Thread Milling

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kstrauss
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Thread Milling

Post by kstrauss »

I decided to try the new thread milling capability and am having problems. With the attached sample, the thread mill cuts only a single helical pass even though the initial hole is 0.415 (10.5mm) in diameter and I specified a final diameter of 0.4724 (12mm). This makes the thread far to shallow. I am attempting to cut a M12-1.5 internal thread which requires a custom thread definition (Vectric only includes M12-1.75 in the preset possibilities). What am I missing?
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M12-1.5_test.crv
Thread mill test
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Leo
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Re: Thread Milling

Post by Leo »

on the toolpath dialog box - at the top - There are 3 variables.

Start Depth - 0.0 is probably OK
Max depth - you have a z - that it not OK - set the Max depth correctly
Thread length - you have .177 - If you want the thread to be deeper - change it accordingly

All else looks OK
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kstrauss
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Re: Thread Milling

Post by kstrauss »

Thanks Leo but I don't understand your comments.

According to the diagram (top right) at https://docs.vectric.com/docs/V10.5/Asp ... index.html the Max Depth (M) controls how far the end of the threadmill goes below the surface of the stock. Why is using "Z" not acceptable? It is a variable equal to the thickness of the stock as defined in the "Job setup" dialogue and VCarve doesn't complain when recalculating the toolpath. The "0.177" is not something that I can change but it is display only variable calculated by VCarve as M (Max Depth) minus O (as specified in the tool database for my threadmill).

kstrauss
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Re: Thread Milling

Post by kstrauss »

Leo, rereading your comments, I believe that you may have misunderstood my query. By "far too shallow" I meant that there was insufficient difference in diameter between the crests and valleys of the milled threads rather than that the threaded portion did not extend far enough below the surface of the stock. Sorry for the misleading description of my problem!

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martin54
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Re: Thread Milling

Post by martin54 »

How did you define your initial hole size at 0.415 ?

For an m12 x 1.5 internal thread if you use the option to generate the circle it gives you a smaller hole at 0.4085 :lol:

kstrauss
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Re: Thread Milling

Post by kstrauss »

Thanks, martin54, but the ISO standard for metric threads (see https://en.wikipedia.org/wiki/ISO_metric_screw_thread for a good summary) specifies flat rather than sharp thread crests. Using 0.4085 rather than 0.415 will result in sharp thread crests. Sorry to be pedantic but my machinist training is showing!

My issue is that VCarve generates a single helical pass of the threadmill and thus does not cut the threads deeply enough into the the sides of the central hole rather than that the bore is too large.

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Re: Thread Milling

Post by Leo »

Ahhhh OK.
I was unaware of using "Z"

Now I think what you are talking about is the major diameter of the thread being too shallow, correct??

I think that would be a function of the diameter of the thread mill. It is possible that you may have some deflection going on. You can make the description in the tool data base of the tool diameter smaller, then the cutting of the tool will be bigger. This is similar to what G41, G42 would do.
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kstrauss
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Re: Thread Milling

Post by kstrauss »

Bingo! It appears that I had a finger problem defining my threadmill. I'll try things in the shop later today. Thanks for your help.

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martin54
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Re: Thread Milling

Post by martin54 »

My issue is that VCarve generates a single helical pass of the threadmill and thus does not cut the threads deeply enough into the the sides of the central hole rather than that the bore is too large.

It should be cutting to the depth you have specified, what material are you cutting? I've only used the tread milling toolpath with wood & haven't had any problems but mostly large course threads.
May be some deflection going on as Leo suggested, have you tried running the toolpath twice to see if it cuts any deeper?
What diameter is the neck on your thread mill & are you using a single form or multi form bit? One of the small 60 degree thread mills I bought only has a 2mm neck so that is going to deglect quite easily in harder materials :lol: :lol:

Jan.vanderlinden
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Re: Thread Milling

Post by Jan.vanderlinden »

Does anyone have a source for the threading tool?
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Re: Thread Milling

Post by SteveNelson46 »

The one used in the Vectric video on Facebook is:

https://www.mscdirect.com/browse/tn/Mil ... 4287923947

You will need a 3/8" collet.
Steve

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Re: Thread Milling

Post by martin54 »

Jan.vanderlinden wrote:
Sun Sep 13, 2020 4:39 pm
Does anyone have a source for the threading tool?
Before you go ahead & buy a thread mill have a think about what size threads you want to be able to cut. There are a range of different sized cutters on the site Steve linked to so take a bit of time & try to find something that best matches the size of thread you want to be able to cut. :lol: :lol:
If you use a router & are limited on collet sizes then make sure you check the shank diameters, there is quite a range of different shank diameters on that page. If you are running a spindle then it shouldn't be so much of a problem because of the wider range of collets available.

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Re: Thread Milling

Post by Jan.vanderlinden »

Thank you for the response.
I have an X-carve with a 1/4 in. collet, so I'm very limited.
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