Need some help with an M9x.75 die

[spindlecraft]

I genuinely appreciate all who responded to my most recent post asking for an M11 cheat sheet. But I now come to this amazing group once again seeking some help.

I am trying to make a slightly smaller section, using an M9x.75 tap and die.

For the body, I drilled an 8mm hole, and used the M9x.75 tap with no issues.

For the section, I turned a 9mm tenon - and thats where I'm hitting a snag. The 9mm tenon was too small, and the teeth of the die were barely biting. I did get "some" threads, but they were kind of shallow and "messy" for lack of a better term.

What's more is - when I attempted to thread the section into the body, the tenon can almost fit in without even touching the sides. It was way too small.
No twisting even necessary!

So… I thought maybe my math was wrong. I attempted it a second time, this time turning the tenon to 9.75mm.

The die did bite a bit more this time - however, the threads were still kinda junky, and once again, when I tried to thread it into the body, it was way too small.

There is not an adjustment pin on the die for me to tighten/loosen. So, any chance anybody can tell me what I am doing wrong here?

(Ps - I triple checked my tenon diameters. First run it was ~9.05mm. Second run, a perfect 9.75mm)

 

[duncsuss]

There is something very badly wrong with your die.

M9x0.75 is 9mm major diameter, 8.25mm minor diameter. Meaning - a straight drilled hole 9mm diameter should slide onto the threaded tenon, and an 8.25mm smooth rod should slide into the threaded hole with no slop (okay, realistically "with very little slop").

The tenon should be *just* under 9mm before you start threading it.

After using the die to cut the threads, I would expect the outer dimension to be around 8.8mm.

A hole drilled 8.25mm tapped with M9x0.75 should be perfect. Drilling 8mm before tapping with M9.0.75 will work, but it means cutting away material at the minor dimension which can result in threads which have "broken peaks".

 

[rherrell]

I genuinely appreciate all who responded to my most recent post asking for an M11 cheat sheet. But I now come to this amazing group once again seeking some help.

I am trying to make a slightly smaller section, using an M9x.75 tap and die.

For the body, I drilled an 8mm hole, and used the M9x.75 tap with no issues.

For the section, I turned a 9mm tenon - and thats where I'm hitting a snag. The 9mm tenon was too small, and the teeth of the die were barely biting. I did get "some" threads, but they were kind of shallow and "messy" for lack of a better term.

What's more is - when I attempted to thread the section into the body, the tenon can almost fit in without even touching the sides. It was way too small.
No twisting even necessary!

So… I thought maybe my math was wrong. I attempted it a second time, this time turning the tenon to 9.75mm.

The die did bite a bit more this time - however, the threads were still kinda junky, and once again, when I tried to thread it into the body, it was way too small.

There is not an adjustment pin on the die for me to tighten/loosen. So, any chance anybody can tell me what I am doing wrong here?

(Ps - I triple checked my tenon diameters. First run it was ~9.05mm. Second run, a perfect 9.75mm)

The tenon is too big, ideally it should be just a hair UNDER 9mm. I use the 10% rule, take 10% of the pitch and deduct it from the nominal diameter. .75mm(pitch) is roughly .030", 10% of .030" is .003". Deduct .003" from 9mm(.354") and your tenon should be 8.925mm (351").

 

[darrin1200]

I genuinely appreciate all who responded to my most recent post asking for an M11 cheat sheet. But I now come to this amazing group once again seeking some help.

I am trying to make a slightly smaller section, using an M9x.75 tap and die.

For the body, I drilled an 8mm hole, and used the M9x.75 tap with no issues.

For the section, I turned a 9mm tenon - and thats where I'm hitting a snag. The 9mm tenon was too small, and the teeth of the die were barely biting. I did get "some" threads, but they were kind of shallow and "messy" for lack of a better term.

What's more is - when I attempted to thread the section into the body, the tenon can almost fit in without even touching the sides. It was way too small.
No twisting even necessary!

So… I thought maybe my math was wrong. I attempted it a second time, this time turning the tenon to 9.75mm.

The die did bite a bit more this time - however, the threads were still kinda junky, and once again, when I tried to thread it into the body, it was way too small.

There is not an adjustment pin on the die for me to tighten/loosen. So, any chance anybody can tell me what I am doing wrong here?

