12 X .75 METRIC tap and die sloppy fit

[JLL]

12 X .75 METRIC tap and die sloppy fit - I am using 11.25 drill and a tenon cut at 11.85 - very sloppy not sure why - is this normal ?

 

[Ed McDonnell]

Sloppy is not normal.

12.85 for the tenon isn't right. 11.85?

Measure the drilled hole before tapping to make sure you are not oversizing due to a drilling problem.

Measure the tenon size before cutting the thread and then after. A big reduction in size might indicate your die is too tight, if you are using an adjustable die.

Are you sure you are using M12 x 0.75 for both tap and die?

What material are you cutting threads in?

Ed

 

[JLL]

Sloppy is not normal.

12.85 for the tenon isn't right. 11.85?

Measure the drilled hole before tapping to make sure you are not oversizing due to a drilling problem.

Measure the tenon size before cutting the thread and then after. A big reduction in size might indicate your die is too tight, if you are using an adjustable die.

Are you sure you are using M12 x 0.75 for both tap and die?

What material are you cutting threads in?

Ed

Opps typo error 11.85 tenon yes adjustable die -aluminum

 

[low_48]

Ed is right on. Is the hole to size and round? How sharp is the drill? Do you use a starter drill? If you want dead on, drill undersized and ream to size.

 

[edstreet]

It's obvious from this photo what the problem is.



The fit is around 75% which is fine if you are working on cars and not pens or small fit items like pens etc., what you need to look at is this.






Here we see Dminor is in fact 11.188. Which means your hole size is to large.

 

[edstreet]

Oh and the tenon should be Dmajor, or 12.000 mm.

 

[Cmiles1985]

The big question is: what app is that Ed?

 

[JLL]

12 X .75 METRIC tap and die sloppy fit - I am using 11.25 drill and a tenon cut at 11.85 - very sloppy not sure why - is this normal ?

Btw this is not a a pen cap fitting - another project - finale detail

 

[edstreet]

Does not matter if it's a pen or not.

 

[BSea]

I'd also like to know what app that is.

I do think the tenon is too small when using aluminum. Seems like I've heard that an acrylic blank will flex a little when drilling and cutting. So all things being equal, the threads on something like alumilite or ebonite should be a little tighter than threads in aluminum. I think the 1st thing I'd do is do the piece with the tenon again and use 11.95 of maybe even slightly larger. It's true that your hole may be too large too, but I'd make one part, and see if things improve. If so, but you still think there is too much slop, then you can do the other part.

 

[JLL]

Thanks Bob will try it out never had any trouble before like this - new tap and die set for a finale detail on a new design.

 

[Ed McDonnell]

Android: Check out North American Tool's "Tap Hole Size Calculator" in the play store.

Apple: Don't know....don't care....maybe it's there and maybe it's not.

The calcs are pretty simple. Pick up a used machinist handbook and make a little spreadsheet if apple doesn't have a useful app.


Ed

 

[JLL]

Does not matter if it's a pen or not.

Very true - never had this problem before

 

[duncsuss]

Jake, it just occurred to me to ask: what are you using to measure the tenon? Can you trust that measuring tool?

If you have some reference items -- a 12mm drill bit or transfer punch, for example -- check that your calipers are accurate.

 

[Curly]

I have a couple for the iPhone that I use. There are lots of free or modestly priced apps for machining you just need to poke around a little.

ITAMCO Drill and Tap

iMachinist.