Threading Help

[marrtw]

I'm trying to cut a 20mm 2.5 thread on a Grizzly 14x40. You can see the results in the image below. I'm using an Arthur Warner HSS threading tool (60 degree tip). All gears and associated settings are correct. I keep the threading lever engaged throughout (thread, stop, pull out, reverse, thread again). The setup is rigid. Speed is 70 rpms. Compound is 29 degrees. Thread tool is properly set with a fish tail.

The "left" side of the thread is 30 degrees. The right is much more. Not sure what I'm doing wrong.

 

[12bolts]

My initial response is loose gibs on the compound. I see a parabolic curved cut resisting the advance of the tool into the work. But.
Are you sure the 29* is correct? Possibly the degree markings are not spot on? Check it with a protractor. Are you advancing the cut with the compound, (top slide) or the cross slide?
Depth of cut? The further, (deeper) you cut the thread the more you are taking off each time. May need to reduce DOC as you get further in

Cheers Phil

 

[bosephus]

Not sure about your lathe but on my g0602 I have to set the compound at 60.5 degrees on the scale to thread .

 

[brino]

It looks to me like your compound angle is set wrong.

If your tool is 60 deg. and set "square" to the work with a fish-tail, but the compound angle is off, then feeding the tool in will cause what I see above.
The right-side of the thread is off, but the left side is OK because it is controlled by the tool grind and setup.

How is your top-slide angle measured? Is "zero" parallel to the centre line of the work or perpendicular to it?
Depending on that answer you may need to set it to 60 deg. to get the proper angle.

By the way, those are great close-up photos....those can be hard to get in focus...good work!

-brino

 

[higgite]

The steps on the right side of the thread indicate that your threading tool is set properly but your compound is set way more than 30 degrees from perpendicular to the work piece. The included angle on the threading tool is 60 degrees, so both sides should be 30 degrees from perpendicular. The left side of your thread is as it should be, but the right side is a series of tiny 30 degree steps, caused by misalignment of the compound, that combine to form an angle of 60 degrees.

Tom

 

[Billh50]

It looks like the compound is set to 30 degrees parallel instead of vertical (looking at photo ). Therefore causing a 60 degree on the right side. The tool will still give you 30 degree on the right side.
This of course is if you are using the compound to feed in.

 

[marrtw]

Well, you guys were spot on. Apparently, I needed to set the scale at 60 degrees on the Grizzly (I used 59). Doh! It's my first thread, so please forgive me.

 

[marrtw]

Regarding the pictures, I'm using a cheapo Kodak Z950. The last pic (above) is a bit blurry. I took a better picture but it didn't save (probably cut the camera off too quickly...it's a bit slow to save). My wife has a Nikon D500. However, for some reason, she won't let me take it into the shop. Women.

It's amazing what you can get these days. Take a look at the Cannon Powershot SX60

. The zoom on that thing is INCREDIBLE for the money.

Thanks again guys.

 

[higgite]

Well, you guys were spot on. Apparently, I needed to set the scale at 60 degrees on the Grizzly (I used 59). Doh! It's my first thread, so please forgive me.
<Deleted image>

I'm nit picking, but you actually should set the compound at 61 degrees on the scale to be 29 degrees from perpendicular to the thread. You are forgiven. No one else has ever messed up their first thread before. <I say as I dodge lightning bolts>

Tom

 

[Wreck™Wreck]

It's not necessary to use the compound slide at an angle on such a small thread, just do it from the cross slide straight in.
I realize that this is heresy in the hobbyist world but have been doing it this way for the last 30 years without problem, however once you reach very large very coarse threads (say 2 1/2-4 and above) it may help on a wiggly machine.