Hexagon Head v. Allen/Cap Head screws/bolts

[Michael BriggsParticipant @michaelbriggs82422]

Torque wrench less than 10 lbft, +1

If I need to get a hex head tight without rounding it I use a socket or a ring spanner.

[Mick B1Participant @mickb1]

Posted by Michael Briggs on 27/04/2018 11:18:55:

Torque wrench less than 10 lbft, +1

If I need to get a hex head tight without rounding it I use a socket or a ring spanner.

I'd think most of us do – if we've got one, and if it's not itself bu99ered from some previous misuse, and if we can get at the hex head with it, and if we can apply the torque without canting the socket or ring and chewing up the head that way… if …if…

[MuzzerParticipant @muzzer]

If you are tightening steel bolts into an alloy cylinder head / engine block etc, you'd be daft not to use a torque wrench. If you overdo it (eg 4-5Nm for an M6 etc), you get to strip it down, Helicoil the hole and start again. Undertighten them and you get oil leaks. Best to do it right….

Murray

[Mike PooleParticipant @mikepoole82104]

On an aluminium engine that is regularly stripped down I would be inclined to helicoil small tapped holes to preempt them stripping during rebuild. Tapped holes in aluminium castings seem to let go despite never being over tightened.

Mike

[richardandtracyParticipant @richardandtracy]

Unless the thread is fit & forget, always helicoil aluminium. In for a world of grief otherwise.

Regards

Richard.

[Mike PooleParticipant @mikepoole82104]

The cost of the gear to do Helicoils or other brand inserts is vey cheap compared to a machine shop cost so just crack on and install them. They are also good in Perspex to prevent wear on the threads and effectively you use the next size up of thread but keep the fastener neat and small.

Mike

[duncan webster 1Participant @duncanwebster1]

Posted by Mike Poole on 27/04/2018 19:07:42:

The cost of the gear to do Helicoils or other brand inserts is vey cheap compared to a machine shop cost so just crack on and install them. They are also good in Perspex to prevent wear on the threads and effectively you use the next size up of thread but keep the fastener neat and small.

Mike

If possible I use studs in ally for exactly this reason. When I worked in aerospace, all tapped holes in ally were helicoiled.

[Peter G. ShawParticipant @peterg-shaw75338]

Thanks for all the thoughts re my original query. I suspect that for my purposes, since I'm not into anything drastic like road going vehicles or really heavy machinery, it boils down to whatever is most suitable, probably Allen screws if space is tight otherwise probably hex head.

In respect of helicoils and aluminium, since I tend to use aluminium having obtained a length of busbar type ali (yes, it's darned soft), I have taken to making T-shaped steel inserts which are then glued in position. The T bar is placed such that the strain is such as to force the head onto the aluminium, and the upright of the T is tapped. Thus all the weight and wear of fastening/unfastening is primarily taken by the steel.

Once again, thanks to all,

Peter G. Shaw

[Howard LewisParticipant @howardlewis46836]

A hex head with rounded corners can be unscrewed with a Metrinch socket or ring spanner, or one of the many "flank drive!" imitations. Am not so keen on the open end Metrinch spanners, to my mind they still seem likely to slip.

The advantage of Metrinch is that one size will deal with Whit, A/F or Metric, although at first, the "sloppy" fit seems very odd. Wouldn't be without mine now, if anything tight comes to need unfastening.

Soft Allen keys are a PITA.  Still using the Unbrako  ones that I bought in '58 as an Apprentice

Howard.

Edited By Howard Lewis on 28/04/2018 11:18:21

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