Post by thread:[TECH] Confused about taps and dies

I was trying determine the correct die to thread an item ( a PIC of course ) and I was surprised to discover the following. #1 A 3/8 inch die would not start threading a 3/8 inch rod. I understood that the 3/8 indicated the OD of the thread. The Rod was too large. My calipers say the rod is 3/8 inch OD. #2 A 3/8 inch die will not screw onto a 3/8 inch bolt of the same thread spacing. Bolt is too large. #3 A 3/8 inch tap will not screw into a 3/8 inch nut of the same thread spacing. I resolved the issue by remembering that I had seen "adjustable" dies. I cut a slot in my die so it could expand it's diameter. Then it threaded a 3/8 inch rod and the nut screwed on very nicely. I have photos. Gus

Was this a 3/8 or 3/8 NPT tap/die pair? Mike H. On Mon, Jun 15, 2009 at 10:00 AM, AGSCalabrese<spam_OUTagscalTakeThisOuTgmail.com> wrote: {Quote hidden}> > I was trying determine the correct die to thread an item ( a PIC of > course ) and I was surprised to discover the following. > #1 A 3/8 inch die would not start threading a 3/8 inch rod. I > understood that the 3/8 indicated the OD of the thread. The Rod was > too large. My calipers say the rod is 3/8 inch OD. > #2 A 3/8 inch die will not screw onto a 3/8 inch bolt of the same > thread spacing. Bolt is too large. > #3 A 3/8 inch tap will not screw into a 3/8 inch nut of the same > thread spacing. > I resolved the issue by remembering that I had seen "adjustable" > dies. I cut a slot in my die so it could expand it's diameter. Then > it threaded a 3/8 inch rod and the nut screwed on very nicely. I have > photos. > > Gus > > >

Mike Hord wrote: > Was this a 3/8 or 3/8 NPT tap/die pair? > > Mike H. > > On Mon, Jun 15, 2009 at 10:00 AM, AGSCalabrese<.....agscalKILLspam@spam@gmail.com> wrote: > >> I was trying determine the correct die to thread an item ( a PIC of >> course ) and I was surprised to discover the following. >> #1 A 3/8 inch die would not start threading a 3/8 inch rod. Chamfer the end of the rod, say 1/8" @45 degrees, nothing fancy, easiest is with a bench grinder, but file, a little slower will also do the job. The die should say "start from this side, and that side should be nearest the rod. What are you holding the die with? A die handle, with moderate pressure, and being very careful to keep the face of the die perpendicular to the rod. Many die handles have an adjustable guide on the side away from "start...", after the rod protrudes beyond the guide, adjust the guide to be snug. This will help keep the die perpendicular on longer thread. >> I >> understood that the 3/8 indicated the OD of the thread. The Rod was >> too large. My calipers say the rod is 3/8 inch OD. >> #2 A 3/8 inch die will not screw onto a 3/8 inch bolt of the same >> thread spacing. Bolt is too large. >> The die size should be marked plainly on the die. Are you sure you have an American and not metric nut and bolt? There are numerous sizes that are close to the other family, more so in the smaller sizes. Some of them will start and go about one revolution before binding. One needs to thread a full nut to ensure. Some nuts and bolt thread are tight to the tolerance and may not thread on others. The AN spec. used in aircraft can be this way. And of course, are the bolts, nuts, and die all in tolerance and not damaged. Running a die on one of these special bolts may remove a minimum amount of material. Threads come both with a sharp "V" bottom and top, or radiused edges. A sharp edge bolt and radiused nut will be an interference fit. The radiused include the AN series. The radius reduces the stress riser at sharp corners which is a fatigue issue. >> #3 A 3/8 inch tap will not screw into a 3/8 inch nut of the same >> thread spacing. >> I resolved the issue by remembering that I had seen "adjustable" >> dies. I cut a slot in my die so it could expand it's diameter. Then >> it threaded a 3/8 inch rod and the nut screwed on very nicely. I have >> photos. >> If the die was good condition, should not be necessary. Actually the adjustable dies are almost rare, and mainly used to make threads that are at the edge of normal tolerances, usually to match some thread that is out of tolerance to begin with. And was mentioned in another message, besides fine and course threads, there is tapered pipe threads, which is a much different size (more like 1/2" O.D. since pipe is measured at the I.D. >> Gus >> >> >> --

