Stripped drain plug help needed

[ezeastside 93]

In the middle of a restoration on a 1077. The allen key of the  sundstrand drain plug was rounded out and I had no choice but to drill it out.

The 1/4" drain plug has an actual 9/16 - 18 thread. I have that tap and chased the threads out but now its still sloppy and the 1/4" plug will actually thread right into the transmission.

I have searched high and low for a oversize or double oversize drain plug but can't find one in 9/16.

I don't need to split the cases so I can't use one with the nut on the back side and would be concerned about room inside.

 

My next thought is to go to 5/8 18  and try to repair this.

 

Does anybody have a solution to this that would make my life easy?

 

Thanks,

 

ED

[pfrederi 17,887]

The drain plug hole was tapped for 1/4 NPT (National Pipe Thread) not 9/16 -18.  NPT is tapered 9/16 -18 is straight thread

 

To seal you will need tapered threads or some sort of gasket n a very short 9/16 -18 Bolt

 

EDIT::

Drill the hole out to 9/16"  then buy or borrow a 3/8NPT pipe tap  (Cheapies are abut $10 good ones about $35) and thread it then get a 3/8" plug

 

Edited February 16, 2018 by pfrederi

[R. L. Addison 299]

The drain hole was 1/4 nptf and you put  a machine thread in it. The (N)ational (P)ipe (T)apered (F)ine has a 3/4' taper per foot for the sealing surfaces of the threads. A straight machine thread will not seal because there is clearance at the "root" of the thread, and the o.d. of the thread, on a 75% thread. 

 

 If I was doing I would put in a 3/8' nptf plug with the 3/8' recessed square then there is no hex to round out.

[WHX?? 49,177]

Every two piece transmission I open gets a front drain hole & magnetic plug. 3/8ths NPT.  I use the square head plug and drill a 1/8" hole in it and JB well a cheapy ebay magnet in it.

Edited February 16, 2018 by WHX14

[pfrederi 17,887]

Nice idea...but for the lazier ones of us

 

 

 

[953 nut 55,851]

If you plan to mount a tiller or blade (front or mid mount) that requires an axle bracket you will need a plug that ends up flush with the bottom of the transaxle.

[Achto 27,815]

Given the fact that you already retapped the hole to 9/16 - 18 I would install a 9/16 bolt with a crush washer (copper or brass). This will seal it up for you.

[moe1965 744]

A helicoil might be a option.  You can find them on eBay.  Or local parts store might have them. You are given a drill and a helicoil insert that takes you back to the original thread size.  

  

[WHX?? 49,177]

So sounds like we have some answers to your problem Ed.......when we gonna have some   of that 1077 .... bucket list tractor ya know!

Edited February 17, 2018 by WHX14

[Howie 892]

I do not know if they make a helicoil for the pipe thread. I guess they do, is.   pricey at Fastenal though.

Edited February 17, 2018 by Howie

[ezeastside 93]

Thank you for all the spot on advice. I went searching for a 9/16 18 x  1/2 bolt for the easy fix but that was unobtainable locally.

I was able to get my hands on a 3/8 NPT tap and stopped at the hardware store and picked up a 3/8 pipe plug.

I will definitely try to get a pipe plug with the recessed square hole but at least I have something to put in for now and get this thing ready for paint.

Here are the current pictures of this machine.Trying to get everything in etching primer.

Final paint will be Candy Red urethane that I found in a old post from Rickv.

 

I will do a post in restorations when I get some paint flying... if we can get some good weather.

 

 

 

[ezeastside 93]

Thanks for the direction