Author Topic: Helicoil Confessions  (Read 2148 times)

Offline RichardL

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Helicoil Confessions
« on: 12.02. 2014 23:16 »
Me, "Wise and Enlightened"? Hmmpf! More like, "Enthusiastic, Overconfident and Wordy". It has been very hard getting around to talking about this, due to the frustration and embarrassment, but here goes. *problem* *sad2*

After assembling my crankcase with the crank, cam and sump plate in place, I realized that I had about three bad 1/4-20 BSW threads around the bottom of the timing cover. Believing I was being a dutiful and thorough mechanic, I decided I should coil all threads of this size in the crankcase on the timing side. Further believing that a drill press would be the best way to get perpendicular holes, I made a wooden platform to hold the engine timing-side-up while sitting on the drill-press table. Well, either my platform was not square, or the drill press table reading was not quite right, or I didn't hold the assembly properly, but I ended up with several holes that are not perfectly perpendicular and couple that are noticeably not. I didn't discover this until the helicoils were all in place and I tried to dry fit the inner cover. Two of the inner cover screws are tight going in, one of which is very tight, both due to rubbing the walls of the inner cover holes. Regardless, The inner cover made it to a dry fit, albeit with these tight screws. A few of the outer cover screws are also tight going in, but not as bad as the inners.   

I think all of this bodgery would have been avoided if I had just talked here about the project before going ahead. D*mn it! In retrospect, given the tools I have, I think I might have been better off just using a hand drill so that it would take to the existing perpendicular holes, rather than forcing my way in with the drill press. Does this make sense? My intention, for now and until the engine must come apart again, is to relieve the inner cover holes with a dremmel grinder so that the slanted screws won't rub so hard. Any Objections? Some day, another rebuild will be required and the holes can be remachined and recoiled properly. (Hopefully, this will only be required after I'm dead, but I probably won't be that lucky.) 

About fixing the holes where a coil got in, is there a way that they might be straightened out that would allow the reinstallation of the 1/4-20 BSW coils? Maybe the future holds metric or SAE threads via Timeserts. I don't know right now, but any ideas are welcome.

Yes, in addition to technical advice, I am seeking sympathy, empathy and few good-natured jabs for being a klutz.

Richard L.

Oh, it feels good to get that off my chest because I have been really mad at myself.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline muskrat

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Re: Helicoil Confessions
« Reply #1 on: 13.02. 2014 03:45 »
Don't feel so bad mate, we've all been there. *problem*
In fact quite a few years ago I did exactly the same (not to the BSA thou). My nice new drill press's (made in China) table was not square to the spindle and hence the same outcome.
To rectify it will need to be set up in a mill and drilled square (after the helicoils are removed) with an end mill and the larger timeserts inserted.
Did I tell of the time I put the rHonda 4's barrels on backwards  *eek*.
Cheers
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Online Greybeard

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Re: Helicoil Confessions
« Reply #2 on: 13.02. 2014 09:12 »
I've done some stupid things in my life. Here's just one: The complete rebuild of my 1929 Austin Seven was just finished. In the dark I reversed my Land Rover into the Austin, forgetting that I had not yet put the vintage car back in the garage.  *sad2*

Offline a10gf

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Re: Helicoil Confessions
« Reply #3 on: 13.02. 2014 09:33 »
The forum confession booth is open for business  *smile*

Richard, if needed maybe fill the worst ones with alu weld, and redo the drilling\use thread tap. Done that here instead of helicoil.

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Online bsa-bill

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Re: Helicoil Confessions
« Reply #4 on: 13.02. 2014 10:32 »
Quote
The forum confession booth is open for business
OK so "forgive me farther for I too have  ................."

Yep Richard me too but on a Cylinder Barrel, PO had obviously put a wrong tap down them to clean them I suspect, two had survived or he missed them.
 so I drilled and helicoiled the rest , I can't blame the drill press because only two were out of line but I think your right a hand held drill will follow the line of least resistance ( and end up square).
I relieved the cylinder head and it's fine so far,  Reckon your timming case might be ok as well, only thing is the heads of the bolts would be better if if full contact with the alloy so maybe a need to square them with the angle of the thread (if that makes sense)
All the best - Bill
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Offline Topdad

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Re: Helicoil Confessions
« Reply #5 on: 13.02. 2014 11:56 »
Richard ,why so hard on yourself ? It's still going to go back together and in just a few posts already you've been given ways to sort it but when when YOU feel it's time .I have that much confidence in the members here that I know you'll get even more ideas and help . Knowing you within 6 weeks you'll have dissected the complete system you used ,will work how to remedy the process and will then decide whether to leave has is and ride ( this would be my option  but then I'm a lazy get !) as soon as weather permits or redo. Did I mention my first attempt to fit Valve guides  *doh*
I'm not allowed to go into details as my embarrassmentwould mean I'd have to shoot myself !!! Chin up mate BobH
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Online Triton Thrasher

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Re: Helicoil Confessions
« Reply #6 on: 13.02. 2014 17:50 »
I haven't done any drilling when helicoiling.

