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View Full Version : Aligning center punched work in the 4-jaw?



SirLesPatterson
10-19-2014, 01:31 PM
I have center punched an off center mark on a rectangular block. I want to put it in the 4 jaw to drill then bore a hole there. So far my thinking is to put a center in the tailstock and just keep adjusting the chuck jaws until it seems to line up. Suggestions welcome!

elf
10-19-2014, 01:39 PM
Search: "lathe wiggler plans"

Richard P Wilson
10-19-2014, 01:39 PM
I had the same problem recently. I drilled on the pop mark with a centre drill, put a solid centre in the tailstock, then used this to locate the block against the face of the 4 jaw, with the jaws well open. I locked up the tailstock barrel, then moved the jaws up to touch the block gently at first, then more firmly, a bit at a time on each jaw in turn. Final check was to hold a DTI against the centre, having unlocked the barrel clamp,and rotate the work, making any adjustments needed.
Sound a lot, but honestly, it didn't take long.

Toolguy
10-19-2014, 01:39 PM
The old time way to do that is to make up a long flexible rod with a concentric point on it. Maybe 1/8" diam. X 12" long. Put the square end in the tailstock chuck and the pointed end in the punch mark on the work. Put a dial indicator on the side of the rod close to the workpiece. Turn the chuck and see how far the indicator needle moves. Adjust the chuck jaws to get a constant reading all the way around.

90LX_Notch
10-19-2014, 01:59 PM
The way I do it is a combo of some of the things mentioned above.

Place a center in the tailstock.

Close the center up against the pop/center in the work to hold it against the chuck.

Close the chuck jaws on the work.

Back the tailstock out.

Place a second center inbetween the tailstock center and the work pop/center.

Indicate the second center.

Adjust the chuck until the "floating" second center runs true.


-Bob

SirLesPatterson
10-19-2014, 01:59 PM
I drilled on the pop mark with a centre drill, put a solid centre in the tailstock, then used this to locate the block against the face of the 4 jaw, with the jaws well open. I locked up the tailstock barrel, then moved the jaws up to touch the block gently at first, then more firmly, a bit at a time on each jaw in turn. Final check was to hold a DTI against the centre, having unlocked the barrel clamp,and rotate the work, making any adjustments needed.

Hah. No matter how much tooling I acquire/make I always need something else for the next project. Ok, I like these two ideas for this project, I think they will be accurate enough. I may try the one below first then verify using the method above or vise versa. Thanks for all the info!


The old time way to do that is to make up a long flexible rod with a concentric point on it. Maybe 1/8" diam. X 12" long. Put the square end in the tailstock chuck and the pointed end in the punch mark on the work. Put a dial indicator on the side of the rod close to the workpiece. Turn the chuck and see how far the indicator needle moves. Adjust the chuck jaws to get a constant reading all the way around.

redgrouse
10-19-2014, 02:46 PM
Hi Les, Toolguy is bob on with his method, I use this regularly for a particular item I make, actually they are tumblers (hammers) for sidelock guns. These have a grunion on each side and I make out then centre punch with a optical centre punch then centre in the 4 jaw for each side, I leave one end oversize and finish gripping the other in a collet, this ensures concentricity but they are usually within .002 to .003 TIR out of the 4 jaw.
A simple cheap method, just one point make sure the included angle of the point on your 1/8 rod is less then the incl angle on your centre punch. This ensures better location when setting up in the 4 jaw.

Paul Alciatore
10-19-2014, 06:43 PM
Tail stock mounted electron microscope with 50 inch HD monitor.

Actually I like the thin, pointed rod and DI approach.

Forrest Addy
10-19-2014, 07:20 PM
Editing: Look like a missed previous posts in my haste to posy my own stuff End of edit:

Consider the trick John L Sullivan (old mentor - more later) taught me back when rocks were still soft:

1. File or grind a point on a skinny rod like a foot of bare 1/8 TIG rod.

2. Grip the end of the rod in the tailstock drill chuck,

3. Plug the point in the center punch mark so as the work rotates, the rod flexes to follow the punch mark,

4. Set the indicator contact on the rod.

5. Using the indicator readings, adjust the jaws to center the punch mark.

So long as the rod has a little push on it it will find the point of the punch markand from that you candial inthemark to the resolution of you indicator. But how accurately did you place the punch mark? If a hole location is so all-fired important have you considered toolmaker's buttons?

