Question for machinist

[Dagny]

I keep all my knock out punches in a klien bag in the service van and needed a 3/4 hole today but must have gave my newest one away so tried to use the backup but the threads are not quite right .

I have several draw studs which are really just a 3/4 16 bolt but a very high quality bolt.

All the other punches thread right on but the 3/4 binds about 2/3 rd of the way on most of the bolts and almost all the way on on the oldest bolt.

Think it would pay to buy a tap and run it through there or get some lapping compound and run it in and out.

All the parts seem to be very hard steel. Greenlee made them when I was young.

 

[signcrafter]

I keep all my knock out punches in a klien bag in the service van and needed a 3/4 hole today but must have gave my newest one away so tried to use the backup but the threads are not quite right .

I have several draw studs which are really just a 3/4 16 bolt but a very high quality bolt.

All the other punches thread right on but the 3/4 binds about 2/3 rd of the way on most of the bolts and almost all the way on on the oldest bolt.

Think it would pay to buy a tap and run it through there or get some lapping compound and run it in and out.

All the parts seem to be very hard steel. Greenlee made them when I was young.

Guess it depends on how bad the threads are damaged, doesn't sound like they are too bad if it threads 2/3 of the way on. Also the condition of the knockout would play into my decision. Amazon has a new greenlee 3/4" knockout for just under 50 bucks. A century 3/4x16 tap is about 12 bucks. If the knockout is in good shape besides the threads I would order a tap and fix it and then you have the tap to fix any in the future. I didn't see a 3/4x16 thread chaser but I didn't look real hard. The threads are already cut, just got messed up and need to be reshaped. If the knockout is older or worn I might look into just getting a new one.

 

[whateg01]

Are you sure the one isn't M19-1.5? I would think the punches would be hard, so I wouldn't expect a tap to cut them. Can you file the threads with a small file? Or does a file skate over them?

 

[Dagny]

they are inside

 

[Firebrick43]

I always had luck with 5 micron diamond paste. Apply very little on the threads and screw it in until it almost binds and loosen, and repeat. Every time it will advance slightly, apply another small dab after 30 times or so, then afterwards clean very well

 

[signcrafter]

they are inside

I picked one of these up a few years ago at napa and have used it a few times. Might be an option for you.

https://www.amazon.com/Rotary-Thread-RTK1-1-Starter-Restore/dp/B085LRZZPS/?tag=atomicindus08-20

 

[whateg01]

they are inside

That's why I suggested a small file

 

[JABgj]

Could the stud be stretched from use making it bind up?

 

[Dagny]

The other punches use the same bolt and 3/4 doesn't load the bolt much.