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Tapping plastic during build

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Tapping plastic during build

Old 12-13-2020, 03:06 PM
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Default Tapping plastic during build

I've got a couple new kits that'll be built soon.

Pros and cons of running an appropriate sized tap into the plastic parts to thread them vs letting the screw tap it as it goes?

I've always let the screw tap it. Wondering if threading all or part of the hole will make for a stronger overall build because the threads are cut.
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Old 12-13-2020, 04:41 PM
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I like using a ballstud, it has a longer/tighter hex and I use an electric drill to make it fast. Some holes depending on what they are (like where a steering rack mounts too, or transmission) I'll mostly tap it but leave some new material for the final assembly to help hold it better.

Some times on steering blocks or where plastic is thin I'll camper the holes or use an actual tap as some builds/replacement parts have cracked on me like my early build B74. But updated parts and a quick pass with a body reamer and zero issues.

Ballcups get some black grease on the treads and I work them back and forth to break them in for easy adjustment
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Old 12-13-2020, 05:58 PM
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I personally do not use taps on my builds, all by brute hand strength. Sorta old school like that.
I do use high pressure grease on the screws during the build.

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Old 12-13-2020, 08:28 PM
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As above, I just tap self-tap the screw for that area with black grease using a hex driver.

I use chap stick for the ball cups, and do the reverse thread side on all the turnbuckles first. Then, I use the appropriate screw to tap the regular threaded ball cup. I always make sure to tap these deeper than I plan to run them so they can move in a crash rather than binding and popping off.

If you use an electric driver, depending on the speed and clutch as well as the screw size of you run the risk of overheating the screw and deforming the plastic or stripping the plastic. Take it slow and use a driver like the Hitachi/Metabo with a real clutch (not electronic) if you go the electric driver method.

There's no disadvantage I can think of to tapping the holes with a tap though except the extra time vs minimal benefit. If you have the patience, go for it. The possible advantage is that the chips of plastic have a way of exiting the hole via the slots in the tap as you cut, rather than just compressing the plastic with the threads.
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Old 12-14-2020, 02:22 AM
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if you use a tap you remove material and that means you lose strength.
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Old 12-14-2020, 02:46 AM
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If you have a 3 stage tap set (3 taps) then use stage 1 or 2 but not number 3. With nr 1 or 2 the screw still will be tight. But normally no tap is needed.
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Old 12-14-2020, 03:26 AM
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Roelof's tip might be a good idea, if the plastic is really tough. However there's also the possibility to use a thread forming tool. That doesn't remove any material, it's not a cutting process, it deforms the material. Well, that's basically what any screw does, that is threaded into the plastic the usual way. A thread forming tool has the slight benefit, that it is tapered at the tip, so that you need a little bit less force to do so. But frankly, I'm not sure if it is worth the extra work.

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Last edited by andreas78; 12-14-2020 at 04:30 AM.
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Old 12-14-2020, 05:53 AM
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Don't recall ever using a tap or needing to use a tap in assembling a kit or replacing molded or formed RC parts. Manufacturers generally hold to a tolerance that properly sizes the hole for a fastener to deform on install for best holding power.

Taps, by nature of their design, are cutting tools, not forming tools. Using a cutting tool, e.g., tap, introduces 'stress risers' into the hole and the part. Using the appropriately provided screw into the desired part deforms the thread without introducing a stress riser into the part.

What I have done is pre-form the hole using (usually) a socket head cap screw in and out. The larger head provides better purchase to hold the tool straight and true for initial screw install. On occasion, I will clamp the part while running the screw in and out to hold it steady. Parts and cars these days tend to use smaller button head screws that are hard to work with in initially pre-forming a hole.

[Edit. One thing I have noticed is that some mau's use the shortest screw possible in order to save weight. This does not always provide proper thread length to engage the part to hold securely. Sometimes, it is prudent to use a longer screw in areas where loads are high.)

