A puzzlement - any ideas?

[GaryMc]

About 15 years ago I inherited an old "bachelor chest" type dresser with a mirror swinging between uprights, probably 75-100 years old.  I refurbished the solid-oak top, fixed all the drawers, and stripped/repainted the body.  We used it in a spare bedroom for several years then loaned it to LOML's brother in 2019.  Recently, when he moved from Florida to Virginia, we got back everything (including one drawer where the back finger-joints needed to be re-glued) EXCEPT the mirror hinge screws that held the mirror to the supports.  Those, apparently, were lost in the move or lost in the mountain of stuff he moved.

The original mirror screws were turned-knobs with the screws (like hanger bolts) about 2" long.  I could easily turn new knobs in some period fashion with inserted hanger bolts except I do not know the diameter and thread count of the threaded-inserts in the mirror frame.  I must have 7 million screws and bolts of every known SAE or metric size and variety, but nothing I have will fit - 1/4 inch a little too small, 5/16 inch a little too large - regardless of Coarse or Fine thread count.  I doubt metrics were used back in the day, but nothing I have in comparable sizes will fit.

The ideas I have so far is to measure the ID of the inserts to see if something comes up - like a 9/32" odd size (which may be hard to find).  Or assume somehow the threads were mangled and try to re-tap with 5/16, maybe.  Or try to extract the old inserts (who knows what that may entail) and use new ones with standard diameter/thread.  The only other option I can think of is to abandon the old and use slightly-offset new threaded inserts and new holes drilled in the supporting columns of the dresser.

Any ideas or thoughts here?  BTW, would it be possible to screw a hard-wax or wood dowel of about the right diameter in there to get at the dimensions?

Gary

[EdL]

I have a tap drill chart thats at least 75 years old...nothing listed between 1/4 & 5/16.
A newer one does list a 7mm.....highly doubtfull at the age of your piece. I've been in the machine tool field 40 years and never heard of a 7mm thread.
Did you try a 5/16-24 (fine thread)?

Ed

[Stwood_]

Wondering if it's a number 12. Stanley tools used a #12 thread on mainly the hand planes.
Odd size for sure.
If I think of it I can caliper a #12 stud on one of my planes tomorrow.
It's been a while since I've restored a plane, and don't remember if a #12 is smaller or bigger than 1/4"

[6270_Productions]

Is it old enough or . . . ummmm . . . less expensive enough to have "hand cut" (non-standard sized) threads?

I just had the same problem with some original cast bronze door handles for the exterior doors I built for the County Courthouse. 

No bolts/screws at the hardware store or my own personal private Fastener Warehouse.  Solution? 

Break out the Tap and Die Set and "paint the stick".

[AHill]

Can you re-tap the female side to a larger, more common thread?

[jteneyck]

I'd think about using a screw extractor to remove the old ones and then install new ones.  Otherwise, your idea of offsetting new inserts would be my next option.  

John

[GaryMc]

Can you re-tap the female side to a larger, more common thread?

A bit more info - this morning I calipered the insert (that would be the inside of the threads) and measured slightly less than 1/4 inch - 0.245 to be exact.  Peering in there revealed very fine threads so I suspect the diameter of the screw would be no more than 5/16".  Neither coarse nor fine thread will even start in there, though.

It occurred to me that I have a full set of SAE and metric taps so the next step will be to see if anything will screw in there easily.  More later.

O.K., I think I figured it out.  M7 tap did not work, but a 1/4-20 fit although loosely.  So I tried several bolts and found the 1/4-20s do grab although loosely.  It appears that the insert threads have been worn down to slightly oversize.  Interesting that a brass bolt does seem to fit better.  I will see whether the thread grab is enough to hold the mirror in place.  If not, maybe a thin coat of silver solder on the bolt threads might help?

[Willyou]

I believe I would either try to replace the threaded insert or re-tap the existing one to the next larger size. The latter is probably easier.

[Stwood_]

Stanley 12/20 stud OD measures .212, so it's under 1/4" and smaller than what you have.
Article about stanleys odd size screws/nuts.

https://www.lumberjocks.com/threads/wher...lly.55151/

[iclark]

O.K., I think I figured it out.  M7 tap did not work, but a 1/4-20 fit although loosely.  So I tried several bolts and found the 1/4-20s do grab although loosely.  It appears that the insert threads have been worn down to slightly oversize.  Interesting that a brass bolt does seem to fit better.  I will see whether the thread grab is enough to hold the mirror in place.  If not, maybe a thin coat of silver solder on the bolt threads might help?

What would happen if you tried a layer or 2 of plumber's teflon tape on the bolt thread? Would the bolt tend to back out when the mirror gets pivoted?