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"Form Tapping" V-slot Extrusions

Posted by hobbymods 
"Form Tapping" V-slot Extrusions
August 04, 2020 03:04AM
Has anyone seen this before?

[www.youtube.com]

I'm reading that this is the correct way to tap aluminium extrusions, and that the threads are much better/stronger in aluminium. Anyone heard that before?

They're not cheap compared to normal, but if I'm knocking together a frame I'd like it to be straight and strong. I'm considering using an additional method to add some strength by using an M5 flat head screw in the slot and screwing into the tapped center of the extrusion, as it seems little extra trouble and is apparently and accepted way to use the Openbuilds V slot channel.

I like the idea of having the butted ends pulled in snug, then the corner plates on top of that. Looks like a lot more strength for a little extra trouble.

Any thoughts or experiences with this?
VDX
Re: "Form Tapping" V-slot Extrusions
August 04, 2020 03:16AM
... this is common for connecting extrusions since 30+ years (at least, when I've used it first) smoking smiley


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: "Form Tapping" V-slot Extrusions
August 04, 2020 03:33AM
Quote
VDX
... this is common for connecting extrusions since 30+ years (at least, when I've used it first) smoking smiley

Yes, so I hear and mentioned in my first post.

Can anyone say if it's worthwhile/better/necessary?
VDX
Re: "Form Tapping" V-slot Extrusions
August 04, 2020 04:51AM
... it's a pretty straightforward solution for end-connections, much cheaper than other fixing types with prefabbed parts/modules ...


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: "Form Tapping" V-slot Extrusions
August 04, 2020 07:35AM
To be honest, I thought this was the only normal way to do it. I used to do it by hand in three steps. But now I realize the shops've been lying to me and I can just use the last step tap in a drill and get the same results.

It's a great way to fix beams together. Also, if you want to make a 90º corner, you can drill a hole through the side of the other extrusion and just pull a bolt through.


http://www.marinusdebeer.nl/
Re: "Form Tapping" V-slot Extrusions
August 04, 2020 10:16AM
Assembling the frame that way really only works if the end of the tapped piece is square. If not, you're going to need to use plates to hold the members square to each other. You will probably need to mill the ends to ensure squareness. I've been assembling frames that way from my first printer, but I have access to mills...


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: "Form Tapping" V-slot Extrusions
August 04, 2020 06:17PM
Quote
the_digital_dentist
Assembling the frame that way really only works if the end of the tapped piece is square. If not, you're going to need to use plates to hold the members square to each other. You will probably need to mill the ends to ensure squareness. I've been assembling frames that way from my first printer, but I have access to mills...

Yes that is a point, and shimming things to make them square would not be acceptable to me on a brand new build.

I did note that RatRig had a pretty good aluminium cutting saw that they were talking up on FB, so I'm going to assume/hope that these extrusions are cut nice and square.

Is there a "go to" home mitre saw and blade combo capable of cutting v slot at home to any precision? Has anyone managed precision cuts at home on a budget?

Edited 1 time(s). Last edit at 08/05/2020 02:42AM by hobbymods.
Re: "Form Tapping" V-slot Extrusions
August 05, 2020 03:19AM
The point here is to use an extrusion (thread forming) tap instead of a cutting tap ! They are of course not just to tap Al extruded profiles.
This method gives a stronger thread besides Al is a bitch to machine ! You are more likely to break a cutting tap in Al than in regular steel.
These taps are more expensive, the hole must be the correct size and of course it needs good lubrication.

Edited 1 time(s). Last edit at 08/05/2020 03:21AM by MKSA.


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: "Form Tapping" V-slot Extrusions
August 05, 2020 11:48PM
Quote
MKSA
The point here is to use an extrusion (thread forming) tap instead of a cutting tap ! They are of course not just to tap Al extruded profiles.
This method gives a stronger thread besides Al is a bitch to machine ! You are more likely to break a cutting tap in Al than in regular steel.
These taps are more expensive, the hole must be the correct size and of course it needs good lubrication.

