New acme nut for my mill.

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Terry Keeley

Well-Known Member
Supporting Member
Joined
Jul 24, 2002
Messages
7,116
Not exactly boating related but it's been kinda quiet around here.

Never made an acme nut before but it came out nice.


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If there is one thing in my grass roots machining life I am totally disappointed in it's my ability to thread anything on the lathe . I just have never spent the time to properly learn the process . Everything for me is always how fast I can get something done and out the door . I am going to buy myself a brand new lathe this year or a mint used one . I have a worn Enco rockcrusher now .
 
If there is one thing in my grass roots machining life I am totally disappointed in it's my ability to thread anything on the lathe . I just have never spent the time to properly learn the process . Everything for me is always how fast I can get something done and out the door . I am going to buy myself a brand new lathe this year or a mint used one . I have a worn Enco rockcrusher now .

Hi Tom
Let me know when you want to learn to cut threads. I’ll be glad to come up and show you. I taught 25 students per year for 20 years. Hope I remember how!
John
 
If the thread is a 60 degree v type you set the compound at 30 degrees ie: if you a facing the lathe the compound is set 30degrees to the right. For proper thread cutting most lathes always had a thread chasing dial mounted on the right side of the carriage and engaged the lead screw. The dial let’s you engage the half/splitnut level in the same place each time. Depth of cut is gained by advancing the compound feed. On a square thread the compound would be straight in as the thread face is 90 degrees, on an acme thread it would be set to the right at the angle of the thread face. You get the idea. There’s more details but that’s a short summary.
Thanks John
 
If the thread is a 60 degree v type you set the compound at 30 degrees ie: if you are facing the lathe the compound is set 30degrees to the right. For proper thread cutting most lathes always had a thread chasing dial mounted on the right side of the carriage and engaged the lead screw. The dial let’s you engage the half/splitnut level in the same place each time. Depth of cut is gained by advancing the compound feed. On a square thread the compound would be straight in as the thread face is 90 degrees, on an acme thread it would be set to the right at the angle of the thread face. You get the idea. There’s more details but that’s a short summary.
Thanks John
 
Yup, all good stuff.

You havta think about which way to set the compound (to the right or left) depending on whether you're doing an internal/external or right/left hand thread, lol.

Here's one for ya.

When you do metric threads on an inch machine why do you have to keep the half nut engaged and reverse the spindle to back the carriage out? You would think if you engaged the half nut at the same dial number each time the thread would work but for some reason it doesn't.

Hmmm...
 
Yup, all good stuff.

You havta think about which way to set the compound (to the right or left) depending on whether you're doing an internal/external or right/left hand thread, lol.

Here's one for ya.

When you do metric threads on an inch machine why do you have to keep the half nut engaged and reverse the spindle to back the carriage out? You would think if you engaged the half nut at the same dial number each time the thread would work but for some reason it doesn't.

Hmmm...
Terry,

That's how the crusty old toolmaker I mentored under did it; kept the half nut engaged for metric threads. He HATED metric threads.

Now..... On my Hardinge HLV-EM, it's just a matter of flipping the E-M dial to "M", and I'm good to go.

Everything John just gave you is spot on, EXCEPT.... (and this is more a matter of preference)....

I like to set my compound about a half degree shy of the thread face angle. This ensures you don't "walk away" from the thread face as you advance the compound. On my ProtoTrak lathe, the threading cycle defaults to 29.5 degree advancement (you can change it, which you would obviously have to do for anything other than a 60 degree included thread profile), so they must agree with this approach. I think most other CNC lathe MFRs do as well. Unless you are doing a REALLY deep thread profile, there is little more than a slight skim against the "non-working" edge of the threading tool.

