Taps and Dies

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Could someone help me out and tell me where I could buy a 13/16 x 20 bottoming Tap and Die . I want Make and/or Mod some battery tubes for Aleph / surefire heads and cant get that size Tap and Die over here in Europe . I would have to order it through the mail . Thanks !

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Kenny
 
I get my stuff from msc-direct.com

They ship pretty quick. I do just want to note that the term bottoming tap is a bit misleading. Even they have a taper on the end and don't actually bottom out. I have two taps in 13/16-20. Once is a standard taper to start the threads and the other is a bottoming that I ground down to really bottom out. I've found this necessary when threading heads. Unless you're just chasing threads, you'll need a way to make sure that the taps go in straight. I use my lathe or drill press to do this.

As for dies, I suppose that msc has those too, but I usually cut outside threads on my lathe, so I can't help you out there.
 
Just a heads up on the tap, KBC only stocks the plug version of the tap. A bottoming version can be ordered but at extra time (~2 weeks) and cost.

The catalog price is great for such a tap, bottoming or not. I'm guilty of grinding down plug taps myself to create bottoming taps. IIRC, the selection of dies @ KBC is not as extensive and a 13/16-20 die is definitely a custom order tool.
 
The tap is a "regular" item at MSC and I got mine in a few days.
 
www.travers.com has pretty good prices on the 13/16-20 taps and die. They have plug, taper, and bottoming style taps in 13/16-20. The smallest die size in 13/16-20 is a 2" round.
Oddly enough, they are made in Poland. The tap has a logo consisting of the letters "VIS" on the shank. Perhaps you can track down the manufacturer and get the tooling without having to ship it back across the Atlantic.
 
Thanks you guys . I ordered them from MSC and I got them yesterday .

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Kenny
 
I need some advice from the good folks here.

I was making a backplate adapter to mount a 4 inch chuck on my 7x10 lathe. I'm reworking a steel spindle adapter designed for another chuck and another lathe. It's over 3/4 inch thick, so I had plenty to work with. One side is finished, with the proper recess for the spindle nose.

I sucessfully centered the backplate on my huge (4 inch) rotary table and drilled the 4 hole pattern for the 6x1 mm mounting studs. To my suprise, my locating was right on! The holes are right where they belong and are square.

Here's the problem. I was wearing my bi-focals, and they create an optical illusion that makes straight lines look crooked. I realized this after tapping the first two of the holes. They were at a slight angle. The last two of them went straight in. The end result is that the plate fits perfectly, as long as I have only 3 studs installed. I install all 4 and they don't locate properly.

Is there anyway to straighten out the tapping without drilling it out, retapping and using a bigger stud?

I can also widen one of the holes in the spindle flange, but I'd rather not alter that end of it if I can avoid it.

Any help?

Daniel
 
I wouldn't take any shortcuts on the backplate. Centering and rigidity are critical.

The best thing to do is to start a second series of holes and abandon the first set of holes.
 
NG.

General rule is not to use a pattern of threaded holes (or a single threaded interface) to locate a precision object. You use dowel pins or a shoulder-recess to LOCATE the objects with respect to one another and then use the threaded fasteners to hold it together. A partial grey area is using shoulder bolts to locate and fasten things.

Straighten out a crooked tapped hole? No way to do that. It might be possible to machine a new over-sized hole in the correct position and orientation and then put a thread insert in there. Look up HeliCoil stuff, if you're not familiar with it.

Like wasabe64 said, abandon the bad holes and redo all four. Just think how good the second set will come out now that you practiced with the first set of holes!
 
You could just get the 5" chuck and back plate kit from the little machine shop and take the head ache out of it. The 5" works really well with the mini lathe. I've been running one for a while now and I don't know how I every worked without it.
 
Thanks for the feedback. No way to fix them? Darn!

I'm always lothe to redo a whole project for a simple mistake. In this case, the shoulder of the lathe's spindle does snuggly fit into the recess cut into the adapter plate. The studs and nuts hold it in place. Will it compromise the rigidity if I enlarge one of the holes in the spindle flange by 1/32 or 1/16?

I thought about setting up another series of holes, I did not want to end up with a swiss cheese project. Besides, the silly thing already has an extra 3 bolt pattern out near the outer edge for the chuck it was designed for.

My particular lathe spindle flange has a 6 hole pattern, with 3 holes spaced 120 degrees apart and another 3 holes 90 degrees apart (sharing one hole from the 3 bolt pattern). This allows a 3 bolt or 4 bolt chuck.

