Grinding the Faces of the Jaws on a Three-Jaw Chuck to Reduce Runout
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- เผยแพร่เมื่อ 30 พ.ค. 2019
- I had a three jaw chuck that after fitting a new back plate, I was getting more runout than I wanted. To combat the problem, I used a tool post grinder as an internal grinder to touch up the faces of the the three jaws in order to true them to the chuck.
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Keith, whenever you're doing any kind of grinding on your lathe you should cover the ways to protect them from grinding dust.
CBN inserts and solid carbide boring bars are awesome for this!
Keith- This Rohm is adjustable. Loosening the three cap screws near the bore allows you to bump the scroll around with respect to the body. Look at the symbol stamped next to these three screw heads.
Hey Keith, another way to preload the jaws would be to place appropriately sized blocks between the angled nose flanks of the jaws and draw them together. This would preload the jaws against the scroll in the right direction and leave the gripping faces of the jaws accessible to regrind.
I was thinking you could use longer bolt heads on the jaw bolts and clamp down on a ring with them.
And other ways to do it here: th-cam.com/video/zofS-ewP4Zs/w-d-xo.html
If you need less runout th-cam.com/video/gCUkJydSmdA/w-d-xo.html
Keith, If you take the outer three screws out of each jaw. Than make some snug fitting pins(or special screws with extended heads) in the counter bores that are long enough to chuck on a smaller ring on the inside of the pins. Than you can grind the jaws with the chucking pressure going in the proper way. I will bet you can get the run out even better than .0025".
Peter, What a great idea. I hope Keith does this. I would like to see the results. Both of you put out very informative videos.
I agree, I would put longer bolts thru the jaws and clamp down using them to simulate normal use.
@@bcbloc02 After making this comment I even had a better idea. If, as you say use longer cap screws. Than make three tubular spacers that fit in the c-bores in the jaws and the screws can pass thru. Just bolt those on in place of the jaw screws. This could be done either with the outside or inside screws depending on what size your ring is. Or if you were grinding the ID of the jaws or the OD chucking out.
@@chris0tube If you put a ring in the back of the jaws you will grind your jaws bellmouthed. You want the force to the outside so you get max grip at the face of the chuck when holding parts. if the ring is bolted to the outer row then it would not be any further out than the face of the jaws so forces would be normal.
Interestingly in 2013, Keith did ground a 3 jaw chuck with the jaws in compression (vs expansion) using longer jaw screws. th-cam.com/video/nALN0qGZbgY/w-d-xo.html
As others here have suggested, replace the outer bolts with longer ones going through holes in a circular plate, that way the jaws can be placed under load with inward tension, not outward.
THANK YOU...for sharing. Enjoyed.
amazing how well you can seen spark shape...thanks Keith
Hi Keith, I appreciate you taking the time to share what you've learned and how you go about addressing issues with me and all the know-it-alls on TH-cam.
@J T
OK, OK! Not necessary to yell! Jeez!
An interesting technique. One more method to use to solve a problem. Good video.
Keith, great video thanks for sharing.!.!.!.
Great information please keep making these videos.
Cheers from Brazil, great job.
I like all your content, very useful!
5:01 - And spreading grit all over the ways and chuck.
Always interesting thanks for sharing Keith 👍🍺
Thanks Keith
thankyou Mr Rucker, this was clear, fast and no annoying music. I will check my three jaws and correct if necessary.
I would also suggest that you place a damp cloth over the bed before you start the grinding process. Grinding grid is a killer.
Great job ! - Now I need to build myself a tool post grinder from an old AC motor and rig it up to straighten out my lathe chuck which has some serious runout issues !
The results show that no one can argue that it isn't way better than it was before!
Nice job 👍
I have a 9 inch south bend and replaced the chuck exactly like you did. The machinist next door showed me how to grind the inside of the jaws just like you did. I used a Dremmel tool hose clamped to the taper attachment and wala! 30 years ago. May he rest in piece.
I like the technique you used in 2013 better but the results were similar so I guess it doesn't matter. Thanks for the video.
