bodged thread repair

[Clive FosterParticipant @clivefoster55965]

A standard M6 Timesert has an 8mm Ø countersunk section at the top going down a couple of mm or so. This will take out the top end of your hole taper and give a clean entry to the screw. There may be a small portion of the insert not completely supported where the taper runs out but that should be no problem.

I've successfully done similar repairs in "abused" holes using Timeserts installed as per book. I used Loctite for additional back up strength but whether that was necessary is a matter of opinion. Worked for me on jobs rather more heavily loaded than your job appears to be too.

There is no doubt that the all one piece bush style construction of a Timesert deals much better with abused holes than the simpler, spring style, helical construction. I'm convinced that the solid ring at the top is a major contributor to this as it ensures a clean entry to the screw or bolt. Pretty much every problem I've seen with helicoiled holes has been due to the screw or bolt not entering cleanly and subsequently being forced.

Bad point about Timeserts is the very high cost. Although I have to wonder if there are quality / performance issues withe the economy range helicoil clone kits which may mean they are best restricted to less ambitious duties.

Clive

Edited By Clive Foster on 27/02/2023 13:42:56

[Mick BaileyParticipant @mickbailey28509]

I've notice that the cheap helicoil clones don't have a well-formed section to the insert and don't give the correct internal thread profile or engagement. I use the Australian Recoil kits and have never had any problems. Timeserts look good, but the basic 6mm kit is over £190 in the UK.

[peak4Participant @peak4]

Posted by Mick Bailey on 27/02/2023 14:01:39:

I've notice that the cheap helicoil clones don't have a well-formed section to the insert and don't give the correct internal thread profile or engagement. I use the Australian Recoil kits and have never had any problems. Timeserts look good, but the basic 6mm kit is over £190 in the UK.

Baerfix are certainly cheaper, though I've never used them myself, but a downside is the 9.3mm drill for an M6 thread.
https://uni-thread.com/tr_baerfix_metric_kits_detail.php?01581-6

Bill

[Dave HalfordParticipant @davehalford22513]

Given the corrosion caused by the ali/water/stainless mix would it be better to use stainless studs and nylocks? The Loctight would keep the water out.

[duncan webster 1Participant @duncanwebster1]

Probably a daft idea, but 1/4 UNC would be just a tad bigger than M6, and a slightly bigger tapping hole than is strictly necessary wouldn't weaken it significantly

[Clive FosterParticipant @clivefoster55965]

£160 is indeed outrageous for a 6 mm Timesert kit that can be got for around $90 in the USA.

Found an Amazon listing at £133 but you'd need to get the longer inserts on top as that only has the standard shorter ones. Another £30!

There is an apparent Timesert clone branded Sennmonn which are also one piece with rim and proper thread lead in. Around £80 on Amazon for M6 x 1 kit. Stainless steel inserts make them attractive but they are simple bushes which, unlike Timeserts, aren't expanded into place. Need to use high strength Loctite to retain them which ought to be fine.

Realistically £160 (if you get via Amazon) for a Timesert kit isn't too stupid if it gets you a known good repair that just works. Any sort of welding and other mechanical work to give clean hole for a helical or a filled hole to drill and tap yourself is liable to end up a similar cost. At least if you go the timesert route you have the kit for other jobs. Or, given the known outrageous price, odds are getting around half your money back via E-Bay, Facebook Marketplace et al seem pretty good.

The Sennmonn kit seems a pretty good option as its effectively the same as making your own bushes but you get all the tooling too.

Clive

Edited By Clive Foster on 27/02/2023 16:12:30

[Mick BaileyParticipant @mickbailey28509]

The £133 kit looks to be shipped from the USA. If so, then it could attract additional import charges. I'll take a look at the other options – the main thing is not to have to remove any more metal.

I like the idea of 1/4UNC, but as a Helicoil insert. The tapping drill is 6.7mm, so would be a decent fit, though I don't know about the reduced core area.

[duncan webster 1Participant @duncanwebster1]

according to interweb 1/4 UNC has bigger core diameter than M6.

[Mick BaileyParticipant @mickbailey28509]

Thanks, I took a look at my 1/4" UNC tap and compared it with an M6 screw and found the same. I also have some 1/4"x24 taps and dies, but finding inserts for that size is more difficult.

After a lot more pondering I've concluded that there's enough metal in the boss to tap it out to M8 down to where the spoke web comes to, which should be amply strong enough with a stepped stud machined up from a stainless allen bolt. The maximum major diameter given by Helicoil for an M7 insert tap (which would have been my other choice) is 8.422mm, so an M8 tap would be slightly better. Looking at the retaining ring and how the wheel hub fits into the drive box it looks like the ring is only really there to prevent the axial movement of the cush drive, which is very limited anyhow. Three M6 bolts suggest that can't be that much force on the ring.

