Trouble squaring stock

[datosi81]

It seems no matter how careful I am with set up, I can't get my stock cut nice and square. I'm working on something that requires a block of 6061 5"x3"x1-1/2". I'm using a 3" screwless vise, a parallel and a peice of wire on the moveable jaw side. I've also tried it in a 4" drill press vise as they are the only 2 vises I currently have. The piece comes out visibly out of square when looking at the end, not by a ton, but enough to pick it up by eye I think is pretty bad. What usually causes this and how can I fix it? My approach is what I've seen online using 1 parallel, wire on the moveable side, and rotating the piece 90* after each cut. Could head nod contribute to this? I'm anal about my X tram, but haven't done a lot about the Y.

Any advice is appreciated.

 

[stevehuckss396]

Indicate the fixed jaw to be sure your jaw is aligned with the Z axis. Some times the jaws are tilted forward or back. Put an indicator in the spindle and stroke it from top to bottom of the jaw and see if it's within a .001 or two.


If you are fly cutting tram the head to be sure the fly cutter is square or parallel with the table and hopefully the fixed jaw.


Clean the part and the fixed jaw before you insert the piece into the vise and be sure you deburr the corners because that can hold you out also.

That's where I would start.

 

[kvom]

Assuming you have a machinists square, check squareness after every cut. If any are off then that will tell you where to look. Normally you can't tram the y axis, so X and Z are your only choices. Check the bottom of the vise for flatness (i.e., nothing under it to cause it to tilt. I would also use two parallels once you have a flat side on the bottom.

 

[sssfox]

When you mount the block in the vise, let the end stick out a little so you can use your square to make sure that the face next to the fixed jaw is perpendicular to the table. When you have finished your cut, check to make sure the top is perpendicular to the front face. If it isn't, you need to tram the head.

It is a little more difficult, but you also need to make sure the top of the block is parallel to the table in both directions. I use a set of dial calipers for that, using the depth rod. You can also use a set of outside calipers. Then, check to make sure the bottom is parallel with the top in both directions. If something isn't square or parallel, you will know where to check.

Why aren't you using two parallels to hold the piece up? It makes things a lot easier.

Steve Fox

 

[datosi81]

Thanks guys!
I've been using 1 parallel because that was what I had seen when researching online. My understanding is to only use 2 parallels when the 3 faces touching (fixed jaw, moveable jaw, and bottom) are already square.

I use a 3/4" endmill for squaring, I assumed once I get something nice and square, then I'll use a fly cutter for finishing.
I'm wondering if my vise could be causing issues. Next on the purchase list is milling vise from LMS but the 3" jaws only open 2.95" and from what I've read, the 4" won't work. Too bad cuz I'd love to get the 4" if it'd work with my mini. I bought the screwless vise when I got the mill and just went with the one suggested by the guy working at the Grizzly store. (which I took a beating on, $140 for a 3" screwless vise)

I need to check my Z tram, I did check it once, but I've moved the mill around a bit since then when I installed the air spring conversion and DRO's.

 

[lennardhme]

No tramming will get the mill perfect. Make some vice jaws from CI, brass or alum. & machine the top inside edges while on the mill & fix your workpiece in those machined ledges. As the jaws are machined on the mill they will be perfectly square to the quill. On the inside edge of the machined ledge cut a relief for any burrs on your workpiece - a cleaned up hacksaw cut will do - doesnt have to be perfect.
Remember, if you take the vice off the mill, remachine the ledges again - only needs a small cut.
If you are buying another vice, spend a few extra dollars & get an anglelock vice which pulls the jaws down as well as clamping.
I have many sets of jaws made over the years for holding different shapes. Using these also negates wear on the vice jaws themselves.

 

[Swifty]

Datos81, I believe that you are using the correct sequence. What I have always done and taught others is the following way.

1. Hold rough block in vice, with widest face up to be machined first. Only use roller on moving jaw if block is too far out of square.

2. Turn block 90 deg with machined face to fixed jaw, use 1 parallel under block. Use roller on moving jaw. Machine.

3. Turn block upside down, first machined face against fixed jaw, second machined face sitting on 1 parallel, use roller on moving jaw. You can now tap the block down onto parallel. Machine to size required.

4. Rotate block so last face to be machined is uppermost. Rest block on 2 parallels, do not use roller. Tap block down onto parallels, machine last face to size.

It is important to machine the widest face first, them machine the other sides to this face. This will give you the best chance of getting it square. I always use a roller about 1/4" round, I see that you are using a piece of wire, I believe that this is too small. The only way that your blocks will be out of square now is if the mill head is not square.

I have only explained for 4 faces, the ends should be easy after this. Just wondering why you are using an endmill first, then finishing with a flycutter. It would be better to just stick with the flycutter from the start, this saves repeating the machining process.

Paul.

