M10 too small in 10mm hole.

Joined: March 31st, 2018, 6:57 am

August 5th, 2018, 7:28 am #1

Good evening Ladies, gentlemen and others.
                                                                        A request for advice, please.
I have a cast aluminium Eames knock-off chair base which originally had plastic/nylon glides fitted into holes at the end of the five-spoke base.
I have one original glide and it fits perfectly into the holes. Outside diameter is 10mm.
I have purchased new, non-original bases which use an M10 bolt as a stem.
Replacement original bases sell for 74 euros per set. The local replacement cost under NZ$50 for five.
Now, the puzzle.
The M10 stems have 1-2mm clearance in the holes.
Should I just seat them with Araldite or such or is there a more elegant solution?
Thank you.
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Joined: January 1st, 1970, 12:00 am

August 5th, 2018, 7:39 am #2

That's common. Most threaded fasteners these days have "rolled" threads- the peaks and valleys are pressed onto the rod by a couple of grooved dies, with one moving past the other, spinning the rod between them.

It's far faster than cutting them, and makes a stronger thread besides. The problem is it's inherently an "upsetting" process- the diameter of the finished part is determined by how much metal is displaced from the rod. That's not always a terribly precise process, and even when it is, almost all bolts and screws are made to be slightly under nominal size, so they'll fit a nominal size hole.

Pouring the holes full of a 2-part epoxy like Araldite (or more commonly in the US, something like JB Weld or Devcon) might be a quick fix, but if it's into a plastic part, there's no real way of knowing how well it'll bond.

But hey, give it a try. 😁

Doc.
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Joined: March 31st, 2018, 6:57 am

August 5th, 2018, 7:53 am #3

Thanks, Doc.
It never occurred to me that a 10 mm blot could not be 10mm D.
They are going into cast, good quality aluminium, the insert glides are plastic.
I might also try to find 1mm wall, 10mm diameter plastic tube.
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Joined: January 11th, 2016, 8:57 pm

August 5th, 2018, 10:17 am #4

Try using some 10mm helicoil thread repair inserts. Measure one in the shop and see if it is bigger in OD than the insert tubes OD. If so, buy 5 and their tap, thread the diecast to suit, and screw the helicoils in, then screw in the 10mm glides..If it seems like the helicoil inserts may be a sloppy fit, put some Araldite on the outsides of the inserts before you screw 'em in, let it set, and then screw the glides in.
Breakfast.com halted. Cereal port not ready.
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Joined: September 16th, 2014, 7:01 am

August 7th, 2018, 10:23 pm #5

And if the hole is too big for the Helicoil to tap and fit, find something fatter with a 10MM matching thread on the inside - Rivnuts would be one possibility, or threaded standoffs for circuit boards and such.  Might have to drill out the holes in the chair base a bit, and rough up the OD of the threaded inserts so the epoxy will have tooth grab...  Then epoxy in the inserts.
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Joined: March 31st, 2018, 6:57 am

August 14th, 2018, 11:03 pm #6

Solved.
Three layers of heat-shrink tubing.
The third layer will only force on halfway but the trial piece is solid in the hole.
Thanks for the help.
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