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How I Made A Thread Tap On My Lathe.
- Thread starter 6literZ
- Start date
- Joined
- Jan 11, 2013
- Messages
- 1,837
Cool! I look forward to your updates!
Bernie
Bernie
- Joined
- Mar 22, 2015
- Messages
- 84
fallowing for sure...
I needed to chase the threads on my Mauser project, which I'm converting to 45acp, the old barrel came apart rough, the threads were badly galled.
I decided this was a good project for the lathe.
So I began by purchasing O-1 drill rod from my local Fastenal hardware distributor, O-1 is tool steel that is easy to machine and then it is hardened by quenching in oil. I would have preferred water hardening, but it sufficed.
Second I took the thread pitch diameter measurements from the new barrel and recorded them, I also had a jam nut for the new barrel which I checked the threads with.
I also made a 55 degree threading bit from HSS, but later used 60* as it seems that my new barrel is cut at 60*.
I began by forming the area that would be the shank, and then transitioning into the area which would be threaded, cut the threads to match the barrel and then followed by another section turned down to 5/8" to clamp into the tool holder for cutting flats and flutes on the lathe.
I used an end mill to cut wrench flats on the shanks on both ends, and then a ball end mill to cut the flutes.
After the flutes were formed I parted off the shank used to clamp the tap in the tool holder.
I also made a small furnace from a soup can and plaster to bring the tap up to temperature. It is heated until it loses its magnetism and then immediately quenched in oil.
I didn't temper the tap, but it could be beneficial if a tool needed a longer life.
It worked well, and was very hard and brittle, there were a few stress cracks after quenching, but it held up during the thread chasing process.
The barrel fits well, next I will have to weld up a spanner wrench!
I decided this was a good project for the lathe.
So I began by purchasing O-1 drill rod from my local Fastenal hardware distributor, O-1 is tool steel that is easy to machine and then it is hardened by quenching in oil. I would have preferred water hardening, but it sufficed.
Second I took the thread pitch diameter measurements from the new barrel and recorded them, I also had a jam nut for the new barrel which I checked the threads with.
I also made a 55 degree threading bit from HSS, but later used 60* as it seems that my new barrel is cut at 60*.
I began by forming the area that would be the shank, and then transitioning into the area which would be threaded, cut the threads to match the barrel and then followed by another section turned down to 5/8" to clamp into the tool holder for cutting flats and flutes on the lathe.
I used an end mill to cut wrench flats on the shanks on both ends, and then a ball end mill to cut the flutes.
After the flutes were formed I parted off the shank used to clamp the tap in the tool holder.
I also made a small furnace from a soup can and plaster to bring the tap up to temperature. It is heated until it loses its magnetism and then immediately quenched in oil.
I didn't temper the tap, but it could be beneficial if a tool needed a longer life.
It worked well, and was very hard and brittle, there were a few stress cracks after quenching, but it held up during the thread chasing process.
The barrel fits well, next I will have to weld up a spanner wrench!
I believe it cracked during the quenching process. Two reasons; one was my oil was diluted with coolant (damn boat money pit), water cools more rapidly than oil and could have caused the cracking. Secondly it should only be cooled to around 150-200 degrees and then immediately annealed. I skipped that because it requires long periods at hundreds of degree in a controlled environment.
- Joined
- Mar 3, 2014
- Messages
- 634
Nice work, and enjoy the good quality pics.
Having a way to make thread chasers and taps is so handy at times.
Having a way to make thread chasers and taps is so handy at times.
- Joined
- Apr 12, 2013
- Messages
- 560
I'm betting the cracks are from stress risers...sharp edges are natural crack formation points during quenching. Even O-1 will crack, especially with a little water (coolant) in the oil. Water quench steels are 100x MORE prone to this...something to consider when you are wishing for water quench steel on a project like this. The forgiving nature of O-1 makes it ideal for this type of application... A low temp temper might help too. BTW, loss of magnetism is an okay sign but still a little low for anything above W and 10xx series steels. Don't be afraid to run O-1 up 50-100 degrees above non-magnetic.
Even a oven temp 350-400 degree temper will help the brittleness...
To heat your oil and boil off the water, just find a piece of scrap steel, heat to red hot, quench, voila your oil is warm. Repeat as necessary to get the oil to near 'uncomfortable warm'.
Even a oven temp 350-400 degree temper will help the brittleness...
To heat your oil and boil off the water, just find a piece of scrap steel, heat to red hot, quench, voila your oil is warm. Repeat as necessary to get the oil to near 'uncomfortable warm'.
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