Milling Small Parts

[HBilly1022]

I've been milling scrap steel to get the feel of the mill and process and have started a real project, a small lathe stop. I've got an RF30 clone and the cheap vise that came with it. The vise was warped and the jaws were not parallel. So I trued the vise ways and jaws to the mill. That worked great for the bigger pieces of steel, that rested on the vise ways but there is a small part that is only 0.5" x 0.5" x 1.0" that is driving me crazy. I can't get it square. I'm using parallels to raise it just high enough to clear the top edge of the vise but no matter what I try, every time I clamp the part the movable vise jaw lifts and causes the part to rotate. I found a suggested remedy that involves using a piece of round bar between the movable vise and the part. I tried that but the jaw still causes the part to rotate up and lift off the parallels. I tried tapping the part back down after tightening and that gets the part resting on the rear parallel but it is still rotated. I am using the methods described in various youtube videos and info threads here, on how to square a block and always placing the newly surfaced face against the stationary jaw.

So is there another way of resolving this or am I doomed to miserable failure until I get a better vise?

 

[Bill C.]

Try tightening the gibs on the movable jaw. Might need to add shim stock to the bottom of the gibs. Sounds like you are doing the right thing. Some parts are a bear to hold.

 

[Bill Gruby]

Be advised that at times, no vise made will work alone. A dedicated holder to fit in the vise or even just the table may be needed.

"Billy G"

 

[Wreck™Wreck]

A fixture to hold the part, mill the fixture in place in the vice and leave it until finished.
Like so, make the blank with slot, cross drill and tap for clamping the part then mill the recess in place going past the sharp corners with the endmill. Make the fixture the width of the vice jaws plus enough to access the clamping screw.
Make parts.

 

[Line_Bore]

If the solid jaw is properly trammed on the X (side to side), the tilting is likely caused by the solid jaw being out of tram along the Z (up and down) or your head/quill is not square to the work. A tiny but of lean in the solid jaw or droop in the head will cut a flat but angled surface. Tramming the head to the table on the 4 cardinal points is easy, but time consuming until you learn the quirks of your machine. If the vise body is warped, you're kinda stuck unless you have access to a surface grinder.
If the problem is the vise, the fast and cheap solution might be soft jaws. Measure and replicate your jaws from aluminum, then you can skim them square after they're installed. Careful to miss the bolts and vise body, though!
Another method (assuming the head is trammed) is to 5 side machine your parts. Hold the stock by ~1/8" and face the top. Without touching the vise, mill the sides flat. You now have a 5 sided block as accurate as your machine will allow.

Tramming the head, free. And necessary.

Grinding the vise square, best bet - if you can do it, or know someone with the tools willing to do it.

Soft jaws or shimming the vise - a bit of a stop gap measure until you decide to fix or replace.

I hope this helped, I know all too well the frustration you're feeling.

ETA: If you use soft jaws, remember that you are pressing the shape of your stock into the aluminum (displacing material). Usually not an issue for a secondary op, but you have to be mindful of the damage caused by raw stock.

Caught somewhere in time.

 

[RJSakowski]

I've been milling scrap steel to get the feel of the mill and process and have started a real project, a small lathe stop. I've got an RF30 clone and the cheap vise that came with it. The vise was warped and the jaws were not parallel. So I trued the vise ways and jaws to the mill. That worked great for the bigger pieces of steel, that rested on the vise ways but there is a small part that is only 0.5" x 0.5" x 1.0" that is driving me crazy. I can't get it square. I'm using parallels to raise it just high enough to clear the top edge of the vise but no matter what I try, every time I clamp the part the movable vise jaw lifts and causes the part to rotate. I found a suggested remedy that involves using a piece of round bar between the movable vise and the part. I tried that but the jaw still causes the part to rotate up and lift off the parallels. I tried tapping the part back down after tightening and that gets the part resting on the rear parallel but it is still rotated. I am using the methods described in various youtube videos and info threads here, on how to square a block and always placing the newly surfaced face against the stationary jaw.

