What is correct? 29.5 vs 30 vs 59.5 vs 60 vs 60.5 compound setting?

[dave2176]

Dave,
So you are saying the scale is correct and set to 29.5 on the compound? I just checked and with the compound at "0", it it perpendicular to the face of the chuck so the setting at 29.5 is correct? My scale doesn't go up to 59.5 on the compound or maybe if I jam it all the way.
Thanks,
schemer

added: So looking at the bottom of this page, the tool this guy made is the correct way to set it correctly right?

http://dezignshack.com/blog/?cat=3

The bottom picture in that link looks like he is 30* off. My scale actually read to 60 but the decal or paint isn't impervious to coolant so it is washed out quite a bit. I use a sine bar for setting important angles. I've tried both ways of threading from 0 or 29.5 on many a thread and both work well.

Dave

 

[Pat of TN]

You can tell how your compound is marked easily, and which degree to go off of - it's whichever one is closer to perpendicular to the bed rather than parallel with the bed.

On the Jets and Sharps at school, we thread at 59.5. At home on my 6x18 Atlas, I thread at 29.5.

Your compound may also be mismarked slightly. You could check with an accurate protractor from the face of a chuck or spindle to the compound. Sometimes the compound markings are off a little. There's also some complex trigonometric methods as well. Watch "Splitting a Hair on the Atlas Lathe" by Tubalcain on Youtube for that.

 

[schemer]

The bottom picture in that link looks like he is 30* off. My scale actually read to 60 but the decal or paint isn't impervious to coolant so it is washed out quite a bit. I use a sine bar for setting important angles. I've tried both ways of threading from 0 or 29.5 on many a thread and both work well.

Dave

Dave,
I went back out to the shop on the way to go grocery shopping and while the wife was waiting in the van with the dog, I cleaned my scale on the compound and it does in fact go to 60*. The problem I had was I didn't loosen the nuts enough and when I turned it it was getting stuck at 55* so I figured it would not go any further. After I cleaned the corner of the scale that had some oil and dirt in there I could plainly see the scale goes to 60* and loosened the nuts some more and got it set. The pic in the image at that link where he shows and states it is wrong (shown below), is how mine looks at 29.5 and in the last pic with his tool (gauge) inserted is how mine looks at 59.5* which is hopefully correct. The compound handle is just to the right of the crossfeed handle as opposed to the pic below where is what mine looked like when set to 29.5*


Thanks,
schemer

 

[Ulma Doctor]

Dave,
I went back out to the shop on the way to go grocery shopping and while the wife was waiting in the van with the dog, I cleaned my scale on the compound and it does in fact go to 60*. The problem I had was I didn't loosen the nuts enough and when I turned it it was getting stuck at 55* so I figured it would not go any further. After I cleaned the corner of the scale that had some oil and dirt in there I could plainly see the scale goes to 60* and loosened the nuts some more and got it set. The pic in the image at that link where he shows and states it is wrong (shown below), is how mine looks at 29.5 and in the last pic with his tool (gauge) inserted is how mine looks at 59.5* which is hopefully correct. The compound handle is just to the right of the crossfeed handle as opposed to the pic below where is what mine looked like when set to 29.5*


Thanks,
schemer

you are 29.5 perpendicular to the face of the chuck making the compound at 60* relative to the bed, you may want to keep swinging the compound rest to achieve 29.5 or 30* relative to the bed ways.
you will be threading in that direction
see frostheave below

 

[frostheave]

Hi schemer

I also have a G4003G and this is how I set-up the compound for threading.





Approximately 60.5 degrees.



Bob

 

[schemer]

Hi schemer

I also have a G4003G and this is how I set-up the compound for threading.

View attachment 80839



Approximately 60.5 degrees.

