Grinding Table and Ways without Scraping
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  1. #1
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    Default Grinding Table and Ways without Scraping

    One of the companies I do work with just had a few of their Bridgeports rebuilt. A couple were in very bad shape, as in gouges 0.050" or more deep in the saddle. They came back with the knee, saddle, and table all ground with no sign of scraping. The shop guys say they are as good as there were new, but there is no flaking/scraping marks on anything. Would this be acceptable? The shop guys are happy with them, but I found it odd. I'm wanting to have my Bridgeport rebuilt, but not sure if this is the guy to use. I hate to spend the money on an incomplete repair.

    Any insight is greatly appreciated. I would like to find someone close by, but I'm not aware of many options in the southeast.

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    Bridgeport grinds the ways and 1/2 moon flakes them for oil lube and for looks. 1/2 moon flake marks average .002" deep and in my opinion ways wipers do not clean out the holes and lets the dirt into the ways. I would guess the rebuilder glued Turcite on the bottom and top of the saddle as it is hidden and not exposed to the dirt and chips. I teach to flake the unexposed surfaces and the rebuilders probably think that way too. Ask them what they charged and what sort of guarantee they offer. I say "As good or better then new" and if proper maintenance is followed and I guarantee my work for 1 year. I have had some customers ask me to oil flake the exposed are'a so they look like a new Bridgeport. Rich
    Last edited by Richard King; 08-28-2014 at 05:27 PM.

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    I wouldn't be happy if the machine ways have been ground all over without any flaking having been done. Flaking isn't just decorative, it has a purpose. As Rich says it should be done on the un exposed parts of the machine. You really need to speak to whoever did the job and find out what was actually done. Regards Tyrone.

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    I think I am right in saying Churchill grinders are not flaked and are ground on both faces ,pretty sure that is how mine is ,these are lubricated under pressure from the hydraulic system, theory was that the surface finish from a cup wheel was sufficient for lube retention.

    I seem to remember that there were problems with this system and it was not used on later machines.

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    I have heard that before Sable, so you could very well be right...

    I have also heard that I think it was Myford or Jones and Shipman or some such manufacturer for a V and flat on their grinders, would grind in the flat and one side of the V, then the other side of the V was scraped to fit..

    I was also reading somewhere on here about jigmills and how Deckel and such would mill the ways of their machines on big jigmills and they would not need much scraping in for fitting..

    As always there always seems to be many ways to skin a cat...

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    When I was a teen or early 20's, my Dad did a lot of work for a company called Nortronics and they did medical parts. They had dozens of Myfords and we rebuild several of them over the years. It was exciting as hell as they had women operators...it would take me a few hours to et used to seeing all these pretty women...lol...was distracting as hell if you get my drift...anyway as RC said, the ways were ground on 2 of the ways and the opposite sides were scraped. We used to wonder why as the were usually gauled on the middle of the ground sides because as they wore, they got stick-slip like rubbing gage blocks together. No scraping low spots to hold the oil. Many always talk about high spouts but low spots are as important to hold the oil. Years later in the late 80's I met a scraper hand at Detroit Diesel in Indianapolis who had apprenticed at Myford and he told me how Myford would grind the ways of the flat an vee on base and table and then scrape the v- and Flat on the base \ __ and then scrape the / vee on the table, then blue up the ground sides and scrape fit them to the opposite sides because doing it that way the ways would be parallel to each other. No King-way or parallel gage was needed. He did admit it took for ever as they had to clean up and re-blue it each time after the scraped. We scrape both sides and make the ways in the base parallel with the King-Way and also scrape the table and match fit it. Also on Myfords we have added BiJur auto lube pumps as it helps because the gravity flow rollers that feed Myfords leads to no oil and stick slip. Rich

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    if you mill it. the surface will naturally have a rougher than ground surface and the mill waves will hold oil. since i check my milled machines surfaces with a 0.0001" indicator i know the waves tend to be around .0002"
    .
    getting bigger deeper wavy surface is easy. increase feed rate. a rough mill surface can easily have waves over 0.005"........ it is not hard to make it what ever you want and verify it with a 0.0001" indicator with an end fairly small or less than .060" dia tip
    .
    also cutting oil grooves is easy on a cnc mill after the way surfaces milled

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    Quote Originally Posted by sable View Post
    I think I am right in saying Churchill grinders are not flaked and are ground on both faces ,pretty sure that is how mine is ,these are lubricated under pressure from the hydraulic system, theory was that the surface finish from a cup wheel was sufficient for lube retention.

    I seem to remember that there were problems with this system and it was not used on later machines.
    I think a few machine builders thought slideway grinders were the answer to all their prayers when the grinders first came out. They soon found out this wasn't the case.

