PDA

View Full Version : Question For Forrest or other "real Machinist."



ibewgypsie
09-09-2005, 05:15 PM
My Rohm chuck came in yesterday. I have a backing plate to mount it onto.

It has a recess a smaller diameter than the faceplate. I only have "one" faceplate so I don't want to screw it up. I (question) need cut cut the face to (A) just shoulder fit into the hole, then drill the holes, OR (B) cut shoulder just exactly deep enough to bottom out inside the chuck then drill the holes?

I have the L00 Mount chucked up and running sqare in the 3jaw.. I need to mount it in thou don't I instead of in the chuck. I should remove the old chuck and attach the faceplate directly?
To me that makes more sense since I would not have any error in the 3jaw translated and multiplied to the 4jaw mount.

SO? before I turn a chip, do I need to cut just a shoulder or a exact one to bottom out?

bob308
09-09-2005, 05:29 PM
the way i mount the chucks is firt mount the plate to the spindle not in a chuck that way you dont have run out adding up. then i cut about .125 shoulder to slip in chuck. then drill and tap holes. then you are on your way.
you are right about putting it on the spindle. and the error adding up if you do it in chuck.

RD51
09-09-2005, 05:57 PM
I don't know if I'm considered "a real machinist" but I was payed to be one for almost thirty five years.The only way I've ever done the "new chuck" setup is to mount the backing plate on the spindle first.True the backing plate to the spindle.If a recess is required don't make it project to the point of interfering with the chuck.1 or 2 thousandths between the plate and the chuck should keep things nice.Take measurements often.It's hard to add material back once you've removed it.I wish you luck with your Rohm.I mounted a 12 1/2" on the Hendey I have.The chuck cost more than the lathe.It's okay but it doesn't repeat well on stock under 1".Anything over that and it does just fine.I'd really like to find an 8"or10" 3 jaw for the L1 mount and do away with this large chuck.

egpace
09-09-2005, 06:24 PM
Here's what you need to know. Be aware, this may turn into a pissing contest.
Have fun,
Ed

http://www.lathes.co.uk/latheparts/page7.html

ibewgypsie
09-09-2005, 06:27 PM
Thanks.. I will cut the faceplate tomorrow when Hopefully I am feeling better.

I got too hot today, moving things around again making room for a new multi-tool. Hard to walk with a pup hitting you in the back of the knee with a toy to throw. I have neglected him while laying in the house sick. Like a kid he wants to make up for it in one day.

1 or 2 thou, who are you talking to? HA.. If I hit it within a thou I am happy. As a machinist I am a good electrician. I try thou.

Herm Williams
09-09-2005, 09:18 PM
Hello
I have a friend who has more than seventy years experence and he says that three jaw chucks were never intended for better than three to five thou accuracy. He only uses a four jaw.
re

egpace
09-09-2005, 09:44 PM
<font face="Verdana, Arial" size="2">Originally posted by Herm Williams:
Hello
I have a friend who has more than seventy years experence and he says that three jaw chucks were never intended for better than three to five thou accuracy. He only uses a four jaw.
re</font>

I'm guessing he never used a Buck Adjust-Tru chuck.

Harold_V
09-09-2005, 10:31 PM
<font face="Verdana, Arial" size="2">I'm guessing he never used a Buck Adjust-Tru chuck.</font>

As nice as they are, they still don't come close to the performance of soft jaws.

Harold

Forrest Addy
09-10-2005, 03:05 AM
You guys who make favorable comparisons of 3 jaw chucks over 4 jaws for accuracy don't know what you're taking about. Three jaw chucks are good until the first major wreck. Even the best adjust-true chuck will not hold work straight if the scroll is deformed to the body distorted.

I've used three jaws all my working life and among them were Cushman heavy duty three jaws chucks costing 4 times as much as Buck's finest.

My three jaw still holds concentricity to 0.002" but I take it off and use a 4 jaw for accurate work. How accurate you say. I call accurate when I have to warrant 0.002" concentricity of all features on a finished part.

Many jobs respond well to soft jaws but your jaw prep and your work's second op reference diameter has to be right on the money. I used soft jaws a lot when I ran a lathe im my younger days. Can't beat them for all-diameter work if you have more than three parts to make.

I keep telling you newer guys that once you get some practice in it takes less than a minute to dial in a simple diameter on a 4 jaw. If you have to pad the jaws and make the best of reference diameters and faces that won't quite agree then you can take as long as ten minutes.

