Heli-Coil vs time-sert vs other? - Application specific?

[Pdsmith505]

As I was diligently torquing the alternator cover bolts on my '17 KTM 690E to 10 NM, and no more (per the shop manual), after replacing a defective gasket, one of the bolts pulled out the threads from the case...


So, now I get to repair a thread. That's exactly what I wanted to have to do after all.

Anywho, the question now is what thread repair solution to employ.

The way I understand it... Heli-Coil takes a smaller drill (advantage, less risk of inadvertantly really buggering things up) but can't handle as much torque (disadvantage). Time-sert takes a bigger drill (potential disadvantage, depending on how much meat is in the case) but can handle more torque (advantage).

I'm leaning towards heli-coil since the spec is only 10 NM.

What would the hive mind use in this application?

 

[Danno]

The biggest unknown with a helicoil as a reserve method, is metric to standard conversion. If it is a 6mm bolt then a 1/4-20 or 1/4-28 bolt can be used. No sense in tapping the hole as there would be lucky if .010 of material exist. Basically get a 1/4-28 for fine thread or 1/4-20. Put a drop of 20w50 and work the bolt back and forth till its home. Whip out the torque wrench or elbow click and it is done. If this doesn't work then heli coil is next. Too dang easy...I have a machine tool degree and my redneck buddy showed me this 30yrs ago on valve cover bolts. Dont tap the threads but roll new ones!

 

[MVI]

Danno - neat trick

I was going to say buy a ROLL TAP

in general it it needs to be fluid tight, then I use TIME SERTS they are not cheap, but a $12K KTM dirt nike aint time to cut corners.

just a mechanical joint, heli-coil it

since that is a silly screw, worse case clean it well , JB weld it shut and drill out and tap. it is a screw , not a BOLT

 

[sc-surfer]

Helicoils are pretty cheap and easy to install. Less complicated than the timesert. For that application that's what I'd use. I put a helical in a striped out head stud hole on a 1200GS. Torqued it to spec and let 'er rip. Still going strong.

 

[Shinyribs]

I've installed hundreds of helicoils with zero failures. Even in high load situations. Back in the car drag racing days we would helicoil every bolt hole on a new aluminum head before doing anything else. Including the rocker studs, which were 3/8" threads working against 800lb valve springs and a lot of rpms. I've also helicoiled big block Chevy head studs that torqued to 90ft lbs. I trust them completely.

I've installed a few timeserts. I'm not a big fan. They require removing a lot of additional material and you don't always have room for that. Helicoils generally have a more aggressive outer thread ( depends on the fastener size your repairing, of course) compared to timeserts, so I always felt they held in better.

The guy over at Project Farm on YouTube did a strength test against various thread repairs and he too found helicoils to be stronger. That video might be worth a look so you can decide for yourself.

The only time I won't use a helicoils is if it's a fastener that will require high strength/ red loctite. I feel you run a chance of things getting all bound up, but I have to say I've not actually run in to that issue, I'm just wary of it.

 

[Shinyribs]

The biggest unknown with a helicoil as a reserve method, is metric to standard conversion. If it is a 6mm bolt then a 1/4-20 or 1/4-28 bolt can be used. No sense in tapping the hole as there would be lucky if .010 of material exist. Basically get a 1/4-28 for fine thread or 1/4-20. Put a drop of 20w50 and work the bolt back and forth till its home. Whip out the torque wrench or elbow click and it is done. If this doesn't work then heli coil is next. Too dang easy...I have a machine tool degree and my redneck buddy showed me this 30yrs ago on valve cover bolts. Dont tap the threads but roll new ones!

I'm not sure I'm understanding you. Helicoils are available in all metric sizes. You don't have to try and bodge in a standard size repair coil. Ignore me if I completely misunderstood you 😂

 

[Shinyribs]

PS. Use personal discretion when torquing things according to a manual. Yamaha seems to be famous for supplying torque specs based on fastener dimension rather then it's actual use case. Prime example, CP3 oil pan bolts call for 35ft lbs! They also call for like 120ft lbs on the rear axle. Top yoke nut, tiny fine threads, 85 ft lbs.

Guys were blowing oil pans apart, destroying axles and killing steering stems left and right until they put the torque wrenches away and just started snugging things down.

I know, I know..."engineers", and all that. But still, be careful. And good luck! ✌️

 

[MVI]

I've installed hundreds of helicoils with zero failures. Even in high load situations. Back in the car drag racing days we would helicoil every bolt hole on a new aluminum head before doing anything else. Including the rocker studs, which were 3/8" threads working against 800lb valve springs and a lot of rpms. I've also helicoiled big block Chevy head studs that torqued to 90ft lbs. I trust them completely.

