×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Tapping thick aluminum with m12 1.75 tap
4

Tapping thick aluminum with m12 1.75 tap

Tapping thick aluminum with m12 1.75 tap

(OP)
I'm trying to hand tap 1.5cm thick aluminum with an m12 1.75 tap, but can't get it to tap more that two thread revolutions before turning it becomes impossible (I actually damaged the wrench attempting to get it to continue turning.)

I'm using a 10.2mm drill bit with cutting fluid to drill all the way through the aluminum. I then start manually tapping (also with cutting fluid) with the m12 1.75 tap. I get about two full thread rotations before I can't tap any further. I can successfully thread the bolt easily through the threads that do get cut. I just can't cut any further.

- Is tapping a sheet this thick unreasonable?
- Should I partially drill out the hole to clearance (13.5) and just thread a few millimeters?
- Is my tap just garbage (should I buy a better quality tap?)

RE: Tapping thick aluminum with m12 1.75 tap

Are you reversing the tap every 1/4 to 1/2 turn to break your chips?

RE: Tapping thick aluminum with m12 1.75 tap

I would also look at your tap, if it is a 4 flute you may be better off with a 2 flute machine tap.
B.E.

You are judged not by what you know, but by what you can do.

RE: Tapping thick aluminum with m12 1.75 tap

(OP)
@SwinnyGG
I have been, but it didn't seem to help.

@berkshire
It's a four flute. I'll look into 2 flute.

RE: Tapping thick aluminum with m12 1.75 tap

My tap chart has 10.3mm pilot hole diameter for M12-1.75 and 75% thread and 10.9mm for 50% thread so at the very least I would increase from 10.2mm to 10.3mm drill. Depending on your application you could open it up even further.

Have you measured the pilot holes after drilling? Are they coming in at the expected size?

What type of tap are you using? A taper or plug tap would cut easier than a bottoming tap because of the increased lead in chamfer.

RE: Tapping thick aluminum with m12 1.75 tap

According to https://www.kennametal.com/us/en/resources/enginee... the torque to tap metric threads in aluminum is a bit over 4N-m

Tapping depth is not a consideration - the amount of material being cut per turn is the same once the tap is fully engaged.

Running crooked will make tapping difficult. If it's a bottoming tap being hand turned, it will be harder to run straight. It doesn't take much. Tapered taps are easier to manage.

In a previous question about poor drilling capacity it turned out to be due to a poorly made drill bit - perhaps there is a problem with the tap - buy a new one from a reputable source.

RE: Tapping thick aluminum with m12 1.75 tap

(OP)
@3DDave

Based on looking at the camfer, I think it's a bottoming or plug tap. I've ordered some higher quality taps, as well as a 10.9 mm drill bit. I'll let people know what works. Thanks for the advice!

RE: Tapping thick aluminum with m12 1.75 tap

(OP)
OK. It was pretty simple. The tap was crap :D It was new, but I replaced it and the aluminum threaded like going through butter.

Thanks to all for the input and suggestions.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Engineering Report - Top 10 Defect Types in Production
This 22-page report from Instrumental identifies the most common production defect types discovered in 2020, showcases trends from 2019 to 2020, and provides insights on how to prevent potential downtime in 2021. Unlike other methods, Instrumental drives correlations between a variety of data sources to help engineers find and fix root causes. Download Now
White Paper - Addressing Tooling and Casting Requirements at the Design Stage
Several of the tooling and casting requirements of a part can be addressed at the design stage. If these requirements are not addressed at the design stage, lot of time is spent in design iteration when the design reaches the die caster. These design issues lead to increase in time and cost of production leading to delay in time to market and reduced profits for the organization. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close