Using Two Dies to Cut Threads??

[Scottl]

Since your small lathe would likely struggle to cut those threads, alignment could be a problem when using dies for hand threading. I therefore suggest that you make the screw blank longer and turn a pilot diameter to start the die. I would suggest you use the 1/2-12 die only.Use a traditional die handle and a vise to hold the workpiece and you should be fine as long as you use lots of cutting oil and remember to back off the thread periodically to clear chips.

 

[richard newman]

Is this mostly a cosmetic restoration? If the threads on the original screw are still ok, I'd chuck it up in the lathe and cut the buggered head down to a 1/4" post. Hold it in a sleeve so as not to crush the thread.Then make a new head with a blind 1/4" hole and silver braze it on.

If you want to learn how to thread, go to it. But if you just need a bolt ....

 

[Joe Henderson]

Just find someone local that can machine the threads for you if you are unable to cut them.

 

[rogertoolmaker]

Using a 12 TPI die and getting the thread straight without first single point chasing the thread first is depending on luck. Chase the thread and finish with the die. "Backup". No time like the present to learn single point lathe cutting of threads. Do yourself a great favor. You may be surprised how easy it is and it stays with you the rest of your life! Look on YouTube for thread cutting instruction. Its best to do it right! The quality you accept is the quality that exists.
All the Best
Roger

 

[rons]

I started with 3/4” cold rolled steel rod and turned the bottom length to 1/2” using my small Emco Compact 5. Unfortunately my lathe skills are limited and cutting threads using the lathe is not an option at this time.

Get two or three 60 degree pointed brazed carbide bits from Travers and a 1/2" diameter wood dowel. Practice.
Your 1/2-12 is going to need approx. 083 pointed into your what was once a straight bar. I looked at the manual for
your tool. I would go no more than a few thousands at first. If you can get more than .005 on each pass I would like to see it.
I myself go slow if I'm not in a rush to screw something up.

 

[MilGunsmith]

If you buy or grind a HSS threading tool, you can cut the threads at a slow enough speed to see what you are doing and also avoid crashing at the end of the cut.

 

[boslab]

Get some free cutting mild steel rod , might help!
Mark

 

[bill jones]

---when I installed a riser block on my 10x54 milling machine I found out that the four bolts that hold the entire top section down into the main body turret had 1/2"x12 threads per inch
---I installed an eight inch tall riser block and that required longer bolts
---I had some 5/8" hex bar stock so I machined pieces and threaded them on my lathe
---really wasn't much of any issue---just a little time consuming

---so I have four 1/2" x 12 tpi bolts that I have not found any use for
---these are 6.5" OAL---5" x 1/2" shank with 1-1/2" of 1/2"-12 threads

---if you were to show what your bolt needs to look like and the dimensions maybe machine shops where their mills have riser blocks installed might be a source

 

[metalmagpie]

1/2-12 hardware is available from McMaster-Carr.

 

[djed]

---when I installed a riser block on my 10x54 milling machine I found out that the four bolts that hold the entire top section down into the main body turret had 1/2"x12 threads per inch
---I installed an eight inch tall riser block and that required longer bolts
---I had some 5/8" hex bar stock so I machined pieces and threaded them on my lathe
---really wasn't much of any issue---just a little time consuming

---so I have four 1/2" x 12 tpi bolts that I have not found any use for
---these are 6.5" OAL---5" x 1/2" shank with 1-1/2" of 1/2"-12 threads

---if you were to show what your bolt needs to look like and the dimensions maybe machine shops where their mills have riser blocks installed might be a source

Thank you that’s very kind. Pictures to follow though I think I’m set.

 

[djed]

Thanks to all that contributed. As it turns out, cutting to 0.497”, chamfering the edge, starting with the 9/16-12, and following with the 1/2-12 worked. I can’t test for sure until I turn the rod (where the head is) down to fit. Pictures attached.

 

[EPAIII]

You say that single pointing the thread on your lathe is out of consideration. I say you should consider single pointing the thread to about the 90% point and using the die to finish it. It is not as hard as you imagine and will be a great learning experience. And the die will zip along with only the final 10% to cut. This way you should easily get an almost perfect thread.

This applies for any thread form.

 

[mhajicek]

Thanks to all that contributed. As it turns out, cutting to 0.497”, chamfering the edge, starting with the 9/16-12, and following with the 1/2-12 worked. I can’t test for sure until I turn the rod (where the head is) down to fit. Pictures attached.

If you were so inclined, you could weld up the buggered head and recut it, saving the old bolt.

 

[djed]

If you were so inclined, you could weld up the buggered head and recut it, saving the old bolt.

I only own a Lincoln Electric MIG welder with which I have limited experience. A buddy of mine suggested the same thing but said I would need to TIG weld the buggered head and recut at a 90 degree. I don’t own a TIG welder and have never used one. Is this repair possible with a MIG welder? I’ve attached a picture to show that the center of the head is drilled and tapped to insert a cover plate.

 

[mhajicek]

I only own a Lincoln Electric MIG welder with which I have limited experience. A buddy of mine suggested the same thing but said I would need to TIG weld the buggered head and recut at a 90 degree. I don’t own a TIG welder and have never used one. Is this repair possible with a MIG welder? I’ve attached a picture to show that the center of the head is drilled and tapped to insert a cover plate.

Possible, but might be a bit tricky if you don't have much welding experience.

 

[bill jones]

---what is this inside hole?
---what does the inside diameter measure?
---is it threaded?
---how deep is it?
---if it's threaded how deep do the threads go in?
---what is the holes purpose?
---what fits into that hole?
---what is the purpose of the slot?
---is this threaded piece with the damage magnetic"
---how hard is the steel of the damage part?
---can you easily touch it up with a file OK?
---are the used 1/2"-12 threads good enough to use as is ?
----------------------------------------------
---it looks to me like you could simply braze across the entire top
---then machine the top flat and the OD to what ever diameter you want
---then center drill the hole
---then carefully one way hack saw the slot with a nice new blade---and not using any back strokes to dull the teeth
---------------------------------------------
---if the slot is not wide enough using one hacksaw blade maybe try using two new blades at the same time to widen out the slot
---might want to try this idea on a similar sample piece of steel first

 

[ratbldr427]

If you were to try to weld the head with a mig make a thick washer out of some larger round mild steel scrap with a snug fit hole for the head .Put it flush with the top of the head. Don't use as much heat and feed as for joining metals .Weld up then turn off the scrap and face the head as to original then slot.
It is very easy to make round die holders to chuck in the tail stock out of solid bar and bore for whatever length you need. You are limited by your lathe size though.

I have a bunch for 3/4",1",1-1/2" dies I use for quick threading. I single point when necessary. Sometimes turning an undersize pilot helps and cut off the pilot when done. Putting a center in the pilot on a long part allows you to use the two handle die stock and rest it against the carriage.

 

[Bill D]

I think welding will cause a problem to retap the internal threads. Some slag will get into the internal threads and you would have to catch the existing threads below the bad spot.
Bill D

 

[ratbldr427]

I think welding will cause a problem to retap the internal threads. Some slag will get into the internal threads and you would have to catch the existing threads below the bad spot.
Bill D

Welding and repairing the bolt head has nothing to do with internal threads? He wants to keep the bolt head like original.

 

[Bill D]

Welding and repairing the bolt head has nothing to do with internal threads? He wants to keep the bolt head like original.

I read it that the original bolt head has small internal threads inside the head as well as standard external threads on the other end.
Bill D