Anyone know of any 3mm tapping countersunk hex screws that can replace tamiya JIS?

[nowinaminute 2815]

A bit of a random one but I recently brought a load hex head tapping screws to retrofit to various models just to make them a bit easier to work on and more uniform without the need to try and convert to machine thread. 

The only thing I'm having trouble with is the countersunk screws. M3 machine thread/hex head screws have a head diameter around 5.7-6mm but TAPPING countersunk/hex head all seem to be 6.8-7mm so they wont fit into the chasiss holes properly.

Anyone ever seen anything suitable? I know most people either stick with the stock JIS or convert to machine thread but I'm been working on a lot of older cars that already have threads in them from self tappers so these hex+tapping screws have been a great compromise.

Failing that, what's the best way to go to machine screws? Can you just screw them straight in or is it better to use a tap to make a thread? Are the holes large enough to tap fresh out of a kit or do they need widening? And if the holes have already had self tappers in will they be too loose to use machine screws?

[Jontea 334]

Tap the threads, it's very therapeutic, and satisfying once finished and everything bolts together so nicely. 

Gonna do it to all my builds from now on.

You'll struggle tapping pre screwed holes, but fresh holes just need a 3mm 0.5 tap.

[DeadMeat666 1675]

I love tapping threads. I tapped every single screw hole on the M07 and all the holes on the TT02 hard blue chassis before assembly. Screws fit in so much more easily and lock in with a satisfying change in torque that is easy to detect, which helps avoid stripping.

[davidwj95 152]

Dont use a normal tap, use a fluteless thread forming tap for plastic. 

[nowinaminute 2815]

I'll be honest I have had bad experiences with thread forming taps and plastic including the plastic cracking and splitting. I seem to get the plastic springing back to shape afterwards too and resulting in the screws being super tight.

Always found a fluted tap works better by removing some material even if the overall strength of the threads is technically weaker. It just seems to put less stresses on the plastic. Ymmv.

[DeadMeat666 1675]

The thread tap I use is fluted, and I've had zero issues so far, but to be fair I only use it on strengthened plastics and not the soft type. It does create some shavings when I use it, but it's a really small amount.

[TwistedxSlayer 1290]

Tamiya make a lovely tap just for this occasion. I have one in my tool kit.

[Manix92 121]

The Tamiya tap in the UK is like £20, I saw the price and just thought forget it. The fact that you can get a set M3 1st, 2nd and 3rd taps by the likes of Presto or Dormer for much less sealed the deal for me.

[martinjpayne 273]

I've been using these on both soft and reinforced plastics, instead of the Tamiya thread forming tap (which I also own), for the last 15 months with no problems... put a fresh dab of Vaseline on the tip (I keep a lip salve tin on my workbench for this) before cutting a thread and clean with a brass wire brush when they start to clog. The advantage is I can easily do ball connectors for turnbuckles with the left-hand thread.

 https://www.ebay.co.uk/itm/Select-Variations-M1-2-to-M22-HSS-Right-Hand-Thread-Forming-Tap-for-Aluminum-/113917056796?var=&hash=item1a85fc571c

https://www.ebay.co.uk/itm/Select-Variations-M2-to-M16-HSS-Left-Hand-Thread-Forming-Tap-for-Aluminum-/123932650618?var=&hash=item1cdaf62c7a

You'll want them in M3 x 0.5 size.

[AJB123 107]

On 8/12/2020 at 10:20 AM, martinjpayne said:

I've been using these on both soft and reinforced plastics, instead of the Tamiya thread forming tap (which I also own), for the last 15 months with no problems... put a fresh dab of Vaseline on the tip (I keep a lip salve tin on my workbench for this) before cutting a thread and clean with a brass wire brush when they start to clog. The advantage is I can easily do ball connectors for turnbuckles with the left-hand thread.

 https://www.ebay.co.uk/itm/Select-Variations-M1-2-to-M22-HSS-Right-Hand-Thread-Forming-Tap-for-Aluminum-/113917056796?var=&hash=item1a85fc571c

https://www.ebay.co.uk/itm/Select-Variations-M2-to-M16-HSS-Left-Hand-Thread-Forming-Tap-for-Aluminum-/123932650618?var=&hash=item1cdaf62c7a

You'll want them in M3 x 0.5 size.

Sorry to revive an old thread, but I'm looking at getting an M3 thread forming tap to use with some Tamiya carbon reinforced plastic parts for my XV-01. Can't decide whether to get the really expensive Tamiya one, or a 3rd party ebay one.