Keith, an old timer taught me this technique many years ago when I worked in a tool room. Thanks for the refresher as I need to dial in my chuck. One other item he taught me is to place shop rags on the bed ways to collect as much of the grit as possible. It's a real pain to get all the grit off otherwise.
Cool video Keith. Happy belated Birthday
Glad it worked for you. Not would most would do but you made a improvement.
You could've used shoulder bolts or something similar to preload the jaws in the right direction. Just put shoulder bolts in the holes for the bolts that hold reversible parts of the jaws and clamp onto a ring. It's actually very convenient comparing to solid jaws.
thats a good idea
I like the machining, but I love your dog! :)
I agree on protecting the ways .
Keith, if the speedometer shop can't fix the tach, take it to the airport where there is an aviation repair station. They can send it to a certified aviation instrument shop that can overhaul it. It appears to be a standard aviation tach anyway, and they aren't all that expensive for a certified used one. See you at the Bar-Z. Jon
It’s always nice when your chuck is “acceptable”...hats off ‘two thou!’ Again, and as always, thank you for filming and editing an informative and very interesting video. On our farm your videos are required watching because the average age of my tractor fleet is 54 years old with the baby being an ‘93 Case 1194 and the senior being a 1947 John Deere 440 track kit skidder. My cars and truck seem quite modern by compare but barely. My 60,000 sq’ barn was built about 110 years ago so I’ve spread out my shop and business in there. This means I hear grinding or squealing and find out what broke, watch a few ‘Rucker videos’, screw up my adventuresome spirit and go out to the metal shop and cast and machine a new one. You may appreciate that you’ve saved me thousands over buying new replacement parts!
Managed to sneak in first... You bring up a good point: If you can turn a part in one setup, then the chuck runout doesn't matter.
Chuck runout ALWAYS matters except when turning the entire circumference, the entire length of the part. Even in one op, the runout will still matter.
Nice share from Keith. Hello puppy.
Lance & Patrick.
Now you have ground it, filling the inside with carborundum dust you will have to take it all apart and clean it again!!! The dust inside will make the scroll wear faster and the run out will get worse quickly!
A shop vac tube placed near the far end of the main spindle would have stopped this AND better for your lungs too!! K
and how is he going to talk while a super loud shop vac is on ?
@@joeygonzo Suggest he shut up and add audio later.
Simple way is to take about a 3" pipe x 2 1/4" (smaller for a smaller chuck) and mill 3 short slots on one end 120 degrees apart with your superspacer or whatever. Wide enough that your jaws protrude inside a little when you clamp on the slots. Now just run your grinder in there and clean them up. Took me about 20 minutes to come up with it and make. Works perfect. My own idea. It's easier than folks think
Karl, would you please provide a picture of the completed ring?
I can't visualize this tool.
Thanks
Thanks for this tutorial. I need to realign my jaws as they are way out.
I don't own nor use machine-shop gear, but if it was me, I would loosen the bolts holding the chuck to your back plate and see if a few simple hammer taps would cure the runout. Next I would try removing the three bolts and rotating the chuck against the backplate. Maybe I missed it, but I never saw you indicate the chuck nor the backplate and I don't understand how you can say the workpiece has runout without checking the chuck & backplate.
I was going to suggest that but there's a taper between the chuck and the back plate so no sideways movement.
@@greybeard3759 I hear ya. That assumes the taper fit is 100% perfect. I still think I'd give it a shot to loosen, indicate, tap-tap-tap, only because you could be done in 3 minutes if it worked. 10 minutes if the chuck was rotated against the backplate (remove bolts, twist, replace bolts) The chuck-to-backplate bolts have some potential be slightly off because of the way they were center punched. Again, I could have missed it, but I don't recall seeing Keith indicate the diameter of the chuck to be sure there's no runout on the diam.
@@pneumatic00 Right you are, it couldn't hurt! .002" can hide in a lot of places, eh?
I love that lathe
Even better might come if you swap outer jaw bolts longer and snug the ring behind the bolts. Either way nice content again. Enjoyable every time....
That was also my thought, along with making some blocks, drilled and counterbored to accommodate cap heads and properly clamping down the jaws as well as a compression ring.
th-cam.com/video/nALN0qGZbgY/w-d-xo.html
Like so
Thank you for posting. However, why not protect the ways while grinding? And load the jaws in the proper direction?
the whole lathe is going to be torn down for a rebuild before any serious use.
