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View Full Version : Lathe chucks leave marks on work ?



Bill736
12-24-2011, 06:59 PM
After 3 years of collecting accessories and refurbishing, I'm starting to use my old South Bend heavy 10 lathe. I have a 3 jaw chuck, a 4 jaw chuck, and a set of 5C collets. It's fairly obvious that the jaws on both chucks will leave marks on any shaft I chuck up . The 3 jaw chuck has an aggressive toothed pattern on the jaws. What's the best procedure for avoiding leaving jaw marks if I'm turning something that won't be parted off ? I can see wrapping the shaft with thin brass or aluminum shim stock, or attaching pieces of shim stock directly to the jaws using spray on glue or thin double sided tape. But those are only guesses, since I've never tried either. Any suggestions ?

jimsehr
12-24-2011, 07:09 PM
Learn to bore soft jaws to shaft size.
Jim

tdmidget
12-24-2011, 07:14 PM
Yes you have right idea. You can also get thick (like 4 gauge) copper wire and put a ring of it around the end in the chuck. Especially good if you have a center in the other end.

Deus Machina
12-24-2011, 07:17 PM
For anything not demanding on the runout, I use pieces of cardboard. Usually from soda boxes.

If it need to be close, break out the scissors and a beer can. Cut strips of that.

Dr Stan
12-24-2011, 07:18 PM
I prefer to use copper or lead shims instead of aluminum or brass as the copper & lead are softer.

2X on boring soft jaws, but keep in mind a lot of work can be done in a three jaw and any marks will not be an issue.

Bill736
12-24-2011, 08:03 PM
Thanks for the ideas. I think they all will work in different situations. ( The beer can strips certainly has special appeal.) A material that sticks magnetically to the chuck jaws might be convenient. If there was one material that might cover all the bases, perhaps it would be thin shim stock made of magnetized dead soft steel, covered on one side with copper. Maybe there's an idea for a new product ? Refrigerator magnet material is probably too soft, and might not compress evenly.

Darrp
12-24-2011, 08:34 PM
I always used to use a thicker paper, but last summer my 6 year old was in my shop while I was doing something and she left a few playing cards there. A couple months ago I was searching for some paper and I came across the joker from my daughter's deck. I used it and it worked great, I got a deck of cards from the house and now I keep them in the shop just for that.

I should say I also use the beer/pop cans when I think Aluminum would be better. ;)

armedandsafe
12-24-2011, 08:36 PM
I buy sheets of 5 mil brass from the hobby shop and use that, cut to appropriate size. I usually get 5 to 8 uses on 3/8 bolts when clamping to the threaded end. Soda can material is 3 mil aluminum and beer cans are 4 mil domestic (US) and ~5 mil imported.

Pops

tdmidget
12-24-2011, 08:47 PM
When a machinist says "mil" it's millionth of an inch. Catch up here.

Forrest Addy
12-24-2011, 09:02 PM
Yup. Pad the jaws. Annealed copper works best for brass, bronze, and steel. Stout cardboard and gasket material works well also. Send me your eMail addy and I'll send you Word.doc files with photos of two articles I wrote for HSM; one on the three jaw chuck, one on the four jaw.

armedandsafe
12-24-2011, 09:22 PM
When a machinist says "mil" it's millionth of an inch. Catch up here.

Machinery's Handbook - page 2403 - 1 mil = 0.001 inch

Dad's cousin, master machinist for NASA projects - 1 mil = 0.001 inch

Dictionary - online "1. A unit of length equal to one thousandth (10-3) of an inch (0.0254 millimeter), used, for example, to specify the diameter of wire or the thickness of materials sold in sheets."

Webster's - "Definition of MIL
1: thousand <found a salinity of 38.4 per mil>
2: a monetary unit formerly used in Cyprus equal to 1⁄1000 pound
3: a unit of length equal to 1⁄1000 inch used especially in measuring thickness (as of plastic films)

Common usage by the machinists teaching at our high school, community college and at several of the professional shops I pester regularly: 1 mil = 0.001 inch.

