Solid Inserts continue to strip

[greesha]

Question is regarding an audi aluminum block.
Bolt hole in question needs to be torqued to 35nm. It holders one of the pulleys attached to the timing belt tensioner.

It is the hole for the dark bolt on the top left of the pulley with the red rubber in the middle of the picture.

THE PROBLEM:

As the hole was previously repaired with a helicoil, by the previously owner, that backed out, I put in a big sert. Bolt is a M8x1.25

I was unable to remove the big sert with an easy out, and drilled it out.

I ran a tap through the threads, cleaned them up, and tapped threads farther into the drilled hole.

EZ Loks use a m12 outer diameter for their M8 internal diameter insert.

Would it be possible to use a m16 outer diameter inert that has a m12 inner diameter, and place the m8 insert inside of it.

I measured, and there seems to be just enough material around the bolt hole for a 14mm drill bit.

 

[FastKat]

I don't see why you couldn't use an EZ Lok in another EZ Lok. Use plenty of Loctite!

I have two alternate ideas:

A) I am working with something like this right now. I am going to make my own insert:

1) Find a bolt with the desired outside thread size
2) Weld the head of bolt flat to a piece of steel so the threads bolt points straight up
3) Mount the piece of steel to a drill press
4) Drill and tap the center of the bolt to the desired size
5) Cut off the bolt to the desired length and install with Loctite

By making your own, you get to pick exactly the sizes you need. You can even match SAE and metric if necessary.

B) Use an SAE EZ-Lok. For instance, there is one with a 9/16-12 OD and 5/16-18 ID. 5/16 is REALLY REALLY close to 8mm, and 9/16 is pretty darn close to 14mm.

 

[greesha]

thanks for the advice!
I would have done that, but dont know how to weld, or own a drill press.


Could there be something I am doing wrong that I am constantly stripping bolts? I use mostly new bolts form mcmaster, and they all have a bit of oil on them, am i supposed to be using anti seize of some sort? and do my torque specs need to be altered if i do?

 

[jrlp]

Oiled bolts require 20% less torque than clean dry threads. Even more in aluminum. Look up the torque sheet that gives you percentages to reduce torque based on type of lube.. Also look up the torque specs for your size/grade bolt. The torque of a m8 bolt in aluminum with oil should reduced by 40% iirc.

Sent from my Galaxy Nexus using Tapatalk 2

 

[1fastvx]

Maybe your torque wrench is broken or off spec? What brand/model is it? Have you ever had it calibrated?

John

 

[greesha]

the two i use most often
1/2 inch gedore 20-200nm
a 1/4 inch pedros pro torue wrench 572041

and a couple of old snap on and matco ones

the pedros is brand new, was a couple of months ago, always kept in case, at lowest setting, never dripped
the gedore i got new a year ago, but stopped by a tool truck and had them test it, with the other snap on and matco one I have, as well as the craftsman.

Anyone have a link to these spec sheets of torquing bolts with oil?
I also dont think that these are stripping because I am over torquing because I took out a bunch of helioils that could not hold hand tight, before I even got to a toruqe wrench, and same with the stripped big sert.

 

[tdkkart]

An 8mm bolt in GOOD aluminum shouldn't be torqued to much more than about 200 in/lbs, or about 22.5nm. In places where the aluminum gets hot, like next to an exhaust port closer to 150-160 in/lbs(18nm) is much safer.

THATS probably why you're having troubles to start with.

If you've got good 12mm thread now you'd be best to use them if possible, never go any bigger than you absolutely have to, or before long you will be totally screwed.

 

[purplezr2]

I would just get it tight and loctite it so it doesn't come out, that torque spec seems alittle high are you sure it correct