Nothing about the rod has to be accurate or hardened. The rod is a throw-away made quick on a bench grinder.

John called this the "pointed rod trick" and it's different from the wiggler as traditionally used from a rotating spindle. But you can use a wiggler in place of the pointed rod. I discourage this because the tip of the wiggler can be damanged from scrubbing in the punch mark and since the wiggler tip is short, attainable accuracy suffers proportionaltely. I learned this trick in 1968 and have passed it on countless times since so now I'm passing on John Sullivan's legacy to you guys.

Short bio: John L Sullivan was an old railroad machinist who could hardly read or write. He was 71 when I knew him in 1968. Wonderful kindly old grandfatherly guy, tall, skinny, and a little bent. Always wore pillow tick overalls and a grubby fedora hat. He liked my middle name so he called me "Cedric". Since John was nearly illiterate but knew a zillion old machine shop tricks and since I was a young guy who could read plans and shop paperwork he taught me his tricks and I 'splained his jobs and did his math. I don't know how John felt but I think I made out like a bandit.

I should probably mention he was a WWI, Banana War, and WW II Marine veteren (several hitches). a widower, deacon in his church, and long time Odd Fellow. He mined coal, was a farm laborer, but most of the time he was a round house machinist when he could find the work. He used to tell me horror stiries of failed shrinking loco wheel tires and repairing damage from train wrecks. I also got some recipes for welding rod coatings - he called it 'lectric welding rod - and the rod material was wire coat hangers - with variations. He had an FDR picture in his tool box along side family photos and had lost a fingertip in a union scuffle. Yeah, he was an interesting old dude and a hero to me.

oldtiffie
10-19-2014, 07:32 PM
Don't use a full "point" as the end will engage with the small central "flat" (from the drill end) in the bottom of the "hole" - just leave a small flat end on the "rod" and the taper of the "rod" will engage the taper on the "hole".

Ideally the "cone" on the "rod should have a taper that is a bit larger than the "drilled hole".

Frankly if it were me I'd drill the holes on my pedestal drill up to a rod size allowing for later boring. Put the rod in the hole, locate it in the lathe with the dial indicator as before and start boring.

Its dead easy to locate a centre-punched hole with the drill end/tip and start drilling.

mickeyf
10-19-2014, 07:48 PM
This very crude and ugly but effective wiggler took me about 5 minutes to make using only a drill press (well and maybe a hacksaw and file). Sorry if the last pic is not too clear - it's looking at the pointy end that sticks in your punch mark. I think I dinged the rod with a hammer to make the ball a press fit at that spot. The rod is maybe 12" long, and you adjust the chuck until the far end of the rod is in line with the tailstock center. I have found it to be quicker than using a dial indicator.

ball on shaft (http://thesweetoasis.com/wiggler/ball-2.jpg)

ball seat (http://thesweetoasis.com/wiggler/ball%20seat-2.jpg)

assembled (http://thesweetoasis.com/wiggler/assembled-2.jpg)

oldtiffie
10-19-2014, 08:55 PM
Just to be sure that no (minimum?) errors have crept in - scribe (calipers) a circle - any diameter - using the centre-punch hole (before drilling) as a check on the lathe before boring that all is OK 0 use a scriber/pointer (in the tool post) to check for any eccentricities that may have occurred and adjust to suit in the lathe chuck - before boring.

dp
10-19-2014, 09:18 PM
Frank Ford's solution: http://www.frets.com/HomeShopTech/Tooling/WigglyCenter.jpg/wigglycenter.html

legendboy
10-19-2014, 10:46 PM
I just did this the other day. Needed to bore some holes for new servo motor mounts. (mill out of commission) Just scribed center lines and lined them up with a center in the tailstock. Worked out good. Franks method looks really good for more accuracy, thanks for sharing that :)

http://members.shaw.ca/corey.s/dmm%20retrofit/IMG_1115.JPG

boslab
10-19-2014, 11:04 PM
Use a toolmakers button
Mark

DR
10-20-2014, 01:23 PM
Use a toolmakers button
Mark

Yes, I was about to add those to the discussion.

I'm not a big fan of center punching. Aligning to the center punch is one thing, but how accurate was the center punch itself anyway?