My 2cents. Cheers. 'AC'
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Last edited by AHR43; 12-14-2020 at 06:10 AM.
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Old 12-14-2020, 06:49 AM
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why make things difficult?

I use a low voltage cordless drill with the softest clutch setting and let it do all the work, on some of my 1/8 cars I'll need to increase the clutch when going into new plastic, but during rebuilds I typically go back to the lower clutch settings... once you get your clutch figured out then that is the only "tool" necessary for efficient builds.

I've been using this drill here for a couple years now and have never stripped a thread when rebuilding any of my diffs, perfect amount of torque every time!
Amazon Amazon

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https://www.rcgroups.com/forums/show...-the-pit-table

*** When building camber links you definitely want to "break in the threads" like this:

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Old 12-14-2020, 06:49 AM
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Originally Posted by Silverbullet555 View Post
I've got a couple new kits that'll be built soon.

Pros and cons of running an appropriate sized tap into the plastic parts to thread them vs letting the screw tap it as it goes?

I've always let the screw tap it. Wondering if threading all or part of the hole will make for a stronger overall build because the threads are cut.
Originally Posted by Alexv2024 View Post
I like using a ballstud, it has a longer/tighter hex and I use an electric drill to make it fast. Some holes depending on what they are (like where a steering rack mounts too, or transmission) I'll mostly tap it but leave some new material for the final assembly to help hold it better.

Some times on steering blocks or where plastic is thin I'll camper the holes or use an actual tap as some builds/replacement parts have cracked on me like my early build B74. But updated parts and a quick pass with a body reamer and zero issues.

Ballcups get some black grease on the treads and I work them back and forth to break them in for easy adjustment
I've never greased threads prior to threading for easier adjustment. Makes sense.

Originally Posted by Juglenaut View Post
I personally do not use taps on my builds, all by brute hand strength. Sorta old school like that.
I do use high pressure grease on the screws during the build.
I don't know if using a tap is new school or old school. Saw someone using one at the track and thought I would ask.

Originally Posted by mushroomed View Post
As above, I just tap self-tap the screw for that area with black grease using a hex driver.

I use chap stick for the ball cups, and do the reverse thread side on all the turnbuckles first. Then, I use the appropriate screw to tap the regular threaded ball cup. I always make sure to tap these deeper than I plan to run them so they can move in a crash rather than binding and popping off.

If you use an electric driver, depending on the speed and clutch as well as the screw size of you run the risk of overheating the screw and deforming the plastic or stripping the plastic. Take it slow and use a driver like the Hitachi/Metabo with a real clutch (not electronic) if you go the electric driver method.

There's no disadvantage I can think of to tapping the holes with a tap though except the extra time vs minimal benefit. If you have the patience, go for it. The possible advantage is that the chips of plastic have a way of exiting the hole via the slots in the tap as you cut, rather than just compressing the plastic with the threads.
Good thoughts. Well aware of the over heating or stripping. One reason why I won't let me son use an electric driver.

Originally Posted by UK.hardcore View Post
if you use a tap you remove material and that means you lose strength.
Not necessarily.

Originally Posted by Roelof View Post
If you have a 3 stage tap set (3 taps) then use stage 1 or 2 but not number 3. With nr 1 or 2 the screw still will be tight. But normally no tap is needed.
What's a 3 stage tap? Link. Quick google look in between work stuff didn't yield much.

Originally Posted by andreas78 View Post
Roelof's tip might be a good idea, if the plastic is really tough. However there's also the possibility to use a thread forming tool. That doesn't remove any material, it's not a cutting process, it deforms the material. Well, that's basically what any screw does, that is threaded into the plastic the usual way. A thread forming tool has the slight benefit, that it is tapered at the tip, so that you need a little bit less force to do so. But frankly, I'm not sure if it is worth the extra work.

Andreas
I'm not sure either. Trying to decide that as well.

