Sump bolts

["Slack Alice" Simon]

Philosophical note:  I have been wondering why I so easily come up with what are often horrible bodges - making do with a short helicoil instead of pulling it out and starting again?


I think I am mentally stuck in my twenties, when the car was the only means of transport, getting us to work in the morning - no matter what, it had to be back on the road by 07.30 or life got difficult.

Now, of course, I have more time and money to do things better, and usually do.

[Chris KC]

For what it's worth another way is to drill & tap oversize, Loctite in a threaded plug (metal of your choice, but I would suggest aluminium) and start again with a fresh hole. A helicoil is undoubtedly easier; though the plug method may present the opportunity not to drill quite through into the sump (ref discussion on oil leaks).

Simon, I'm not sure I'd worry about a 'short' helicoil, certainly in this application. As long as it's soundly done it will be stronger than the original threads. My big end bolts screw into 1D helicoils.

[Parazine]

For what it's worth another way is to drill & tap oversize, Loctite in a threaded plug (metal of your choice, but I would suggest aluminium) and start again with a fresh hole. A helicoil is undoubtedly easier; though the plug method may present the opportunity not to drill quite through into the sump (ref discussion on oil leaks).

This is a sound method for fixing holes where a previous mechanic has drilled them oversize (sump bolts out to 5/16 BSW for example) as you can tailor the plug to fit whatever outer size you want, metric, UNC, BSP, anything really.
I looked into this many years ago and usually, when I have to do this in aluminium, I use Brass for the plug, as the thermal co-efficient of expansion is not wildly dissimilar to Ali.

It has to be said that inserting a helicoil (of whatever brand) is much quicker though and it's worth the expenditure on the kit.

[morrisminor]

Thank you Slack much appreciated

[A G Wood]

Another thing you may find handy MM, (particularly if you're trying to place a helicoil/V coil in situ above your head)  is to grab your drill press and make up a two-hole guide block with one hole drilled to minimal clearance on the o.d. of the helicoil/V coil drill and the other hole drilled for minimum clearance on the o.d. of the helicoil/V coil tap. I use scrap 50mm lengths of 30 x 10 merchant flat bar, you can either clamp the bar or hold it in your other hand depending on the job.
Invaluable if  you [like me] wear glasses, have a full beard and dislike being externally lubricated while you are trying to drill/tap squarely!

[Zetomagneto]

I often make up drilling/ tapping guides similar to A G . On a sump flange I drilled a plate on the pillar drill with 3 holes which corresponds to the bolt centres , drilled the centre hole with in my case, the Timesert drill then bolted the plate to the crankcase with the 2 outer bolts and then drilled the hole into the crankcase. Then remove the drilling jig, back to the pillar drill to tap the centre hole with the Timesert tap, bolted back to the crankcase then tap.The hole is bound to be square in all planes and you have no trouble starting the tap.
Sounds a bit long winded but works well .

[Chris KC]

Yes it can be a challenge for mere humans to get a tap to go in straight. Wherever possible I chuck it in my pillar drill and set the workpiece level beneath it, then turn the drill chuck by hand. Obviously no good for in-situ repairs.

Others have described threading a nut on the tap first to provide at least a small square contact face.

Parazine, yes brass by all means. But I had a case last year which had been done in steel and it is then very hard to repair once the steel inserts go bad.