I'll stick with what I know, thank you.

Pops

lynnl
12-24-2011, 09:39 PM
When a machinist says "mil" it's millionth of an inch. Catch up here.

You must learn to interpret things in their proper context.

38_Cal
12-24-2011, 09:41 PM
My old business cards from my former employer are too stiff & scratchy for toilet paper, but just right to use in the milling machine vise and as pads on the three and four jaw chucks in the lathe. :D :rolleyes:

David

tdmidget
12-24-2011, 09:45 PM
Machinery's Handbook - page 2403 - 1 mil = 0.001 inch

Dad's cousin, master machinist for NASA projects - 1 mil = 0.001 inch

Dictionary - online "1. A unit of length equal to one thousandth (10-3) of an inch (0.0254 millimeter), used, for example, to specify the diameter of wire or the thickness of materials sold in sheets."

Webster's - "Definition of MIL
1: thousand <found a salinity of 38.4 per mil>
2: a monetary unit formerly used in Cyprus equal to 1⁄1000 pound
3: a unit of length equal to 1⁄1000 inch used especially in measuring thickness (as of plastic films)

Common usage by the machinists teaching at our high school, community college and at several of the professional shops I pester regularly: 1 mil = 0.001 inch.

I'll stick with what I know, thank you.

Pops
We disagree.

Bill736
12-24-2011, 10:57 PM
Be nice, guys. Santa is watching .

Ohio Mike
12-24-2011, 11:08 PM
I keep a stack of index cards in one of the tool cabinets. Handy as a build card (writing specs for some parts grouping etc) but also handy to rip into strips to place around pieces I don't want marked up. I also keep brass sheet around for placing under the clamp screw on the lathe dogs.

integerspin
12-25-2011, 12:42 AM
What would a millionth of an inch be called?
Microinch. First heard mils refered to by a bloke into electronics, I realised he meant thous, I have no idea what they measure in thous though.

I picked up a lot of odd bits of lead when someone had the flashing on their roof replaced, I cut strips and use that in the chuck, or if I can't find that I use strips of ali, failing that plastic strips from old plastic bottles.

Punkinhead
12-25-2011, 06:04 AM
Microinch. First heard mils refered to by a bloke into electronics, I realised he meant thous, I have no idea what they measure in thous though.
In the electronics world the pitch between leads used to be imperial and referred to in mils (thousandths of an inch). These days it's mostly metric, but old habits die hard. If the pitch is 0.5 mm a lot of people in the industry will call it 20 mils.

As far as in metalworking, maybe it's a regional thing, but I've heard the term mils used for thousandths of an inch all my life here in the midwestern US.

Lew Hartswick
12-25-2011, 09:50 AM
When a machinist says "mil" it's millionth of an inch. Catch up here.
NOT for the last 50 years or so around here (or really in PA where I
was during that period)
Mil is from the Latin which refered to "thousand" as in the
Mile a millia One thousand miles and also where millimeter meaning
one thousandth of a meter. Micro is for millionth. If you insist on
accuracy.
...lew...

Tony
12-25-2011, 09:50 AM
same goes for the east coast, mid-atlantic anyway.. though mils is
usually used when referring to paper or plastic stock. maybe theres
a lot of paper industry out here? bookbinders, etc.

i'm wondering if 'mils' (as in "millionths") has been adopted (in some circles)
to discren between "thous" (as in 'thousanths')?

-Tony

Peter.
12-25-2011, 10:34 AM
I use gasket paper, I keep the sections I cut from sheet after making a decent sized gasket.

tdmidget
12-25-2011, 11:26 AM
NOT for the last 50 years or so around here (or really in PA where I
was during that period)
Mil is from the Latin which refered to "thousand" as in the
Mile a millia One thousand miles and also where millimeter meaning
one thousandth of a meter. Micro is for millionth. If you insist on
accuracy.
...lew...
Look at armed and safes dictionary references and you will see that one says "for sheet goods sold in rolls" and the other specifially mentions plastic sheet.
I am refering to the common language of machinists. A thou is .001 and a millionth is a "mil" or millionth. In a machine shop "microinches" is used in reference to surface finish.

