Tapping question ??...

[56type]

56type, If it is a bottoming tap, you can easily taper 3 or 4 of the first threads on the tap with a fine wheel on a bench grinder. I've taken many taps that broke up where the full threads are and tapered the first few threads and they worked fine. Good luck, JR49

That's the next piece of equipment on the "buy list". After some of the posts by other members I think the problem is that as you said I have a bottoming tap, and a slightly undersize hole that just aren't playing well together. Thanks for the tip, I definitely see myself trying that in the future when I can get some experience on the bench grinder. Be a great to salvage broken taps that way.

 

[carlquib]

Since you are using a threaded chuck, open the jaws all the way and see if your mt adapter is threaded, many are. If it is, it will probably be a left hand thread for just what you are experiencing. You screw the chuck tightly onto your arbor and then apply the left hand screw to keep your chuck from backing off the mandrel when running in reverse.

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[56type]

Since you are using a threaded chuck, open the jaws all the way and see if your mt adapter is threaded, many are. If it is, it will probably be a left hand thread for just what you are experiencing. You screw the chuck tightly onto your arbor and then apply the left hand screw to keep your chuck from backing off the mandrel when running in reverse.

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What I have is a Craftsman 1/2in. drill chuck that is thread onto a shaft that has a MT2 taper on one end that goes into the tailstock. Workpiece is being held in a 4-jaw chuck threaded onto the headstock spindle of the lathe. No reverse on my lathe since running it in reverse could cause the 4-jaw to unscrew itself from the headstock. The thread on the MT2 shaft that goes into the tailstock is RH.

I tried turning the 4-jaw on the headstock spindle by hand in reverse and as soon as the tap tried to cut into workpiece it locked hard and began unscrewing the Drill chuck mounted in the tailstock from the threaded MT2 shaft. Then I tried leaving the MT2 tapered shaft loose in the tailstock bore to act as a guide to keep things straight, this time turning the drill chuck holding the tap by hand into the workpiece. Still no luck, the tap refused to start & just chamfered the edge of hole without cutting any threads.

At this point I thought I should take a step back and find out where I'm going wrong before damaging either the workpiece, the tap, or both. Here's a pic showing the drill chuck mounted in the tailstock (note I have since cut threaded portion of the MT2 shaft to gain a bit more rigidity)...

 

[56type]

Pic of the workpiece....before I attempted using the tap. Hole now has a chamfered edge thanks to the tap.

 

[DAT510]

If you are having trouble getting enough torque on the tap turning the drill chuck by hand, you might try mounting the tap in a standard tap wrench, and then mount a tap guide in the tailstock chuck to keep the tap aligned with the bore of the barrel.

The tap guides are spring loaded so the guide stays in contact with the end of the tap wrench (and therefore aligned) as the tap cuts deeper into the barrel. Just make sure the tap wrench you use has a guide hole on the top.

Tap Guide http://littlemachineshop.com/products/product_view.php?ProductID=1963

 

[56type]

If you are having trouble getting enough torque on the tap turning the drill chuck by hand, you might try mounting the tap in a standard tap wrench, and then mount a tap guide in the tailstock chuck to keep the tap aligned with the bore of the barrel.

The tap guides are spring loaded so the guide stays in contact with the end of the tap wrench (and therefore aligned) as the tap cuts deeper into the barrel. Just make sure the tap wrench you use has a guide hole the top.

Tap Guide http://littlemachineshop.com/products/product_view.php?ProductID=1963

Thanks fr the link !! I bookmarked it to add to the next order from LMS. Also I'll make sure any tap handles I buy come with the tap guide hole.

 

[Zathros]

Just à answer from à eu dude who Works with every tread that is thinkable. First for Some treads we use 2 or even 3 differend irons. Foretap, middle tap and end tap. Often when Used one tread iron 'sorry for My bad english' I use the lathe Lets say for the first half of the tread. I saw à huge amount of Good tips here, grinding à sharper edge or bevel to both If needed. But I see you want to make à m14 and most lathe machines can hold tools to start female tap treads at M12 (½ ") and it Looks that your machine can do that. And for the left hand tread you can scree à bolt at the MT 2 other end throug the hollow axle of the machine. That Will hold your left hand turn Ok. I have not read all the posts but I night even double up in answers My apologies for that.
Grts.
Ted.


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[brino]

Grts. Ted.

Welcome to the group Ted!
Your english is way better than most people's second language. (I have none!)
I am glad you're jumping in and contributing.

-brino

 

[Zathros]

Thanks,
Me is always happy talking about any tecnology. My main work is in small metal parts. Any metal. Done à lot of tech stuff and diy projects. Worked in construction, ships building, cars, bikes of any kind, spray paint and body shop, as à kid already with electronics, the chip didn't exist yet. So from building or changing à machine up to working with it and everything in between I most lightly done it.
Really threading withwort, tpi, iso or exotic threads like in bycicles or ships and all in between it's done. Left and righthanded.
Just à Tiny bit of My background for your info all.
Grts
Ted.


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[Wreck™Wreck]

You don't need a chart for tap drill sizes they are the major diameter minus the lead, in your case 14mm Major diameter X 1mm lead thread. A 13 mm drill.

This is true of all 60 Degree threads, a 3/8-16 tap drill would be 5/16. The lead is 1/16, 3/8-1/16 = 5/16.

There are exactly 25.4 mm per inch as set by international standards use that number for converting dimensions back and forth.