Would I have balancing problems or warping problems if I use one of the holes from the three bolt pattern (only about 30 degrees off). That would leave me with a stud at 0, 120, 180, 270 degrees.

I don't have any more 4 inch diameter steel stock, so I have to find a local source for cut-offs if I start over. It might not be a bad idea anyway to do a nice, clean one from scratch.

Daniel
 
gadget lover, I know that presents a bit of a problem. I thought about making my own backplate as well. The thing that kept me from tackling that was that I consider machining a means to an end, rather an end in itself. The short of it is that the time spent making the plate would have been time NOT modding, so I decided to just buy the stuff.

As for the 4" chuck, just consider the 5" an upgrade that you've been needing to make. With the 5" chuck, I actually parted at 2" diameter piece of stock in my mini, without the use any sort of steady rest. The chuck is that massive.
 
You make a good point, Chop. It's not the most productive. Well, unless you count my lack of experience. I decided the experience working with a large chunk of steel was worthwhile. I felt kind of intimidated going into this, and feel much more at ease about it now, even though I screwed it up a bit.

I'm still only 1/2 done, as next I need to do the face that the chuck will mount to. I'll sleeep on it and decide tomorrow.


Daniel
 
Just a little nudge.

It took me all of ten minutes to get up and running, once it came in. That includes the time it took to get the muck off of it.
 
Daniel, use the 3 bolts and (red- I forget the number) LocTite the assembly. I'm guessing it will be sufficient.

Larry
 
Chop, you are evil! It's not like I need encouragement to buy spare toys. I am trying to watch my toy budget a bit closer. I must say, though, that your encouragement is probably just my Karma catching up with me. This month I convinced a friend that he needed a lathe, and I even picked it up form him.

Thanks for the suggestion Larry. Is the red the permanent one? Were you suggesting a set of holes every 120 degrees, or just using 3 of the 90 degree offset holes? I'm worried about vibration as well as holding it tight.

Daniel
 
[ QUOTE ]

Here's the problem. I was wearing my bi-focals, and they create an optical illusion that makes straight lines look crooked. I realized this after tapping the first two of the holes. They were at a slight angle. The last two of them went straight in. The end result is that the plate fits perfectly, as long as I have only 3 studs installed. I install all 4 and they don't locate properly.


[/ QUOTE ]

How much off-straight are the threads? Also, does the chuck mount to the backplate with studs (threaded both ends) or capscrews? If the holes aren't too much off-straight, you might want to try using a pulley tap (tap with extra-long shank ground to the clearance diameter of the appropriate screw). Mount the chuck to the backplate using the "good" holes, with the "bad" onces roughly halfway between one lining up and the other lining up, and tighten the 2 screws really well. Then, re-tap the bad holes using the pulley tap (it'll guide into the start of the threads) - the "brute force" of the tap being held in line by the clearance hole for the screw is frequently enough to be able to get screws in. We do this fairly often at work.

If it's still a bit too much, the next step is "Michigan screws" - you've gotta make your own, to fit the application. They're capscrews that are ground to a smaller diameter starting just below the surface of the threaded plate, and ending about 1/2" below the head. The reduced diameter lets them move a bit more to the side than a full-diameter screw.

It's too late now, but you should get yourself a piloted tap wrench (KBC part numbers 1-397-101, 102, and 103). After drilling the holes, you leave the part set up in your indexing table and clamp the "hat" of the tap wrench in the drill chuck (other piloted tap wrenches don't have a "hat" - on those, you grip the pilot loosely in the drill chuck) and slide the pilot of the tap wrench into the "hat". Since the hole is directly under the drill spindle, and the pilot keeps the top of the tap wrench concentric with the spindle, you'll tap it straight every time.
 
Thanks for the idea Rwolff. It uses studs, not capscrews. The threads are only off a bit, maybe 10 or 20 degrees or so. The problem appears to be that I held the piece differently, so one leans to the left and the other to the right. When all 4 studs are inserted the two bad ones fight each other, with one pressed against the left side of the mounting hole and the other rubbing against the right hand side of the hole.

I've thought of making a stud that is threaded 6x1 on one end and 5x1 at the other. That would provide the clearance.

Thanks for the pointer to the piloted tap wrench. I think I need one more than most people. /ubbthreads/images/graemlins/smile.gif



Thanks for all the info and advice.

Daniel
 
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