[Neil AParticipant @neila]

I note that Tracey Tools sell Helicoil type thread insert kits in UNC sizes. Their prices exclude VAT and delivery, that might suit your needs.

Neil

[Mick BaileyParticipant @mickbailey28509]

I went ahead and tapped out the hole to M8 for a depth of 15mm and this has worked out well with a stepped stud machined from a stainless allen bolt. I think when this is Loctited in with high-strength retainer there should be no further problems.

Posting here has been a great help in considering different options and increased my knowledge of different insert types, so thanks to everyone who has replied.

[Bdog507Participant @bdog507]

Good afternoon all.

 

Good job well done by the sound of it.

I see this sort of thing on a regular basis in my workshop. My preference would have been to mill the hole out with a 7mm slot drill, & make a bush with an M8x1 thread.

It's amusing when some oaf (usually the customer & his mate) have had a go at 'drilling' it out. I have been known to ask if they were wearing a blindfold during the attempt.

On the subject of thread inserts. Both Helicoil & Timeserts have their place. . A Helicoil can be cut down to size. I've put as little as 4 twists in shallow holes. A Timesert cannot be cut down, nor can they be fitted in blind holes unless they're deep, because the tool that expands the insert has to pass right through it in order to secure the insert.

A Helicoil can also jump a gap, like in a single pinch bolt on a clutch lever perch.

However, Timeserts are stronger. So for stripped sump plugs, & wheel spindle threads in fork lowers etc I use Timeserts.

As one poster said, the Australian Recoil inserts are the way to go. They're excellent!

 

Cheers.

 

Stewart.

Edited By Bdog507 on 01/03/2023 16:38:42

[Pete RimmerParticipant @peterimmer30576]

Posted by Bdog507 on 01/03/2023 16:36:22:

However, Timeserts are stronger. So for stripped sump plugs, & wheel spindle threads in fork lowers etc I use Timeserts.

Stewart.

There was a fairly well done comparison video some while back that found the opposite to be true.

[Mick BaileyParticipant @mickbailey28509]

Posted by Bdog507 on 01/03/2023 16:36:22:My preference would have been to mill the hole out with a 7mm slot drill, & make a bush with an M8x1 thread.

What's your technique for making such a thin walled bush? Looking up the major and minor diameters gives a minimum wall thickness of 0.5mm. I'd like to experiment with making up some inserts like this for future use.

[Bdog507Participant @bdog507]

Posted by Pete Rimmer on 01/03/2023 19:06:47:

Posted by Bdog507 on 01/03/2023 16:36:22:

However, Timeserts are stronger. So for stripped sump plugs, & wheel spindle threads in fork lowers etc I use Timeserts.

Stewart.

There was a fairly well done comparison video some while back that found the opposite to be true.

It would be interesting to see that. I'll have to see if I can find it.

I've used both for the last gawd knows how many years, & have found the opposite. With either they need to be properly installed, i.e. Timeserts need to be fully expanded in order to work correctly. If they're not they often unscrew instead of the fastener within them, & they can also pull out of the thread they're screwed into.

I have yet to have either fail out of the thousands I've installed, but that's what torque wrenches are for. I've seen many badly installed ones fail however.

II still reckon on using helicoils for 95% of occasions. Not only are they more versatile, they're a damn sight cheaper too.

Cheers.

Stewart

[Bdog507Participant @bdog507]

Posted by Mick Bailey on 02/03/2023 09:31:10:

Posted by Bdog507 on 01/03/2023 16:36:22:My preference would have been to mill the hole out with a 7mm slot drill, & make a bush with an M8x1 thread.

What's your technique for making such a thin walled bush? Looking up the major and minor diameters gives a minimum wall thickness of 0.5mm. I'd like to experiment with making up some inserts like this for future use.

Very good taps and dies basically. I usually make such things out of EN8 it being a little stronger than normal mild steel.

All done in the lathe. I put the outer thread on first with the die expanded a little & then drill the tapping hole slowly. Then I use a spiral point machine tap by hand & carefully. Good SP taps cut the thread more progressively than even a taper hand tap. Then if need be I close the die up & carefully take a little more off the external thread.

It's a faff, & I reckon on getting one bush out of two tries.

I used to have some hand tap sets where each tap cut the thread more deeply. Obviously one had to pass all three taps through in order to get a full thread. These were excellent for such delicate tapping. I can't remember what make they were, nor do I know if such things are still available.

Cheers.

Stewart.

[Bill PhinnParticipant @billphinn90025]

Posted by Bdog507 on 02/03/2023 09:42:58:

Posted by Pete Rimmer on 01/03/2023 19:06:47:

Posted by Bdog507 on 01/03/2023 16:36:22:

However, Timeserts are stronger. So for stripped sump plugs, & wheel spindle threads in fork lowers etc I use Timeserts.

Stewart.

There was a fairly well done comparison video some while back that found the opposite to be true.

