South Bend Milling Machine - squaring the head

jakes_66

jakes_66

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
Sep 21, 2017
Messages
119
I've enjoyed setting up the South Bend VMM I bought a few weeks back. I've been doing a pretty thorough examination of the machine and noticed something that has me worried. The head is not 'square' to the table. Some explanation is needed:

The head on this machine does not 'nod' in the same way a Bridgeport machine does. I mounted my 0.0005" Starrett Last Word indicator in a collet in the spindle and spun it by hand to 'tram' the head to the bed. I was able to adjust the head left-to-right to my liking, but front-to-back is out by 2.5 thousandths over the 9" width. I have tried moving the round ram in and out, cleaning and oiling it, cinching the ram pinch-bolts down in various ways, readjusting the knee gib, rotating the collet in the spindle (relative to the indicator), rotating the spindle (relative to the indicator) all with the same results.

How does one compensate for this inaccuracy? Has anyone been down this road before?

-Jake

2017-09-19 21.10.22.jpg
 
Last edited:
Maybe there's some dirt and/or chips or burr in between the two sections that bolt together for head rotation??? Wouldn't take much to throw things off... If it were me, I would probably disassemble and hone the mating parts with a nice flat stone, clean things up good, put a light coat of oil on them and see if it improves. Same with the ways/gib for vertical on the knee and table. There's probably a booger in the works somewhere! :(

Good luck,
Ted
 
20170919_142809.jpg I have the same mill, mine is 1956 vintage. While mine is not spot on, it is a bit better than yours. I looked at mine closely and I do not see an adjustment point, the best I can see is possibly shimming the ways... if that is even possible.

I am wandering if this is an indication of worn ways
Vintage machinery.organization has a better manual, it gives a better parts breakdown.

I plan or rebuilding my machine this winter, and ßome of the suggestions made by Ted will be considered. Keep us posted on what you find and try.

Off topic here, I have not had the chance to ask another owner any questions, I have only read old posts on various forums about this machine. What taper does your spindle have, mine is a 30 taper. How are you solving holding tooling. I have a taper 30 to er40 collet system. It's a bit of a pain because I have to mill 2 45 degree indents into the hardened spindle for any taper 30 holders I use. Wonderful machine, stiff, enough power, in my case fairly accurate, though the head will move when you are pushing material thru too hard (lots of retramming)
Thanks for any info

Rich
 
Last edited:
I am curious, does the head and table "squareness" change with the knee position, try setting a dti on the knee and vertical way and move the knee up and down. The same for moving the table in and out on the y axis. You mentioned trying the ram, so I am just thinking what is causing the unalighment.
I don't think the point where the head mounts the ram would be the issue, if there is anything in there as ted suggests, I would think it would move or change when moving the head.
Though loosening the head and spinning it might not be a bad idea. If you have a way to hold the head, overhead crane, engine hoist or chain hoist, might be a good idea to pull the head and check the mating surfaces, if unchanged, the next would be the table and the knee.

After that, I would check for wear in all those areas. I would like to know what you discover, like I said, mine is nearing a rebuild, spindle bearings, and possibly scraping the ways on the knee and table.

I guess this is basically exactly what ted mentioned, sorry, I started to brainstorm how I would do mine...

Hth
Rich
 
I do not suspect that the ways are worn, my machine does not appear to have had excessive use during its life. I did attempt to see if there was some wear in the knee ways by extending the quill as far as it would go, extending the indicator as far as it would go and cranking the knee down maybe 8 to 10 inches. The squareness issue was exactly the same at 2.5 thousandths over 9 inches. I think the best plan is to remove the head at the rotation point, clean and stone the surfaces and reassemble.

I was very fortunate to get the original master collet holder with my machine. It's an NMTB30 taper like yours with the notches for the set screws to retain it. Keep your eyes peeled for the older Weldon quick change toolholders of the same size, they appear to already have those notches for the set screws. The collets on mine are a strange type I've not seen before, but I got a full set that is in nice shape.

I just bought the machine a couple weeks ago, so I'm looking forward to giving it a good workout. It's been all light cuts so far.
 
richl said:
View attachment 243841 I have the same mill, mine is 1956 vintage. While mine is not spot on, it is a bit better than yours. I looked at mine closely and I do not see an adjustment point, the best I can see is possibly shimming the ways... if that is even possible.

I am wandering if this is an indication of worn ways
Vintage machinery.organization has a better manual, it gives a better parts breakdown.

I plan or rebuilding my machine this winter, and ßome of the suggestions made by Ted will be considered. Keep us posted on what you find and try.

Off topic here, I have not had the chance to ask another owner any questions, I have only read old posts on various forums about this machine. What taper does your spindle have, mine is a 30 taper. How are you solving holding tooling. I have a taper 30 to er40 collet system. It's a bit of a pain because I have to mill 2 45 degree indents into the hardened spindle for any taper 30 holders I use. Wonderful machine, stiff, enough power, in my case fairly accurate, though the head will move when you are pushing material thru too hard (lots of retramming)
Thanks for any info

Rich
Click to expand...

This is a nice picture of that mill. Is that a split in the main body right above the vertical ways??? If so, that's another area where you might have a interference, BUT the GOOD news is that would most probably make a great spot to shim things to resolve your problem!

Ted
 
Is it possible to turn the upper section of the column 180 degrees? Maybe it's installed backwards? If not then doing some
work on the rotation point like you mentioned is probably your best bet.
Mark S.
 
You must log in or register to reply here.
Back
Top