[How do I?] Squaring Up Stock - What Am I Doing Wrong?

[j ferguson]

Working on a Sherline 2000 mill with Sherline's vise: I've indicated vise and it is as close to square as i can measure. I'm trying to square up small pieces of 1/4 X 1 hot-rolled, which of course starts out with crowned surfaces and pretty rough. My first cut is to clean up one edge. I then turn piece over in vise and clean up other edge, which I would assume would produce parallel edges, but for some reason doesn't - about .002 off in an inch of length.

My thought was that if i can't get two faces parallel it is never going to get better. It seems possible that the crown on the one inch wide surface is somehow causing the piece to lift in the vise when I tighten it up. It occurs to me that maybe I should put something on the slide face that's softer to better grab the piece and force it against the stationary face.

Maybe the question would better be how to get a reliable grip on rough stock.

???

 

[T Bredehoft]

Use the surface you cut on the first pass against the fixed jaw of the vise for the second pass. After that always put a cut surface against the fixed jaw.

 

[core-oil]

J.Ferguson,
This might work, machine one edge 1/4" face turn round and clamp with this face against fixed jaw, with parallels under other broad face, tap down as near as you can get it parallel in vice, then machine this broad face, Re-clamp with this broad face against fixed jaw, When clamping try putting a round bar (say about 3/8"dia.) between movable jaw & black surface, about half way down work -piece clamp & tap down work-piece on to bottom of vice.
Sometimes an inbuilt stress can distort steel as it is machined This is due to rolling.

 

[Wreck™Wreck]

Is .002 per inch within tolerance? If so you are good to go, if not.
Use a soft hammer and tap the part down onto the parallels in the vice after clamping, many inexpensive or old worn mill vices will lift the moving jaw (and part) upwards in Z, do not tighten the vice more than needed as well. If you can not get it square within the allowed tolerance use a surface grinder if you have one. If not shim the low side with a piece of ordinary notebook paper which is .002-003 thick.

 

[george wilson]

Machine one BROAD face. Then,turn it over and rest firmly on good parallels. Do not assume that ground HSS lathe bits are parallel: They aren't. After you machine both the broad sides,clamp the piece narrow side up and machine the top surface. Clean out the vise carefully,and make sure the just machined narrow surface beds snugly against the base of the vise. Most of the time,even in good vises,the work will lift a little bit. I use a dead blow hammer to swat the work down tight when the vise is almost fully tightened.

Make sure there are NO BURRS on the corners of the work you are clamping. They can throw you out of parallel.

The way you HAVE been doing it is,you are cutting an edge,then clamping against rough,non precision surfaces,expecting the other cut to come out true. It won't. Always only clamp against precision surfaces when making the second surface,etc..

 

[j ferguson]

Thanks Guys, i can see how i was screwing it up now.

john

 

[chevydyl]

Journeyman tool and die maker taught me to face the big face first, turn over on parallels and face that side but also leave enough sticking out the end of the vise to run an end mill on the y axis of the part just enough to cleanup and set it on a parallel in the vise, then face that face flip over and do the last face, you should be square and parallel now, and use the dead blow hammer if needed, and remember you don't need to hammer the vise tight, close the jaws and put moderate force on the handle to tighten....

 

[KMoffett]

There are several videos on Youtube for step by step squaring stock.
Google: Youtube squaring stock in mill

Ken

 

[joshua43214]

The only thin I can add to this is to use a soft spacer between the movable jaw and the work. This will help make sure that the freshly machined surface is in full contact with the fixed jaw.
Almost anything will work, I like the heavy nylon straps that boxes and crates come wrapped in. Thin aluminum or brass shims work, heavy paper works, a steel ball with a flat ground onto it (so you do not damage the vise) works.
I would also reiterate not over tightening the vise. It takes surprisingly little force to hold the work in place, and it is surprisingly easy to distort the vise.

 

[stenerso]

There are many ways that are used. here is one more. Mill one surface flat and put it against the fixed jaw and then use a piece of round stock horizontally between the part and the movable jaw to hold the piece tight against the back jaw. That helps assure the milled surface is flat against the fixed jaw.