Muy practico y sencillo ese metodo de mejora bastante aceptable del mandril excelente trabajo maestro
Love the dog 🐕
Did you forget to cover your ways while truing/grinding?
Also, idk anymore on which channel it was, but someone else had basically the same task at hand and he put some long bolts into the outer mounting holes of the jaws and then clamped on a ring between those.
Just went and looked for that video again, and I was stunned to find out it was actually one of your older videos th-cam.com/video/nALN0qGZbgY/w-d-xo.html
That introduces its own issues without both ends being clamped tight. Maybe you could machine some spacers, so that the outside screws are tightening on the jaws.
@@xenonram yeah, that's sonething I considered too, would be definitely beneficial
3:50 Lol "when you turn it on you can see that grinding wheel is uh... grinding". Couldn't have said it any better myself. That's a nice tool post grinder you have there too I wish I had something like it.
Use a stud and nut on your jaw bolts and then grip around a ring with the tension on the compression side- or use some wedges between each jaw- most 3 jaw chucks have the scroll wear on the compression side. so that's where you need to do the grinding. I did a Chinese 3 jaw and got it to less than 0.001.
Impressive 😊
use a large hose clamp on the inner jaw projection, then the tension is correctly applied in compression i.e. in the correct direction (inwards)
By “we” you mean you and your lovely dog, right?🤣
Put in longer screws holding the jaws on so that they stick out a little. That will give you a ledge to clamp a ring down with the screw heads in the right direction for grinding.
It is about time someone said it.
Keith! For Shame! Learned from an old master machinist way back in 1963: Put 3 pieces of plastic,(we used nylon at the time), cut square or rectangular say 1 inch wide between each jaw. As you tighten down, the jaws contact the sides and are squeezed together as the teeth try to meet at the center. Tighten firmly & they will stay in place. If the grinder hits them in the process of truing the jaws, no mind; they just get cut away. Now you have true jaws with the proper alignment & tension as they have in machining use. Quick; accurate; simple. I always machined my 3 pieces on the mill together so they were exactly the same width. Just sayin'. Very good shows though. I like them a lot and eagerly await your country short cuts every week. I was trained by a machinist who could have been a nazi. Be within a ten thousands of an inch or do it over.
The jaws on my 9” 3 jaw chuck is warn at the front, and I so short stock has a lot of runout if I don’t use a steady or a tail stock. How would I go about milling them down? I take it that all 3 the jaws need to be the same height, how did you ensure that you killed yours flat? I haven’t been machining for long and any help would be appreciated thanks
Keith, I still think the problem all originated from the taper on the backplate being too large causing the chuck to not seat down completely onto it. Sure the bolts pulled it tight but it doesn't mean the bolts would align things. All it did was bend the backplate to conform to the chuck since the chuck is a larger, heavier piece of metal.
I ground my 6 jaw chuck in a similar way, but I was able to put spacers in the jaws and tighten the jaws inward, not outward like you did. I ended up with just a couple of tenths runout. If you can figure out a way to tighten the jaws inward instead of outward you might have better success.
I love Elliott's new hair-do!!!!!!!!!!!!!!!!!
Liked the video,long time viewer. Had to cringe a little when you dressed the wheel with no cover on the lathe bed and carriage. I usually remove one screw from each jaw and replace with all thread with a nut on the jaw surface to keep the jaw tight then use the all thread inside surface to tighten against a ring in normal compression. This pre-loads the jaws in a normal fashion. Good job,thanks for the video.
I think your partner needs to come to Camp Mikey in Texas for the summer. We'll teach him to be a ranch dog.
Well, Keith Rucker, I thought you were a more precise engineer than that, preloading the chucks jaws in the wrong direction. !!!!!
you could make a ring that has holes to line up with the jaw bolts and you could put the jaws under tension the other way for grinding.
On a side note ... I want to hear more about that Philmont Ranch Belt I saw in another video.
How about putting longer screws (with some bushings) in the outer hole of the jaws and use them to clamp a ring?