Offline muskrat

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Re: Helicoil Confessions
« Reply #7 on: 13.02. 2014 19:20 »
That is the case , TT, if the thread is totally RS or you have a good tapper/starter tap. The kits down here only come with an intermediate tap.
The other problem encountered is the hole may be square but the tap is inserted at a slight angle. Giving the same results. I use the drill press to start the tap a few threads.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline chaterlea25

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Re: Helicoil Confessions
« Reply #8 on: 13.02. 2014 20:45 »
HI All,
My late Dad used to say "the man who never made a mistake never made anything"  *ex*
I wont bore you all with the "dogs" I have buried  *sad2*

A couple of tricks I use
1) use a tap wrench to twist the drill into the damaged old thread hole, its easier to keep square that way

2) When working on an assembled bike where you cannot get the part  onto the drill or mill table
 I drill a block of alloy square through with the tapping drill,  then a second hole the distance from an adjacent casing hole, hold the block in place onto the  desired position with a  suitable screw/ bolt
the drill will then follow the hole in the block square to the casing face,
Then go back to the mill / drill and use this to keep the tap square and tap the block with the helecoil tap
refit and tap through to the casing
(It takes longer to describe than to do  ;) )

HTH
John

1961 Super Rocket
1963 RGS (ongoing)

Offline morris

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Re: Helicoil Confessions
« Reply #9 on: 13.02. 2014 22:41 »
Been there to Richard. Exactly the same..... *pull hair out* *angry* Barking mad I was.
2 of the holes I drilled and tapped weren't perpendicular.
Solved it by drilling and tapping to M10, and turned an aluminium M10 threaded stud on the lathe. Screwed it in with some Loctite and ground it down nice and flat to the crankcase. Put on the covers and then drilled and tapped to 1/4 ww. Saved!
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Offline terryg

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Re: Helicoil Confessions
« Reply #10 on: 14.02. 2014 08:10 »
"I use the drill press to start the tap a few threads."
That would be the drill press with the out-of-square table then, Musky?

I've had alignment issues with hand drilling before tapping for the helicoil.  That was with cam cover studs on a car engine - so a tweak (= bend!) on the stud was enough to allow assembly.  Next time I'll rig some sort of alignment collar to help keep the drill perpendicular to the face I'm drilling.  Live and learn, as always.
Terry
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Offline muskrat

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Re: Helicoil Confessions
« Reply #11 on: 14.02. 2014 11:59 »
Yes Terry, after the 2nd job on the drill press was to square the table  *idea*.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline RichardL

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Re: Helicoil Confessions
« Reply #12 on: 14.02. 2014 16:19 »
Gents,

You've provided lot of good technical advice, food for thought and moral support. Thanks, guys. *good3*

Muskie, yep Timeserts do seem that they might be the cleanest ultimate solution. I don't think they make them in BSW, but maintaining thread originality on this bike may be the least of my problems.

Graybeard, the deal with the Austin sounds like tears must have been shed. It's OK, you're amongst friends.

e, I assume the forum confession booth is open 24/7 to cover all time zones or just messing-up late into the night. With the Alu Weld, is it possible to get down to the bottom of the hole?

Bill, I think I remember you telling us the story of the bad threads in the barrels. I do think that, for now, my easiest way forward is a bit of relief in the inner timing cover. As for full contact with the shoulders around the holes in the covers, squaring the heads to slant won't work (if that's what you meant) because they won't be in the same rotation twice (come to think of if, I suppose you could force that issue). I think with the force required to hold the timing covers in place, less than perfect circumferential contact will be OK, in any case, if anything, the uneven force might tend to mold the shoulders to the matching slope.

Bob,  I do think that I will opt for being able to ride over solving this problem right now. Your compliment regarding my persistance is generous and appreciated. Hmmm, valve guides? Do I use the same confessional for that topic or is there a dedicated one? After I installed new ones, following reaming, the machine shop pointed out that the valves set a little funny in the head. (Oh God no! This turns into another off-angle story!)

TT, That's interesting, going with the tap, only. Sounds like something I'd like to experiment with, but in a piece of scrap and not with the precious tap that came with the helicoil kit.

John: Wish I had done the drill-in-a-tap-wrench approach, as it sounds like a safe solution. In the afterthought of this, it occured to me that an old inner cover fitted with drill bushings installed would make a good fixture. I also like your idea of the one-hole-at-a-time fixture.

Morris, Very clever, basically making your own Timesert and maintaining BSW.

Terry, Your tweaking the bolt idea is a another experiment I might try in a piece of scrap to see if the helicoil can moves enough in its hole while staying stable enough to do the job.

One of my ideas for a possible fix involves another experiment in scrap wherein I drill an off-angle hole and tap for the helicoil. Then, drill a perpendicular hole (with no helicoil in place) at the same center. Then, run the tap down as near to perpendular as I can get it. Then (have I reached my "then" limit?), install the helicoil using permanent Loctite. Before the Loctite sets, run in a screw with antisieze (to avoid the Loctite) and try to assure perpendicularity of that screw until the Loctite sets.

Thanks, again, guys. Looking forward to more thoughts. I defy you to find anything on YouTube that touches on this subject.

Richard L.






Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Online Greybeard

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Re: Helicoil Confessions
« Reply #13 on: 14.02. 2014 17:10 »
Graybeard, the deal with the Austin sounds like tears must have been shed. It's OK, you're amongst friends.

Off topic I know but here is a picture of me in the aforementioned Austin Seven 'Chummy' prior to me bending one of the front wings with my Land Rover.

Offline a10gf

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Re: Helicoil Confessions
« Reply #14 on: 14.02. 2014 17:21 »
^^^ Great automobile, Graybeard.

The threads i got fixed, was for a few screws for the drive side cover, brought the crankcase to a welder, who managed to fill deep enough for me to afterwards file the surface flat, drill new holes and use a thread tap. No problems since.

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