Black_Moons
10-20-2014, 02:32 PM
Tail stock mounted electron microscope with 50 inch HD monitor.

Actually I like the thin, pointed rod and DI approach.

You may be joking, but a $30 deal extreme USB microscope might work well really well, especially if its a CNC or you already have a shop PC. (Rotate chuck and make sure center point stays at same spot on screen)

Rosco-P
10-20-2014, 03:06 PM
I have center punched an off center mark on a rectangular block. I want to put it in the 4 jaw to drill then bore a hole there. So far my thinking is to put a center in the tailstock and just keep adjusting the chuck jaws until it seems to line up. Suggestions welcome!

What is the block for? How accurate is your layout? What machines are available? How accurate does the location of the hole have to be? + or - how much? Diameter of the hole and tolerance? Depending on the answers, this might be simple drill press work or upgraded to being done on a milling machine.

mike4
10-20-2014, 06:48 PM
How large is the centre punch mark , I just pick the smallest centre drill that I have and align it by eye into the mark then lightly drill , note how concentric the drill cut is with the punch mark .

If there is 60-80% contact ,start drilling , thats near enough for a drilled hole.

All of the other methods take a lot longer , require a tool to be made , or set up tools , when time is critical learn to do it quick and reasonably accurate.

Yes there will be those who will argue that my method is not accurate enough , well they need to remember it is a drilled hole , which can be moved a few thou if necessary .

Also this is the start of a part where more machining is required , if the hole is slightly out ,correct that when machining the outer edges either with the lathe or a mill.

No wonder some people take ages to get started , all of the debate over a punch mark and different ways to precisely centre the mark.

Michael

oldtiffie
10-20-2014, 09:13 PM
I have center punched an off center mark on a rectangular block. I want to put it in the 4 jaw to drill then bore a hole there. So far my thinking is to put a center in the tailstock and just keep adjusting the chuck jaws until it seems to line up. Suggestions welcome!

If it were me and given that the job is to be or can be held in a 4-jaw chuck, I'd mount/clamp the chuck to the mill table and locate the drill/bore location with respect to at least one edge of the square/rectangular block and drill and bore it on the mill.

The distance from an edge can be measured with a round rod (inside the hole) and a micrometer measuring over the rod and (to) the outside edge.

Though I'd be more inclined to forget the chuck and mount the job on parallel strips and locate it to the mill table with several stop blocks.

Toolguy
10-20-2014, 10:32 PM
The OP didn't say if he had a mill to do this with, but if I were doing it in a mill, I'd stick it in the mill vise and go from there.

oldtiffie
10-20-2014, 11:45 PM
The OP didn't say if he had a mill to do this with, but if I were doing it in a mill, I'd stick it in the mill vise and go from there.

True - he did not.

I don't like mill vices at all as they are a poor relation to clamping/fixing the work to the mill table direct - that's from someone (me) that has a good range of mill vices.

JCHannum
10-21-2014, 07:58 AM
Pump center described here;
http://www.homemetalshopclub.org/projects/pmpcntr/pmpcntr.html

Jan Michaels at Tall Grass Tools, (TGTools here) offers a variation of the center tester in kit or completed form;
http://www.tallgrasstools.com/Page.html

Rosco-P
10-21-2014, 08:18 AM
Since the OP hasn't stated the intended purpose of the block and accuracy requirements of the hole location, any and all methods that approach "NASA precision" are a waste of time.

As suggested by one member, picking up the center punch mark with a drill point is probably sufficient.

SirLesPatterson
10-21-2014, 11:03 AM
What is the block for? How accurate is your layout? What machines are available? How accurate does the location of the hole have to be? + or - how much? Diameter of the hole and tolerance? Depending on the answers, this might be simple drill press work or upgraded to being done on a milling machine.

I had intentionally kept my question simple so readers eyes wouldn't glaze over but I should have known better on a forum like this. I'm just a home tinkerer and a small amount of off center will not be detrimental to this whatzit, I'd like to keep it centered within say 0.005" if possible (I just made that up). For the first time I have employed my surface plate, gauge, scribed, then used an optical center punch to mark it.

