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  1. #1
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    Default How To: ways gib

    I need to fabricate a replacement gib for a small manual milling machine I'm refurbishing. I plan on creating something close using mill, then bringing it to proper tolerance on surface grinder. I had seen some comments in another thread indicating that holding the gib onto surface grinder using magnetic chuck was undesirable as the magnetic chuck would distort the gib resulting in warped end product. Was wondering whether folks feel this is a problem, and if so how they hold the gib if so.

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    Put the material on the chuck, don't magnetize it, shim under high spots, then activate the magnet...rinse and repeat until desired results are achieved.

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    Good idea, thanks!

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    I manufacture quite a few tapered gibs, milling them to within ten thousanths of finished dimensions, and then grinding them. If I don't have a master gib, I grind the first one on a sine bar with the correct size spacer to give me the taper I need. I DON'T use a magnetic sine chuck, but I do have it held down to my magnetic chuck which is on. I have a blocker to keep the gib from flying off the sine bar, and take pretty small passes. Once I get the first gib to clean up on both sides, I now have a gib I can use to lay my other gibs on, one at a time. It's held to the chuck with the chuck on, but the gibs I grind are simply laid on top, with any pieces of proper thickness steel, to make a nest to keep the gib from flying off. Since it's blocked in, grinding the rest of the gibs goes pretty quickly. I still don't take big passes, but since the gib can't move,it goes quickly. I flip the gib several times. Since it's NOT pulled down to the chuck with the magnet , the gibs turn out flat. takes less time to grind a gib, than to type this post.

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    Quote Originally Posted by [email protected] View Post
    I manufacture quite a few tapered gibs, milling them to within ten thousanths of finished dimensions, and then grinding them. If I don't have a master gib, I grind the first one on a sine bar with the correct size spacer to give me the taper I need. I DON'T use a magnetic sine chuck, but I do have it held down to my magnetic chuck which is on. I have a blocker to keep the gib from flying off the sine bar, and take pretty small passes. Once I get the first gib to clean up on both sides, I now have a gib I can use to lay my other gibs on, one at a time. It's held to the chuck with the chuck on, but the gibs I grind are simply laid on top, with any pieces of proper thickness steel, to make a nest to keep the gib from flying off. Since it's blocked in, grinding the rest of the gibs goes pretty quickly. I still don't take big passes, but since the gib can't move,it goes quickly. I flip the gib several times. Since it's NOT pulled down to the chuck with the magnet , the gibs turn out flat. takes less time to grind a gib, than to type this post.
    As you say light passes. Too much and the gib will heat and expand into the wheel.

    Tom

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    Be sure to use coolant when grinding the gibs. What sort of mill. You may want to call H&W machinery and check and see if they have one if it is a Bridgeport or Bridgeport clone. If you have the old gib, you can apply Turcite to it and use it instead of making a new one. Don't worry about them bending as you can straighten them. We just talked about gibs in The Machine Reconditioning forum a few weeks ago. Picture is showing how I used 2 mag chucks to make a mag sign to grind the gib after I indicated the gib in to the proper taper. After I had the right taper I glued Turcite to it and hand scraped it to fit.
    Attached Thumbnails Attached Thumbnails 20181002_120952-1-.jpg   20181002_123730-1-.jpg  

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    You might be interested in the YouTube video that Stefan Gotteswinter just posted on making tapered gibs:

    YouTube

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    Richards method of setting the whole gib on a chuck flat sold at the desired taper is best, but the gib may be longer than your surface grinder chuck., and you may not have an extra chuck or a long-sine chuck.

    I have ground short gibs on a mag chuck with a bumper block at the go side and the gib set on shims to make the taper. This is tricky because the shims have to be set in exact position. Like Stefan Gotteswinte”s video showing where your micrometer edge is, you have to think where the exact edge of your shim is to make the needed taper. A 6” long gib should have 4 shims for the taper or the wheel pressure will cause the shim to deflect away and so not come out straight, Shims set in the wrong place will make the gib not straight,
    I have double back taped a gib to a long parallel and then with shims under the parallel for making taper ground gibs that way. Doing this method, the mag chuck’s pull can distort the parallel so good to have an adjustable magnetic chuck and use very little magnetism or none. Yes you might Jo-block mid place to assure the parallel does not bend (a 2"x3"by 36" parallel will mag bend if not mid supported)

    The slightest burn will tend to warp a long flat part so Wet Grind, and a course wheel is best. Perhaps a 36i white aluminum oxide might be best and being very careful/perhaps a pause at the off-ends. With counting sparks.

    With having good straihtening skill you can straighten a little out of straight , but If you bend too much you can break a CI gib.

