|
Post by tarheeltinkerer on Feb 26, 2009 11:56:43 GMT -5
Hi Yall,
Well, the jeweler was unable to weld anything to the end. He drilled out just enough to see the faint edges of the original threading, but that is all. I have not been able to pry out the remains of the screw as it must be rusted in good and tight. Does anyone know a good way to get this out perhaps chemically, and if not, what size tap fits the reproducer locking screw hole?
|
|
diggr
New Member
Posts: 16
|
Post by diggr on Feb 26, 2009 17:01:10 GMT -5
Judging from the pictures at the beginning of this thread, that thumb screw appears to be the same one as in my carriage. If you don't have an answer by tomorrow morning, I'll take one of mine in with me in the morning and see what the thread is. That's where my mics, pitch gages and Machinery Handbook are.
Hopefully there is enough good thread so the tap can pick up the lead. But it's going to be a delicate operation to my mind because cast iron is not all that forgiving especially in fine thread pitches. At first glance the screw appears to be either a #8 or a #6 but the pitch looks a little fine for the commonly available fasteners. As an example, the crank handle on my Amberola has a male thread that appears to be 1/4". The two most common 1/4" threads today are 1/4-20 (UNC) and 1/4-28 (UNF). The crank however measures to be 1/4-24, a valid number per the charts.
|
|
|
Post by bostonmike1 on Feb 26, 2009 18:58:13 GMT -5
Hi Yall, Well, the jeweler was unable to weld anything to the end. He drilled out just enough to see the faint edges of the original threading, but that is all. I have not been able to pry out the remains of the screw as it must be rusted in good and tight. Does anyone know a good way to get this out perhaps chemically, and if not, what size tap fits the reproducer locking screw hole? the screw size is neither a #6 or #8---- it is a 5-40 thread. why do i still see the screw engaged in the picture in this thread and not broken off as stated? if you need one i will send you one from my machine shop. michael
|
|
|
Post by tarheeltinkerer on Mar 5, 2009 19:01:53 GMT -5
I'm sorry for not posting photos of the drilled out screw...I'm in the process of moving and just plain tired right now. I received my D mandrel bearings, locking screws, and case decals. Unfortunately, the first decal simply crumbled when I tried to apply it, and the second crumbled at the top of the E in the long extension. I'm just a bit annoyed that the one decal was junked and the other damaged, but well, #*@& happens. I'm hoping to have the case shellaced later tonight with one or two more coats, then a sanding tomorrow so I can put everything back together. In regards to the D, I don't see how you can get it to operate the four minute gearing unless you flip the mandrel gear.
|
|
|
Post by tarheeltinkerer on Mar 6, 2009 9:18:25 GMT -5
The shiny bit of metal you see by the hole is the edge of the remains of the old reproducer screw. The darn thing refuses to loosen.
|
|
|
Post by maroongem on Mar 9, 2009 16:12:54 GMT -5
The shiny bit of metal you see by the hole is the edge of the remains of the old reproducer screw. The darn thing refuses to loosen. You have a couple of options. As mentioned earlier, this is a 5-40 NC thread (I brought a carriage arm in to the shop today and checked it with a thread gage) so you can get a roll tap and with a little oil on the tap, re- cut the threads. It appears that the jeweler drilled through so you should be able to do this. I dug through my parts box and came up with a Standard carriage arm with set screw. It needs to be repainted but is in good shape otherwise. If you are interested, PM me and I can supply pix and a price. Bill
|
|
|
Post by bostonmike1 on Mar 9, 2009 18:30:02 GMT -5
The shiny bit of metal you see by the hole is the edge of the remains of the old reproducer screw. The darn thing refuses to loosen. You have a couple of options. As mentioned earlier, this is a 5-40 NC thread (I brought a carriage arm in to the shop today and checked it with a thread gage) so you can get a roll tap and with a little oil on the tap, re- cut the threads. It appears that the jeweler drilled through so you should be able to do this. I dug through my parts box and came up with a Standard carriage arm with set screw. It needs to be repainted but is in good shape otherwise. If you are interested, PM me and I can supply pix and a price. Bill A roll tap DOES NOT "re-cut " a thread---- a roll tap forms a thread and is not used for a repair such as this! you want to cut/remove the remaining screw using a standard spiral cut tap for this repair. a roll tap WILL NOT achieve this. P.M. me for the correct hole size needed and detailed instuctions before you do future damage and end up with a worthless carraige . enough damage has been done already but it can be saved . my only concern is if the person who drilled the hole drilled it on relatively "true center".
|
|
|
Post by maroongem on Mar 9, 2009 18:55:22 GMT -5
Mike,
I will have to beg to differ with you. A roll tap will do just fine in this application providing the original threads weren't damaged by the jeweler's drill. If the threads are gone, no tap will help and the only other alternative is to resize the hole and go to a 5-44 or larger, which would of course defeat the purpose as you would have to go to a non-original screw.
Bill
|
|
|
Post by bostonmike1 on Mar 9, 2009 19:09:42 GMT -5
Mike, I will have to beg to differ with you. A roll tap will do just fine in this application providing the original threads weren't damaged by the jeweler's drill. If the threads are gone, no tap will help and the only other alternative is to resize the hole and go to a 5-44 or larger, which would of course defeat the purpose as you would have to go to a non-original screw. Bill a roll tap displaces material. it does not cut. do you expect him to displace a steel screw into a cast iron carraige? ever hear of a heli-coil if the thread is damaged?
|
|
|
Post by maroongem on Mar 9, 2009 19:13:02 GMT -5
Mike,
The screw has been pretty much removed. He's not going to be displacing enough material to warrant a spiral tap in my opinion.
Bill
|
|
|
Post by bostonmike1 on Mar 9, 2009 19:23:49 GMT -5
Mike, The screw has been pretty much removed. He's not going to be displacing enough material to warrant a spiral tap in my opinion. Bill why do things wrong when you can do it correctly? i tell the men in my shop, why use the wrong tool for the wrong job? it is just from their lack of knowlege from time to time. they do eventually learn from my 38 years of tool making and fixture design.
|
|
|
Post by maroongem on Mar 9, 2009 19:58:03 GMT -5
Mike,
Doing things wrong is a subjective term. You may have a way of machining that works for you that someone else has a different way of doing that works and works well, depending upon the application.
What's the name of your shop? We are always looking for someone to help us pick up the slack in making fixtures when our manual dept. can't keep up with the demand. And whom do I ask for when calling?
Bill
|
|