View attachment 80840

Bob

Hi Bob,
Yep, I figured it out. But I just set it from 60.5 back to 59.5 ! I found my protractor with the square back plate as oppsed to the round one (even though I could eyeball it) and checked it from the crossfeed center. All is good and that is how my compound looks. I guess the main confusion was why would someone think that they would need to set something to 59.5 or 60.5 when the instructions all over the internet say 29.5. :whistle:Or the better question is why did the Chinese that makes the lathe put the degree plate on the machine based on a different axis? :angry: So now what is the magic number 60.5 or 59.5 and what is the difference in why you would use either/or?
Thanks,
schemer

 

[Don B]

The compound angle is just not that critical, it's only really important that the tool is ground accurately and set to the work accurately, you can be off a degree or two, even if you over do the angle and get steps on the back side of the thread it just doesn't matter, as long as on the last couple of cuts you plunge the treading tool straight in, so on your finishing cuts you get nice even little curls off both sides of the tool, if your tool is ground and set properly you know the tread is formed right when material is being removed from both side on your last cuts.
I always cut threads with my compound 90 degrees, and plunge straight in, I advance the cutter by times with the compound depending on the material and conditions.)

 

[Bluedog]

Hi Bob,
Yep, I figured it out. But I just set it from 60.5 back to 59.5 ! I found my protractor with the square back plate as oppsed to the round one (even though I could eyeball it) and checked it from the crossfeed center. All is good and that is how my compound looks. I guess the main confusion was why would someone think that they would need to set something to 59.5 or 60.5 when the instructions all over the internet say 29.5. :whistle:Or the better question is why did the Chinese that makes the lathe put the degree plate on the machine based on a different axis? :angry: So now what is the magic number 60.5 or 59.5 and what is the difference in why you would use either/or?
Thanks,
schemer

I use 60.5

90 - 29.5 = 60.5

 

[schemer]

You can tell how your compound is marked easily, and which degree to go off of - it's whichever one is closer to perpendicular to the bed rather than parallel with the bed.

On the Jets and Sharps at school, we thread at 59.5. At home on my 6x18 Atlas, I thread at 29.5.

Your compound may also be mismarked slightly. You could check with an accurate protractor from the face of a chuck or spindle to the compound. Sometimes the compound markings are off a little. There's also some complex trigonometric methods as well. Watch "Splitting a Hair on the Atlas Lathe" by Tubalcain on Youtube for that.

Thanks Pat,
I guess mine is mismarked by about 30 degrees. :thinking: I have it sorted for the most part, more experience will get it all dialed in as I will try all the suggestions and make up my mind. I will check out that video too.
schemer

- - - Updated - - -

The compound angle is just not that critical, it's only really important that the tool is ground accurately and set to the work accurately, you can be off a degree or two, even if you over do the angle and get steps on the back side of the thread it just doesn't matter, as long as on the last couple of cuts you plunge the treading tool straight in, so on your finishing cuts you get nice even little curls off both sides of the tool, if your tool is ground and set properly you know the tread is formed right when material is being removed from both side on your last cuts.
I always cut threads with my compound 90 degrees, and plunge straight in, I advance the cutter by times with the compound depending on the material and conditions.)

Don,
I will try what you said and in the end I guess it will all make sense and one way will be either quicker or better than the other. More experience cutting threads is what I need. I usually use bolts and screws from the hardware store. :whistle:
Thanks,
schemer

- - - Updated - - -

I use 60.5

90 - 29.5 = 60.5

Thanks Bluedog. Will do some tests on all the angles and techniques.
schemer

- - - Updated - - -

you are 29.5 perpendicular to the face of the chuck making the compound at 60* relative to the bed, you may want to keep swinging the compound rest to achieve 29.5 or 30* relative to the bed ways.
you will be threading in that direction
see frostheave below

Thanks Mike...I think I finally got it. )

 

[Craig_J]

If your dial reads 0 degrees when the compound is perpendicular to the long axis of the lathe, the angle is 29.5. If your dial reads 90 when perpendicular, the equivalent reading would be 60.5. My understanding is the reason for the 1/2 degree is to keep the back side of the cutting tool in contact with the thread, so it would be cutting a miniscule amount on the back side. Probably the biggest difference between feeding with the compound at 29.5 or feeding with the crossslide is that the latter takes more power, significantly so when you are deep into the thread.