ruffrecords

Self tappijng screws and aluminium extrusion
« on: July 26, 2020, 04:57:12 PM »
Most of the aluminium extrusions I use for building mixers etc have tapped holes so they can be affixed to side plates. These are fine if you only want to use the standard length extrusions but if you need to cut the extrusion you need to tap the cut end so it can be affixed. However, I have several times come across extrusions that use self tapping screws instead of taps and machine screws. Now I always thought self tapping screws were really only meant for sheet metal and not for the half inch or so depth required to support an extrusion. Are self tapping screws a viable alternative for this application?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


Rob Flinn

Re: Self tappijng screws and aluminium extrusion
« Reply #1 on: July 26, 2020, 06:35:08 PM »
I had a job where they specified thread forming screws as opposed to self tapping.   They seemed much better.   In a nutshell instead of removing material to make the thread they shape the material into a thread.  The resulting thread is superior to that of a self tapper.
regards Rob

ruffrecords

Re: Self tappijng screws and aluminium extrusion
« Reply #2 on: July 27, 2020, 03:09:45 AM »
Interesting. I found a couple of thread forming types at Farnell but their data sheets said they were for use in plastic. In the job you mentioned were they specified for use in metal?

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Rob Flinn

Re: Self tappijng screws and aluminium extrusion
« Reply #4 on: July 27, 2020, 10:49:08 AM »
Interesting. I found a couple of thread forming types at Farnell but their data sheets said they were for use in plastic. In the job you mentioned were they specified for use in metal?

Cheers

ian

We used them into Aluminium extrusions for led lighting strips that were going into a Museum in Saudi Arabia.    They were Stainless Steel screws.  No idea where they came from, possibly RS.
regards Rob

JohnRoberts

Re: Self tappijng screws and aluminium extrusion
« Reply #5 on: July 27, 2020, 12:05:26 PM »
yup, my first generation drum tuner used a custom aluminum extrusion (I designed) and it took a little trial and error to get the optimal sized screw but works fine for modest number of assembly/disassembly cycles. 

===

At Peavey  I designed one U shaped aluminum extrusion that mated with bent steel top/front/back cover. This was a very flexible and cost effective package.

With typical extrusion profiles if you strip out the boss, you can just use a longer screw.

JR
It's nice to be nice....

abbey road d enfer

Re: Self tappijng screws and aluminium extrusion
« Reply #6 on: July 27, 2020, 05:01:19 PM »
Quite often I see a problem where it is actually very difficult to screw, which often results in stripping the Pozidrive recess, or the bit. Indeed it would not happen with Torx... Anyway, that's why most of the times I tap the holes. All things considered, it does not take much more time, and it's less stressing.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

rackmonkey

Re: Self tappijng screws and aluminium extrusion
« Reply #7 on: July 27, 2020, 05:20:34 PM »
I tend to agree with Abby here.

But if you're averse to tapping or trying to save time, another option is self-cinching nuts. Drill hole, press in nut, done!
Whether you think you can or you think you can't, you're probably right.

ruffrecords

Re: Self tappijng screws and aluminium extrusion
« Reply #8 on: July 27, 2020, 05:33:58 PM »
I tend to agree with Abby here.

But if you're averse to tapping or trying to save time, another option is self-cinching nuts. Drill hole, press in nut, done!

I agree with you both, tapping is best. However, some of the extrusions I have do not have metal round all 360 degrees. There is a small gap of 10 to 20 degrees. When I try to tap these what tends to happen is the metal just bulges at the 10 to 20 degree gap. I am hoping thread forming screws will not suffer from this.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JohnRoberts

Re: Self tappijng screws and aluminium extrusion
« Reply #9 on: July 27, 2020, 11:00:52 PM »
I agree with you both, tapping is best. However, some of the extrusions I have do not have metal round all 360 degrees. There is a small gap of 10 to 20 degrees. When I try to tap these what tends to happen is the metal just bulges at the 10 to 20 degree gap. I am hoping thread forming screws will not suffer from this.