I've installed a few timeserts. I'm not a big fan. They require removing a lot of additional material and you don't always have room for that. Helicoils generally have a more aggressive outer thread ( depends on the fastener size your repairing, of course) compared to timeserts, so I always felt they held in better.

The guy over at Project Farm on YouTube did a strength test against various thread repairs and he too found helicoils to be stronger. That video might be worth a look so you can decide for yourself.

The only time I won't use a helicoils is if it's a fastener that will require high strength/ red loctite. I feel you run a chance of things getting all bound up, but I have to say I've not actually run in to that issue, I'm just wary of it.

I have also helicoiled big block Chevy head studs. That was in 1991. Still working with no issues.

 

[Danno]

The only bad part of 6mm to 1/4in is a mismatch of tool sizes. At the shop we fixed alot of other shops thread fix tries, which was fill the hole with weld then get me to redrill and tap. But there are magical thread rolling bolts. Saved me many times. The best was a 12mm hitch bolt on rusty sheet metal honda chassis. The 1/2in thread roller went right in with grease and the gun. $5 bolt. Dead give away is a triangle taper on the end. But I fixed many 6mm to 1/4 in soft aluminum with just a drop of oil and 2 mins. Even handlebar clamp bolts. Will never strip again if thread depth is in check.

Most auto manufacturers use some form of cutting/rolling/ forming fasteners in various sizes.

 

[MVI]

Danno do you have a good source for roll taps ? roll bolts ?

 

[Shinyribs]

The only bad part of 6mm to 1/4in is a mismatch of tool sizes. At the shop we fixed alot of other shops thread fix tries, which was fill the hole with weld then get me to redrill and tap. But there are magical thread rolling bolts. Saved me many times. The best was a 12mm hitch bolt on rusty sheet metal honda chassis. The 1/2in thread roller went right in with grease and the gun. $5 bolt. Dead give away is a triangle taper on the end. But I fixed many 6mm to 1/4 in soft aluminum with just a drop of oil and 2 mins. Even handlebar clamp bolts. Will never strip again if thread depth is in check.

Most auto manufacturers use some form of cutting/rolling/ forming fasteners in various sizes.

A hitch bolt in a sheet metal Honda chassis. Lord have mercy, that brings back bad XJ memories!

 

[Danno]

Danno do you have a good source for roll taps ? roll bolts ?

Tricor? Was the 1/2"..... the bolts are out there all over the auto industry. I have made my own for soft metal br grinding a triangle taper. If you do run across some of these odd forming bolts double/triple check the thead pitch. Some have a pitch the doesnt match anything!

Ha another extreme was a $1600 valve body for a snow plow pump. Had machine thread with o-ring groove. Customer stripped...a blizzard and I'm ten trucks behind. Shop owner wants helicoil. I measured and partially tapped then rolled the threads to pipe fitting with a steel fitting. Then changed hoses to match. 10 mins to fix and refill with fluid. Held to 3500psi and never came back.

 

[JimVonBaden]

Helicoils are pretty cheap and easy to install. Less complicated than the timesert. For that application that's what I'd use. I put a helical in a striped out head stud hole on a 1200GS. Torqued it to spec and let 'er rip. Still going strong.

I completely agree!

 

[Danno]

A hitch bolt in a sheet metal Honda chassis. Lord have mercy, that brings back bad XJ memories!

Bolt was 12mm to hold a hitch. Not enough meat to tap. Big time suck had to put a plate and carriage bolt from inside out sometimes.

I eliminated it all. The 12mm doesnt hold spin it tighter with gun and then spin it out. Grab 1/2in thread former dab of grease and bang in with gun. Saved about a 1 hr of time that we didnt get paid for but I charged for $5 the bolt the other way.

 

[Stormdog]

Just jumping in here for the hell of it.
I think you all are overthinking this.
There is a good chance that there are still enough threads inside the case to just use a longer bolt, especially if you stripped the threads torquing the bolt correctly, you might have used too short of a bolt.

 

[Danno]

Just jumping in here for the hell of it.
I think you all are overthinking this.
There is a good chance that there are still enough threads inside the case to just use a longer bolt, especially if you stripped the threads torquing the bolt correctly, you might have used too short of a bolt.

Yup can be verified then a custom length cap screw. Drives me nuts when aluminum thread depth isnt sufficient.

 

[Pdsmith505]

Guess I'll probably just run a Heli-Coil.

