# What am I doing wrong?



## matzo (Nov 19, 2017)

My threads are not vertical but seem to layover to one side. Using a sharpe 60 degree cutter, compound set at 29 1/2 degrees, cutter at 90 degrees to work.

I have added some photos of my setup. The pictures of the thread were taken through a magnifying light. I am keeping the cross slide at zero and feeding with the compound.


----------



## Ed ke6bnl (Nov 19, 2017)

I am far from an expert BUT did you use a fishtail device to set the V at 90 degrees to the work


----------



## Latinrascalrg1 (Nov 19, 2017)

Just looking at it it would appear that your cutter is not 90° to the work or your cutting bit is not evenly ground to 60° triangle so that both sides are equal.

Going by the thread work it looks like the right side is at the 60° cutting angle but the left side is at 90°.

When feeding the cutting bit into the work you do so using the compound that is set to the 29.5° so that the bit cuts only on 1 side of the bit instead of plunging  the tool bit into the work at 90° which will cut on 2 sides at the same time.  Hope this helps some.

Please post a few pictures  of your cutting tool so we can possibly  tell you more.


----------



## Cobra (Nov 19, 2017)

I would check that your compound is really set to 29 degrees.


----------



## pineyfolks (Nov 19, 2017)

You have just cut your first successful buttress thread.  Just kidding.
I agree that you need to use a center gauge to get your tool perpendicular to your work.


----------



## mikey (Nov 19, 2017)

Very interesting looking work piece. I assume the odd shape of the work is an artifact of the lens? It looks trumpet shaped in one picture and bent in the other.

With regard to your thread form, I suspect the issue is that the compound is set at the wrong angle. Set it to 60.5 degrees and try again.


----------



## JimDawson (Nov 19, 2017)

Looks like a buttress thread     I'm going to guess that your compound is set to 29.5° from the wrong start point.  Start from the compound at 90° to the lathe centerline and rotate 29.5° counterclockwise.


----------



## JR49 (Nov 19, 2017)

matzo said:


> My threads are not vertical but seem to layover to one side. Using a sharpe 60 degree cutter, compound set at 29 1/2 degrees, cutter at 90 degrees to work.


 
   I believe you had your compound set to 29 1/2 degrees off the spindle axis.  It needs to be 29 1/2 degrees off perpendicular to the spindle axis.  Not sure if I said that correctly, but basically the way your compound protractor scale is set up, you need to set it on 60 1/2 degrees.  Hope this helps,  happy machining,  JR49


----------



## JerryK (Nov 19, 2017)

The cross feed stays at  zero, feed in the compound  ( Maybe )


----------



## British Steel (Nov 19, 2017)

With your belly at 6 o'clock, the 29 degrees you want is with the topslide handle pointing at 5'o'clock, not 4, and the threading tool needs to be pointing directly at 12

Dave H. (the other one)


----------



## Dave Paine (Nov 19, 2017)

Been there, done that.

The scale on my lathe only goes to 55 deg, hence I foolishly assumed the 29.5 deg I could see on the scale was the one to use.   Wrong.  For some reason Grizzly decided to end the scale at 60 deg instead of 60 deg.

The 29.5 deg mentioned in other replies is an angle from the face of the chuck.   My scale on the compound is with respect to the bed ways.

Since I have no scale to read and I wanted a consistent method to set the compound, I just cut a block of wood to 29.5 deg on my table saw, which has a decent mitre gauge.   I epoxied a rare earth magnet in the face.

I then wrote the angle on the wood to remind me this was a jig and not a piece of scrap.

I now just attach the wood to the compound then swivel it so the block is flush with the chuck face.


----------



## bfd (Nov 19, 2017)

to check that there is not somethin else going on dont use your compound and thread just with your crossfeed. set your toolbit square to your work piece and do a test thread with the cross feed. I know people are saying you cant do that. but you can. most people are taught to thread with the compound ,as was I, but I have cut many successful threads with  this method then you know you compound if set wrong but if not then I would need to see your lathe to correct the problem bill


----------



## brino (Nov 19, 2017)

I believe the folks above nailed it......29.5 degrees from the wrong starting point.
Some lathes call the 0 degree mark square to the work, other call 0 degrees parallel to the work.

This question comes up often, see:
http://www.hobby-machinist.com/threads/what-am-i-doing-wrong.54207/#post-449384
http://www.hobby-machinist.com/threads/threading-help.49488/

I like the jig idea.....another item on the list.

