I have a question about the HF 7 x 10 3 jaw chuck.

[Metal_slicer]

I have a question about the HF 7 x 10 3 jaw chuck.

When I put stock in the chuck and spin it it wobbles a little bit. To check to see if the raw stock was out of round or the chuck, I put in a 3/8 end mill in and it wobbled. So the three jaws are closing off center. Is this normal with all self adjusting chucks? Is their an adjustment I can do?

Sorry I'm a few days new to this. I did a search on the forums but didn't find anything outside of round tables.

Thanks,
Mike

 

[Herbiev]

Is each jaw in its correct slot ? Someone else with a similar lathe may be more specific but jaws are numbered and must be inserted in correct slots.

 

[Tin Falcon]

how much wobble/run out .

there are three possible conditions :

Normal run out

improperly installed jaws/jaws not installed in order.

Jaws need grinding can be done with a dremel tool.

these chucks are not set true.

some run out is normal.


Is the chuck running true. that would be the first place to look.

Tin

 

[goldstar31]

I suspect that you are missing something fundamental about three jaw self centring chucks. They are all inaccurate- to a certain extent.

You can have a sophisticated three jaw which can be set spot on- by adjusting the jaws independently. This may be called a Grip Tru or similar.

As for the particular chuck mentioned, it should clock new within about 3 thous eccentricity. Worse than that- send it back.

As for this 'Black Art' of grinding jaws to ensure concentricity or whatever, this is an urban myth. You cannot grind a set of jaws to do this apart from improving. I had bell mouthing from incorrect usage but as for grinding generally- you can grind dead on- but only in one diameter. The rest will be still out.

And please, please don't respond describing jigs, gimmicks, moon beams from a lesser lunacy and what someone else has tried- but never you. You cannot do it- end of story.

 

[Metal_slicer]

the chuck body seems fine, the jaws just close off center. if i turn a piece of stock it runs true but if I remove the piece and reinsert it, it runs un true again. I can check to see if the jaws are out of sequence. saw a taig video on this so i know what to look for.

I appreciate the help guys. I have a lot to learn!

 

[goldstar31]

the chuck body seems fine, the jaws just close off center. if i turn a piece of stock it runs true but if I remove the piece and reinsert it, it runs un true again. I can check to see if the jaws are out of sequence. saw a taig video on this so i know what to look for.

I appreciate the help guys. I have a lot to learn!

Obviously, if your lathe has a bit of metal in the chuck, it will - or should end up parallel and concentric. If you put a piece of metal in to off set the holding, it should turn it parallel and concentric but-- if you stick a piece of round bar in it and simply clock it in the chuck, what readings do you get? Then put a centre drill in- and do the same. You should reasonably centre with it.

If you don't, you will drill some awfully oversize holes. or break the centre drill. in the process.

You must start- first things first. Get hold of a decent book like old Sparey's the Amateurs Lathe. It isn't comprehensive but no one book is.

Nevertheless it was written by a man of considerable experience and will repay for itself many times.

 

[canadianhorsepower]

if i turn a piece of stock it runs true but if I remove the piece and reinsert it, it runs un true again.
That's kind of normal for a 3 jaw chuck. If you loosen it up and rotate your part it should line up again

I can check to see if the jaws are out of sequence. saw a taig video on this so i know what to look for.

No you don't!! the way a Taig chuck is assemble is not the same thing
as what's on yours. I know I have both lathe

I appreciate the help guys. I have a lot to learn!

are you using a dial gauge or simply relying of the next cut your taking??

 

[Metal_slicer]

I do need to get a book.

I don't have a dial indicator so I cant make any readings. I plan to buy one as soon as I can. For the time being, all I have done is take an endmill which I know is true and watched it do a hola hoop dance when in the chuck. I need to take some video and post it on you tube so you all can see.

 

[John Rus]

Head over to your local HF and pick a dial indicator so you can get some numbers, one dimension is worth a 100 expert opinions!

John.

 

[Metal_slicer]

Head over to your local HF and pick a dial indicator so you can get some numbers, one dimension is worth a 100 expert opinions!

John.

Agree! Well I have created a video anyway so you all have a look.

[ame]http://youtu.be/nwzTJoJFjWU[/ame]

 

[kf2qd]

I think you replaced the jaws in the wrong order. On the back of each jaw there should be a number and a letter - 1A 2A 3A for one set and 1B 2B 3B for the other set - Mine did not have the jaw slots marked so I labelled 1 as position 1. Turn the scroll in the direction to remove the jaws and turn until the scroll just clears the slot for the number 1 jaw. then inser the #1 jaw and turn the scroll in the direction to close the jaws, but stop just before the scroll is at the slot for jaw #2. Insert jaw #2 and repeat for jaw #3. If should be close to centered at this point.

Putting 1 jaw in incorrectly can be a way to create an eccentric, just have to live with an eccentric the jaw can produce.