Do you think that your Tamiya and non-Tamiya ones make threads exactly the same size? The 3rd party ones seem to be 6HX, which apparently means "very slightly oversized" and is apparently normally used on thread forming taps as the tapped material will spring back a bit (I never knew there was so much I didn't know about taps!!). I was just wondering if Tamiya was the same, or if it was smaller because they know they want a tight bite in soft plastic that will stretch again with the real screw anyway.

If there's a size difference I'll fork out for the Tamiya one, if not I'll save my money and get something cheaper!

[Manix92 121]

3 hours ago, AJB123 said:

Sorry to revive an old thread, but I'm looking at getting an M3 thread forming tap to use with some Tamiya carbon reinforced plastic parts for my XV-01. Can't decide whether to get the really expensive Tamiya one, or a 3rd party ebay one.

Do you think that your Tamiya and non-Tamiya ones make threads exactly the same size? The 3rd party ones seem to be 6HX, which apparently means "very slightly oversized" and is apparently normally used on thread forming taps as the tapped material will spring back a bit (I never knew there was so much I didn't know about taps!!). I was just wondering if Tamiya was the same, or if it was smaller because they know they want a tight bite in soft plastic that will stretch again with the real screw anyway.

If there's a size difference I'll fork out for the Tamiya one, if not I'll save my money and get something cheaper!

You are fine just getting standard taps, as I mentioned earlier you can get a full set of Presto or Dormer 1st, 2nd and 3rd taps for less money which makes the tamiya price a joke.

Put that in context, at best the Tamiya version may be the same the quality, if you are lucky, as Presto or Dormer. You use Presto and Dormer in industry.

 

[martinjpayne 273]

45 minutes ago, Manix92 said:

You are fine just getting standard taps, as I mentioned earlier you can get a full set of Presto or Dormer 1st, 2nd and 3rd taps for less money which makes the tamiya price a joke.

Put that in context, at best the Tamiya version may be the same the quality, if you are lucky, as Presto or Dormer. You use Presto and Dormer in industry.

 

Actually, you're not. 1st, 2nd and 3rd taps remove material to form the thread: this is okay for hard metals but not for plastics (and some softer metals), hence the need for a thread forming tap which displaces the material and does not compromise strength.

4 hours ago, AJB123 said:

Do you think that your Tamiya and non-Tamiya ones make threads exactly the same size? The 3rd party ones seem to be 6HX, which apparently means "very slightly oversized" and is apparently normally used on thread forming taps as the tapped material will spring back a bit (I never knew there was so much I didn't know about taps!!). I was just wondering if Tamiya was the same, or if it was smaller because they know they want a tight bite in soft plastic that will stretch again with the real screw anyway.

If there's a size difference I'll fork out for the Tamiya one, if not I'll save my money and get something cheaper!

Okay, checked both my Tamiya and Chinese unbranded thread forming (roll) tap: dimensionally they are identical, square with rounded corners min 2.8mm max 3.1mm. Placed alongside each other the threads mesh with no gaps. The Tamiya one is HSS with a flat tip, the Chinese one is HSS with a TiN coating and has a pointed tip. (this may be a problem if your screw needs to reach the bottom of a blind hole).

**Unscientific test warning** Compared to an M3x0.5 tapped hole in a sample standard ABS TT02 chassis there is less play in the formed hole, and the torque required to strip an M3x8mm screw is higher.

I've used the Chinese unbranded thread forming tap on Tamiya ABS, ABS-GF, PA and PC plastics with no problems on a good fifteen or more models.

[nowinaminute 2815]

11 minutes ago, martinjpayne said:

I've used the Chinese unbranded thread forming tap on Tamiya ABS, ABS-GF, PA and PC plastics with no problems on a good fifteen or more models.

Which is interesting because the very first time I used a forming tap on a DT-03 chassis I suffered multiple cracks/fractures. Also on an M-05 steering rack because I didn't like how tight the brass ball joints felt so I thought I'd use the tap first but it still split.

Do you drill the holes at all first? I feel like not all Tamiya screw holes are made equal. The ones intended for self tappers seem a little smaller than ones Tamiya intend you to put machine screws in.

And presumably using a manual hand wrench and not any kind of power tool?

[matisse 1581]

Picked up the thread forming tap and hand chuck from Plaza a while back and they were a game changer. 
 

had been cutting threads using a standard tapping tool from machine mart and had fouled a few holes, not happened yet with the forming tap 

[Manix92 121]

2 minutes ago, martinjpayne said:

Actually, you're not. 1st, 2nd and 3rd taps remove material to form the thread: this is okay for hard metals but not for plastics (and some softer metals), hence the need for a thread forming tap which displaces the material and does not compromise strength.