So is there another way of resolving this or am I doomed to miserable failure until I get a better vise?

Many types of vises have the clamping screw lower than the work being clamped. This creates a torque which tends to lift the work on the movable jaw side. Additionally, jaws which are not perfectly vertical or don't have adequate structural support can cause the workpiece to lift up at the movable jaw. It is common practice to tap a clamped workpiece in to seat it.

You didn't say what type of vise you had but if it is a lock down type., patterned after the Kurt vise, e.g., removing excess clearance in the ways, as suggested by Bill C., and smoothing the lock down mechanism will help to keep the movable jaw from lifting.

For small work, a tool maker's vise may serve you better as the clamping mechanism simultaneously clamps the work and pulls the movable jaw down.

 

[HBilly1022]

Lots of great advise and thanks for that.

I previously "trued" the vise to the lathe, when I found it to be warped. I used a 3/4" end mill and milled the ways until I got the same DTI readings in all 4 corners and then side milled the replaceable faces on the fixed and moveable jaws. After doing that I did my first milling by just facing a 3" x 6" x 1 1/2" scrap steel to make it square in accordance with the info I found on this site. After following the recommended procedure I checked the block for square and thickness and was impressed. It was within 0.0015" ...... yeehaa I've got a mill and it works great. After that things have gone downhill so to speak, I ruined the sides of my 3/4" end mill by side milling the 1 1/2" block, so I bought another one. Then I had the issue with the vise moving and after getting that fixed I find my 5/8" end mill is also dull. I've got to figure out how to sharpen these things or I'll go broke buying new ones.

Well after an overnight break away from this I went back to the shop and tried squaring the cut again ...... same thing. I reassess and get the DTI out and check the vise to make sure it is still trammed. NO IT's NOT. It must have moved when I had a part catch and kick yesterday. No wonder it won't cut square. I tram the vise and now it's fine but my end mill is dull already. So far I've dulled a 3/4" and 5/8" end mill and I haven't even made a simple little lathe stop. Part of the learning process I guess. I did try putting a piece of shim material under the moveable jaw and that seemed to help a lot.

Frustration has kicked in and it's the first sunny day here in a week so I'm taking a break from the mill and will do something outside. Maybe get my recently built forge out and melt some scrap aluminum for a future lathe / mill project.

 

[janvanruth]

invest in carbide end mills, reground ones are commomly for sale at the regrinders and are the best bang for the buck

 

[HBilly1022]

Janvanruth, I'll see if I can locate a regrinder around here and give that a go.

Last night I discovered another issue that was a probable contributor to the problem. When I trued the vise I milled the ways first, then the jaw faces but when I did the faces I kept the bottom of the end mill above the ways. As a result in the corner that required the most material removal on the ways, there is a small ridge just below the vise face and when I use the parallels the one side sometimes rides up onto that small lip. Going to fix that today.

 

[Bill C.]

I've been milling scrap steel to get the feel of the mill and process and have started a real project, a small lathe stop. I've got an RF30 clone and the cheap vise that came with it. The vise was warped and the jaws were not parallel. So I trued the vise ways and jaws to the mill. That worked great for the bigger pieces of steel, that rested on the vise ways but there is a small part that is only 0.5" x 0.5" x 1.0" that is driving me crazy. I can't get it square. I'm using parallels to raise it just high enough to clear the top edge of the vise but no matter what I try, every time I clamp the part the movable vise jaw lifts and causes the part to rotate. I found a suggested remedy that involves using a piece of round bar between the movable vise and the part. I tried that but the jaw still causes the part to rotate up and lift off the parallels. I tried tapping the part back down after tightening and that gets the part resting on the rear parallel but it is still rotated. I am using the methods described in various youtube videos and info threads here, on how to square a block and always placing the newly surfaced face against the stationary jaw.

So is there another way of resolving this or am I doomed to miserable failure until I get a better vise?

How did your small part come out? Small parts can be a bear to hold. I wound use a piece of brass stock to tap the part down on the parallel. Thinking about those old days.