Timeserts or Helicoils

Knut - what about a larger diameter Big sert being stronger than a smaller diameter regular time sert. Or any brand of larger diameter insert. That one should be easy to calculate.

Jim,

there are at least 4 failure mechanisms at work here -- the most likely failure mechanisms are bolt rupture and combined shear/bending stress failure at thread root of the aluminum block.

The bolt rupture before insert failure we see in the video will manifest itself for low grade bolts only, like ISO 4.8 . For higher grades (ISO 8.8 and above, > 115000 psi), we will see insert failure before bolt rupture.

Without knowing the thread form of "normal" and "big" Time Sert inserts, it's impossible to assess the advantage of using a "big" insert. The aim for increased capacity depends not only on the increased middle diameter.

- Knut

Choosing an insert appears to not be as simple as one might hope. I still think that most of the insert failures we see on Norton heads and cylinders are from over-torquing, not a failure of the design per se. But, that is, as usual, just my opinion.

Ken

Well, since any brand of insert is stronger than the aluminum thread you are inserting it into, I don't see how it matters which insert you choose to use.

I've used Helicoils for years, mostly in marine work but in doing some research as a result of this thread (NPI), I discovered that when Helicoils were developed, they weren't designed or envisioned to 'repair' threads. They were designed to accommodate frequent disassembly of parts/components in aluminum or other soft metals and were installed at the engine (or whatever) factory during assembly. So strictly speaking, although they are now commonly sold/used to repair threads, that wasn't their purpose.

Hey, some folks use WD40 as an arthritis pain reliever so "re-purposing" a product for a different-than-intended use isn't uncommon!

MexicoMike said:

I've used Helicoils for years, mostly in marine work but in doing some research as a result of this thread (NPI), I discovered that when Helicoils were developed, they weren't designed or envisioned to 'repair' threads. They were designed to accommodate frequent disassembly of parts/components in aluminum or other soft metals and were installed at the engine (or whatever) factory during assembly. So strictly speaking, although they are now commonly sold/used to repair threads, that wasn't their purpose.

Click to expand...

And this seems to be the reason why NVT fitted them in the crankcase drillings for the socket head cylinder bolts when they launched the 850.

MexicoMike said:

Hey, some folks use WD40 as an arthritis pain reliever so "re-purposing" a product for a different-than-intended use isn't uncommon!

Click to expand...

I thought is was a joke, but apparently not! Madness indeed, and no success story.

I think the top hat on the Timesert is a bonus as, so long as the item being clamped is of a small enough ID, the surface of it will sit on the top of the flange / top hat.

In doing this, much of the torque loads are not being fully transmitted to the base material as the Timesert will clamp up just like a nut would clamp up.

mdt-son said:

I thought is was a joke, but apparently not! Madness indeed, and no success story.

Why desperate patients are using WD-40 on their painful arthritic joints

www.mailplus.co.uk

Click to expand...

This was many years ago...my parents were golfers well into their late 80's. Several of their male and female golfing buddies used WD 40 on arthritic joints and claimed it worked without the side effects of medication. Fact or psychological, I can't say.

I've heard that at the turn of the previous century, coal oil was used for the same purpose so maybe...

Fast Eddie said:

I think the top hat on the Timesert is a bonus as, so long as the item being clamped is of a small enough ID, the surface of it will sit on the top of the flange / top hat.

In doing this, much of the torque loads are not being fully transmitted to the base material as the Timesert will clamp up just like a nut would clamp up.

Click to expand...

However.... this requires the Timesert to be exactly flush on installation, and with a guarantee that it won't lift one micron on reassembly - not really feasible IMHO.
Nor will it pass any clamping force into the cases themselves. A nut spreads the torque load into the assembly the same as a bolt head. This Isn't true for the insert.

In reality, I play it safe and ensure the fitted insert is slightly below the surface. After all, it's the casings being clamped, not the insert, which is still liable to some movement on assembly.

One positive for helicoils is the ready availability of 2.5xD inserts for high stress applications (like head studs). Not seen 2.5D Timeserts, but I haven't looked that hard either!

Here's a photo of a 3/8 - 16 x .562" long standard helicoil and a .520" long timesert. I could trim the helicoil so they match and perform a test. But if the timesert won - would anyone believe it?