Tolerances For My Die Holders

[JoeLee]

For those who may not have seen my thread on U-bolts, I'm making a couple die holders for the 1/4" & 5/16" round split dies I just got.

I'm just wondering on the tolerances for each. The 1/4" round die measures about .995 on the OD and the 5/16" measures about .998. Of course if you open the die up a little for a tighter thread fit the OD will increase. They are factory set and fit just right on a bolt.

So........... what would be a recommended hole size for dies?? How much clearance should I allow??
Also the guide hole in the holder for each size, how much clearance should I allow there??

I'm guessing probably 1.005 on the hole for the die and maybe + .10 on the starting or guide hole for the rod.

For a reference my Ridgid 1/4" bolt die guide hole measures .270. That seems like a bit much.



JL....................

[David Powell]

For those who may not have seen my thread on U-bolts, I'm making a couple die holders for the 1/4" & 5/16" round split dies I just got.

I'm just wondering on the tolerances for each. The 1/4" round die measures about .995 on the OD and the 5/16" measures about .998. Of course if you open the die up a little for a tighter thread fit the OD will increase. They are factory set and fit just right on a bolt.

So........... what would be a recommended hole size for dies?? How much clearance should I allow??
Also the guide hole in the holder for each size, how much clearance should I allow there??

I'm guessing probably 1.005 on the hole for the die and maybe + .10 on the starting or guide hole for the rod.

For a reference my Ridgid 1/4" bolt die guide hole measures .270. That seems like a bit much.



JL....................

OH oh, what a can of worms here ! I have been using tailstock die holders for over 40 years. First one was a present from my now ex wife,it was from Reeves Model Engineers suppliers, it is double ended and has diameters of 1.011 and .822 However, I have found that, although it works well for most jobs, sometimes it holds a bit off center and sometimes dies will not fit. So I have a further drawer ful which measure 1.002,.984 ( For dies from Canadian Tire corpn) 1.006 .786 and 1.177. That's just in the drawer for the small die holders. In answer to unsaid queries, yes I can screwcut, do know how to measure threads, but I find life is too short to make every non critical thread that way. Have fun, work safe and, if its just a hobby don't worry too much . Regards David Powell.

[dalee100]

Hi,

Everyone fears clearance. There are very, very few things in this world that need tight tolerances. I've had far more problems with overly tight tolerances than too loose. You need clearance to get the dies into and out of the holders. Too tight, and nothing will fit. And even if the die goes in to the holder clean, getting it back out might prove difficult.

Make your die holders 1.000" +.010/-.000. And that is pretty tight. If being a bit off center is a critical issue, then die cutting the threads is the wrong process.

[Dan Dubeau]

Make it larger, and if you're concerned about centering the die in the holder make set screws at the 4 quadrants to center it up. Me think you'll be fine though...

[David Powell]

IT took me a while to catch on.

Hi,

Everyone fears clearance. There are very, very few things in this world that need tight tolerances. I've had far more problems with overly tight tolerances than too loose. You need clearance to get the dies into and out of the holders. Too tight, and nothing will fit. And even if the die goes in to the holder clean, getting it back out might prove difficult.

Make your die holders 1.000" +.010/-.000. And that is pretty tight. If being a bit off center is a critical issue, then die cutting the threads is the wrong process.

I make almost all of my own parts for the model steam engines, nuts and bolts, steam fittings etc. In earlier years I would sometimes very carefully turn a blank for a thread, example 1/4" by 40 use a die in the purchased die holder 1.011 without giving it much thought. However, often the threads would come out undersize by 5 to even 10 thous, there is not much to play with in such fine threads and later troubles would ensue., experience made me realise that with the die out of center in the die holder some teeth were actually reducing the diameter of the work as well as cutting the threads. I began experimenting and the plethora of die holders is the result. I have far more die holders than I mentioned earlier, each one made for a specific different die, the dies remaining in the holders probably for my lifetime. If I want a particular thread the die is ready in the holder and I know the thread will be pretty good. Hope this explanation helps David Powell.

