plead for 3 jaw chuck knowledge

Superburban said:
Thank you for stepping back in Mkiey. For a few minutes there I thought this had turned into a rich mans only board, and us on limited budgets were not wanted.
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Nah, that's the nice thing about HM - everyone has something to share, teach, learn or joke about. The vast majority of us are hobbyists, which is what makes it so nice for all of us. One thing I have seen repeatedly is that a new guy may be new to machining but will often have skills in another area that astound me. So enjoy the community, learn and have fun. Well, that's what I try to do anyway.
 
When you get to the point where you are asking yourself "what do I need to make or fix" instead of "what do I need to buy" then your shop is relatively well equipped.
For a while anyway. Till the next Harbor Freight catalog comes.
Mark
 
On a 3 jaw scroll chuck the threads on the jaws are offset 1/3 of the scroll thread lead from the part holding surfaces. In the case of a .125" lead .041xxxxx", it does not matter which slot the master jaws are in so long as all three are in the same thread in the correct order. To simplify jaw changes it is useful to number the slots and jaws but is not required, as seen below.

Turn the scroll until you see the beginning of the thread and install jaw #1, rotate the scroll until the start appears in the next slot and install jaw #2 and so on. The relationship lies between the threads of the scroll and master jaws. Keeping each jaw in the same slot helps with repeatability as any error remains in the same place, if indeed the OEM finish ground the hard jaws in place then slot placement is important as the error in radial slot location either advances or retards the work holding surfaces.

Many chucks that I have used have the slots numbered inside the groove where they are not easily seen much like the jaws are numbered down in the slot which can not be seen until removed.

I do not know why this is done but surmise that it makes for a cleaner looking product, high end products often have the numbers laser/chemical etched where they may be seen. Also take into consideration that the employees at the chuck factory need to know where the parts belong in a given assembly.

Buy yourself a set of number stamps and mark it for your own use, you will not be able to to do so on the hard jaws however.
 
Superburban said:
Thank you for stepping back in Mkiey. For a few minutes there I thought this had turned into a rich mans only board, and us on limited budgets were not wanted.




I beg to differ. Not the number of threads, but the position like has been stated a few times already.

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I was incorrect by stating the number of threads vs the thread offset. I suppose the number of threads are important for strength when larger stock is in the chuck. When I took the jaw out of my chuck I didn't count the threads and I didn't take all three out so I didn't have a comparison. I do have the mechanical aptitude to understand the installation order sequence based on thread offset or number of threads if that were the case. I stopped posting because I didn't want to become more verbose, specifically in regards to numbered jaws and slots. The link to Mikey's earlier explanation covered this. This was my atempt to convey in post #15. If the jaws and slots are numbered then this is the position they should be installed. Mikey, RJ and Wreck Wreck gave good examples and photos (including your photos). If a person isn't familiar with installation sequence they could miss the timing on the end of the scroll and end up with major misalignment, which takes us back to the OP.

This topic got deeper (and this is good) when we started discussing quality versus mystery metal imports where the jaws or slots are not numbered. Then we took a turn on what is spent, e.g. rich vs. poor. The reality here is this isn't about $$$ it's about information given that's correct. It shouldn't make a difference if you do this for your daily paycheck or you do this for a hobby, correct information is important and I'm not willing to get knotted in semantics. The real $$$$ issue comes in when we move into the **time is money arena**. If I have three jaws that are numbered I'm ahead of the game on installation after repair, restore, etc. If I have jaws and slots numbered I'm ahead of the game on accuracy in regards to runout, i.e. accuracy. Everyone who visits here isn't a hobbist and we shouldn't pretend that's the case. On the other hand if it were only hobbist a lot would be missing if you leave out the professionals who are willing to spend their time here dispensing valuable information. As a business owner I'll estimate I have 100K invested in equipment, and I have friends and acquiantances who have 1-2m invested in equipment and they still come to me to get projects done, so if you think the comment was about rich or poor you missed the point.
 
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The information in this thread would be good to pear down just to the pertinent info, and make it a stickey, or FAQ, some where.

I was only trying to correct your thread count comment, there was no intention to slam you, and I hope you are not taking it that way. The only part directed at you, was what was posted after the quote from your post. The rest was aimed at the others that were just showing off, and contributed nothing to the OP's question.
 
I was only trying to correct your thread count comment, there was no intention to slam you, and I hope you are not taking it that way. The only part directed at you, was what was posted after the quote from your post. The rest was aimed at the others that were just showing off, and contributed nothing to the OP's question.[/QUOTE]

As I stated I was incorrect to state thread count, but if we look at you correction can you see that technically you correction is incorrect too. If the chuck and jaws are not numbered then there is no correct location(s) unless the owners manual instructions detail the direction the jaws are inserted. The importance would be placed on the offset of the threads, as in RJ's photo in post #20, and the #1 jaw would be on the left. It makes sense for a manufacture to cut the threads the way they do so all of the jaws have the same number of threads. The jaw number would be accomplished by offsetting the jaw in the manufacturing process to match the insertion sequence. In regards to location, if the manufacture doesn't mark the chuck there is no correct location. You can install the #1 jaw at any location. I'm guessing from your photo that the jaws and chuck are numbered based on the 679 which I am also guessing is the S/N of the chuck, and I'll add that the jaws were matched to the chuck.

One thing I got out of this will be directed to anyone choosing to purchase from CL or EBay, especially if the lathe, specifically the chuck isn't assembled. It would be easy to end up with two jaws that are the same based on visual inspection if the jaws were not aligned as a set.

In regard to being slammed. I didn't take it that way, and as I stated I'm a machinist neophyte, although I addressed the rich man poor man based on your comment and I'm not sure how you arrived there. I didn't read any comments from anyone showing off. I made my comment based on casca92's post. I hope we didn't lose him.

casca92 said:
ahh a light is starting to come on , not real bright but that is some guidance I was hoping for.
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Casca 92 I hope the light is still on and you're healing. Arrange your chuck jaws as RJ's #20 post and watch this from around the 17 minute mark.

 
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RJSakowski said:
To further clarify the order in which chuck jaws are reinserted, here is a photo. Line the jaws up so they are all even and the distance of the tooth to the inside of the jaw is increasing. The jaws will now be in their correct order.

The chuck jaw with the tooth nearest the inside of the jaw (the left one, in this photo) is the first jaw seated. I place the jaw in the slot and turn the scroll backwards while maintaining gentle inward pressure on the jaw. At some point, the jaw will come off the scroll and drop down to the next position on the scroll. Turn the scroll forward to engage the jaw. Now insert the second jaw in its slot and continue turning the scroll until it captures the jaw. Repeat the process for the third jaw. The jaws will now be in their correct orientation.
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Laying out the jaws is the way I do it. Sometimes, I forget and get the order backwards.o_O Once you put the second jaw in, it becomes obvious. :rolleyes:
 
If your chuck jaws are not marked in any way, you can designate the order easily by drilling one, two, and three small dots on the non-contact faces of the jaws. I use a carbide printed circuit drill bit to mark the hardened jaws. Lacking the carbide drill bit, short light lines made with a Dremel will also work. The face of the chuck should be marked as well. It is not hardened so you will be able to drill the spots with a HSS bit.

Double check that you have the orientation correct and mark with a marker to avoid mis-marking. Should you make a mistake, there's nothing wrong with having three, four, and five spots. Just don't go too crazy.
 
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