3/16 - 32 Screw and VN Dividing Head Teardown

[Shopsweeper]

Today I started a tear-down on a frozen 7.5 Van Norman Dividing Head that I toted home recently. It was frozen up - or rather super hard to turn.

I noticed that 2 of the 3 bolts on that hold the index plate on have a messed up head - screwdriver slot (same with 1 of the 3 for the index plate).

I started looking around the usual places (Grainger, Fastenall, Small Parts) for screws. I cannot find 3/16"-32 x 1/2L" or 3/16"-32 x 3/8" flat head machine screws.

It looks like M5 - .8 is quite close size wise. I have some of these in socket cap screws in my bolt bins. I hate to go with a non-standard.

Any sources for 3/16" -32tpi flathead screws? Any opinions on jamming metric in there?

ALSO:

Also, I have the nose off and the index sub-assembly (side part that supports the worm gear and crank) off, but I can't figure out how to get the Ring Gear that interfaces with the Worm drive off. It had a hex grub screw that is now loose - but no joy on the movement. Any ideas before I get out the gear puller?

 

[Bill Gruby]

Are you sure that is not a 10-32?

"Billy G" :thinking:

 

[Shopsweeper]

Hmmm.

My ancient thread gauge says 3/16 x 32 for the hole that matches perfectly to my screws.

But: 3/16" = 0.190 = 10

So you may be on to something. I presume that modern screws are sold under the 10-32 name.

One should always be suspicious of a thread gauge that calls screws "threaded pins".

Thank you

 

[Bill Gruby]

I asked because 10-32 and 3/16-32 are the same. And yes, today you ask for 10-32. I have a thread gage like yours. I had to put it in another tool box so I would not mess up. :lmao:


"Billy G" )

 

[Tony Wells]

Actually, if you go back far enough in thread standards, you will find that the 3/16-24 is a slightly different animal. Of course, we all know that 3/16" is 0.1875 for the major diameter, but for #10 screws, the major is 0.1900 (basic), 0.1890 max and 0.1818 min. The fractional screw size is thought to originate with the Whitworth system, and for all practical purposes is interchangeable with the numbered system. On your older machine, it probably is a true 3/16"-24, but a modern standard 10-24 will substitute just fine.


Tap drill size is different too. 10-24 calls for a 0.1470 diameter, and 3/16"-24 calls for 0.1495"


Correction:
Should be 3/6" and #10 32 TPI threads I was discussing. Dimensions I provided will be a little different due to the finer pitch, but the principle is the same. My mistake.

 

[Bill Gruby]

How did we get to 10-24? He needs 10-32. Explanation is pretty much the same though.

"Billy G")

 

[jumps4]

thanks tony
that is why my 3/16 24 set screws i got in a assortment would not work for me. the chinese assortment has 3/16 24 and a 10 24 tap is too small. I thought is was poor quality but all the other ones were fine. I just thought the chinese were calling 10-24, 3/16-24. after checking i see the 3/16-24 tap is available.
steve

 

[jumps4]

3/16 32 taps and dies are also available i just learned something new.
steve

 

[Cal Haines]

Today I started a tear-down on a frozen 7.5 Van Norman Dividing Head that I toted home recently. It was frozen up - or rather super hard to turn.
...

... I have the nose off and the index sub-assembly (side part that supports the worm gear and crank) off, but I can't figure out how to get the Ring Gear that interfaces with the Worm drive off. It had a hex grub screw that is now loose - but no joy on the movement. Any ideas before I get out the gear puller?

Photos please.

Cal

 

[Tony Wells]

My mistake, Bill.....multitasking a little too much this evening. Same basic thing on 3/16"-32 though.