[JoeLee]

Won't a die usually center itself as long as it's not being forced or restricted to one side?? I've seen "drunken threads" where the nut does not go on square to the bolt and that's what the whole purpose of the holder is, so your threads start square to the bolt.
If there is .010 or so clearance in the starting hole of the holder that should allow the die to center on the rod being threaded.
I've never seen threads that were cut heavy on one side and shallow on the other.

JL...............

[David Powell]

Won't a die usually center itself as long as it's not being forced or restricted to one side?? I've seen "drunken threads" where the nut does not go on square to the bolt and that's what the whole purpose of the holder is, so your threads start square to the bolt.
If there is .010 or so clearance in the starting hole of the holder that should allow the die to center on the rod being threaded.
I've never seen threads that were cut heavy on one side and shallow on the other.

JL...............

I think I may have picked up and crossed my wires. I am talking about tailstock die holders, you seem to be talking about hand held die holders with guides. I very seldom use those, even with good ones I seldom can cut really nice threads. Sorry for creating any confusion. Regards David Powell.

[JoeLee]

I think I may have picked up and crossed my wires. I am talking about tailstock die holders, you seem to be talking about hand held die holders with guides. I very seldom use those, even with good ones I seldom can cut really nice threads. Sorry for creating any confusion. Regards David Powell.

Not really much difference between the hand held or wrench driven ones I'm making with a guide hole or the tail stock mounted ones.

JL.................

[J Tiers]

I make almost all of my own parts for the model steam engines, nuts and bolts, steam fittings etc. In earlier years I would sometimes very carefully turn a blank for a thread, example 1/4" by 40 use a die in the purchased die holder 1.011 without giving it much thought. However, often the threads would come out undersize by 5 to even 10 thous, there is not much to play with in such fine threads and later troubles would ensue., experience made me realise that with the die out of center in the die holder some teeth were actually reducing the diameter of the work as well as cutting the threads. I began experimenting and the plethora of die holders is the result. I have far more die holders than I mentioned earlier, each one made for a specific different die, the dies remaining in the holders probably for my lifetime. If I want a particular thread the die is ready in the holder and I know the thread will be pretty good. Hope this explanation helps David Powell.

Since I assume you are referring to making a number of parts all the same, why not do what the turret lathe folks do?

Make the die holder adjustable for center, so that you can slap it in, and adjust it to center up on the rod. That way you do not need so many holders, and any arbitrary die you pick up can be centered perfectly.

Here is a drill and reamer holder, made in two parts so that the actual holder can be shifted around a matter of +- 20 thou or so in order to get it on-center. It is made for a turret, but could as easily have a taper shank to fit the tailstock.

[dalee100]

I make almost all of my own parts for the model steam engines, nuts and bolts, steam fittings etc. In earlier years I would sometimes very carefully turn a blank for a thread, example 1/4" by 40 use a die in the purchased die holder 1.011 without giving it much thought. However, often the threads would come out undersize by 5 to even 10 thous, there is not much to play with in such fine threads and later troubles would ensue., experience made me realise that with the die out of center in the die holder some teeth were actually reducing the diameter of the work as well as cutting the threads. I began experimenting and the plethora of die holders is the result. I have far more die holders than I mentioned earlier, each one made for a specific different die, the dies remaining in the holders probably for my lifetime. If I want a particular thread the die is ready in the holder and I know the thread will be pretty good. Hope this explanation helps David Powell.

Hi,

OK, been there done that too. Generally if you are cutting that far off center to reduce the OD, you can see it as you cut the thread. That often indicates that you are holding everything too rigidly and have your tooling over constrained or your original alignment is bad. You need to have a bit of "float" in a tapping or die cutting operation so the tool can find it's own center. Hence all the "floating tool holders" that exist. Make everything looser in this case. Not tighter.