If I had my way (by cracky!) you guys wouldn't get to use a 3 jaw until you've mastered a 4 jaw and used it for a full year (home shop; two months in a production shop) on all classes of work.

[This message has been edited by Forrest Addy (edited 09-10-2005).]

IOWOLF
09-10-2005, 05:56 AM
I agree with Forrest,to a point.
You should know how to use a four jaw chuck as a machinist. It is not nessassary as a HSM unless you need to know how to use one.
The average HSM doesnt need .002 acuracy,but sometimes needs to do escentric work.It never hurts to know it.
IMHO

------------------
The tame Wolf !

bob308
09-10-2005, 07:46 AM
egpace's link was about how i was trying to say to do it. only they do abetter job of it.

my first lathe i bought at an auction with no chucks. i bought a new 4 jaw from sears and used that for 6 years. then i got around to a 3 jaw.

J Tiers
09-10-2005, 09:07 AM
Odd. I'd use a 4 jaw anytime for concentric boring etc......

I would NOT usually use one for eccentric work....

Beyond a certain amount of eccentricity, and depending on the diameter of the work, the "side" jaws are not hitting the work even partly centered. So they either get in a bind, or push the work oddly... hardly better than a 2 jaw chuck.

For small amounts of eccentrcity, or large sized work, etc, its OK.

But as for HSM's not needing a 4 jaw? Eh?

Someone mebbe needs to see what sort of things HSMs around the country and world actually do.... Quite a bit of their work is nicer than a run-of-the-mill commercial shop, they want it perfect if possible, which a shop don't get paid to do.

[This message has been edited by J Tiers (edited 09-11-2005).]

Charles Ping
09-10-2005, 12:35 PM
I have 3 jaw, 4 jaw and a lovely multibore collet chuck set that goes from 1/8 to 2".
Each has it's place.

Charles

egpace
09-10-2005, 01:18 PM
"...if the scroll is deformed to the body distorted"

Forrest,

Yes, I agree, bad 3 jaw chucks can't compare to good 4 jaw chucks. For that matter, they don't fair well against good 3 jaw chucks either. http://bbs.homeshopmachinist.net//wink.gif

It's obvious the reason they both still exist is because of their unique capabilities.

I fully understand the benefits of a 4 jaw chuck over a three jaw. It was explained to me by my Dad in somewhere back in the 50's, and put into practice by me soon after. If I was limited to only one chuck, it goes without saying, it would be a 4 jaw.

I balked over the statement...

"never intended for better than three to five thou accuracy."

The Buck Adjust-tru chuck, and other adjustables, by design, were created to overcome this liability.

I just didn't like the thought of someone walking away with the impression that 3 jaw chucks could not be used for parts requiring better than "three to five thou accuracy". It's just not true.

Ed

Harold_V
09-10-2005, 01:34 PM
Forrest said:
<font face="Verdana, Arial" size="2">Many jobs respond well to soft jaws but your jaw prep and your work's second op reference diameter has to be right on the money.</font>

That forces the operator to learn good machining practices and improves skill levels tremendously.


<font face="Verdana, Arial" size="2"> I used soft jaws a lot when I ran a lathe im my younger days. Can't beat them for all-diameter work if you have more than three parts to make.</font>

Yep! All true-----except for the three parts. I've been known to machine soft jaws for one item, which, in the long haul, is more economical that fighting a setup. Soft jaws lend themselves to holding objects that otherwise are difficult to hold, let alone to get running true. I offer a washer shape as an example. Soft jaws that have been properly bored will hold the object true within a half thou easily, and not mark or distort the object. You could spend a half hour dialing in such a piece in a 4 jaw and end up with junk in spite of your efforts.

All chucks have a place. I wouldn't want to be without a three, or a four jaw chuck.

Harold

[This message has been edited by Harold_V (edited 09-10-2005).]

Norman Atkinson
09-10-2005, 01:52 PM
I am NOT an expert- or anything near.

I do- and have had a lot of 3 jaw self centreing chucks of all sorts of conditions of wear.

The average 3 jaw chick cannot hold anything better than 3 thous, The only chuck to hold better than that is a grip true- or similar. Normally, to keep to that tolerance, the sensible machinist establishes which of the 3 jaws gives the best result- and sticks to that one.
In the course of the years, I have read all sorts of things and even to the eventual trueing of worn jaws by inside rings, outside rings and by internal grinding onto a mandrel- with a paste of abrasive dust stuck to it.With all these permutationsd, the best is only at one diameter- but bettering the 3 thous is never achieved on other dimensions.