-brino


----------



## matzo (Nov 19, 2017)

bfd said:


> to check that there is not somethin else going on dont use your compound and thread just with your crossfeed. set your toolbit square to your work piece and do a test thread with the cross feed. I know people are saying you cant do that. but you can. most people are taught to thread with the compound ,as was I, but I have cut many successful threads with  this method then you know you compound if set wrong but if not then I would need to see your lathe to correct the problem bill


Thanks I'll try that, I added some additional photos


----------



## matzo (Nov 19, 2017)

Dave Paine said:


> Been there, done that.
> 
> The scale on my lathe only goes to 55 deg, hence I foolishly assumed the 29.5 deg I could see on the scale was the one to use.   Wrong.  For some reason Grizzly decided to end the scale at 60 deg instead of 60 deg.
> 
> ...


Good idea!


----------



## matzo (Nov 19, 2017)

JimDawson said:


> Looks like a buttress thread     I'm going to guess that your compound is set to 29.5° from the wrong start point.  Start from the compound at 90° to the lathe centerline and rotate 29.5° counterclockwise.


You are right, the compound needed to be set on the other side (59 1/2 - 60 degrees)
Thanks


----------



## matzo (Nov 19, 2017)

matzo said:


> My threads are not vertical but seem to layover to one side. Using a sharpe 60 degree cutter, compound set at 29 1/2 degrees, cutter at 90 degrees to work.
> 
> I have added some photos of my setup. The pictures of the thread were taken through a magnifying light. I am keeping the cross slide at zero and feeding with the compound.


Thank everybody, the problem was the compound was incorrectly set at 29 1/2, should have been 59-60 degrees.


----------



## TakeDeadAim (Nov 19, 2017)

If you want to use the compound then it should be feeding at the same angle, to the centerline of the work, as one half of the thread angle.  Different machine makers put their degree scales with the angle reading either from the centerline or off perpendicular to the centerline (ex; 30 degrees either side of perpendicular.  Dave Pane shows a sure fire way to make sure your set up at the correct angle.

I have the compound removed from my lathe and the QCTP mounted direct to the cross slide to increase rigidity this means I must cut threads by feeding the cross slide.  With a good sharp tool this presents no issues and I actually find I get better threads with the set up I have.  Cross slide seems to be the weak link on a lot of lathes.

I cant see the insert tool you have close enough to tell so forgive me for asking, is that a specific threading insert or a standard 60* insert?


----------



## KevinL (Nov 19, 2017)

The above is correct, turn your compound to 59-60 and it will work out for you.


----------



## RJSakowski (Nov 19, 2017)

If you want to advance your compound in at 29.5º, you will have to set it to 60.5º.


----------



## Mitch Alsup (Nov 19, 2017)

29.5º  from 90º is 60.5º not 59.5º


----------



## matzo (Nov 19, 2017)

TakeDeadAim said:


> If you want to use the compound then it should be feeding at the same angle, to the centerline of the work, as one half of the thread angle.  Different machine makers put their degree scales with the angle reading either from the centerline or off perpendicular to the centerline (ex; 30 degrees either side of perpendicular.  Dave Pane shows a sure fire way to make sure your set up at the correct angle.
> 
> I have the compound removed from my lathe and the QCTP mounted direct to the cross slide to increase rigidity this means I must cut threads by feeding the cross slide.  With a good sharp tool this presents no issues and I actually find I get better threads with the set up I have.  Cross slide seems to be the weak link on a lot of lathes.
> 
> I cant see the insert tool you have close enough to tell so forgive me for asking, is that a specific threading insert or a standard 60* insert?


The tool that I took the picture with is a standard 60* tool, I am actually using a Mesa Tools threading tool with a carbide insert. After I reset the compound with the jig that Dave Pane showed it cut a nice 60* thread. 
Thanks for the help.


----------



## matzo (Nov 19, 2017)

matzo said:


> The tool that I took the picture with is a standard 60* tool, I am actually using a Mesa Tools threading tool with a carbide insert. After I reset the compound with the jig that Dave Pane showed it cut a nice 60* thread.
> Thanks for the help.


Just curious,should you not use a standard 60* insert tool to cut threads?


----------



## Asm109 (Nov 19, 2017)

If you are talking about the  equilateral triangle inserts, they will work but you cannot thread close to a shoulder with them.