 

[datosi81]

I have been using the endmill for roughing because I assumed it was preferred method. I didn't want to risk too aggressive of a cut with the fly cutter on my little machine. I believe you may be right on the wire being too small, I will try a larger diameter rod the next time and see if that helps. A little off topic, but does anyone have any input on maybe picking up the 4" vise from LMS for use on the mini mill? I know it specifies right on the site that it's too large, but I'm wondering what they mean by that. Too large in what way? If that's the case I'll go with the 3" but it looks like I need to wait for them to come back in stock. If I can get away with the 4" I think the added mass would help with rigidity.
Thanks again for the input guys, it's much appreciated.

 

[ShopShoe]

If you have to back up a step, get some stock for testing and clamp it to the mill table, see if top and bottom turn out parallel. See if you can make square and parallel pieces without a vise. That way you'll answer the question regarding the quality of the vise.

Did you check the table adjustment and tightness as well as the tram of the column to the mill?

--Just some random thoughts. Good Luck

--ShopShoe

 

[aonemarine]

Having had some issues myself with a problem like yourself... First things first, put a piece of tgp (turned ground and polished) stock into the collet and check for spindle run out. Then tram head to the table. Then indicate your vice and see if it is true to the z axis. I had to remachine my vise to get things to par. who would have thought that some ape man in the past life of my mill could have bowed the vise by tightening it up with,,,,I assume a 3' cheater pipe.....

 

[sssfox]

A little off topic, but does anyone have any input on maybe picking up the 4" vise from LMS for use on the mini mill? I know it specifies right on the site that it's too large, but I'm wondering what they mean by that. Too large in what way?

That vise is over 12" long. That means that the mounting bolts would be on the front edge of your table. If you mounted it centered, you would only have an inch or two of travel. It might fit sideways, but I don't think it would work very well that way. In any event, you wouldn't want a vise that you could only mount sideways. I think you want to limit your length to 8" or so. I have one that is 6" and one that is 8" or so. Most of the time, you mount the work with the longest dimension sideways.

There are many ways to mount larger work. You don't need a vise for everything.

Steve Fox

 

[rodw]

The best tutorial for this I have found is buried in one of these 10 videos.
http://techtv.mit.edu/collections/ehs-videos

I learnt so much watching these. He also shows you how to square your vice.

 

[Swifty]

Rod, I watched a fair bit of the video, but the download was running a bit slow so did not see it all. A couple of things that stood out for me were, the way that the quill was brought down to be closer to the workpiece, always thought that it is better to have minimum quill projection by bringing the job up close to the ram. A bit more rigid this way, especially with interrupted cutting.

The second thing was the way he ran his finger over the block with the rotating cutter so close, asking for trouble.

Paul.

 

[datosi81]

That vise is over 12" long. That means that the mounting bolts would be on the front edge of your table. If you mounted it centered, you would only have an inch or two of travel. It might fit sideways, but I don't think it would work very well that way. In any event, you wouldn't want a vise that you could only mount sideways. I think you want to limit your length to 8" or so. I have one that is 6" and one that is 8" or so. Most of the time, you mount the work with the longest dimension sideways.

There are many ways to mount larger work. You don't need a vise for everything.

Steve Fox

Thanks for the advice. I think I'll wait for the 3" precision to come back in stock and go with that. Reason I was looking at the 4" was, being a total newb to this hobby, I didn't realize you could move the jaws around to accomodate larger work. So I was thinking the 3" would only allow gripping stock 2.85" max.

 

[rodw]

The second thing was the way he ran his finger over the block with the rotating cutter so close, asking for trouble.

Paul.

Yes, there are heaps of comments about his unsafe work practices in a number of his videos. A lot of the time, I think it is the camera angle compressing the scene making his finger look closer than it is! I am happy to ignore his oversight because this series is so good for a noob. In other videos, he is very good explaining how to hold pieces in a sefe manner on the grinder and band saw. A lot of the stuff or some variant of it lives elsewhere, but not in such a step by step structured series of lessons.

I am conscious of the quill length so I must have learnt that somewhere else!

I am lucky enough to have 100 mb cable at home so I don't have much trouble with streaming video....

I will echo thoughts on not getting too big a vice. I bought a 4" one which sort of worked on my old mill but it was really too big, it is however a good match with my Seig Super X3, if you have something smaller than this, then I would not get a vice over 3".

 

[rcaffin]

Some things come to mind:
1) The mill head is out of alignment. The cure is obvious.
2) The vice jaw is out of square: check and fix. Btw, wire is a bit too localised. I use some red fibreboard instead: a strip about 5 mm wide and 1 mm thick. It handles any tilt in the moving jaw.
3) The block did not stay square when the vice was being done up. A gentle tap on the top with a dead hammer as you tighten the vice is indicated.
4) The vice is mounted over dirt or rubbish, so it is not square.

Cheers