To add to the pissing match- David has a faceplate- and the suggestion of making an accurate register to take the new chuck has been propounded. With careful machining- David will still not better being 3 thous out.

Two of the finest brains in English engineering have come up with the use of something akin to the Grip Tru. Instead of making the face place register exact- they added a small amount of slop. This enables the three holes for the chuck to be oversize. This enables the chuck to be knocked over- and clocked against a 2/10th thou. clock gauge- and finally tightened up.
Who were the two? Professor Dennis Chaddock and Martin Cleeve- and authors of impeccable repute.
In the Quorn construction articles, Chaddock did precisely that and Cleeve published his stuff using a Boxford grinder clock gauge.

Have I tried it? Well, I just happen to have a Boxford clock gauge- Hum!

Norman

IOWOLF
09-10-2005, 06:05 PM
Norm, I wasn't in a pissing match with any one,Least of all you. This Bbs is for opinions we all have them thats all.

------------------
The tame Wolf !

egpace
09-10-2005, 07:59 PM
<font face="Verdana, Arial" size="2">Originally posted by IOWOLF:
Norm, I wasn't in a pissing match with any one,Least of all you. This Bbs is for opinions we all have them thats all.

</font>

Ahhh, back to my original reply...

"Be aware, this may turn into a pissing contest." http://bbs.homeshopmachinist.net//wink.gif

P.S. 2 jaw chucks are hands down better than 6 jaw chucks. If I were alone on a desert island without a lathe, I'd rather have a 2 jaw chuck than Kim Bassinger with 6 jaw chuck! http://bbs.homeshopmachinist.net//biggrin.gif

Jesse168
09-10-2005, 08:25 PM
I don't care what style self centering chuck you have. It won't run any truer than the
O D of your material. If your material isn't perfectly round or if it has flats and they are not exactly the same size your part will never run true.

Self-centering chucks are not for exact specs. They are for general work. So do the best ya can on turning the register of your plate and drill your bolt holes correctly and make parts where you turn; bore; and thread on the same chucking and don't worry about the rest.

Mcgyver
09-10-2005, 09:14 PM
The thing i find amusing in these threads is the suggestion that .002 runout vs .005 runout matters. NOT!

your work is going to be one of three types

1) accurate requiring multipe set ups - whether its .002 or .004 does not matter. either are unacceptable, you use the 4 jaw or collet
2) accurate, one setup. you mount in the three jaw and do all cutting in one set up - every thing is concentric regardless of TIR of the chuck
3) not accurate. you're making a screw driver handle and .002 or .004, you don't care.

I just don't get where .004 busts the bank but .002 is ok. and i disagree that a home shop doesn't need a four jaw - its an absolute requirement (3 jaw is a convenience) of quality work, otherwise how could ever get concentric work on jobs requiring more than one set up??

J Tiers
09-10-2005, 10:18 PM
<font face="Verdana, Arial" size="2">Originally posted by Mcgyver:
The thing i find amusing in these threads is the suggestion that .002 runout vs .005 runout matters. NOT!

your work is going to be one of three types

1) accurate requiring multipe set ups - whether its .002 or .004 does not matter. either are unacceptable, you use the 4 jaw or collet
2) accurate, one setup. you mount in the three jaw and do all cutting in one set up - every thing is concentric regardless of TIR of the chuck
3) not accurate. you're making a screw driver handle and .002 or .004, you don't care.

I just don't get where .004 busts the bank but .002 is ok. and i disagree that a home shop doesn't need a four jaw - its an absolute requirement (3 jaw is a convenience) of quality work, otherwise how could ever get concentric work on jobs requiring more than one set up??</font>

+27 1/2 ...... that is SO true..... every bit of it!

Evan
09-10-2005, 10:56 PM
What Mcgyver said. I use both but mostly the 4 jaw. Incidentally, I mounted my Bison 3 jaw 23 years ago in the manner explained by Norman. It works well and doesn't shift. It's like a poor man's Adjust Tru.

speedy
09-11-2005, 12:38 AM
My old Lantaine lathe (which was my first home lathe) always ran with its 200mm P/B 4jaw. In the 6 years that I had it i never used the 3 jaw at all; If you can learn to master setting up in a 4 jaw, you should, it`s a breeze. If you don`t give a cr*p about accuracy and 0.1mm or worse is OK then you can do that as well http://bbs.homeshopmachinist.net//smile.gif.
Why bugger around changing chucks when it isn`t necessary? I can`t see the point myself.
Ken

Norman Atkinson
09-11-2005, 01:38 AM
With the greatest respect, I intended to say that my experience cannot compare with the years of professional know how from many of you. I read- and learn from all of you. Better still, I enjoy the good humour that runs through the pages. We do, to be sure, get a little heated at times, but there is precious little wrong with that.