Originally Posted by AHR43 View Post
Don't recall ever using a tap or needing to use a tap in assembling a kit or replacing molded or formed RC parts. Manufacturers generally hold to a tolerance that properly sizes the hole for a fastener to deform on install for best holding power.

Taps, by nature of their design, are cutting tools, not forming tools. Using a cutting tool, e.g., tap, introduces 'stress risers' into the hole and the part. Using the appropriately provided screw into the desired part deforms the thread without introducing a stress riser into the part.

What I have done is pre-form the hole using (usually) a socket head cap screw in and out. The larger head provides better purchase to hold the tool straight and true for initial screw install. On occasion, I will clamp the part while running the screw in and out to hold it steady. Parts and cars these days tend to use smaller button head screws that are hard to work with in initially pre-forming a hole.

[Edit. One thing I have noticed is that some mau's use the shortest screw possible in order to save weight. This does not always provide proper thread length to engage the part to hold securely. Sometimes, it is prudent to use a longer screw in areas where loads are high.)

My 2cents. Cheers. 'AC'
Interesting about stress risers. I would've thought forming the threads would introduce more stress risers than cutting the threads. I'm not 100% convinced that manufacturers ever really consider the stress of tapping the screw other than will it crack or not. Often times, building a kit without the extra work is acceptable and fine. However, in the same token, sometimes the top tier (of which I am not) do the extra things that make a difference. Back in the day (late 80's) most people didn't spend a lot of time on hinged pins. Some of us, ran reamers through parts to ensure a smooth fit without slop. We also polished pins to improve the suspension without introducing movement. I realize materials are much better these days. Back then, most everything was nylon so it had more flex to it than today.

Anyway, not sure it is needed or even desired which is why I asked the question.
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Old 12-14-2020, 06:51 AM
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Originally Posted by billdelong View Post
why make things difficult?

I use a low voltage cordless drill with the softest clutch setting and let it do all the work, on some of my 1/8 cars I'll need to increase the clutch when going into new plastic, but during rebuilds I typically go back to the lower clutch settings... once you get your clutch figured out then that is the only "tool" necessary for efficient builds.

I've been using this drill here for a couple years now and have never stripped a thread when rebuilding any of my diffs, perfect amount of torque every time!
https://www.amazon.com/Metabo-HPT-DB...oupsconvert-20

Best investment I ever made out of any tool I own!
https://www.rcgroups.com/forums/show...-the-pit-table

I wouldn't call it difficult. I would call it adding some steps that in the long run might make it better. I'm not convinced it well which is why I ask the questions. We will be adding a cordless driver, but I'll have to keep it away from my son until he learns the finer touch.
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Old 12-14-2020, 08:23 AM
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This is such a set: The one stripe is stage-1, the 2 stripe is stage-2 and the no stripe is the actual full sized thread. You can see a clear difference of the depth of the thread.....

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Old 12-14-2020, 08:26 AM
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Originally Posted by Juglenaut
I personally do not use taps on my builds, all by brute hand strength. Sorta old school like that.

“I do use high pressure grease on the screws during the build.
I don't know if using a tap is new school or old school. Saw someone using one at the track and thought I would ask.”

I am old school in the sense that I do not use powered hand tools yet, key word. And have been using some sort of faucet grease since the 90’s can’t remember what it is called.. high pressure thou and use it on orings all day.
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Old 12-14-2020, 08:33 AM
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I will put it this way there are drill bits made for plastic so are taps. If one uses a tap made for metal on plastic it will remove material.

Use one made for threading Plastic and thats all it should do.

Tap it or pre-thread, but I do not recommend Anything besides a screw.
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Old 12-14-2020, 08:39 AM
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Originally Posted by Juglenaut View Post
I will put it this way there are drill bits made for plastic so are taps. If one uses a tap made for metal on plastic it will remove material.

Use one made for threading Plastic and thats all it should do.

Tap it or pre-thread, but I do not recommend Anything besides a screw.
Thanks for that additional comment. I should have known that, but hadn't thought about it that way.
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