JTier's suggestion of die holders similar to the ones used on turrets will work well also. But are geared to production levels of use than the normal ones-twoes we do at home. And wouldn't be my first choice at home because I think they are a slow to setup operation. YMMV though.

[J Tiers]

Hi,

.....

JTier's suggestion of die holders similar to the ones used on turrets will work well also. But are geared to production levels of use than the normal ones-twoes we do at home. And wouldn't be my first choice at home because I think they are a slow to setup operation. YMMV though.

There are quicker ways

You can put a stub screw in the die, with a point on the end, and line it up before you tighten down.

You can put a longer screw with a straight shank in and hold the screw in a collet etc while you tighten down.

For turret use, a model part in the collet (one not cut off at the end pf operations) can let you set drills etc to the centraized position needed, and rough-locate cutters. Should work as well with taps and dies, and is pretty quick.

For one or two, not worth it. May not be worth even mounting the die holder. When you get up to wanting 20 pc or so, it can be well worth the effort, compared to the alternative methods.

Mr Powell:

Are you mounting one in the T/S, or are you using a T/S turret? If you are making screws, I figured you may be using a T/S turret.

[JoeLee]

I make almost all of my own parts for the model steam engines, nuts and bolts, steam fittings etc. In earlier years I would sometimes very carefully turn a blank for a thread, example 1/4" by 40 use a die in the purchased die holder 1.011 without giving it much thought. However, often the threads would come out undersize by 5 to even 10 thous, there is not much to play with in such fine threads and later troubles would ensue., experience made me realise that with the die out of center in the die holder some teeth were actually reducing the diameter of the work as well as cutting the threads. I began experimenting and the plethora of die holders is the result. I have far more die holders than I mentioned earlier, each one made for a specific different die, the dies remaining in the holders probably for my lifetime. If I want a particular thread the die is ready in the holder and I know the thread will be pretty good. Hope this explanation helps David Powell.

I can see where that could happen if there isn't sufficient clearance in the guide hole of the holder.

JL.................

[JoeLee]

Since I assume you are referring to making a number of parts all the same, why not do what the turret lathe folks do?

Make the die holder adjustable for center, so that you can slap it in, and adjust it to center up on the rod. That way you do not need so many holders, and any arbitrary die you pick up can be centered perfectly.

Here is a drill and reamer holder, made in two parts so that the actual holder can be shifted around a matter of +- 20 thou or so in order to get it on-center. It is made for a turret, but could as easily have a taper shank to fit the tailstock.

JT, I'm not sure what I'm looking at in your pictures. Floating die holder parts would be my first guess.

JL................

[David Powell]

There are quicker ways

You can put a stub screw in the die, with a point on the end, and line it up before you tighten down.

You can put a longer screw with a straight shank in and hold the screw in a collet etc while you tighten down.

For turret use, a model part in the collet (one not cut off at the end pf operations) can let you set drills etc to the centraized position needed, and rough-locate cutters. Should work as well with taps and dies, and is pretty quick.

For one or two, not worth it. May not be worth even mounting the die holder. When you get up to wanting 20 pc or so, it can be well worth the effort, compared to the alternative methods.

Mr Powell:

Are you mounting one in the T/S, or are you using a T/S turret? If you are making screws, I figured you may be using a T/S turret.

HI. I do both. I have a Hardinge turret for my 9" Southbend, I set that up if I am going to do a batch of over about 20 items. Most of the time I find I need ones or twos at a time so use a morse adapter in the tailstock.. For most of my sizes I can hold the die holders in my fingers, I have a DC drive on the Southbend, will soon install one on the Myford. A quick switch over to reverse gets the dies off the threads. I do have a couple of Coventry die heads that I got fairly recently but haven't got into using them yet, Someone sometime in the future will be VERY puzzled by 4 BA threads with 1/4" AF hex heads!!!!. Regards David Powell.