I belong to the old farts- division of the Forum. I also belong to the strictly amateur division. So, I have to be an amateur old fart!

On this autumn morning in the autumn of my life(say, AH!), I looked at the postings
with a certain amount- wisdom-(EH?), and wished that there had been a crowd of you blokes out there when I started my rocky road, knocking bits of metal into another shape those many years ago.

Smileys all round. I am going to learn how to post them- but Rome wasn't built in - a lifetime?

Norm

Allan Waterfall
09-11-2005, 01:40 AM
<font face="Verdana, Arial" size="2">Originally posted by IOWOLF:

The average HSM doesnt need .002 acuracy IMHO

</font>

They do where I live.

Allan

Evan
09-11-2005, 01:50 AM
Here as well.

speedy
09-11-2005, 04:24 AM
<font face="Verdana, Arial" size="2">Originally posted by IOWOLF:
It is not nessassary as a HSM unless you need to know how to use one.
The average HSM doesnt need .002 acuracy,IMHO
</font>

You must have a sense of humour wolf. This was a wind up...right?? http://bbs.homeshopmachinist.net//confused.gif

Ken



[This message has been edited by speedy (edited 09-11-2005).]

IOWOLF
09-11-2005, 06:23 AM
Ahhh, then you must all be above average HSM'rs.

------------------
The tame Wolf !

Your Old Dog
09-11-2005, 08:55 AM
I was staying out of this because Gypsie ask for real machinist only but let me sneak in a quick one!

As a backyard machinist I'd have to side with Wolf. I don't need that kind of accuracy for projects I do. Hell, I only use the lathe and mill because it's easier to remove the metal that's in my way then to beat it into submission with a sledge http://bbs.homeshopmachinist.net//biggrin.gif

Norman, you're dead nuts on about the fun of reading all these! Even when they load up on lager and whip out the fun tool it's a trip ! I once worked with someone I considered to be a pure genious. I used to pick arguments with him just to see the beauty of his mind at work. He used words I never heard before. When I'd check them out in the dictionary I'd find a little known word that was used in precisely the manner/situation for which it was coined. I'm sure he would remember me as not much more than a piss ant on the evolutionary chain but I remember him for what he showed me the human mind was capable of. May he rest in peace.

J Tiers
09-11-2005, 08:57 AM
Naw, IOWOLF is right about it, except he should have said "farmers" instead of HSMs.

Not that farmers don't understand precision, the problem is economic.

When you have corn to get in before the next week of rain, a bearing fit of 100 thou starts to look real good, if it will let you keep running.

DFMiller
09-11-2005, 09:06 AM
So whats is the answer to the original question?
How exactly do you cut the shoulder to mount the chuck. You guys got my hopes up. I was waiting for the answer from Forrest on exactly how to go about this important procedure.
Dave

larry_g
09-11-2005, 09:22 AM
When you have corn to get in before the next week of rain, a bearing fit of 100 thou starts to look real good, if it will let you keep running.

I resemble that remark....
lg
no neat sig line

ibewgypsie
09-11-2005, 10:12 AM
Yeah..

I used to be a "perfect" electrician. If a piece of conduit was not within 1/8" I'd make the apprentice redo or do it myself. If he smacked it onto the ground to straighten it I'd have to show him the numerous places he bent it while pulling in/out the bend.
Nobody pays for perfect anymore. They get that anal retentive a-hole off the job the first chance they get. (my stuff don't smoke)

My machinining is a hobby. I relax while I am running the machines. If that means shutting off the lathe in the middle of a pass to take a nap? Ohh well. Good thing I take notes of what I am building. The big chuck is setting on the ways on the lathe on a board. I am quite sure this alone would get me crucified by some of the readers. Won't it nick/warp/scratch/deflect/ 0r just mess up the classical good looks of a antique machine?
My machines are scroungy. I sprayed the 3jaw off with light oil, then took steel wool to it for a hour. Now it is "purty" again.
Using the kind of flood coolant I have I have had to scrub the bed of the mill with steel wool and light oil a few times to keep the red rubbed off.

