the scribe marks and you're done with that, a real time saver.

Ken


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## Splat

Necroposting this because this morning I had a thought of making a 29º angle block to use up against the compound. Using that and a dial indicator I would dial in the compound. However, since I already have 30º angle blocks I'm wondering about this.....

Using a 3" long 30º angle block affixed to the vertical side of the compound; using a DI to get the 30º vertex end away about 0.0227" by rotating compound counter-clockwise.   Using a sine bar I figure 3" length piece at 30º is 1.50" height. A 29.5º setting is 1.4773" (rounded) height. So 1.50" - 1.4773"= 0.0227".

Would this get me a 29.5º compound setting? Am I off my rocker and laying on the ground?     Forgive the crude drawing but wanted to show you what I'm talking about:




To the OP, sorry for hijacking your thread here.


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## RJSakowski

Splat said:


> Necroposting this because this morning I had a thought of making a 29º angle block to use up against the compound. Using that and a dial indicator I would dial in the compound. However, since I already have 30º angle blocks I'm wondering about this.....
> 
> Using a 3" long 30º angle block affixed to the vertical side of the compound; using a DI to get the 30º vertex end away about 0.0227" by rotating compound counter-clockwise.   Using a sine bar I figure 3" length piece at 30º is 1.50" height. A 29.5º setting is 1.4773" (rounded) height. So 1.50" - 1.4773"= 0.0227".
> 
> Would this get me a 29.5º compound setting? Am I off my rocker and laying on the ground?     Forgive the crude drawing but wanted to show you what I'm talking about:
> 
> View attachment 368494
> 
> 
> To the OP, sorry for hijacking your thread here.


Short answer, yes.  The 29.5º angle isn't critical.  It is used because it is slightly less than the 30º flank angle of the thread so as the compound is advanced, it make a light shaving cut on flank parallel to the compound advance, cleaning up any step that might have formed from the previous pass..  Any angle less than 30º will work with 0º being equivalent to the advancing in with the cross slide that some prefer.  For that matter, you could go up to 30º in the opposite direction which would result in the main cut being on the right. ( I wouldn't recommend it as the cutting pressure would be aiding the feed rather than opposing and any backlash could create a problem.)


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## Splat

I should've mentioned I'm familiar with the whole angle debate. I've been using my above method for 30° but lately I eyeball for about 29°.  I see my lathe's compound angle scale is off by about 0.3°.  A jig or more precise way to measure would be ok with me, hence my question. Was just wondering if my proposed setup would work like I'm thinking. Thanks RJ.


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