Yes that's pretty much where I'm at about it. I want the better/stronger thread enough to pay for the forming tap. I've actually always enjoyed machining aluminium, but yes it is sensitive about lubrication/cutting speeds/tool sharpness/etc.

I've had a stroke of luck, as our local "mens shed" (I think it's an Australian equivalent to American "Makerspace") has 2x lathes, cut off saw and a milling machine in their metalwork section. This is a bit unusual as most Mens Sheds focus on woodwork, and it's 15 minutes from my place as well so I'm happy.

My hopes are I might be able to mill the ends of my vslot then plunge a tapping drill (if the extrusion hole isn't correct already) and the tap all on the machine.

Edited 2 time(s). Last edit at 08/06/2020 12:03AM by hobbymods.
Re: "Form Tapping" V-slot Extrusions
August 06, 2020 06:39AM
I don't think he type of tap you use means much other than the mechanical effort required to use the tap. If you get about 1 cm of threads in the hole for the screw to grip it will be fine and you won't be able to strip the hole by turning the screw with a hand tool.

If you're talking about tapping 2020 t-slot your joints will be tight and strong, but the t-slot will still be flexible as over cooked spaghetti.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: "Form Tapping" V-slot Extrusions
August 06, 2020 05:40PM
Quote
the_digital_dentist
I don't think he type of tap you use means much other than the mechanical effort required to use the tap. If you get about 1 cm of threads in the hole for the screw to grip it will be fine and you won't be able to strip the hole by turning the screw with a hand tool.

If you're talking about tapping 2020 t-slot your joints will be tight and strong, but the t-slot will still be flexible as over cooked spaghetti.

Actually, it seems that these forming taps are the choice of manufacturers working with the old T slot extrusion. From what I found they regularly cited a better/stronger thread with the forming tap.

Yes, this kit is 2020 V slot, but there's sections of 2040 and some cross bracing. It seems they've given it some thought, but I'll look at reinforcement as well. For starters there'll be a full ally sheet on the back and floor at least. I won't tolerate a wobbly chassis, that's no way to start the build. The reviews have said it's pretty solid.

I really hope the ends are cut square from the factory, that would save some drama.

**While I've got you here...what do you use to measure longer lengths precisely?

Edited 1 time(s). Last edit at 08/06/2020 05:41PM by hobbymods.
Re: "Form Tapping" V-slot Extrusions
August 06, 2020 11:40PM
The longest pieces in the frame of my printer were too long for the Bridgeport mill table I used to square and match their lengths. I ended up clamping the pieces together then squaring one end, flipping it over and squaring the other end. Those are vertical corner pieces of the frame and the absolute length wasn't critical, just the relative lengths. Even the squareness didn't really matter because nothing bolts to the ends of those pieces. I was able to fit all the shorter pieces on the mill and cut both ends to accurate/matched lengths and square. The DRO on the mill let me mill them to better then 0.1 mm accurate length and much better than that relative lengths.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: "Form Tapping" V-slot Extrusions
August 07, 2020 06:30AM
Just a brief note about squaring up extrusions. In the distant past, before 'T' slot extrusion was popular, my father had to make up an aluminium frame from 1" square aluminium bar. Hd did this with a hacksaw, some files, a Moore and Wright square, a test flat and some machinists blue - and most importantly, a scraper made from a modified wood chisel. This last because it is just about impossible to use a file to get anything flat.

While I would always take any extrusion to a helpful machine shop to have it cut and machined square, I should point out that this would take me half a day and cost whatever they felt like charging: My father did 12 ends to at least the accuracy of a decent milling machine in the same time and without having to pay for the machine shops time.

If, for lack machinary or machine shop, for lack of money, because of time constraints, or for any other reason you are unable to get the work done on a power machine, it can still be done. Most importantly, the knowledge (or an old book on workshop techniques), a scraper, machinists blue, a test flat and considerable patience are critical to success.

Mike
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