PixMan
12-25-2011, 12:15 PM
I've lived in Massachusetts all my life, but have traveled nationwide. In New England, the only people in this machining business who use the term "mils" in any way are those who don't actually work in this business. Most often, an engineer fresh out of college. ;)

I know I get confused when I hear it, wanting to convert to "thousandths" and "tenths" (meaning 1/10,000th) whenever someone uses the term.

The most-common environment in which I hear the term here is that of plastics sheets (blown film lines) and paints/coatings.

Merry Christmas!

spope14
12-25-2011, 12:24 PM
I use copper sheet, masking tape, old file foler stock, 600 to 1000 grit wet/dry sand paper, business cards from vendors that drop by and I am not going to call anyway, old political signs, thin rubber gasketing and most enjotyable - beer can stock (personally inspected in advance for freshness as old ones that have been emptied more than 15 minutes have aged, thus I must find a can that has not yet been old aged aluminum, empty it and then immediately use the aluminum).

The key for the noob is NOT to wrap it all around, but to keep constant thickness for each jaw, meaning only one shim for each jaw, do not make a wrapper that may make two layers on one jaw.

mil? good conversation, but regional trade dialects and the shop type make it so you should be able to decipher both correctly in context - mil or thousandths.

In my area, I often hear mil refering to millimeters or millionths of an inch, but out west I heard mil from engineers for .001 inch. Now that I am involved in plastics and plastics coatings, I am starting to hear it as a reference, and darned glad I stopped by here, in my mind I was thinking millionths, PIXMAN set me straight. Then again, they also deal in angstroms, which I get as well.

Forrest Addy
12-25-2011, 12:26 PM
Painters and platers, makers and sellets of sheet goods use "mils" and use it correctly. The military uses "mils" to express elevations: one mil equals one yard elevation at 1000 yards range .

Machinist don;t have a monopoly on fine tolerances. People who make paper and plastic film use mils and tenths of mils all the time. They use mils we use thousandths.

Never sneer and the other guy's trade except in jest - except for them despicable toolmakers. Are you watching BeBop?

sasquatch
12-25-2011, 02:31 PM
"Mil" to me always refered to the first Million i made.


Well,,,,,,,,,,,,,,,,,,,,,,ok,,, but we all thought we'd make a "Mil" when we were young and foolish and dreamers!!:D

MichaelP
12-25-2011, 04:05 PM
"Mil" to me always refered to the first Million i made.


Well,,,,,,,,,,,,,,,,,,,,,,ok,,, but we all thought we'd make a "Mil" when we were young and foolish and dreamers!!:D
"With time we learned that the word "Mil" really refers to 1/1000 of the amount. It was then when the dream, finally, came true. Yet some of us (those who used 1:1,000,000 ratio) were less fortunate".

:o

armedandsafe
12-26-2011, 12:34 AM
Gentlemen, please accept my apologies for getting this thread off topic by referring to brass and aluminum sheet sold in rolls as having thickness referred to in mils.

Pops

danlb
12-26-2011, 02:56 AM
I don't know how valid the practice is, but when making delicate flashlight parts we often use a single layer of masking tape. It protects the finish rather well. If you over tighten you will penetrate the tape, but by that point you are also distorting the thinwall flashlight tube.

Dan

vpt
12-26-2011, 09:58 AM
I as well am a soda can user. If the stock is bigger I cut out strips and put one between each jaw and the stock. If the stock is smaller I just cut out one piece and wrap it around the stock not overlapping itself.

moe1942
12-26-2011, 01:04 PM
+1 for masking tape..