It's not really a motoring question, but one for those of us who've moved on to mote leisurely forms of transport- e.g. mobility scooters. I've got a problem with the folding stock on mine. It's locked with an M6 bolt to engage teeth on the lock. Unfortunately the bolt and I suspect the internal screw are now damaged and it won't lock tight. I've ordered an M6 HELICOIL kit and new m6x80 bolts. Q for those experienced in helicoils- should I drill out the outer so that the bolt engages the coil after the damaged thread ( my favoured option) or drill the inner or just drill out the entire thread and glue in the coil in the outer.

Drill out the old thread completely with the correct size drill for the helicoil tap. You shouldn't need any adhesive to retain the helicoil. 

Yep, as moley said, the kit should come with an assortment of drill sizes that are matched to the helicoil insert that you intend to use, so yes drill out the old thread and you should have no need for any fixative at all.

With helicoils you need to drill in at least 2.5 times the nominal diameter, that's 12mm for coil length (2xnominal) plus threading clearance - so at least 15mm, drill using about 6.25/6.3mm mm drill (supplied). Actually no harm in thread locking (if helicoils aren't self lock) but you'd have to clean the thread lock out of the coil before use. You can't just blow a 6mm clearance hole right through it and just put a nut on the back?

I would go up a size drill 6.5 / 6.8mm and tap it out to M8, will be future proof and less likely to strip than an M6 thread

Zero experience with helicoiling, although did once drill a stripped thread and tapped a new thread in (mine was possibly the only Nissan Bluebird with a BSW thread and bolt as part of the cam assembly!),  but I do have a mobility scooter, with a folding stock, so am interested.

 

Thread needs before, during and after photo's.

 

Gaz

Edited 19 June, 20205 yr by IamGaz

GAZ - mine is a shop rider. Possible cause of problem is that

a) - the original bolt was too short so that lowering the stock meant that the end of the bolt damaged the end of the thread.

b) a longer bolt as standard would have prevented this . I changed the bolt ( but i suspect that the damage had occurred)  and fitted a lock nut to other end of the bolt to stop the bolt retracting too far.

However I also suspect that it's not possibly designed to potter around the tracks in our local parks  ,as I've already had to reire the battery compartment with heavy duty cable- like giving it a re map.

Next step is a helicoil along with a change of bolt as the bolt thread is damaged -hence the question, as I wondered if only drilling partially from the outer might give the helicoil something to lock against.

Next step I suspect will be to drill out the inner 10mm collar and fit an M6 internal threaded tube. Problem might be fixing this to the origonal metal.

NJ- at present as a temporary fix, I've got a 6mm nylock on the opposite end to the handle and use a socket to lock the front stock up.

 

 

5 hours ago, VWD said:

Next step I suspect will be to drill out the inner 10mm collar and fit an M6 internal threaded tube. Problem might be fixing this to the origonal metal.

 

Do you have sufficient room to fit a rivnut insert rather than a helicoil?.

 

it will not be as robust as a coil insert, but may be an easier option to fit if you are not really familiar with helicoil procedures

Thanks- but I'd prefer the more robust option as I often go of track.

What about getting replacement parts - lots on eBay, although of course not as much fun as an engineering solution.  Shoprider bits should be readily available - which model do you have?

 

I use a Pride Go-Go as a boot scooter at the mo'.  Bit of a big ask for my 6'4" and 16st, but it does okay.  Electric bike for anything more, but if planned hip joint replacement doesn't turn out as planned, I'm going all out for a TGA Breeze S4 or Horizon Aztec/Mayan.

 

Bought and sold many a Shoprider when I worked for a local Charity for disabled people.

 

Good luck with getting it sorted.

 

Gaz

 

On 13/06/2020 at 12:33, IamGaz said:

Zero experience with helicoiling, although did one drill a stripped thread and tapped a new thread in (mine was possibly the only Nissan Bluebird with a BSW thread and bolt as part of the cam assembly!),  but I do have a mobility scooter, with a folding stock, so am interested.

 

Thread needs before, during and after photo's.

 

Gaz

Sorry ,Gaz. I mentioned M6,but it was really M8, M8. ( pun). Started after last dog walk ,circa 1900, and then sky darkened,with spots of rain. So I had choice of photos or get it done pronto. Simply enough- I had to drop a drill size to allow cordless to work( started with 7.5, then 8 ) before going on to tap drill of 8.3mm. Little problem with tap, just go forward a few steps and then back a lot more. I ended up using WD40 to help. ( Amazing how much of an engineering HND course you remember, even if it's electronics , where we were forced to look at other branches of engineering). Kit came with an inserter and a tang removal tool. Wind in the helicoil into the tapped hole( using the insertion tool), use the tang removal tool ( hit it with a hammer)to remove the tang  and Robert is aunts husband. I did cheat and looked at n online U Tube video of how to do it. Found it dead easy .

Shop rider parts are available at a cost. As an engineer, I'm more interested in a "fix it myself " solution. Recent fix involved no more than replacing the low current wiring in the battery box ( drive wiring was at most 5A, and a lot of the wiring points were showing signs of HR, with melted wiring, with 17A wire and new properly terminated fuses.. My 4 wheel pavement model now has no fears of doing a bit of of roading, with the xtra drive to the motor. Hip op- might be nice around here, but my place is also known as a centre of disease production.

GAZ - First pic is of the package. From L-R = Insertion tool, Tang remover, drill, tap and helicoil. Second pic shows a helicoil "upside down " as it would be placed in hole. (i.e. tang goes in first).

1- drill ot the hole . I ended up starting with a 7mm drill and moving up to the tap drill.

2) Fit the tap into a tap holder and slowly tap, stopping and reversing if the tap is difficult to rotate. This removes swarf from the hole. I also used WD40 as a lubricant.

3) Place the helicoil in the hole with the tang (horizontal leg) downwards( PIC 2). The insertion tool has a slot on the bottom, which will align with the tang ans allow you to screw it in. I found that the suggested depth is a thread or two below the surface.

40 -REF PIC 2 - place the tang remover in the helicoil and give a sharp blow ( I nearly said tap, but that might confuse) to remove the tang.  .I used a hammer to apply said blow.

My next step was to remove the damaged bolt from the lock handle. That meant removing the  rubber cover from the knob. It simply unpeels, like an orange skin, but in one bit. The bolt simply drills out. I decided to re invent the wheel and fitted a M8 bolt from the other end , lock into to place and fit a nut in the handle. I'm still looking at how to re fit the rubber cover on the plastic knob. I think it's going to be a compression job.

If tapping a blind hole (no exit wound) then flush hole with WD40/air for the last bits of swarf. Aluminium can 'gall' (bind on) a thread and loose steel swarf rusts easier than the metal it's cut into, both risking seizing the fastening.

Thats a plug tap thats why you would be struggling. Better off with a taper tap.

 

and the best lubricant is saliva believe it of not, nice bit of spit on the tap and it will go in no bother

7 hours ago, BigJase88 said:

Thats a plug tap thats why you would be struggling. Better off with a taper tap.

 

and the best lubricant is saliva believe it of not, nice bit of spit on the tap and it will go in no bother

 

It'd have to be taper, intermediate and plug tap to get a helicoil in a blindhole, but it is the debris that needs removing to stop problems with the final fixing picking up tapping crap, be that aluminium that will gall (seize) or iron that would rust. Spit is convenient and works after a fashion, being basically thick sticky water, but any handy oil for steel, and usually paraffin is good for ally. Or proper Rocol tapping fluids if you've deep pockets!

Edited 20 June, 20205 yr by NJRJ
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