Was going to suggest the same thing.
Keith ! I suspect the 2 .5 thow run out is because your setup.... when you pressed the jaws tight against the ring they are pushing OUT, they should be pressing IN , not out ! to do that replace the back bolts on the jaws with long ones so you can press IN on another smaller ring... that should get you much closer to perfect !, for what it's worth keep it up ! love your videos !
even as it is, 2.5 thow is quite an improvement, and I'ed use it like that myself ! thanks ! Bob...
This is not a negative comment but a suggestion. Remove the jaw outer screws and replace with longer set screws and a nut to pull jaw down tight, then clamp on the extended setscrew with a smaller ring, this will put the jaw under compression/tension and will use the other side of the scroll surface. Unless you suspect the bearings on the lathe are worn.
It might have been worth indexing the chuck on the backing plate to see if it might come closer to zero runout. Clamping a ring using the jaw screws would apply pressure to the scroll as it would be in use.
Scroll backlash? What if you reverse the jaws, direct clamping force inboard rather than outboard, then grind the jaw surfaces, which are now on the outer diameter? Return the jaws to normal position and retest. Love the channel.
I was having the same question...
I am not a machinist, so just a thought experiment for me....
I suppose you'd be constrained by the "jaw thickness discrepancies (inner to outer)...?
good work, l like your accent!
The dog wondered who you were talking to.
I don’t particularly like grinding with the pressure going outwards. last time I tried it I ended up with twice as much run out as I started out with. In your case it worked, so I guess it has its merits.
i guess with bolt on jaws you could take some some longer screws and make a ring with the bolt hole pattern and bolt it on top of the jaws and apply pressure inwards. i just would be careful with how much pressure. just a quick idea. edit: i scrolled through some comments and other people suggested similar things. should work
Thank you for posting, but I have a question. The fact that the run-out is different depending on how far it is measured from the chuck indicates that either that the test piece a little bent, or that the jaws of the chuck are seriously misshapen. Misalignment of the head stock might also be something worth checking first (easy top do). Any thoughts?
Drill and tap 3 bolts through your ring, let the threads stick out by half an inch, and insert them in the hex bolt heads of the jaws. This way you can tension the jaws in the right direction, and grind ALL the deviation out of the chuck.
Looks like the dog got his summer haircut!
Interesting. I've never seen that done.
Who is the dog? I don't remember him I remember a cat or two, but not a dog. Woof to him!
Thanks.
I end up using 3/8" alum flat bar pcs with slots cut in end to pinch the jaws. I wanted it to be clamped in normal position.
I was wondering when you did the clean up video on the chuck and showed the runout. On a Rohm chuck I would expect the back recess and the jaws to be more concentric than that. It looked to me like the index recess was in the back cover plate, is it possible that you clocked the back cover plate when you reassembled the chuck?
On a good name brand chuck like that I expect the final grinding is all done based on a fully assembled chuck, and on a good name brand lathe like that I would expect the backplate you made to be be very concentric with the spindle, so the only two variables I can think of are clocking the back cover plate on the chuck (the cover plate that holds the scroll in, not the back plate to mount it to the lathe), or the previous back plate was not concentric and the chuck had already been ground to fit that one.
Who's your buddy, there in the background?
Does your lathe have an electric feed like the Hardinge machines?
cover the ways during that job could be a good idea...
This is intriguing. I wonder if a Dremel tool can be used as a tool post grinder for a mini lathe?
No protection on the ways from dressing the wheel?
nor the inside of the chuck...
you don't do this cover over bed i
What about outward-facing teeth?
Nice Dog
I have a question Keith. Being that the inside surface of your jaws are now ground in, how about the outside portion of the jaws that you use to grip inside a piece? Are they " true " as well or do they have to be ground in as well ?
"Build Something Cool" tried regrinding his Chuck teeth on his last video, and it was a self proclaimed epic fail. Don't know why he would move from Atlanta to San Francisco of all places? Love his enthusiasm with his projects.
4:45 really hurts. The dust from dressing grinding wheels is really death to all machinery if it gets on ways and such...
Surprised you do not protect the ways from grinding dust.