I need a 4 jaw to set up eccentrics, it has these nifty t-slots to use the same hardware as the mill table to bolt things to the chuck. I might get a wild hair and put in a harley cylinder, or flat plate, or model engine crankshaft, who knows? I bounce around my hobby.

Too much discussion on "who is right" Too many inflated egos bumping bellies. If you just accept the fact we are all different on different paths in life you can then become happy with yourself and your goals. This is not a race, nor a competetion of right. The most important judgement to happen to you is not going to happen in "this life". SO..

Be happy, enjoy life. If I mount this chuck and it shakes the whole building, I'd do something different, and be happy about it.

I was a critical person, always unhappy. I got a hardees breakfast, got to the "mountain" to eat it. Took the van ferry down inside the mountain. Went to the lunch room, opened my bag, got out the food, No fork. I became so angry I could have mass murdered the whole crew at Hardees, the lights dimmed in the room. I got explained to me by someone who I respected a lot, I had breakfast, if I had to eat it with my fingers I still had more than a lot of people in this world.

I appreciate all the help this forum has gave me in past/future projects. I accept each morsel gladly.

Each person has something to contribute, each person has different views and opinions.

Dang, did I wake up a hot air balloon today. Going to take a pill and eat something. Chuck is still on "that" board.

------------------
David Cofer, Of:
Tunnel Hill, North Georgia

Norman Atkinson
09-11-2005, 11:25 AM
David,
You can take a horse to water- but a pencil must be lead.

From another old nag.

Your Old Dog
09-11-2005, 01:22 PM
"If you just accept the fact we are all different on different paths in life you can then become happy with yourself and your goals. This is not a race, nor a competetion of right. The most important judgement to happen to you is not going to happen in "this life". SO.."

Thanks David, nicely put. A good thought for all of us to carry around for a bit.



[This message has been edited by Your Old Dog (edited 09-11-2005).]

mochinist
09-11-2005, 01:46 PM
<font face="Verdana, Arial" size="2">Originally posted by IOWOLF:
Ahhh, then you must all be above average HSM'rs.

</font>
They just think they are.

IOWOLF
09-11-2005, 04:56 PM
Thanx David, I Do Get a little upity, so I need a humbleing moment once in a while.

------------------
The tame Wolf !

Norman Atkinson
09-12-2005, 02:04 AM
Every prehistoric man had to tangle with the odd wolf. I am pretty prehistoric- and you're an odd wolf.

Keep 'em coming.

Norm

IOWOLF
09-12-2005, 05:06 AM
More like, I am a prehistoric Wolf and You are an Odd Man.LOL

------------------
The tame Wolf !

ibewgypsie
09-13-2005, 09:12 AM
Well guys, I read the above article, liked the way it sounded, I cut the L00 mount, it was cast iron. I really don't like cutting cast iron but I sharpened up my tooling and started away, when I got the step up, insert cut within about 50 thou I undercut it like the article said, then cut my depth to match.

Then with a file, ( yeah I know ) cut/polished it the rest the way out on the insert. With the undercut it stopped it from having a rounded curve at the base of the insert. I would file for a minute, stop measure, measure the chuck (yeah I was up at 2am so I did it lots) When I got it exact, I polished it just a tad more with a fine file.

I just took the mount off the lathe, rubbed some light oil in it, laid it on the chuck, put about five pounds of pressure and it ker-thunked together with a sweet sound, Looking all the way around it has "no gap" on the outer ring, inside is about one to three thousandths short of bottoming out.

I was so happy I just quit. Now I am going to town to pay my welding supply bill.. Later when I get around tu it.. I will drill out the holes.. SINCE I suck at tapping cast should I nut- and bolt it? I'll try to tap it, but...

Ohh yeah, it made me happy. Slow and easy.
I love that old leblond.

David

Rustybolt
09-13-2005, 09:33 AM
Dave. You can use the holes in the chuck as a tap guide. Make sure your tap is sharp(new) and drill and tap the first hole.Tap it dry.Clean up(deburr) and install the mounting bolt. Now drill and tap the other holes. Clean up and assemble.

ibewgypsie
09-13-2005, 10:47 AM
Rusty.. I may go buy some transfer punches.. Be a shame to cnc-the holes wrong....wrong center, etc...