Is there sucg a thing as a 1.75mm allen wrench?

stoneaxe · May 8, 2020

I have a few small cap screw counter bores with interchangeable pilots- the pilots are held with a set screw with an approximately 1.75mm internal hex. The wrenches I have don't fit..1/16" too small, 5/64" too big, 1.5mm to small. 2mm too big.
These were Polish made tools, , IIRC. Any idea on what size allen wrench I need or where to get one?

sfriedberg · May 8, 2020

I don't know about 1.75mm, but 9/64" is definitely a standard Allen wrench size.

MattiJ · May 8, 2020

sfriedberg said:
I don't know about 1.75mm, but 9/64" is definitely a standard Allen wrench size.

umm, 9/64" would be double size.
9/128" would be close but never heard of such a thing.

Tiny hex heads have sometimes quite large oversize tolerance. And low cost hex keys can be quite a bit undersize. Result is "no-can-do"
I have sharpened more than few tiny hex keys to smaller size so they fit exactly on the screw head. Setscrews in some multiturn potentiometer knobs are notoriously bad in some older electronic equipment.

TeachMePlease · May 8, 2020

My micro precision Wiha set has 1.2mm 1.5mm and 1.8mm... It's not this exact one, but similar: https://www.mscdirect.com/product/details/58770934

sfriedberg · May 8, 2020

MattiJ said:
umm, 9/64" would be double size.

Sorry, was going off "5/32 is too big" and didn't notice that was not a close upper limit. If you want something bigger than 1/16, then 5/64 and 3/32 are both standard Allen sizes, too.

stoneaxe · May 8, 2020

I edited the post- I meant 5/64" was too big, not 5/32 which is WAY to big.
I will take a look at the micro metric set.

EPAIII · May 8, 2020

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There is now.

Drop by and you can borrow it. SASE and you can have it.

Now where's my tee shirt? Surely this ranks one.

stoneaxe said:
I have a few small cap screw counter bores with interchangeable pilots- the pilots are held with a set screw with an approximately 1.75mm internal hex. The wrenches I have don't fit..1/16" too small, 5/64" too big, 1.5mm to small. 2mm too big.
These were Polish made tools, , IIRC. Any idea on what size allen wrench I need or where to get one?

PeteM · May 8, 2020

I've never seen a 1.75mm hex wrench or had a fastener that wanted one. Have at least half a dozen sets (do a lot of small metric instrument work) and there's always that jump from 1.5 to 2mm - and never a metric-origin instrument that wants something midway between. Might be out there - but not in my experience. The 1.8mm listed above also a surprise. On edit: the 1.8mm linked above looks to be for a flat screwdriver tip. There is what looks to be a hex size near 0.070 - about midway between 1.5 and 2mm.

I have seen hex wrenches many thousandths under size and sockets worn enough that the original wrench would no longer work. 1/16 isn't too far off . . .

Six strokes on a stone might get the next size up to fit?

Milland · May 8, 2020

Do you have a CNC mill? Set up a standard 5/64 bit in a vise, use an 1/8" or so stub endmill and size the hex to your needs. If you take a couple thou off at a time you can fit to the socket. Just make sure to use a sharp endmill so it cuts properly.

[I like small endmills for this sort of work, puts less "energy" into the cut and cheaper if you dull or damage it]

mike44 · May 9, 2020

Take another look at the head, could the "allen" screw be a Torx instead. I tried to remove a chuck from an old corded drill that was shot but the chuck was still serviceable. Was difficult to see the screw head and finally realized the screw had a Torx cap screw head.
mike

dian · May 9, 2020

T-7 = 1.85 mm.

EPAIII · May 9, 2020

If you use a good quality bit or hex key for this operation, you will probably need to use an abrasive "point" to trim it. If it cuts with a milling cutter, even a TC one, then it is probably too soft to actually use for tightening anything.

Just an observation from someone who has actually done this.

Milland said:
Do you have a CNC mill? Set up a standard 5/64 bit in a vise, use an 1/8" or so stub endmill and size the hex to your needs. If you take a couple thou off at a time you can fit to the socket. Just make sure to use a sharp endmill so it cuts properly.

[I like small endmills for this sort of work, puts less "energy" into the cut and cheaper if you dull or damage it]

stoneaxe · May 9, 2020

EPAIII said:
Whap, whap!
Whap, whap!
Whap, whap!

There is now.

Drop by and you can borrow it. SASE and you can have it.

Now where's my tee shirt? Surely this ranks one.

Actually I grind them to size- it is just a hassle as the modified wrench grows wings.

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