Member postings for Mick Bailey

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.

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.

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.

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.

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.

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.

I hit a few unexpected problems getting the remains of the original bolt out. The other broken one drilled out easily, but I found that the screw in this location was hardened. Despite using a firmly clamped 5/16x3" plate with a hardened, press-fitted bush, the slot drill had a really difficult time and created a much larger hole than its 6mm diameter. However, the resulting hole is straight and centred in the boss, but tapers from 6.8mm at the top to 6.1mm from just over halfway down. I have probably 12mm of depth that would take a 6mm Dx2 insert with full thread engagement.

The 6mm insert kit I have uses a 6.3mm tapping drill. I'm thinking that I either go out to a 7mm insert and get another kit, or use the 6mm insert and ream the upper tapered section parallel to 7mm to take a stepped set screw, This would have a plain 7mm section to act as a dowel, whilst the rest of it would be 6mm. This may be preferable to drilling out the hole for a 7mm insert and losing more material.

At least the hole diameter that runs into the spoke web hasn't been affected too much and I can avoid any welding.

The Helicoil removed easily so my next step is to remove the remains of the bolt. I need to make up a really rigid jig because of the angle formed when the Helicoil drill veered off. I don't have a milling machine, but my pillar drill is fairly rigid and so long as everything is bolted down firmly it should be OK. I just need to make a threaded adapter for the slot drill this afternoon.

I'm taking a fresh look at this today to see how I can locate a hardened bush to get a slot drill to at least square-off the bolt remains.

I saw the wheel in Germany, though it looks in poorer condition overall than my own (apart from the damaged threads). There's an issue with the VAT I can't figure out. The price is shown with differential VAT applied at the point of sale, according to German rules. To import it, I'm unable to clarify if the seller has to recalculate the item less differential VAT (which of course gives away their buy-in price) and I import the wheel VAT-free at the point of entry and pay UK VAT, customs and handling fee prior to receipt. I can see this adding up to around £250 total, which is a lot to take a gamble on. If it's returned ,I then have to reclaim the costs (less fees) and argue to over the postage.

I thought of a stepped stud. Maybe even an M8, or as previously mentioned, an M7 Helicoil. I can't see how much of the remaining M6 stud is left, but getting that out cleanly first and taking a look how much of the original hole is left is perhaps the best path. I was even thinking of removing the Helicoil and filling that hole with a solid slug of threaded alloy bar, coated with JB Weld and made a very tight fit, then treating the job as though it had never been Helicoiled. Because that hole is much shallower then the original, and it runs sharply away from the stud, it may be that the re-threaded original hole would not extend too far into the JB welded slug. Whilst the original bolt is M6x20, the hole is 22mm deep - easily enough to get at least a 1.5D insert into good metal and maybe even a D2.

I don't think there's much force on the retaining ring that the bolts hold - they went from 6 screws to 3 in later years and the ring is fairly thin gauge sheet steel.

The cheapest new wheel I can find is £1391.97. I can't find a used one that matches mine - the brake offset is different on the ones I've enquired about, and they're all in Europe. I've been bitten buying used parts from EU breakers and trying to return scrap. Also, the screws coming loose and breaking when they hit the webbing in the drive box is not uncommon and I don't want to risk buying something that still needs repairing. Buying in the UK would be a better option to avoid the prospect of return postage and import costs. To get the bike on the road I'd prefer a good solid repair for the time being and if a wheel becomes available buy a replacement, if necessary.

The threaded hole extends into the spoke web, but the Helicoiled depth is fairly shallow.

Here's a picture;

I'm going over my newly-acquired Moto Guzzi T5 Polizia and removed the rear wheel to change the tyre. It was disappointing to find that the retaining ring for the cush drive was missing and it didn't take long to find out why. The ring is held by three M6x20 bolts - one is stripped, another broken 8mm below the surface. These have been a straightforward repair, but the third one is problematic:

The bolt is broken below the surface and an attempt has been made to drill it out, but this has not been done right and the drill has wandered into the aluminium. It has been Helicoiled at an angle, the coil being 1/3 in the remains of the steel bolt, and 2/3 in the aluminium. There is very little metal surrounding the area. My initial thought is to remove the helicoil and make a core drill to remove the remaining bolt, but then what to do.

Ideally it would need welding, but the hole is deep. I wondered if it could be filled with a spool gun, or MIG to get to the bottom of the hole. I don't know about TIG - it seems to be too small and too deep to get to the bottom of the hole effectively.

Does anyone have any suggestions?

I'll see how it bores out, though I do fancy the idea of having it professionally ground. I think I'll give it some more thought before coming to a final decision. I take the point about lapping a taper. I've only previously done this with brass plug cocks - just a few turns with Solvol to get a final fit.

Would that not be the reverse for boring the taper?

Anyhow, I think this is the best way to rescue the taper in the absence of a toolpost grinder I have a very rigid boring bar that should do the job and could always lap the bore afterwards for a fine finish (must remember to turn up an aluminium lap with the same topslide setting).

I've been using a short piece of bar in the chuck as a centre, as you recommend.

The issue for me is that collets I use for clockmaking don't run true. I can get around it with rudimentary split collets made from hex brass bar, but when filing pivots there's always the danger of rotating chuck jaws. Collets are a lot safer and easier to use. I've put up with the lathe as it stands for over 30 years and would really like to get it sorted out, but cost is a factor and I don't think I could afford to buy a new spindle assembly from Myford.

The Ebay spindle looks to me to have evidence of being cleaned up with emery or similar - it's suspiciously free of any regular wear marks. This leads me to wonder what level of precision the spindle has, and how it would fit up. Would it be better to locate a complete assembly with bearing shells?

Does a brand new hardened spindle with bronze bearings need to be scraped? If it does then perhaps the same issues of alignment exist. I have some experience of hand fitting using engineer's blue and scraping, though in engines not lathes.

The outside does run true and apart from the taper damage everything else is fine. When the damage originally happened I bought an MT2 reamer from Tracy Tools and cleaned up the bore, but it left 0.005" runout and it's still slightly oval. The original damage was caused when I was reaming a large aluminium bronze bush - the reamer grabbed hard and got pulled into the spindle (I have a lever feed tailstock, so there's no limiting on travel like you'd have with a screw feed). By the time I'd reached for the off button the reamer had broken a flute and badly chattered the spindle, but with more damage on one side.

I contacted Myford and apart from replacing the spindle and bearings, the suggestion was to bore out the spindle parallel and fit a hardened precision ground sleeve. If I could just replace the spindle it would be much easier for me.

I'm looking to swap out my 1953 ML7 spindle because of damage to the internal taper. My options are either to find a complete original spindle with bearing shells, a spindle on its own, or a new hardened spindle with bronze bearings from Myford. The last time I checked with Myford they did not have any new assemblies and in any case they were over £400 (I think plus VAT).

I wonder if I replaced the spindle on its own and kept my shells, whether there would be excessive wear as the mismatched items bed in. Maybe taking off a shim or two and scraping the shells could be an improvement.

Any thoughts?

I've etched my own (though for other purposes, not loco related) using the toner transfer method using a laser printer and cheap inkjet photo paper, and hydrochloric acid/hydrogen peroxide mix as an etchant. It leaves a really crisply defined edge with no undercutting. My main use for this was etching PCBs for audio development projects and prototyping, but it gives excellent results with sheet brass or copper.

There's a bit of a learning curve and maybe for a single model it would be more straightforward to buy from someone who's already set up. Diane's work looks excellent.