(Ps - I triple checked my tenon diameters. First run it was ~9.05mm. Second run, a perfect 9.75mm)

Something seems very out of whack. Do you have a picture of the die?

 

[Paul in OKC]

Dies can be hard to start. Possibility of the die not moving as it's run on the tenon, then stripping it?

 

[spindlecraft]

So - per everybody's response, here is probably way more information that you need – but will hopefully help to elicit some additional help.

So – for starters, I took a bunch of scrap cutoffs that I had, and turned a couple of different tenons.

I also drilled an 8mm hole into a blank, and threaded the hole with a M9 tap:

This lead to a hole with an 8.16mm inner diameter (after the threads were tapped into it):

The first tenon I cut, was at 8.93mm (per @rherrell 's suggestion)

Here is a video of me turning the tenon (please ignore the shaky camera work. It's not easy trying to hold a phone and turn a tenon at the same time)

The result of this attempt lead to semi-decent threads, but too small of a tenon. After I turned the threads onto the tenon, the resulting diameter was 8.03mm.

And as you can see from the video below, the result was a non-fitting tenon into the tapped hole:

For attempt #2, I turned a slightly larger tenon at 9mm exactly.

This attempt resulted in some slightly nicer threads – and it actually works in that you can screw it into the threaded hole. But - as you can see from the video below, it's still a really loose fit, until you get towards the back of the threads:

And finally, for those who asked, here are some pics of my tap & die:

Alright – so.. with all of this information, does anybody have any tips on what I might do to tighten up the fit a bit?

One thought I had might be that because I am drilling an 8mm hole instead of an 8.25mm hole, it might be making the fit a little wonky. But – I don't know if there's any truth to that or not. I'm also not sure how easy it will be to find an 8.25mm drill bit.

Any other thoughts, suggestions or ideas?

 

[duncsuss]

Here is a really simple way to test whether that die is correctly specified.

All you have to do is turn a straight tenon (1" or more long, doesn't really matter how long but make it bigger than the thickness of the die). Aim for 8.25mm diameter along the entire length of this tenon.

Now see if you can slip the die onto it without it catching.

If the die is truly M9x0.75, it will be a slip fit on a tenon 8.25mm diameter, no force necessary. If it slips over the tenon, there is no reason why it should ever cut a thread that is a loose fit in a properly tapped M9x0.75 hole.

If the die won't slip on the 8.25mm tenon, they have marked it with the wrong size.

 

[JamesC]

Here is a really simple way to test whether that die is correctly specified.

All you have to do is turn a straight tenon (1" or more long, doesn't really matter how long but make it bigger than the thickness of the die). Aim for 8.25mm diameter along the entire length of this tenon.

Now see if you can slip the die onto it without it catching.

If the die is truly M9x0.75, it will be a slip fit on a tenon 8.25mm diameter, no force necessary. If it slips over the tenon, there is no reason why it should ever cut a thread that is a loose fit in a properly tapped M9x0.75 hole.

If the die won't slip on the 8.25mm tenon, they have marked it with the wrong size.

I genuinely appreciate all who responded to my most recent post asking for an M11 cheat sheet. But I now come to this amazing group once again seeking some help.

I am trying to make a slightly smaller section, using an M9x.75 tap and die.

For the body, I drilled an 8mm hole, and used the M9x.75 tap with no issues.

For the section, I turned a 9mm tenon - and thats where I'm hitting a snag. The 9mm tenon was too small, and the teeth of the die were barely biting. I did get "some" threads, but they were kind of shallow and "messy" for lack of a better term.

What's more is - when I attempted to thread the section into the body, the tenon can almost fit in without even touching the sides. It was way too small.
No twisting even necessary!

So… I thought maybe my math was wrong. I attempted it a second time, this time turning the tenon to 9.75mm.

The die did bite a bit more this time - however, the threads were still kinda junky, and once again, when I tried to thread it into the body, it was way too small.

There is not an adjustment pin on the die for me to tighten/loosen. So, any chance anybody can tell me what I am doing wrong here?

