End OD deburring or Taper Cutter

[Ronno6]

I have need to deburr or cut a short taper on the end of 3/16" dia. plastic.
Problem is that the end is not accessible from any position except axially from the front.

I am looking for a tool to be applied from directly in front of the rod, and it cannot be any larger than 1" O.D.
Taper angle is not important.....
Kind of a pencil sharpener, but for a rather stubby (3/8" long) pencil.

This is needed in order to ease starting a threading die to the end of the material....

Any pointers ?? (pun intended....)

[WobblyHand]

Is there any reason you can't use an ordinary lathe tool mounted to come in along the spindle axis?  Typically on a tool post there is a cross-axis mount and an axis mount.  If you use a v tool mounted like < you can come in along the spindle axis.  You can use the same tool to do OD's and ID's.

If you show a picture, of what you need to do, it might be easier to suggest a solution.

[Ronno6]

I cut the original probe off 1/2 to 3/8" from the base, and need to thread the resulting nub......

[WobblyHand]

@Ronno6, not sure I understand, as I am unfamiliar with this assembly, do you mean the part pointed to by the arrow?  And this is all one piece?

If so, I'd still try a lathe tool installed like a boring bar to chamfer it.  Are you using a four jaw to hold this?  Must be fun, just to indicate it. 

If my assumption was wrong, could you show the part mounted in the lathe, which would make it more obvious what you are trying to do...

[eeler1]

What Bruce said, I think.  But to be clear, you want to chamfer the tip slightly so you can then more easily use a die to thread that short probe on the bolt?  Yeah, what Bruce said.  Although seems kinda difficult unless you can take that thing apart and hold just the bolt in a lathe chuck.  You also might consider just using a file to break the edge.  I know we always want to use our machine tools, but sometimes it’s more effort than just using simple hand tools.

[WobblyHand]

Still going on the assumption of that little bit needs to be chamfered...  Haven't heard back from Ron.

I have no idea how one would get a die in there and have it start straight.  I'd go with some disassembly is required, first.  Then things would be a lot easier.  If it cannot be disassembled, a file might work.  Just takes patience.

[sb327]

Might be best to just cut the nub off, drill and tap for desired thread and insert a threaded stud. If the part is one piece, it appears to be some cast mystery metal and a stud insert would be stronger.

Dave

[Ronno6]

The part indicated by the arrow gets cut off about 1/2" from the bolt carrier body...the rectangular part.
For reasons mentioned, I am not chucking it up in a lathe.....
I stand it vertically in a drill press vise, and have the die mounted in a sleeve w/1/2" I.D.
That I.D. slides over a 1/2" rod mounted in the drill press chuck.
This is for purposes of squareness of the thread.....
The die holder is rotated manually to do the threading.
As mounted, the end of the stub is squared off using a disc sander, but the resultant shoulder is square and sharp....the die doesn't start easily.
The die would thread more easily if the shoulder was tapered...even if just a little.........

If I had an EDM machine and could plunge a rectangular cavity in a piece of metal with a round shank,
I could insert the carrier body into the cavity, chuck up in the lathe and turn to my heart's content.......

I use the stud method for Daisy bolts, but there I am replacing a .22 probe of the new bolt assy with a .177 probe.
This Crosman bolr has a .177 probe, but I am mounting a .22 probe over the .177 original..... Fits perfectly...

[sb327]

A case deburring tool with center stem removed would work. You haven’t mentioned the material. If you have a piece of drill rod, you can make a similar deburr/chamfer tool to your own specs.

Dave

[Ronno6]

A case deburring tool with center stem removed would work. You haven’t mentioned the material. If you have a piece of drill rod, you can make a similar deburr/chamfer tool to your own specs.

Dave

Now we're talking...depending on size..
Material is plastic, but I do not know exact which one....polystyrene I suspect or similar.

[WobblyHand]

The part indicated by the arrow gets cut off about 1/2" from the bolt carrier body...the rectangular part.
...
As mounted, the end of the stub is squared off using a disc sander, but the resultant shoulder is square and sharp....the die doesn't start easily.
The die would thread more easily if the shoulder was tapered...even if just a little.........

A little confused.  The stub is made out of what material?  Plastic or metal?  This may sound strange, or trivial, but are you starting the die with the tapered side or the sharp side?  If you didn't know already (my apologies if you know this!) one side of the die is the start side and has a lead in to make it easier to start.

The rectangular part is made of plastic or metal?  It looks like there are marks on the side, almost like pin locations to hold the bolt.

[Ronno6]

Once I cut off the last 1" or so that includes the magnet, the remaining part is all plastic.
"Plastic" is the last word in the opening sentence in my original post.....

I am familiar with the lead side of the die...

The following was cut and pasted from the Wikipedia entry on "Tap and die."

"The work piece (blank) to be threaded, which is usually slightly smaller in diameter than the die's major diameter, is given a slight taper (chamfer) at the end that is to be threaded. This chamfer helps center the die on the blank and reduces the force required to start the thread cutting.[7] Once the die has started, it self-feeds."

The chamfer is what I seek......