I want to drill then bore on the lathe because it has a few different diameters at different depths with the larger being in the center. I feel this would be best attacked on the lathe by drilling a hole then single point boring which seems like it will let me reach inside there real nice like.

justanengineer
10-21-2014, 11:54 AM
Skip the four jaw, use a face plate instead. You simple have to run a tailstock center into the punch point and hold it there with the tailstock while you clamp the part to the faceplate.

SirLesPatterson
10-21-2014, 12:53 PM
Skip the four jaw, use a face plate instead. You simple have to run a tailstock center into the punch point and hold it there with the tailstock while you clamp the part to the faceplate.

I like that idea but I don't have a faceplace for this lathe and I don't need another project right now. My boring bar setup is decent on this lathe, wet noodle on my smaller lathe for which I do have a faceplate.

Rosco-P
10-21-2014, 01:19 PM
I had intentionally kept my question simple so readers eyes wouldn't glaze over but I should have known better on a forum like this. I'm just a home tinkerer and a small amount of off center will not be detrimental to this whatzit, I'd like to keep it centered within say 0.005" if possible (I just made that up).


Then the 0.0005 would be ridiculous. For non critical work 0.01 (even 0.05) is probably fine, unless your intention was to make this a practice project. Tolerances are usually specified as + (some number), - (some number), a single figure is meaningless unless it's specified as "plus or minus 0.xxxx".

SirLesPatterson
10-21-2014, 02:37 PM
Then the 0.0005 would be ridiculous. For non critical work 0.01 (even 0.05) is probably fine, unless your intention was to make this a practice project. Tolerances are usually specified as + (some number), - (some number), a single figure is meaningless unless it's specified as "plus or minus 0.xxxx".

Pretty much all of my projects are "practice projects" since everything I make is for my own desires and the entire fate of absolutely nothing hinges upon success. I figure as a home hobbyist learning machining I will always plan to .001 and get as close as I can to that, hopefully improving accuracy with each project. I have found that I learn a great deal from mistakes so it's a win-win either way. For this reason I often find myself taking on projects that I know are beyond my skill level. Fun stuff spinning handles.

Black Forest
10-21-2014, 02:59 PM
" I have found that I learn a great deal from mistakes"

Then you need to come visit me if you want to learn a lot!!!!!!

cameron
10-21-2014, 04:49 PM
Then the 0.0005 would be ridiculous. For non critical work 0.01 (even 0.05) is probably fine, unless your intention was to make this a practice project. Tolerances are usually specified as + (some number), - (some number), a single figure is meaningless unless it's specified as "plus or minus 0.xxxx".

"Centered within 0.005" makes perfect sense. "Centered within plus or minus 0.005" would have been not only meaningless, but ridiculous.

justanengineer
10-21-2014, 05:39 PM
I like that idea but I don't have a faceplace for this lathe and I don't need another project right now. My boring bar setup is decent on this lathe, wet noodle on my smaller lathe for which I do have a faceplate.

Well, do you have a piece of stock that you could hold in the four jaw that could be either drilled&tapped or clamped to like a faceplate? Sorry, not trying to be annoying, just creative.

TGTool
10-21-2014, 08:53 PM
I like that idea but I don't have a faceplace for this lathe and I don't need another project right now. My boring bar setup is decent on this lathe, wet noodle on my smaller lathe for which I do have a faceplate.

I use my four jaw as a faceplate from time to time. I take out the jaws completely and the slots are the right size for one set of T-nuts. Instant faceplate.

David Powell
10-22-2014, 12:12 AM
"Centered within 0.005" makes perfect sense. "Centered within plus or minus 0.005" would have been not only meaningless, but ridiculous.

I am currently making two slide valve style cylinders for a model steam engine from a nasty old piece of vaguely round cast iron bar. I machined 4 flats along the bar, cut it in half to make 2 cylinders, rough faced the ends, marked out ' middle ' of where I wanted the bore on two ends, centre punched, centre drilled in drill press, put in the 4 jaw, used the method described earlier in this thread with 2 centres to set the blanks where I wanted them in the 4 jaw, drilled and then bored the pieces. On completion the bores were both within 5 thous of their calculated positions. Certainly plenty good enough for the job. Luck? Skill? or just the result of 40 yrs in machine shops and a fair bit of reading magazines and now the internet ?. I hope this is encouraging for those with similar needs. Regards David Powell.