Just wondering about the external jaw accuracy. If you were now to grip your ground piece of round stock and then grind the outside gripping surfaces of the jaws this might then be more accurate when spreading the jaws onto a ground ring. Then, with a rinse and repeat, the internal surface of the jaws could be ground. Time consuming yes … more accurate... quite possibly. Just an old toolmaker trick.
sweet
Now, Ive been watching Keiths channel avidly for a couple of years and I’m sure the dog had more hair in the last cameo appearance... and if i'd been paying attention, I’d remember the name of the dog...ahem!
Keith you are a real machinist and I am enjoying your videos for years, thanks.
In this particular case I think you’ve gotten better result if jaws were supported by inside pressure. As of now they are ground to their backlash.
Commented to the wrong video!
real machinists DONT grind equipment !
hes a noob
just buy new jaws
if you have runout is because you used the chuck in the wrong way
Perhaps it's already been suggested, but instead of using a ring to immobilize the jaws, why not reverse them, clamp a machined rod in the chuck, and then grind the OUTSIDE of the jaws. After they're ground, simply reverse them again to their original positions. That way, instead of using the outside edge of the spiral, you'd be using the preferred inside edge.
I would cover the lathe bed before grinding.
If your that worried about .004 runout, and you know it's your mounting plate. Don't ruin a chuck, either fix your mounting plate or make a new one. I find this to one of those can you do it, sure, should you do it, probably not. But this is my opinion, and I don't know everything. Just been a fabricator and machinist for 20+ years..
Did you notice the run out on the wheel when you turned it on and off? Looks like the entire thing moves 1/8" or more.
Wasn't that just the belt pulling? It settles once the inertia is overcome.
Even if that was the case wouldn't that suggest that the bearings on the spindle are loose?
Hi Keith. I've been a welder and mechanic all my life. I really wanted to learn how to machine metal to build things so I bought a lathe and mill about 7-8 years ago and started learning. I can do things but am not that experienced. I see you as someone who has probably been running machines all your life and enjoys it. I have much respect for that. I watched your video on truing a 3 jaw chuck and am wondering why you didn't use some kind of way protection on your lathe to protect from the grinder dust? I do a lot of grinding and hear all kind of bad things on what the dust can do to your lathe and was wondering if you believe it is that bad. Hope you can find time to answer. No hurry. I enjoy your videos and am thinking about building a tool post grinder.
Thanks
Mark
The back of the chuck is no running true?
Tror også at han fik lavet resessen for lille. Dvs. Den styrer ikke som den skal. Plus at man aldrig sliber en centrerpatron med bakkerne spændt den modsatte vej. 🙄
Are you gonna punch index marks on the chuck and back plate so that if they do need to be disassembled, they'll go back together with the same hole orientation?
they are numbered.
@@ScottPankhurst The jaws are numbered, not the chuck/back plate.
Probably a dumb question but wouldn’t u wand to close the jaws all the way, grind the outside of the jaws so they grab that machined ring perfectly then do the inside? Or would that throw off the center line of the chuck spindle?
The inside of the jaws need to be ground with the jaw pressure going inward like it will be holding a piece. I saw this done on another TH-cam channel the other day with the results being much tighter than .0025".
That is correct.
In this type of chuck that has the removable jaws this is also very easy - one can utilize the jaw bolts with the tensioning.
Before grinding though, I would have tried to bumb the chuck onto place. In case the mounting is not symmetric with the scroll then grinding is valid only on the diameter that the jaws were ground with.
feels like he got very lazy and just wanted it to be done, the right way or not, I'm just kinda bummed about all the grinding dust everywhere and not even trying to remount the chuck..
I think your dog is dropping hints.
Outside tension of jaws not equal inside tension of jaws due to sideplay of thread at lathe chuck. Jaws have sideplay inside - outside.
If you want a good precision at inside tension, jaws must be tighteded inside. But it is impossible because if it tightened inside it can't be grinded.
So this job is useless enought. But if you just turn chuck at 60 or 120 degrees on its mount plate you MAY decrease a beating.
May or may not. In any case it will be less destructive for jaws.
Bit late here but I see a chuck key left in the chuck on the lathe behind you, big no no.