thread forming using a screw, instead of taps in aluminum.

[hobby]

Here is a good tip to thread holes without taps, in aluminum stock.

Instead of breaking taps in aluminum workpieces, I decided to drill the hole for a 2-56 screw a little bit oversize, and use the screw itself to do thread forming, instead of thread cutting, this is working real well, I think I can do this trhoughout the whole project for aluminum workpieces, sure saves a lot of wear and tear on my taps, tapping steel works good because of the hardness of the material, no binding of the tap as with aluminum being on the gummy side, causes taps to bind and break more easily.

I don't know how well it works with larger diameter screws, but works excellent for the very fine threads as the 2-56 I'm doing.

But the screw should have cutting oil on it, to keep the screw from sticking and breaking off.
If the screw head does break, it can be redrilled out, unlike a tap, that is too hard to drill out.

But using the proper size drill to allow easy thread forming works good in aluminum stock.
Best to experiment to find the best drill size for the screw being used.
　

 

[Tin Falcon]

Here is a good tip to thread holes without taps, in aluminum stock.

This may work for you but I am not comfortable recommending this.

use the screw itself to do thread forming, instead of thread cutting,

why not just use a thread forming tap. instead of risking breaking off screws.

And please make sure you use proper sized tap holes for forming.
??

 

[hobby]

Hi Tin,

It works for me because I have only a couple of 2-56 taps, and it costs to buy more taps especially with shipping costs, but I have hundreds of tiny machine screws, for me its an alternative to use screws for thread forming, because I have plenty of them to acomplish the task.

With the proper size hole drilled it tightens up real well.

It will only work in aluminum, because its soft material.

That way I can save my taps for threading in steel.

 

[Sshire]

I use form taps for small holes and it works very well. No chips to bind means less chance of breaking a tap. Since I started using form taps for 0-80, 1-72 and 2-56 threading, I have no broken taps. Here is a chart for the correct tap drill sizes for thread forming.

http://www.championscrew.com/form_tap_drill.htm

 

[hobby]

Hi Sshire:

Thankyou for that chart,

I found a 5/64" bit to work real well for my 2-56 screws as tap forming, and just checking the chart, I found that I was very close to actual size drill, used for thread forming taps, my choice of drill was just a bit smaller, than the actual size used.
Not bad for experimenting with drill hole sizes to get the best thread I can get using this method.

 

[barnesrickw]

I use slightly larger drills for aluminum because it's sticky, and I have a large collection of 2-56 and 4-40 broken taps.


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[MCRIPPPer]

using a screw works good for me too. it helps if you grind some flats on the end to help it start.

 

[texta]

i use the correct drill and the correct tap for the job , i also use a lube while tapping and i go very carefully . and i dont break any tiny taps .
i am more likely to break larger taps 3/16 and up because i tend to be a bit harder on them knowing they are more robust so i have broke 2 or 3 of those over the last few years .
i find the smaller taps screw in very easy because of the very shallow depth of the thread .and the main reason i use the correct sizes when tqpping is so that i have the correct depth of thread .

johno

 

[valentin]

Well, the lack of conicity when you use screw instead of tap could result in misalignement of the thread. I think about it as a last option, and always consider better wait for the monday and buy the proper tool!.