[WobblyHand]

Once I cut off the last 1" or so that includes the magnet, the remaining part is all plastic.
"Plastic" is the last word in the opening sentence in my original post.....

I am familiar with the lead side of the die...

The following was cur and pasted from the Wikipedia entry on "Tap and die."
The work piece (blank) to be threaded, which is usually slightly smaller in diameter than the die's major diameter, is given a slight taper (chamfer) at the end that is to be threaded. This chamfer helps center the die on the blank and reduces the force required to start the thread cutting.[7] Once the die has started, it self-feeds.

The chamfer is what I seek......

Kind of surprised there is an issue with starting the die on plastic, although a chamfer always helps.  What is the OD of the piece you are threading?  Maybe it is oversize for the die? 

As an example, you shouldn't thread 1/4-28 starting with 0.2500" rod, the rod is too big.  Should be closer to 0.2464".  According to little machine shop, https://littlemachineshop.com/mobile/die_threading.php  the rod size should be "Die Blank Size is the Major Diameter less 10% of the Pitch".  Basically they are saying the rod diameter for die threading should be the mean major diameter for that thread.

[Ronno6]

The plastic probe is .177 cal, so approximately 4.5mm
I am using an M4.5 threading die.
This is the recommended sie blank size for this size die pet ehr Little Machine Shop link.
Those dimensions are pretty much etched in stone (well, plastic and metal actually...

In fairness, I have been shortening the probe using diagonal cutters.
This left a peak across the diameter more or less in the center of the face.
I would file the sharp edges of that peak at the edge, then start the die and thread by hand...
I need to try with the end sanded flat.. Possibly the flat cross section and holding the die in the drill press will remedy the situation.
..but would be much easier with a slight chamfer at the rim of the face.....

Quoted from the link you posted:  "Reducing the size of a rod you want to thread with a die makes it easier to start the die,
but the real secret is to add a 30° chamfer to the end of the rod."

[Ronno6]

A case deburring tool with center stem removed would work. You haven’t mentioned the material. If you have a piece of drill rod, you can make a similar deburr/chamfer tool to your own specs.

Dave

I'm having a tough time getting a read on this tool's O.D.
If greater than 1" O.D. it will not work.......

Maybe there is one for .223 ??

[WobblyHand]

12-24 is way too big. 

M4.5 x 0.75 has a max major diameter of 4.478mm and min major diameter of 4.338mm, so the idea diameter is the mean of those values.
I think if the rod is flattened and you use the method you mentioned, with the die holder to keep it flat, you should be ok.  That case de-burring tool idea ought to work to get off the edge.  You probably don't even need to take off much.

Looking at most of the deburring tools shows they are too deep for you.  Although it might be worth while investigating if you can take a cheap one and grind it shorter.  You don't need the full integrity of the the tool, since you are chamfering plastic, not tool steel.  Something like https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fimages-na.ssl-images-amazon.com%2Fimages%2FI%2F71i0NuG2ZOL._SL1500_.jpg&f=1&nofb=1&ipt=12d1fcb76d8bc2101aa90314de28a9cc622c789640aef1cbd8c64e98533a007d&ipo=images

[Ronno6]

I'll check that out!
Thanks, Mr. Bruce...

The ideal cutter would be at the end of a 1/2" dia rod, so that I could chamfer, then place the die holder over the rod and cut the threads.....
Can't help it....I'm a dreamer...

Thanks to Mr. David and Mr. Jon as well!

[WobblyHand]

Or something like https://www.aliexpress.us/item/3256803428744008.html?spm=a2g0o.productlist.main.59.5804RTCmRTCmJ6&algo_pvid=e4acff35-7eda-4fb4-b3d6-d2a37d3cdd91&aem_p4p_detail=202306131737148329607959567250018814677&algo_exp_id=e4acff35-7eda-4fb4-b3d6-d2a37d3cdd91-29&pdp_npi=3%40dis%21USD%2160.18%2130.09%21%21%21%21%21%4021021aa216867030344114658d0753%2112000026502725928%21sea%21US%211990566934&curPageLogUid=XGCyXs6MIFjH&detail_p4p_id=202306131737148329607959567250018814677_6
Which seems to be a copy of a Noga tool.  You just need the head and a way to spin it.

[sb327]

I’m not sure of the od of the case deburring tool but it could be ground down quite easily and the unnecessary portion of the flutes ground off, much like suggested above with the other tools.

Realistically though, you could probably center drill a piece of 3/8” stock, then using a hacksaw, cut several slots across the end and you would have what you need. After all, it’s only plastic and the tool wouldn’t even need hardening (unless you were doing a lot).

Dave

[Ronno6]

I’m not sure of the od of the case deburring tool but it could be ground down quite easily and the unnecessary portion of the flutes ground off, much like suggested above with the other tools.

Realistically though, you could probably center drill a piece of 3/8” stock, then using a hacksaw, cut several slots across the end and you would have what you need. After all, it’s only plastic and the tool wouldn’t even need hardening (unless you were doing a lot).

Dave

I'll give that a go!
I will probably use 1/2" rod to allow the above mentioned procedure.