    None of the " Churchill " grinders I've had in pieces have had scraping on the ways as far as I can recall. The way lube systems were very good though. They have shown signs of scraping for alignment though. I remember taking the column off the saddle on a big surface grinder and the top of the saddle had been scraped, presumably to square the column to the saddle alignments. Regards Tyrone

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    Quote Originally Posted by Tyrone Shoelaces View Post
    I think a few machine builders thought slideway grinders were the answer to all their prayers when the grinders first came out. They soon found out this wasn't the case. Regards Tyrone
    .
    on a printing press the cylinders often come with a mirror finish. often we cross hatched them. that is we took 220 grit sand paper and rubbed for 15 seconds at 45 degree to center line and then -45 degree forming a criss cross pattern. it would help process for months til it wore off. the crosshatching held chemical ink
    .
    of course a courser grit will leave deeper marks. i believe a grinder can leave a rougher surface by using a coarser grit wheel. mirror finish is not always better

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    I think on a small machine like this where the surfaces are slow moving it should really not be an issue.

    On a larger machine where either you have larger weights to deal with or faster speeds you would for sure want to have the ways half moon flaked to prevent stick slip and allow pockets for oil.

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    In a recent scrape of a Myford at MN Grinding in Crystal MN.I scraped it and 1/2 mooned a limited amount of the unexposed surfaces on the bottom of the table and wheel head. I say limited because sometimes the table and wheel head when fed to the extreme end of the travel the ways are exposed to the air and grit, so I do not flake those area's, just scrape. Remember 1/2 moon flaking averages .002" deep and scraping is .0003" We did not add a Bijur pump lube to the machine. It showed stick slip tendency so we pulled it apart and added one and that solved the issue. slow moving machines still need oil pockets or Turcite. These machines were hand feed machines and not hydraulic. Rich

    Here are some pictures...I have some more of I will add later of the lube system.
    Attached Thumbnails Attached Thumbnails 2014-02-26_11-10-14_519.jpg   2014-02-24_11-15-17_141.jpg   2014-02-26_10-46-03_350.jpg   2014-03-06_15-12-44_12.jpg  

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    Thanks for the input. I will be back out there next week and post some pics. It was $2800 to do the table, saddle, and knee. They did not do anything on the column. I didn't have a chance to call the shop and get the particulars today. I will do that in the morning.

    Thanks again,
    Scott

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    I work in a shop where we build specialty machines for our own product line, and until I started there a few years ago they sent all of our machines to a local rebuilder for the way reconditioning. This company (who will go nameless) doesn't believe in scraping. They grind everything and apply turcite to the saddle (or whatever the shorter member may be) and then they sand the turcite with what looks like really long strokes using approx 60 grit sandpaper to "fit" the turcite. I can remember when one of the first machines we had them rebuild delaminated the turcite after only 8 months, upon disassembly we discovered this "sanding shortcut", the machine received new turcite and a proper scrape job and has been running great since.

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    I was finally able to get some pictures. Below are some pics of the knees of 2 mills that have been rebuilt. I was told they ground the knee and scraped the bottom of the saddle. One has machine has a smooth ground surface, the other has some slight grooves. Any insight and/or thoughts are appreciated.

    Thanks,
    Scott
    Attached Thumbnails Attached Thumbnails imag2326.jpg   imag2328.jpg  

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    The ways in the second photo look pretty rough. If you hadn't have told me they were ground I would have thought that maybe they had been milled. Thinking about it and looking at the marks they were probably ground with a cup wheel but it's not a great job. Maybe the photo looks worse than reality. Have you run a finger type dial gauge over the steps. Regards Tyrone.

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    Quote Originally Posted by Tyrone Shoelaces View Post
    If you hadn't have told me they were ground I would have thought that maybe they had been milled.
    Beaten to it.

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    Quote Originally Posted by Demon73 View Post
    Beaten to it.
    me too, me too!

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    I disagree with the above, sorry. After grinding I believe some will run a single point cutter (eg fly cutter) with a very fast feed and a "poofteeth" cut along a surface specifically to provide oil retention. It's difficult to judge with just a photo like this, but they certainly don't look like grinding marks to me, not at that spacing. Furthermore, it looks like regular grinding marks on that surface if you ignore the other marks and look through them, and it looks to be conventionally ground to my eye*.

    *Those eyes are pretty weary right now, but that's my take on it anyway.

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    The ideal bearing surface on a machine, or other oil lubricated bearing surface is two pieces so flat that there is a film of oil between the parts. This eliminates any wear.
    Now, in a real world situation that is rarely the case. But flaking makes that surface uneven, and removes a little bit of that oil film. Plus it can hold dirt and grit.

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    Quote Originally Posted by Spyderedge View Post
    The ideal bearing surface on a machine, or other oil lubricated bearing surface is two pieces so flat that there is a film of oil between the parts. This eliminates any wear.
    Now, in a real world situation that is rarely the case. But flaking makes that surface uneven, and removes a little bit of that oil film. Plus it can hold dirt and grit.
    I'd suggest there is such a thing as "too flat" when it comes to the description you just provided. "Too flat" in terms of the overall surface and there won't be an oil film, the surfaces will gall and wear quickly.

    I don't want to pretend I'm a scraping expert, but believe flaking isn't necessary, and the same results can be achieved by a specific scraping technique to do exactly the same job in the last pass. Flaking however looks cool and ensures the oil pockets are evenly placed over the surface.


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