The biggest unknown with a helicoil as a reserve method, is metric to standard conversion. If it is a 6mm bolt then a 1/4-20 or 1/4-28 bolt can be used. No sense in tapping the hole as there would be lucky if .010 of material exist. Basically get a 1/4-28 for fine thread or 1/4-20. Put a drop of 20w50 and work the bolt back and forth till its home. Whip out the torque wrench or elbow click and it is done. If this doesn't work then heli coil is next. Too dang easy...I have a machine tool degree and my redneck buddy showed me this 30yrs ago on valve cover bolts. Dont tap the threads but roll new ones!

Not interested in ramming home an SAE fastener when 1) the threads are part of the engine case, 2) the case material is already finicky, and 3) every fastener on the bike is metric. I hate the mixed bag GM's of the 80's... Not gonna do it here... Especially not on a part that cost more than a grand (and untold hours doing a complete rebuild) to replace.

Suspect hole is indicated by the red arrow.

I've installed hundreds of helicoils with zero failures. Even in high load situations. Back in the car drag racing days we would helicoil every bolt hole on a new aluminum head before doing anything else. Including the rocker studs, which were 3/8" threads working against 800lb valve springs and a lot of rpms. I've also helicoiled big block Chevy head studs that torqued to 90ft lbs. I trust them completely.

I've installed a few timeserts. I'm not a big fan. They require removing a lot of additional material and you don't always have room for that. Helicoils generally have a more aggressive outer thread ( depends on the fastener size your repairing, of course) compared to timeserts, so I always felt they held in better.

The guy over at Project Farm on YouTube did a strength test against various thread repairs and he too found helicoils to be stronger. That video might be worth a look so you can decide for yourself.

The only time I won't use a helicoils is if it's a fastener that will require high strength/ red loctite. I feel you run a chance of things getting all bound up, but I have to say I've not actually run in to that issue, I'm just wary of it.

My old man reminded me that back when he was wrenching on sprint cars, the first thing they did to new aluminum heads was Heli-Coil everything.

Seems like the right application for a time-sert is high torque and/or threadlocker, and neither is called for here. 10NM/7.4 ft-lbs is nearly nothing.

Just jumping in here for the hell of it.
I think you all are overthinking this.
There is a good chance that there are still enough threads inside the case to just use a longer bolt, especially if you stripped the threads torquing the bolt correctly, you might have used too short of a bolt.

If the bolt is too short, then KTM is putting the wrong size bolts in all their LC4 based engines.

EDIT
Sipping my coffee this morning and going down the rabbit hole looking at OEM parts to see if there are any KTM 6mmx35mm screws (so I can keep the neat torx/external hex configuration)... I have realized that I may have fucked up...

Note that there are three different screw specs for the cover... 3 and 5 are 25mm length (5 adds loctite)... 4 is a 30mm screw.

When I pulled it off, I kept track of 5 because I saw it in the torque sheet... Did not notice a difference in the rest.

I'm gonna bet I used a 25mm long screw when I needed the 30mm one

Now I feel like a dumbass. I'm my defense though, the torque chart in the manual didn't mention the 30mm long screw... There are 35mm long screws for the clutch slave cylinder though.

Stormdog , you were probably right after all. My apologies.

/EDIT

 

[Danno]

Guess I'll probably just run a Heli-Coil.



Not interested in ramming home an SAE fastener when 1) the threads are part of the engine case, 2) the case material is already finicky, and 3) every fastener on the bike is metric. I hate the mixed bag GM's of the 80's... Not gonna do it here... Especially not on a part that cost more than a grand (and untold hours doing a complete rebuild) to replace.

Suspect hole is indicated by the red arrow.



My old man reminded me that back when he was wrenching on sprint cars, the first thing they did to new aluminum heads was Heli-Coil everything.

Seems like the right application for a time-sert is high torque and/or threadlocker, and neither is called for here. 10NM/7.4 ft-lbs is nearly nothing.


If the bolt is too short, then KTM is putting the wrong size bolts in all their LC4 based engines.

Sounds like ya got a good plan

 

[Stormdog]

So for giggles I just checked that bolt on my 701
30 mm bolt with 8.5 mm thread engagement
hole depth 42 mm but a 40 mm bolt runs out of threads
35 mm bolt works
if you pulled out the first 30 mm of threads I’m guessing a bottom tap down to 40 mm then
cutting a bolt to 39 would give you more threads then factory.

 

[Danno]

So for giggles I just checked that bolt on my 701
30 mm bolt with 8.5 mm thread engagement
hole depth 42 mm but a 40 mm bolt runs out of threads
35 mm bolt works
if you pulled out the first 30 mm of threads I’m guessing a bottom tap down to 40 mm then
cutting a bolt to 39 would give you more threads then factory.

Wait are you saying a 6mm diameter screw had 8.5mm of cut aluminum thread engagement? If so I'm out of this thread. I wont tap any more ideas.