(Ps - I triple checked my tenon diameters. First run it was ~9.05mm. Second run, a perfect 9.75mm)

I fought the same problem. Finally figured out the die was wrong and the tap was off as well. I bit the bullet and replaced my 10.075 eBay tap and die with a TAPCO. The difference is amazing. Just my 2cents.
Jim

 

[rherrell]

I didn't see a chamfer on the tenon, a chamfer would help but I don't think that's your problem. Bite the bullet and get a better tap and die.

 

[monophoto]

There are others in this conversation who are far more expert on this subject than I am, but as I look at the pictures, I see the tenon being measured prior to threading, and I see a video of the loose tenon slipping into what should be a mating female thead. But I don't see a close photograph of the threaded tenon.

Later, there is a video of a second trial tenon that seems to fit better. In that video clip, we get a very brief view of the threaded tenon before it goes into the female. I may be mistaken, but it seems to me that the tenon is tapered, with the outboard end noticeably thinner than the inner end where the threads finally engage. Is that a correct perception? If so, then that may explain the problem

I've done some limited threading on projects other than pens, and I have had a few instances in which the die failed to cut the threads cleanly. Instead, it seemed to just chew up the tenon, resulting in very shallow threads with the major diameter much smaller than it was supposed to be. What is supposed to happen is that the die cuts an initial thread which then guides the die as it cuts successive threads. But what can sometimes happen is that the initial thread isn't cleanly established, and as the die advances, it damages the preceding threads. I don't have enough experience to know for sure what causes this, but my suspicion was that the tenon and die weren't lubricated. Nowhere in any of the pictures or videos, or in the discussion, is there a mention of lubrication. Are you applying some kind of lubricant to the tenon/die when you cut the threads, or are you attempting to cut them dry.

My knowledge on this subject is limited, but I have heard that common lubricants for this application include light machine oil (3-in-One), mineral oil, cooking spray, and KY.

 

[spindlecraft]

I didn't see a chamfer on the tenon, a chamfer would help but I don't think that's your problem. Bite the bullet and get a better tap and die.

I tend to agree. I think a higher quality tap & die is gonna make the difference here. I checked the Tapco website, and unfortunately didn't see any M9x.75's available. They have some other M9 dies – but no matching taps. I have an e-mail out to them though, so hopefully they have something that I'm just not seeing.

 

[spindlecraft]

There are others in this conversation who are far more expert on this subject than I am, but as I look at the pictures, I see the tenon being measured prior to threading, and I see a video of the loose tenon slipping into what should be a mating female thead. But I don't see a close photograph of the threaded tenon.

Later, there is a video of a second trial tenon that seems to fit better. In that video clip, we get a very brief view of the threaded tenon before it goes into the female. I may be mistaken, but it seems to me that the tenon is tapered, with the outboard end noticeably thinner than the inner end where the threads finally engage. Is that a correct perception? If so, then that may explain the problem

I've done some limited threading on projects other than pens, and I have had a few instances in which the die failed to cut the threads cleanly. Instead, it seemed to just chew up the tenon, resulting in very shallow threads with the major diameter much smaller than it was supposed to be. What is supposed to happen is that the die cuts an initial thread which then guides the die as it cuts successive threads. But what can sometimes happen is that the initial thread isn't cleanly established, and as the die advances, it damages the preceding threads. I don't have enough experience to know for sure what causes this, but my suspicion was that the tenon and die weren't lubricated. Nowhere in any of the pictures or videos, or in the discussion, is there a mention of lubrication. Are you applying some kind of lubricant to the tenon/die when you cut the threads, or are you attempting to cut them dry.

My knowledge on this subject is limited, but I have heard that common lubricants for this application include light machine oil (3-in-One), mineral oil, cooking spray, and KY.

This is great information regarding why the die seems to cut up the threads. This was not something that I had previously considered.

A couple of quick responses though.

a.) I did indeed lubricate both the tenon and the die prior to threading. I use WD40 for my lubricant, which generally works pretty well.

b.) I think the obviously tapered tenon that you're seeing is actually a poorly edited shot/angle. I see exactly what you mean – but that's just where I stopped the threading. The tenon itself was dead on and consistent from front to back.

Overall, I agree with everything you're saying. The only reason I feel like something is up is because I have made several kitless pens prior to this (albeit, using bigger taps & dies). These are my first attempts at using smaller taps & dies – and with all of the trouble I'm having, it's causing me to doubt everything that has been working up to this point.

