custom tap

[EdK]

(05-29-2014, 08:32 PM)chucketn Wrote: If you build something from a drawing, do you change specs to what ever you want, or do you make the part to plan? My friend is making an engine to the designers plan. That's why a 1/4-40.
I'll be the first to admit I'm still at the "that's good enough" stage. I'm getting better, and my setups and tooling is improving. I made the tap as close to spec as I could get. I made a nut with it to use as a gage for the screw thread I need to make. The screw will mate with the tapped hole made by the tap I made... Whooh, I'm getting dizzy...

Chuck

Chuck,

My comment was not aimed at your tap project. Sorry if it sounded that way. I was just rambling.

Ed

[EdK]

(05-29-2014, 08:35 PM)Highpower Wrote: I can afford the time as well. My problem (one of many, I know) is I can't afford to buy all of the precision tools that go along with verifying the work that's been done meets those high "standards" in the end.

I think a few good micrometers of various types would suffice for most things, in my case anyway.

Ed

[Mayhem]

Actually, Chuck raises a good point about changing plans to suit tooling/fasteners at hand. I cannot recall having built anything from plans that had odd fasteners but if I didn't think it would be detrimental to the finished product, then I would have no issues making changes.

I've got a ton of imperial fasteners which I am still sorting through in my late Father's workshop. From memory I have 5/16" bolts with several different thread pitches (20tpi, 22tpi, 26tpi in addition to the common 18 and 24 tpi). My research lead me to the discovery of the UNS (American National Special) thread classification, which essentially means that anything goes!

UNS would permit a manufacturer to make their own (non-standard) fasteners, so you have to buy replacement fasteners from them. Although, I'm sure there are other reasons for this.

One of the first things I do new is check what size/pitch taps I have on hand before deciding on what I am going to use on one of my projects.

[chucketn]

There must be a reason the designer used 1/4"-40 thread. I don't have the drawing set, but I believe it had the directions for both the Screw and tap.
I didn't take it personal, Ed. Just saying my friend is trying to build to plan. I usually modify plans or designs myself to conform to tools and materials I have.
I guess, to be honest, I made the tap to see if I could! I'm getting confident enough to build most anything. You'll see in my posts here and on other forums, I ask questions when I am not sure about a method or technique, but temper any response based on my experience. I really hate being told I can't do something, or you can't get there from here!
That's why I love these forums. I have learned so much from them. The difficult takes me a while, the impossible takes a little longer. I like that! I'm going to add it to my signature!
Wehuuu, time for my pills again...

Chuck

[TomG]

Chuck,

I've made a few special taps and they have always worked remarkably well. You should definitely not use a regular end mill to cut the flutes. The sharp corner created would almost certainly cause the tap to fracture. Just make a ball end mill to suit. All it takes is a radius gauge and a steady hand. The radius isn't even that critical, there just can't be a sharp corner in the flute. As far as the flute depth goes, Machinery's Handbook contains that information, or you can just copy another 1/4" tap. The depth is pretty standard regardless of the pitch.

Tom

[chucketn]

Well the 1/4 tap I made worked to tap a test nut in steel. Must be first timers luck! Of course, I was pooping razor blades while I cut the nut, but it worked. The application is to tap into a hole that is counter drilled on the other end bigger than the threaded part.
After messing up single pointing the screw blank, I contacted ny buddy to tell him to make another screw. I then got hold of the plans he's using and discovered he'd miss read them. He needs 3/8" x 40 tpi, not 1/4"! Waiting to find out if the 1/4 was accidental or if he's building to reduced scale. If accidental, I'll start again, using the advice gotten here to improve the next one. Thanks everyone for their input.
Chuck

[Sunset Machine]

That's kinda funny - I was just thinking someone read it wrong, really wanted a 4-40 thread... Years ago I made a larger tap with square corners in the flutes. Worked fine but dulled fast, heat treated with a propane torch. Final sharpening with the corner of a grinding wheel may have helped.

I seem to recall saying to myself, "the next time put the taper on after the threading". Probably something to do with my tired old lathe and the pitch varying slightly under the increasing load caused by the taper. Might have been my imagination, the quest for perfection and all that. I put the flutes on after threading, the leadscrew backlash left no question in my mind about it..

[kenne]

Every once in a while we are called on to make a single purpose project for the local government installations . One of the things they ask for is some form of security fasteners . But I don't think I have ever seen a 1/4-40 bolt , what was that used for I wonder ?
The picture of the taps is impressive ,nice work . I have to make tools a lot of the time for jobs that are only going to happen out here and you really can't buy them .(besides the profit would go out the window if you drove to town to find it ).
That takes real talent , keep up the good work ................

[chucketn]

The 1/4-40 screw is the fuel adjusting scew for a model airplaine engine. I don't have the plans in front of me (on vacation) but will look it up and post it when I get home. I do remember the designer sells the plans and is from PA. He also sells castings for various tools and lathe accessories.
The friend I made it for has used it sucessfully and it didn't break. He would have made it himself but lost track of his change gears in a move.
Our next project will be a dividing head, and cast aluminum blanks to make a set of change gears for his lathe.
Chuck

[stevec]

(06-29-2014, 05:49 PM)chucketn Wrote: and cast aluminum blanks to make a set of change gears for his lathe.
Chuck

Any thoughts on changing (pun intended) to a quick change gearbox?