How to Face, the end of square bar in mill

[paul simsParticipant @paulsims62082]

Dear Mick Henshall,

Thanks for the above. I have spent a couple of hours to-day checking the mill and found all tests well within the limits I have found on the Internet, it really is a very accurate machine I have also Squared off in the four jaw a a square piece of 25mm bright steel about 130 mm long ( I will accurately measure this before testing) then I will try all the ways suggested above, I also have a Keats Adj Angle Plate that incorporates a V Block that I will mount on the table.

Best regards

Paul

[Mick HenshallParticipant @mickhenshall99321]

Its a good idea to list all potential causes, work through and eliminate one by one till the culprit is found this can be quite exciting, also its good for understanding your machines and their equipment, I'm self taught and a lot can be learn't from running into snags,I do hope you find out what it is and please let us know Neil

Mick H

[Tony Pratt 1Participant @tonypratt1]

Hi Paul,

Squaring off a bar in the vice is one of the simplest operations[well should be] that can be done on a mill so as Mick suggested stick at it! Don't be swayed by trying other methods until you understand what is wrong here, machining is a logical process so there is a logical answer for your problem.

Tony

[JasonBModerator @jasonb]

Which begs the question what are you using to see how square the end of your bar is and is your square actually square? If it does not have a small notch where the blade meets the stock make sure that you remove any burrs raised by the cutter before offering up your square.

J

[JasonBModerator @jasonb]

No John just wondering if the OP is using a square that may be a bit off if its a cheapie or bounced on the floor one time too many.

I would not have asked "what are you using ……." as we can see you are using a square. Also the groove can be seen in your photos but some squares do not have these and it can stop the stock sitting down flush against the work, just trying to rule out anything that may be causing the problem.

J

[NobbyParticipant @nobby]

HI
How would you check a square .I use a bottle square I ground . as I said before if you have an accurate angle plate that's square on the side as well . with a fence fitted just locate on the fence and its square . also on a surface grinder with a mag chuck lay it on its side with with the job in place switch on clamp job . then switch off stand A. P up and you are ready to go . Bear in mind the angle plate must be dead square on all faces . no square required in this operation . Valid on a mill table as well  Try it it works fine
Nobby 

Edited By Nobby on 24/10/2014 23:22:23

[JasonBModerator @jasonb]

The simple way is to find a piece of plate with a good straight edge, put the squares stock against that and scribe a line, flip the square over so the stock faces the other way and scribe another line in the same position, If the two lines do not follow the same path then the square is out.

You could also clamp it flat to the mill table and set the stock to one axis with a DTI, then check that teh blade is true to that along the other axis

[paul simsParticipant @paulsims62082]

Dear All,

I am overwhelmed at the good advice that I have received especially Neil Wyatt for the pre-Load info. I am not a scholar or very experienced engineer and therefore really appreciate the advise that I have received. I will try to Sum-Up my conclusions.

To-day I mounted a 150mm long 25mm square bar in the 4 jaw, (before doing this I draw filed all over to take out any dings etc and faced it, removed it and cleaned off all burrs, I checked it with three of my squares all having the cut-out mentioned earlier and was quite happy with it on all sides. I then mounted my precision 4 inch Pin type Vice accross the table of the mill so that the end of the bar was was facing me and all tapped down, I used a 12mm 4 flute end mill and slowly traversed the bar 6 times forward 6 times return, The vertical error was the same as when the Vice was conventionaly mounted, I then repeated with a half inch 4 flute endmill (i know it is only 0.7 mm larger but it was a much sturdier looking tool and things improved.

This Vice which is new has a vertical V niche in the Vertical and Horizontal direction in the moving jaw, I mounted the bar vertically and milled using the half inch endmill with just one pass for each of the three widths required,

The squareness was comparable with the 4 jaw result with the usual slight wavy ness caused by the cutter, I then used a V block in the vice and obtained the same result, I then mounted direct to the Table my Keats angle plate that incorporates a V block and again ended with a square end.

I conclude that MY errors are probably due to Flexing of the End-mill and possibly play in quill and associated parts ( I did always keep the quill barely extended from the head) if I should attempt to face the end of a largish bar in the mill in future then I should use say a 20mm endmill and make many many many passes, (one of my next purchases will be a 20 mm End-mill), or use one of the V-block ways, or stick to the 4 jaw.

Many thanks again

Paul

[Neil WyattModerator @neilwyatt]

Paul,

What depth of cut are you taking?

Neil

[paul simsParticipant @paulsims62082]

Dear Neil,

For the tests when the bar was laying horizontal in the vice I started with 0.1mm cuts then my largest was 0.3mm, the cutter was nearly new and was taking long swarf off, sugesting cutting was good! but even after say six traverses you could still hear contact in both directions. When mounted verticaly in the V blocks i only did several 0.1mm cuts with single passes at each cut.

Paul

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