Cheers

Ian
This is all by design... when you tool up an extrusion you can pretty much make the shape anything you want... The screw thread and extrusion profile are designed for each other.
----
For TMI back in the 60s I had a HS summer job working in a machine shop (supporting an oceanographic research ship) and I had to tap holes in the ends of 50' long pipes so they could be attached together (using couplings and many screws) to make even longer pipes for drilling and recovering cores from the ocean floor.

For 8 hours a day, weeks at a time, I drilled and tapped holes in steel pipes.. I believe I tapped a lifetime worth of holes that summer.

JR   
It's nice to be nice....


abbey road d enfer

Re: Self tappijng screws and aluminium extrusion
« Reply #10 on: July 28, 2020, 03:38:40 AM »
I agree with you both, tapping is best. However, some of the extrusions I have do not have metal round all 360 degrees. There is a small gap of 10 to 20 degrees.
That is quite common, indeed.

Quote
When I try to tap these what tends to happen is the metal just bulges at the 10 to 20 degree gap.
I have not noticed that. Do you have a picture? Can I suggest your tap is inadequate /worn out? Machine taps are better suited for that task than hand taps.

Quote
I am hoping thread forming screws will not suffer from this.
https://www.workshopshed.com/2015/07/thread-cutting-screws/
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

ruffrecords

Re: Self tappijng screws and aluminium extrusion
« Reply #11 on: July 28, 2020, 04:11:52 AM »
I have not noticed that. Do you have a picture? Can I suggest your tap is inadequate /worn out? Machine taps are better suited for that task than hand taps.
It is quite a while since I last tried tapping an extrusion so I do not have a picture of it. My taps may be inadequate; they were not expensive. They are a set of three - start, cut and finish but I have used them no more that 5 times so I don't think they are worn.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

abbey road d enfer

Re: Self tappijng screws and aluminium extrusion
« Reply #12 on: July 28, 2020, 05:50:40 AM »
It is quite a while since I last tried tapping an extrusion so I do not have a picture of it. My taps may be inadequate; they were not expensive. They are a set of three - start, cut and finish but I have used them no more that 5 times so I don't think they are worn.

Cheers

Ian
I really recommend you buy a machine tap. You can use a cordless drill. Using a combined drill/tap such as this
https://www.amazon.fr/Newder-eu-hexagonale-taraudage-plastique-aluminium/dp/B07PV6JKJH/ref=sr_1_9?dchild=1&keywords=taraud+machine&qid=1595931274&refinements=p_n_availability%3A437882031%2Cp_76%3A437878031&rnid=437877031&rps=1&s=hi&sr=1-9
helps because the drill part helps guiding the tap concentrically.
« Last Edit: July 28, 2020, 06:17:57 AM by abbey road d enfer »
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

ruffrecords

« Last Edit: July 28, 2020, 05:03:59 PM by ruffrecords »
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JohnRoberts

Re: Self tappijng screws and aluminium extrusion
« Reply #14 on: July 28, 2020, 10:50:17 AM »
Wow, I love this place, I never knew those even existed... clever.

I only knew "gun" taps (for use with power tools), with only two wider flutes so the metal chip doesn't clog the hole, and standard 4 flute taps that require backing up every couple turns to break the metal chip and prevent jamming/clogging. 

JR
It's nice to be nice....

abbey road d enfer

Re: Self tappijng screws and aluminium extrusion
« Reply #15 on: July 28, 2020, 11:12:17 AM »
Wow, I love this place, I never knew those even existed... clever.

I only knew "gun" taps (for use with power tools), with only two wider flutes so the metal chip doesn't clog the hole, and standard 4 flute taps that require backing up every couple turns to break the metal chip and prevent jamming/clogging. 

JR
Academically, machine taps should be used with a column drill and an auto-reverse tapping head, but it's not convenient for long aluminium profiles, and the head costs $$$. You have to do a lot of tapping to justify the cost.
These hybrid drill+tap combine conveniently.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

Related Topics

  Subject / Started by Replies Last post
10 Replies
8632 Views
Last post July 19, 2004, 02:04:20 PM
by BYacey
5 Replies
1895 Views
Last post December 16, 2008, 08:00:34 AM
by Ptownkid
18 Replies
4180 Views
Last post June 24, 2013, 06:44:25 PM
by gemini86
3 Replies
1716 Views
Last post July 29, 2013, 09:41:38 AM
by sahib