 

[monophoto]

Overall, I agree with everything you're saying. The only reason I feel like something is up is because I have made several kitless pens prior to this (albeit, using bigger taps & dies). These are my first attempts at using smaller taps & dies – and with all of the trouble I'm having, it's causing me to doubt everything that has been working up to this point.

I'm an engineer (now retired). Many years ago, I took a course on problem solving, and one of the most important takeaways from it was that in troubleshooting a problem, the first question to ask is 'what has changed since it last worked properly?".

If this is the first time you have used that 9mm die, then that's the first thing you should look at as a cause for the problem.

 

[PatrickR]

I may have missed it but have you screwed the tap into the die? This would tell you if they are actually the same size and pitch.
do get a bit that is the correct size for the starter hole. I don't know the effect this may have but it can't be helping.

 

[Pierre---]

The problem could also come from the material you are threading: acrylic, ebonite and alumilite are good, but PR or some other stuff cannot be threaded correctly.

 

[JamesC]

I tend to agree. I think a higher quality tap & die is gonna make the difference here. I checked the Tapco website, and unfortunately didn't see any M9x.75's available. They have some other M9 dies – but no matching taps. I have an e-mail out to them though, so hopefully they have something that I'm just not seeing.

Might try Victor. They have the 9 x.75. They are good

 

[sorins]

So - per everybody's response, here is probably way more information that you need – but will hopefully help to elicit some additional help.

So – for starters, I took a bunch of scrap cutoffs that I had, and turned a couple of different tenons.

I also drilled an 8mm hole into a blank, and threaded the hole with a M9 tap:

This lead to a hole with an 8.16mm inner diameter (after the threads were tapped into it):
View attachment 336962



The first tenon I cut, was at 8.93mm (per @rherrell 's suggestion)
View attachment 336961

Here is a video of me turning the tenon (please ignore the shaky camera work. It's not easy trying to hold a phone and turn a tenon at the same time)

The result of this attempt lead to semi-decent threads, but too small of a tenon. After I turned the threads onto the tenon, the resulting diameter was 8.03mm.
View attachment 336963

And as you can see from the video below, the result was a non-fitting tenon into the tapped hole:

For attempt #2, I turned a slightly larger tenon at 9mm exactly.

This attempt resulted in some slightly nicer threads – and it actually works in that you can screw it into the threaded hole. But - as you can see from the video below, it's still a really loose fit, until you get towards the back of the threads:

And finally, for those who asked, here are some pics of my tap & die:




View attachment 336964

View attachment 336965


Alright – so.. with all of this information, does anybody have any tips on what I might do to tighten up the fit a bit?

One thought I had might be that because I am drilling an 8mm hole instead of an 8.25mm hole, it might be making the fit a little wonky. But – I don't know if there's any truth to that or not. I'm also not sure how easy it will be to find an 8.25mm drill bit.

Any other thoughts, suggestions or ideas?

What I see in the video using the die, is that the die is not perfect centered into the holder, it's quite visible as it makes complete turn. Check the frames at second 11 , respectively 15, the upper point of the die. Cross diametral points on the die are differently positioned relative to the die edge. This might be the reason of your problem. Just be sure the die is dead stable and its frontal plane is parallel with the die's edge's plane (be sure to evenly tight the screws of the holder). (I hope I explained quite clear and correct, English is not my mother tongue, though....)

 

[monophoto]

It appears to me that the die is not cutting clean threads. The threaded tenon is very slightly tapered, and the threads are almost non-existent. I can't tell if that is due to the die or a consequence of technique, but the threads are clearly inferior.

I suggest making another tenon from the same scrap, but threading it with a different die - the diameter is irrelevant since the purpose is to merely eliminate some variables. If that produces a clean thread, then it is likely that the problem is with the die. However, it that attempt produces a similarly inferior thread, then the problem is with either the material or the technique (which are interrelated).

 

[PatrickR]

If the die is not perfectly centered in the holder (probably never are) it will cause out of round at the least. Do not tighten the screws all the way. Only enough to keep the die from spinning. Start by turning cc by hand, allowing the die to self center then proceed to clockwise.