It would be interesting to see that. I'll have to see if I can find it.

Stewart

This is one video that certainly doesn't find Timeserts to be stronger than coil inserts, although one flaw in the video as I see it is that the demonstrator is tapping all the samples by hand; as a result, some threaded holes will no doubt end up closer to perpendicular than others, and this may influence the holding strength of the female threads under test.

[samuel heywoodParticipant @samuelheywood23031]

I see the problem has been solved thankfully.

Just a thought~ shouldn't be beyond the realms of possibility for a home engineer to manufacture there own inserts of any material of their choice?

Not familiar with "Timeserts" but my impression of" helicoils" from my biking days was they do the job but always seem a sloppy fit on the bolt.

Many moons ago (maybe 30years?) my local friendly Yamaha dealer repaired a monkey metal cylinder head for me with various solid steel inserts~

He must have had some engineering experience as he did the job himself & did it well.

These were definitely the dogs danglies & much better than helicoil though to this day i've no idea as to the trade name.

[Bdog507Participant @bdog507]

Posted by Bill Phinn on 02/03/2023 22:11:31:

Posted by Bdog507 on 02/03/2023 09:42:58:

Posted by Pete Rimmer on 01/03/2023 19:06:47:

Posted by Bdog507 on 01/03/2023 16:36:22:

This is one video that certainly doesn't find Timeserts to be stronger than coil inserts, although one flaw in the video as I see it is that the demonstrator is tapping all the samples by hand; as a result, some threaded holes will no doubt end up closer to perpendicular than others, and this may influence the holding strength of the female threads under test.

Good morning all.

That was an interesting video, but as you say there could have been variations in the angle of the thread. However, as most inserts are fitted in situ it follows that most threads would be cut by hand with consequent variations in the angle of the thread and the drilled hole.

I spent the best part of a day fitting dozens of 10mm Recoil inserts to some engine mounting plates from some class of Go Kart.. Being flat I drilled and tapped them on my pillar drill. It's the only time that I can recall where I didn't drill and tap by hand.

Also, if I recall correctly I was told that Timeserts are only for use in Aluminium. I may be wrong, but it was about 30 years ago when I bought my initial Timesert kit. What's more, as I said earlier the insertion tool has to be wound fully through the insert, and it didn't look as if the chap in the video did that. It's certainly more than the lower threads of the insert that have to be expanded, for the expansion tool will only just screw into the insert by a couple of turns if one uses just fingers.

I'd like to see a similar test done in aluminum with the drilling and tapping done by machine, and at least 10 of each would give a better indication as opposed to a one off.

As I said, I've yet to have either type fail when I've done the fastener up. I have had Helicoils fail when the owner has been fiddling with something I've Helicoiled in the past, but that could be ham fistedness on the part of the owner. I suspect that they cross threaded the fastener and dislodged the upper coil of the insert.

Either way, both types have their uses, and applications.

Cheers.

Stewart.

[Mick BaileyParticipant @mickbailey28509]

Posted by samuel heywood on 02/03/2023 22:46:06

:….my impression of" helicoils" from my biking days was they do the job but always seem a sloppy fit on the bolt.

I've also found the same and in some cases had to machine up a better fitting bolt or stud rather than use a commercial one. Typically a commercial M6 thread will be between 5.75mm and 5.85mm in diameter. Making a screw with the die opened up and the thread cut to finish at 6mm results in a better fit. Annoyingly, Chinese-made Clarke kits with their rather inaccurate rounded thread profile are a better fit than the more accurately formed Recoil or Helicoil inserts.

[duncan webster 1Participant @duncanwebster1]

When I worked on aircraft gas turbines, all holes in ally were helicoiled from new. Bolts were not a sloppy fit. Helicoiled hole is stronger than direct tapped as the shear area is bigger, and the helicoil itself adjusts a bit to spread the load over more threads. I never did understand the last bit, it worked, so as an engineer I didn't worry about it.

[A SmithParticipant @asmith78105]

I'd go to a specialist motor/ motorcycle engineering firm that employs a good welder. They would have all the options and could select the most appropriate repair technique. There's a very good one near Bedford with which I have no connection other than as a satisfied customer.

[mark costello 1Participant @markcostello1]

When much Younger I spent My excess time lollygagging in an old time auto parts store. One day a customer came in carrying a very bent up piece of wire. He said that They were fishing many miles down river. They shut off their motor to fish and it would not restart. When peering down the spark plug They spied with Their little eye a piece of metal across the hole. They decided that after many miles use of the running motor the siece of metal was stopping the spark from reaching the fuel and shorting out. So they got in there and unwound the piece of metal. Do You see where this is going? Upon trying to put the spark plug back in They discovered the hole was now much too big. They had to row home with only 1 oar. Bought the wire in the shop among the public to find out what it was.

Many more stories like that.

[Author]

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