First Try at Metric Threading

[erikmannie]

Looks good! Most of what I do is metric. I don’t mind keeping the half nuts engaged and reversing, it doesn’t seem any slower than using the threading dials once you get some practice.

What kind of threading tool is that? I already bought an Arthur Warner on edge holder, but that looks interesting.

Here is the link to the threading tool:

Aloris CXA-8

www.ajaxtoolsupply.com

and blade:

High Speed Threading Blades, 60º, P-6

www.aloris.com

 

[erikmannie]

Are you running a VFD on your lathe? If so, check your deceleration time and shorten it stop quicker.

No VFD. I have an RPC. Wiring is not one of my strengths.

 

[erikmannie]

Erik, you're developing some tearing on the trailing edges of the threads. This might have to do with how the Aloris blade is ground; you may be at the limits of the helix angle that tool will allow. You might also check to see if the blade is level/horizontal; the bolts have some play so check to see if it is level.

The other thing is that your thread relief is a bit too shallow. When the tool runs off into that thread relief there should be no contact of the tool with the work. Typically, the depth of the thread relief is 0.003-0.005" deeper than the minor diameter of the thread. This will not affect the strength of the work piece.

The (single, see photo) bolt was tight, and it is horizontal.

I’m glad you told me that about the thread relief (safety groove). I have been making it the minor diameter.

I have next week off, and I will be doing nothing but making metric nuts and bolts; I will get to see how all my HSS & carbide 60° tools work, being mindful of the previously unconsidered helix angle that you mentioned.

I went to the hardware store and bought M4 through M18 nuts and bolts in both fine and coarse, where applicable. I am allowing myself 7 days to make one nut & one bolt of everything.

 

[7milesup]

Erik, you're developing some tearing on the trailing edges of the threads. This might have to do with how the Aloris blade is ground; you may be at the limits of the helix angle that tool will allow.

I have done no threading on my lathe. Yet.
I am trying to understand the helix angle comment. Is the angle (pitch) of the thread so great that the trailing portion of the thread is in interference with the trailing part of the cutter. Just trying to wrap my head around this.
As a side note, Martin Cleeve's book "Screwcutting in the Lathe" just arrived at my door two days ago. Have only had a chance to look at the first few pages so far.

 

[BGHansen]

Question: why don’t people with inch pitch leadscrews leave the half nut engaged throughout the whole operation for Imperial threading as well, as we do with metric threading? It is no trouble at all, and there is no worry about missing the mark on the thread dial. It would coast the same distance if I used the E-stop button

That's generally how I thread. It goes faster for me since I don't have to wait for the thread dial number to come around. If I'm using the thread dial, I back the carriage up to my number, engage the half nuts, set the cross feed and compound, then fire up the lathe.

On the other hand, I am using the half nuts to back up the carriage so potentially some added wear to the nuts. But it isn't under load and I'm not a production shop.

Bruce

 

[SLK001]

Question: why don’t people with inch pitch leadscrews leave the half nut engaged throughout the whole operation for Imperial threading as well, as we do with metric threading? It is no trouble at all, and there is no worry about missing the mark on the thread dial. It would coast the same distance if I used the E-stop button.

Second question: I’m curious to see what is going to happen when I try a much smaller safety groove and stop the threading pass with my foot brake. When I disengage my power lever to stop power, it coasts for about 8 mm as the chuck is spinning down.

First question: Because it is easier to just manually run the carriage back to the starting position. Also, with a thread dial, you're sure to be able to pick up your sync.

Second question: I don't really depend that much on a safely groove. I rapidly pull back the cross slide once I hit my end-of-thread mark.

 

[markba633csi]

The thread dial would save time if you were doing lots of repetitive threading jobs in a production shop like in the olden days, especially when using a slow spindle speed w/backgears
-M

 

[Ischgl99]

Here is the link to the threading tool:

Aloris CXA-8

www.ajaxtoolsupply.com

and blade:

High Speed Threading Blades, 60º, P-6

www.aloris.com

Cool idea!

Sounds like you are doing the metric threading for your own knowledge. The Germans have a standard for everything, so of course one for the thread relief. You have to pay for the German standards and it’s a copyright violation to publicly post the standards, but the Indians decided to use many of them for their own. This link shows how they do a thread relief to DIN 76-1 standards.

https://law.resource.org/pub/in/bis/S01/is.1369.2.1993.pdf

And this is a link to how they do undercuts for bearings, gears, etc that butt up against a shoulder according to DIN 509

https://law.resource.org/pub/in/bis/S01/is.3428.2009.pdf

 

[mattthemuppet2]

doesn't look like there's any back rake on the threading tool - I found I got a similar finish with a flat top HSS threading tool. I don't get the same problem with a carbide threading insert with back rake.

Having the runoff groove the same as the minor diameter of the thread is actually pretty useful as it gives a nice visual indicator for when you have reached full thread depth as you'll get a scratch pass in the runoff groove.

Plus side of the half nuts is that you can use a much shorter runoff groove as the carriage stops instantly (or thread at a higher rpm). You can even disengage the half nuts with metric threads as long as the carriage doesn't move far enough for a complete revolution of the threading dial. Then retract the tool, wind the carriage back to the threading dial mark, re-engage the halfnuts and reverse the lathe back to the start.

 

[mikey]

I have done no threading on my lathe. Yet.
I am trying to understand the helix angle comment. Is the angle (pitch) of the thread so great that the trailing portion of the thread is in interference with the trailing part of the cutter. Just trying to wrap my head around this.
As a side note, Martin Cleeve's book "Screwcutting in the Lathe" just arrived at my door two days ago. Have only had a chance to look at the first few pages so far.

Have a look through this thread and see if it helps clarify helix angles for you.

Edit: I think Cleeve's book should be required reading for hobby guys.