On Mon, 2009-06-15 at 09:00 -0600, AGSCalabrese wrote: > I was trying determine the correct die to thread an item ( a PIC of > course ) and I was surprised to discover the following. > #1 A 3/8 inch die would not start threading a 3/8 inch rod. I > understood that the 3/8 indicated the OD of the thread. The Rod was > too large. My calipers say the rod is 3/8 inch OD. > #2 A 3/8 inch die will not screw onto a 3/8 inch bolt of the same > thread spacing. Bolt is too large. > #3 A 3/8 inch tap will not screw into a 3/8 inch nut of the same > thread spacing. > I resolved the issue by remembering that I had seen "adjustable" > dies. I cut a slot in my die so it could expand it's diameter. Then > it threaded a 3/8 inch rod and the nut screwed on very nicely. I have > photos. That doesn't make sense, are you sure you weren't using perhaps the NPT tap/dies, they are a different size then the "normal" 3/8" (plus pipe fittings are very slightly conical in shape). I haven't used my tap/die set for a while, but size wise everything seemed correct. A 3/8" die would certainly fit (tightly perhaps) a 3/8" bolt. TTYL

{Quote hidden}> -----Original Message----- > From: piclist-bouncesKILLspammit.edu > [.....piclist-bouncesKILLspam.....mit.edu] On Behalf Of AGSCalabrese > Sent: 15 June 2009 16:01 > To: Microcontroller discussion list - Public. > Subject: [TECH] Confused about taps and dies > > > I was trying determine the correct die to thread an item ( a > PIC of course ) and I was surprised to discover the following. > #1 A 3/8 inch die would not start threading a 3/8 inch rod. I > understood that the 3/8 indicated the OD of the thread. The > Rod was too large. My calipers say the rod is 3/8 inch OD. > #2 A 3/8 inch die will not screw onto a 3/8 inch bolt of the same > thread spacing. Bolt is too large. > #3 A 3/8 inch tap will not screw into a 3/8 inch nut of the same > thread spacing. > I resolved the issue by remembering that I had seen "adjustable" > dies. I cut a slot in my die so it could expand it's > diameter. Then > it threaded a 3/8 inch rod and the nut screwed on very > nicely. I have photos. > > Gus I'm wondering if you have confused BSW/BSF and UNC/UNF threads? Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =======================================================================

The "hole" through the die should be conical. Its larger on one side than the other. You start the thread with the larger side first. If you are threading to a shoulder, the you go as far as you can with the large side leading, back the die completely off, flip it over and cut up to the shoulder with the small side. Regards, Kevin Jones {Quote hidden}>On Mon, 2009-06-15 at 09:00 -0600, AGSCalabrese wrote: > > I was trying determine the correct die to thread an item ( a PIC of > > course ) and I was surprised to discover the following. > > #1 A 3/8 inch die would not start threading a 3/8 inch rod. I > > understood that the 3/8 indicated the OD of the thread. The Rod was > > too large. My calipers say the rod is 3/8 inch OD. > > #2 A 3/8 inch die will not screw onto a 3/8 inch bolt of the same > > thread spacing. Bolt is too large. > > #3 A 3/8 inch tap will not screw into a 3/8 inch nut of the same > > thread spacing. > > I resolved the issue by remembering that I had seen "adjustable" > > dies. I cut a slot in my die so it could expand it's diameter. Then > > it threaded a 3/8 inch rod and the nut screwed on very nicely. I have > > photos. > >That doesn't make sense, are you sure you weren't using perhaps the NPT >tap/dies, they are a different size then the "normal" 3/8" (plus pipe >fittings are very slightly conical in shape). > >I haven't used my tap/die set for a while, but size wise everything >seemed correct. A 3/8" die would certainly fit (tightly perhaps) a 3/8" >bolt. > >TTYL > >