One other thing.... I like to run my dials to zeros. Meaning, I advance the compound to zero and I have the X-axis dial set on zero when I'm chasing threads. After you've cut your threads (hopefully oversized initially) and you check your pitch diameter, if you have to make an adjustment, I'd advise doing it with the X-axis dial and re-cutting the thread, starting over with the compound advancement to zero. This will save you from forgetting that the compound will give you almost double the change you dial off. I had to learn this the hard way. This will also keep you from slamming into a shoulder, if your close enough to worry about it (like I often am), as the X-axis dial doesn't advance the Z-axis location the way the compound does.

Taking notes? :cool:

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC
 
Terry,

That's how the crusty old toolmaker I mentored under did it; kept the half nut engaged for metric threads. He HATED metric threads.

Now..... On my Hardinge HLV-EM, it's just a matter of flipping the E-M dial to "M", and I'm good to go.

Everything John just gave you is spot on, EXCEPT.... (and this is more a matter of preference)....

I like to set my compound about a half degree shy of the thread face angle. This ensures you don't "walk away" from the thread face as you advance the compound. On my ProtoTrak lathe, the threading cycle defaults to 29.5 degree advancement (you can change it, which you would obviously have to do for anything other than a 60 degree included thread profile), so they must agree with this approach. I think most other CNC lathe MFRs do as well. Unless you are doing a REALLY deep thread profile, there is little more than a slight skim against the "non-working" edge of the threading tool.

One other thing.... I like to run my dials to zeros. Meaning, I advance the compound to zero and I have the X-axis dial set on zero when I'm chasing threads. After you've cut your threads (hopefully oversized initially) and you check your pitch diameter, if you have to make an adjustment, I'd advise doing it with the X-axis dial and re-cutting the thread, starting over with the compound advancement to zero. This will save you from forgetting that the compound will give you almost double the change you dial off. I had to learn this the hard way. This will also keep you from slamming into a shoulder, if your close enough to worry about it (like I often am), as the X-axis dial doesn't advance the Z-axis location the way the compound does.

Taking notes? :cool:

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC


HLV-EM, Homer drool!





What do you mean by "walk away" from the thread face? Never did understand why you set the compound 1/2* shy of the actual angle.

I think I get that last paragraph, I set the x axis at zero and run the compound in to the thread depth leaving it at the previous cut. I then back the x axis off, retract the carriage and return to zero. Is that what you mean?

When I got my Super 11 I almost traded my 3 phase motor for a single phase thinking the extra work to hook up a VFD wasn't worth it. Am I ever glad now I didn't! Slowing to a crawl at the end of a thread to a shoulder is sweet...
 
Terry,

Yup. Mine looks just like that, only with many years of chip rash to brag about.

Follow me here....

If you place the point of a threading tool right at the theoretical sharp tip of a 60 degree included angle thread profile, then you walk the threading tool toward the root of the thread profile, at a perfect 30 degree advance, it will end up perfectly at the root of the thread profile, which would be fine. But, if you're a little OVER 30 degrees, it will "walk away" from the thread profile, and will collide with the other side before meeting the root. If you are too far over 30 degrees, this will produce a small "double" thread, and will likely render a useless part. If you are a little UNDER 30 degrees, you are always engaging the "back" side of the threading tool, as well as the "working" side, and, therefore, when you reach the root, you will have a perfect thread profile. At only a half degree, there is so little actual back side engagement, it is all but negligible, but it ensures a perfect thread profile. On a 3/8-16 thread, there's about .0003" actual engagement on the back side of the threader at full profile. Or, so says AutoCad.....

Yes. That is exactly what that last paragraph is describing. I actually use that exact method on my Hardinge, even though it's got a compound retract lever, which should negate the need to even touch the X axis dial. But, I find it not to be as accurate as I'd like, so I just crank the X axis dial in and out. It also keeps me paying attention to the dial, which can sometimes wander around while you're cranking other dials and such.

I always make an undercut behind the thread at the shoulder. This allows me to set the chase kick-out so that the threader stops shy of the shoulder, but doesn't dwell in the material.

We'll make you into a real toolmaker yet....

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC
 
Drop it out and spin the handle as fast as you can at the same place every time.....LOL
Love my old 1952 #9
 
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