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Is it possible to visually determine the wear on the Y axis ways of a Bridgeport mill, or can you only tell by running the table in and out and looking for loose or tight spots?
Is it possible to visually determine the wear on the Y axis ways of a Bridgeport mill, or can you only tell by running the table in and out and looking for loose or tight spots?
Why would you be LIMITED to "bare eyeballs" only... if you were close enough to see it at all?
Are you not allowed to carry-with some form of straight edge and a DI? Move it? Apply any side or twisting forces?
In addition to just "running it in and out."
Which.. by itself.. sounds like the usual way to get f****d, choice of orifice optional?
Speaking of which.. is this a "look but do not TOUCH" cordoned-off type of auction or the like?
Not sure I'd class that as "getting a good feeling here."
The first and worst wear point is going to be the right hand side about a third of the way back. You can get a general idea how worn it is by how much of the original scraping is visible and/or whether there is any significant scoring of the way has occurred. Run the saddle all the way back and have a peek. Of course this doesn't mean that there aren't plenty of other potential issues, but two good indicators of general condition on knee mills are the surface condition of the ways, and how much backlash is in X and Y screws.
There is .028" backlash in the X axis and .010" backlash in the Y axis.
There is .028" backlash in the X axis and .010" backlash in the Y axis.
I don’t think backlash is a good indicator of wear on the ways. It indicates screw/nut wear and can often be adjusted out.
I would go with flaking evidence. If the knee ways were worn smooth, that doesn't mean the mill is shot by a long stretch. If you can still see flake marks and the price is right, buy it.
Straight edge may be a way to check machine ways. I don’t think a DTI is all t hat helpful. The trick to the DTI is working from a known reference to something,
Inspecting a mill for wear and understanding how measured wear translates to a mill’s precision or tolerance holding is nothing to sneeze at. Many discussions and dare I say arguments about this subject here.
True, backlash can often be adjusted out. The fact that it hasn't, somewhat indicates the level of maintenance the machine has seen in the past.
True, backlash can often be adjusted out. The fact that it hasn't, somewhat indicates the level of maintenance the machine has seen in the past. FWIW, I have seen plenty of bridgeports where the split nuts were worn beyond their range of adjustability. Still no big deal as the screws and nuts aren't that hard to replace.
Another indication of condition would be to use a mag base dial indicator, and check for how much the table shucks back and forth as measure from the saddle, and how much the saddle shucks back and forth as measure from the knee. Again, this can usually be adjusted out, but if it hasn't it's an indication of the level of maintenance the machine has seen.
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