----------



## Dave Paine (Nov 19, 2017)

matzo said:


> Just curious,should you not use a standard 60* insert tool to cut threads?



I have an HSS threading tool and a couple of carbide inserts, one is partial profile and one is full profile.  Both cut 60 deg threads.

For fine threads I may use a plunge cut with the carriage, e.g., 1/4x20 tpi.   I also need to cut coarse threads like 1 1/4in x 8pi for wood lathe spindle threads.   I use single point so using the compound at 29.5 deg.   I prefer a partial profile insert for this cut since some of the full profile inserts are not deep enough for this thread.  Check your insert for the maximum TPI it is designed to cut.


----------



## matzo (Nov 19, 2017)

Asm109 said:


> If you are talking about the  equilateral triangle inserts, they will work but you cannot thread close to a shoulder with them.


Is there some secret to getting clean cuts? My lathe recommends 125 RPM and lubricant. They turn out decent but require some clean up with a wire brush and file. I am not taking deep cuts.


----------



## Technical Ted (Nov 19, 2017)

In my experience, I get the best results using a nice, sharp HSS tool and use a good quality cutting oil. Others may have had different experiences, but when I used carbide to thread I found I needed to run at a high surface speed to get good results.

With HSS I've found you can run things slowly and still get good results, so that really helps when threading up to a shoulder.

YMMV,
Ted


----------



## BGHansen (Nov 19, 2017)

Not adding anything, but from your first photo it looks like you're at 60 deg.  On my G0709 lathe I set the compound to just a shade past 60 degrees to get what is conventionally called 29.5 deg.  The gauge idea above is great.  Your compound should be advancing on the angle of the right hand side of the cutter (at 30 deg.).

Bruce


----------



## mikey (Nov 19, 2017)

matzo said:


> Is there some secret to getting clean cuts?



Can you grind an accurate 60 degree HSS tool? If so, try a 15 degree relief angle on both sides and stone a 1/64" flat at the nose. Hone both sides and the top accurately. Use sulfur-bearing cutting oil (thread cutting oil from your local hardware store works) as a lube. Thread cutting is a high-pressure operation and sulfur-bearing oils work well for this. As Ted said, it is very difficult to beat the finish produced by a really sharp HSS tool, especially one that is ground with increased relief angles to reduce tangential cutting forces.


----------



## TakeDeadAim (Nov 19, 2017)

60 degree "Thread cutting" inserts are specific to that purpose.  As I said I can't see the photo clear enough to tell if this is a threading insert or a 60 degree turning insert.

Sorry I did not read down to the end, the Mesa thread tool and insert should work fine.


----------



## matzo (Nov 20, 2017)

matzo said:


> Is there some secret to getting clean cuts? My lathe recommends 125 RPM and lubricant. They turn out decent but require some clean up with a wire brush and file. I am not taking deep cuts.





mikey said:


> Can you grind an accurate 60 degree HSS tool? If so, try a 15 degree relief angle on both sides and stone a 1/64" flat at the nose. Hone both sides and the top accurately. Use sulfur-bearing cutting oil (thread cutting oil from your local hardware store works) as a lube. Thread cutting is a high-pressure operation and sulfur-bearing oils work well for this. As Ted said, it is very difficult to beat the finish produced by a really sharp HSS tool, especially one that is ground with increased relief angles to reduce tangential cutting forces.


I ground a 1/2" HSS blank to your recommended specs and was totally blown away with the quality of the cut, no additional cleanup required with wire brush or file.
Thanks
Brian


----------



## mikey (Nov 20, 2017)

matzo said:


> ... no additional cleanup required with wire brush or file.



Yeah, that's what I found, too. Much easier to hold tighter tolerances when the tool actually cuts what you dial in.


----------



## Aqua-Andy (Nov 20, 2017)

Matzo, don't feel bad.  I made this same mistake just a couple of weeks ago while trying to cut my first threads.  The folks here got me sorted out and my threads look great now.


----------



## jlsmithseven (Nov 20, 2017)

I don't know if anyone said this yet, but....are you threading this between centers or having that entire piece sticking out of the chuck jaws? It looks to me that it is bending as you're threading...you need to turn it between centers if this is happening because it looks like Aluminum and that bends pretty easily compared to Cold-rolled steel.

Also, which way are you threading from left > right or right > left. And which way is your chuck turning, towards or away from you?


----------