Okay, checked both my Tamiya and Chinese unbranded thread forming (roll) tap: dimensionally they are identical, square with rounded corners min 2.8mm max 3.1mm. Placed alongside each other the threads mesh with no gaps. The Tamiya one is HSS with a flat tip, the Chinese one is HSS with a TiN coating and has a pointed tip. (this may be a problem if your screw needs to reach the bottom of a blind hole).

**Unscientific test warning** Compared to an M3x0.5 tapped hole in a sample standard ABS TT02 chassis there is less play in the formed hole, and the torque required to strip an M3x8mm screw is higher.

I've used the Chinese unbranded thread forming tap on Tamiya ABS, ABS-GF, PA and PC plastics with no problems on a good fifteen or more models.

I think most people will find with the glass filled/carbon fibre polymers the standard taps will be fine. I've had no problems.

You can't reform glass/carbon fibre, the polymer you can. That is a quandary in itself.

[Manix92 121]

12 minutes ago, nowinaminute said:

Which is interesting because the very first time I used a forming tap on a DT-03 chassis I suffered multiple cracks/fractures. Also on an M-05 steering rack because I didn't like how tight the brass ball joints felt so I thought I'd use the tap first but it still split.

Do you drill the holes at all first? I feel like not all Tamiya screw holes are made equal. The ones intended for self tappers seem a little smaller than ones Tamiya intend you to put machine screws in.

And presumably using a manual hand wrench and not any kind of power tool?

If the hole has not been called up to tap in the tamiya instructions it is incorrect to use a tap on it be it especially form.

Cut taps have a smaller tapping drill to form taps having a larger tapping drill. This is of especial concern for form taps because they will crack weak material or edge distance is small where the tapping hole is incorrect.

[martinjpayne 273]

@nowinaminute never drilled any holes... most M3 holes on Tamiya chassis are 2.8mm or more by my digital caliper and the M3 thread forming tap drill size is 2.81mm. 🤷‍♂️ Just use vasaline, forming taps need to be well lubricated.

@Manix92 The only chassis I've made which calls up the forming tap in the instructions is the TRF201, however, about the forming tap Tamiya says:

★This handy tap can be used to thread holes for 3mm screws in components such as R/C car chassis. ★It not only ensures that the screw will fit smoothly, yet nice and tightly, it does so without leaving waste plastic in the hole. ★Perfect for those who plan to re-assemble their chassis on a regular basis.

Seems like Tamiya think it's okay.  I would also say we shouldn't be replacing tapping screws with machine screws, except Tamiya will quite happily do so when it suits them.

[martinjpayne 273]

1 hour ago, nowinaminute said:

Which is interesting because the very first time I used a forming tap on a DT-03 chassis I suffered multiple cracks/fractures. Also on an M-05 steering rack because I didn't like how tight the brass ball joints felt so I thought I'd use the tap first but it still split.

Sometimes I think it's down to bad batches of plastic. For instance, screwing the rims to the wheels on my CR01 kit split nearly every screw hole in all four wheels. The replacement wheels I bought went together no problem at all. Similarly, my first DF03Ra's damper mounts cracked screwing the ball connectors in: later ones were fine (this was before I had a forming tap). 🤷‍♂️

Oh, and yes manual hand tool... you get to feel any snagging (not enough grease) or when it bottoms out.

[AJB123 107]

18 hours ago, martinjpayne said:

Actually, you're not. 1st, 2nd and 3rd taps remove material to form the thread: this is okay for hard metals but not for plastics (and some softer metals), hence the need for a thread forming tap which displaces the material and does not compromise strength.

Yes, I do already have a set of "normal" cutting taps, but didn't want to use them on the plastic.

18 hours ago, martinjpayne said:

Okay, checked both my Tamiya and Chinese unbranded thread forming (roll) tap: dimensionally they are identical, square with rounded corners min 2.8mm max 3.1mm. Placed alongside each other the threads mesh with no gaps. The Tamiya one is HSS with a flat tip, the Chinese one is HSS with a TiN coating and has a pointed tip. (this may be a problem if your screw needs to reach the bottom of a blind hole).

Thank you so much for taking the time to measure those - that's exactly what I wanted to know. I'll buy myself a cheaper one then, and feel comfortable that it's going to do just as good a job! I did find one with a flat tip, so think I'll go for that for the reason you said.

[Pylon80 2631]

The Tamiya forming thread tap is a fantastic tool as long as you use plenty of grease. Else the results are disastrous, at least they were in my case.

If you really want self tapping screws then Square makes some. They are titanium and will set you back at the very least 1$ each. They fit right into the thread left by the Tamiya kit tapping screws for an easy retrofit.