 

[Swifty]

If one jaw is placed in incorrect sequence, the bar would be wobbling all over the place by miles, the jaw would be out of place by a complete tooth on the scroll. I would check the run-out of the backing plate if there is one, I'm not familiar with this lathe.

Paul.

 

[goldstar31]

Not withstanding the replies to your new post, might I respectfully ask how much improvement you have achieved from the earlier information which many of us supplied?

Regards

Norman

 

[Cogsy]

I have virtually the same lathe and I did manage to get my jaws out of sequence recently and had to refer to some cribs notes I made to fix it. The wobble you're getting is comparable to how much I was experiencing with out of sequence jaws.

I know these are cheap lathes but from my experience they're more accurate than what you're getting in your video.

Edit to add : Swifty - I don't think he's a tooth out on engagement of the jaws, if that's what you mean (then the wobble would truly be extreme) but he's got the jaws inserted into their incorrect slots, ie. number 3 jaw is in the number 1 spot.

 

[Metal_slicer]

Not withstanding the replies to your new post, might I respectfully ask how much improvement you have achieved from the earlier information which many of us supplied?

Regards

Norman

Since I cant run to my local grocery store and pick up a pair of brass blanks to machine. Im at a stopping point. Am I not allowed to ask further questions in the mean time? This is a discussion forum right? or am I missing something?

 

[goldstar31]

I am unable to answer whether you are missing something or not.
Had I been stuck with the problem, I would have gone into your grocery shop, bought a cheap felt tipped pen and a can of soda.

I would have drunk the drink and cut up the can with a pair of household scissors into strips and made packing strips to fill- or nearly fill the space behind the gibs. Used the felt tip as marking blue and kept the remaining strips to act as packing up lathe tools and to keep another to act as a height gauge for the lathe tool setting.

That is what I'd do but I'd then remember that I have another 'lathe' but this one is angled at 90 degrees from how a more normal lathe is sited.

Now at my tender age of 83 years, I miss few things in life. One is an education having left school at 14 in a war torn country from the age of 9.

If I am missing something- perhaps it isn't a lot.

Regards

Norman

 

[wackyvorlon]

To my eye, it looks like the chuck is out by about two or three thou. That's totally normal. Remember, eccentricity is *very* visible to the eye when something is rotating. You can see surprisingly small amounts of runout.

There are some things that can be done. Only tighten from one hole. Usually one of them will have a punch mark. That will be the one that produces the least runout. Check the body of the chuck. If its not centred, remove it from the backplate. There's a locating register that the chuck fits onto. You can machine this in situ to get it true.

Finally, you can grind the jaws. You need to put a block in the back so that you can tension the jaws. And you will need to build a tool post grinder. These aren't terribly complex. Bear in mind, though, it will only be accurate at the diameter you ground it for.

If you want something dead on, you have to use a four-jaw chuck or collets. You can get a 5C collet chuck for about $200, and a set of 5C collets isn't too expensive.

 

[petertha]

I dont know that particular lathe chuck, so this suggestion may or may not apply. When I google a HF 7x10 pic, it appears the chuck body is bolted to a backplate mount, which in turn is threaded (or pinned) onto the lathe spindle nose?

If so, another quick thing to check is that the chuck is mounted axial to the back plate. If its off, it will run eccentric even if the jaws are centering perfect. Typically the chuck will have a relief in the back that fits (snugly) to a matching boss protrusion on the backplate. But if its a loose fit for whatever manufacturing reason resulting in the chuck is sitting on one side & tightened down that way, that might explain the runout.

Quick & dirty in the temporary absence of a dial indicator: slowly feed in the recommended felt pen to just touch the test bar while rotating, like in your movie. Now do the same on the chuck & the backplate segment. Compare all 3 marks. If the backplate has a full contact line, its running true to the spindle. But meanwhile if the chuck and test bar show a short length mark indicating the same high spot alignment, the chuck is probably not set proper. If the chuck mark = backplate mark but different than test bar mark, then its probably a jaw issue. Good luck.

 

[Metal_slicer]

petertha great idea. I would have never thought of doing that. I have to take my daughter to confirmation class to night so I my not have the time to try this out but as soon as I can I will give it a shot.

 

[John Rus]

Since I cant run to my local grocery store and pick up a pair of brass blanks to machine. Im at a stopping point. Am I not allowed to ask further questions in the mean time? This is a discussion forum right? or am I missing something?

What he is saying is we can't help you any farther untill you try to do something, like swaping out the jaws to find the combination that has the least runout or something like that. That way you have rulled out improperly placed jaws. It can be kinda, what's the right word, annoying but to a much lesser degree to try to help someone when you don't try to do something. Not saying you can't inquire more info but all that can be said has already been said and now needs to be set in action.

I hope you don't take it the wrong way, just trying to help.:hDe:

Cheers,
John.