Heat or Chuck Dressing Time?

pdentrem said:
Also don’t lay the pieces inline with the wheel. Thin materials should be at an angle. Light cuts.

Most of the wear in the ways will be in the center portion of the travel. Try to set up on the ends of the chuck and if you can move the chuck over to one side as much as possible. Indicator will show nothing about the taper of the ways.

SG are sold off when they are worn out, and we buy them for our home shops due to their precision capabilities. Companies are not willing to scrap the ways so rebuild the machine, and the machines are written down on their books over the years of use.

Unfortunately or fortunately most of us don’t need the ultimate precision that a new SG can give but can tolerate a worn machine.
Click to expand...

There's only so much angle you can get with a 12" piece on my chuck, but I tried both angled and nearly parallel with the chuck axis and got the same results.

This SG has ball ways with V on one side and flat on the other. The shop it came out of went out of business when the owner retired and they had an auction. They had really nice stuff that generally went pretty high, this SG was clean and I don't think they did a lot of grinding (it was set up for dry) and the only SG in the shop. The picture above is how it looked when I unloaded it....it wasn't dirty and all beat up so I doubt it saw much use. I did replace the balls with new precision balls and the ways looked really good when I pulled the table. That's not definitive, but I don't think it was being used all day every day like many of the SGs you see at auction.
 
pdentrem said:
Also don’t lay the pieces inline with the wheel. Thin materials should be at an angle. Light cuts.
Click to expand...
I would hate the look of angular lines vs straight lines on my parts.
I disagree with that recommendation. While I won't put the effort into looks if it's not necessary, having the (apparent grain) from grinding go angular would upset most looking at it. Like the kid who put my air conditioner compressor/evap at an angle to the house. He said it didn't matter, my wife and I looked at it and said it did, it was too far off and just looked wrong. for an apprentice, he just didn't care.. most would like to do the job well... he had short cut after shortcut. didn't seal the holes in the siding, both for the lines, and then when he came back with a different crew to put the intake and exhaust in.. forgot to seal it. I reminded him and he still didn't do it... Nor did he finish taping the duct work that they joined. He left 2 huge gaps... Right before he left, I pointed out that there were gaps... I thought he would tape them... Nope, when he left, I went down and still open. END OF RANT.
 
Angling the work is a great way to control heat build up. I try to make my finals passes (to dimension) parallel to the long axis of the work. But then I'm taking sub-tenths passes.

I use flood coolant when I use coolant, as I am very sensitive to breathing in the mist from the spray coolant devices. Even when they are set to create large droplets, there are still a lot of aerosols created...

G-ManBart said:
I'm trying to wrap my head around the idea of waiting 10-15 seconds at the end of travel. For a 12" long work piece 2.5" wide like this was, it would be 30 minutes of waiting if I was taking .020" steps each pass.
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I'm confused by this. I would never take a total of .020 off of any work using the SG. Even after heat treat, the most I have ever needed was .010, and that was due to warping. Didn't you mill your parallels first? I would mill to .010 oversize, then heat treat, them remove the scale (I heat treat in salt so there is minimal clean up). This leaves about .005 or .006 to grind on the SG.
 
Dabbler said:
Angling the work is a great way to control heat build up. I try to make my finals passes (to dimension) parallel to the long axis of the work. But then I'm taking sub-tenths passes.

I use flood coolant when I use coolant, as I am very sensitive to breathing in the mist from the spray coolant devices. Even when they are set to create large droplets, there are still a lot of aerosols created...


I'm confused by this. I would never take a total of .020 off of any work using the SG. Even after heat treat, the most I have ever needed was .010, and that was due to warping. Didn't you mill your parallels first? I would mill to .010 oversize, then heat treat, them remove the scale (I heat treat in salt so there is minimal clean up). This leaves about .005 or .006 to grind on the SG.
Click to expand...
what kind of salt are you using? I thought salt corrodes, especially when wet or heated to extremes. (unless borax is a salt)
 
I dunno. I got it from the guy I bought my heat treat furnace from, used.
 
woodchucker said:
I would hate the look of angular lines vs straight lines on my parts.
Click to expand...
Not an argument, just a comment. I've seen it recommended to use angles because it's hard to make perfectly straight lines that are perfectly parallel with the work. If the lines are something like 30 degrees off it doesn't upset folks because they're so far from parallel it doesn't look like a mistake (or something along those lines).
 
Dabbler said:
I'm confused by this. I would never take a total of .020 off of any work using the SG. Even after heat treat, the most I have ever needed was .010, and that was due to warping. Didn't you mill your parallels first? I would mill to .010 oversize, then heat treat, them remove the scale (I heat treat in salt so there is minimal clean up). This leaves about .005 or .006 to grind on the SG.
Click to expand...
I was talking about .020 steps not depth of cut. If the work is 2.5" wide that's 125 passes at .020 step over each pass. With 15 seconds of wait time after each pass it would be 30 minutes, plus the time of the actual pass while cutting. That seems really slow.
 
G-ManBart said:
I was talking about .020 steps not depth of cut. If the work is 2.5" wide that's 125 passes at .020 step over each pass. With 15 seconds of wait time after each pass it would be 30 minutes, plus the time of the actual pass while cutting. That seems really slow.
Click to expand...
Grinding takes time. Flood coolant dramatically decreases the time to do good work. 30 minutes is nothing. I reground a toolmakers vice in D2 tool steel that took me 3 hours. And I was rushing it a bit.
 
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