    First time I used double back I bought special grinder tape...Think I paid 40.00 for a roll and now forget where I bought it from...later I found that carpet double back works just a well. Still have a roll that is like masking tape with sticky on both sides..Don't know if they still make that kind but it is/seems about .0000 flat.
    Oh, counting sparks is you look close at your sparks when the part is not warmed up...then as you are grinding if the sparks get closer together you slow down or pause.. Yes not so easy when grinding wet.

    I should set up Gib grinding and offer that service...

    I have a 46I Carborundum white aluminum oxide that runs cool enough for such work but a 46I of most other manufacturers likely would not be ok,

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    As an addendum to my post on grinding gibs, I ALWAYS surface grind with coolant, and coolant that's directed at the point of contact. Surface grinding gibs, that aren't held down with a magnetic chuck is a somewhat delicate task. made possible with carefully applying coolant at the point of wheel contact. I use two coolant nozzles, one that goes the width of the wheel, but another aimed RIGHT at the leading edge of where I'm grinding the gib.

    I guess I may assume that MOST people use coolant on a surface grinder. Can't imagine not, as my parts grow rapidly with no coolant. Even with careful use of coolant, striving to get the coolant right into the wheel at the point of contact, it's tough to not get the part to grow with heat. Certainly dressing the wheel coarser gets a cooler cut, but then you sacrifice finish. It's a real balancing act between the dress speed, and what I feel is an acceptable fine finish on a ground part. Dress too fine, and even with coolant, your part can burn.

    Fortunately the gibs I grind the most are nine inches long, and I have a ten inch sine plate. I can set my taper angle perfectly, using the sine plate, where using spacers under the gib, relies on an exact location to get the angle right. I also should point out, I grind the taper on the gib, before I cut the angles on both sides of the gib. Grinding the fully machined gib, with opposing angles on the sides plus the taper, with no magnet on, is too time consuming, as the wheel wants to push the unsupported side of the already angled gib down, rather than grinding material off. A process that I've fine tuned over 19 years, through the process of errors. Now that I know how to do it fast and efficiently, it's gotten boring.

    I just watched most of the video that was linked to. Interesting techniques, but for me way too slow. I mill my gibs on a fifty taper mill using a 10 inch Kurt vice, using a 1 1/2 inch carbide round insert able milling cutter My gibs are all castings that are already tapered, however they're rough, not flat have no really square sides. I mill the width of the gib, that later will be angled, two at a time in the vice. The tapers are opposed to each other so my vice is sort of squeezing two parallel sides. But I use WOOD on both sides of the gibs, so my vice can really hold them with much better contact than with the rough cast surface. i usually run ten to twenty gibs at a time, so I don't go slow. Takes two passes per side to get my gibs into at least two parallel sides so I can clamp them to cut the tapers. Cutting the tapers is easily done by just laying a master taper gib onto a parallel, laying the gib to be milled on top of it, and then clamping the jaws of my monster vice. two passes with my button cutter per side of the gib. I do ten or twenty of one side, then raise my table and do the other side of the gibs. Takes about two hours to do the sides and the tapers from a raw casting to do about ten gibs.

    Off to the grinder to grind the taper, and then back to the mill to cut the sides to the mating angle of my dovetail. I use the vice simply to hold a dovetailed cross slide with the dovetail UP. I cut a piece of OAK hardwood to exactly match the width between my dovetails, less the width of the gib. I simply slide the tapered gib into the space, and HAMMER it in, until it's tight I tap it DOWN to make sure it's seated, and then cut the top of the gib to the angle in TWO passes, making sure my cutter is going in the direction that it would TIGHTEN the gib into the taper, instead of backing it out. I run all of one side, and then readjust heights and then do the second side. At this point the gib is right at the same height as the top of my saddle I'm using as a fixture. Doing gibs ten at a time, I may have twenty minutes a gib, from casting to completely machined and ground. My only "fixture" is one carefully ground tapered gib I use as a master, and then one cross slide i use for cutting the side angles.No finicky adjustments, but most of important is I'm blasting the material off in the mill using a robust mill, a huge vice and a cutter that cuts the entire width in one pass. despite the production line method, my gibs are FLAT because I'm able to grind them without having the magnet on, in the surface grinder. Whatever stresses my material had are gone because they were ground without the magnet.

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    Some REALLY helpful techniques in this thread, very useful!

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    Quote Originally Posted by Mike Henry View Post
    You might be interested in the YouTube video that Stefan Gotteswinter just posted on making tapered gibs:

    YouTube
    This

    Stefan does a very good job of explaining making taper gibs. I might also reach out to Richard King for some of the finer points of scraping a gib to a proper profile - he had mentioned in a scraping class that you want to relieve the center of the gib slightly (e.g. 2 tenths/thou) to accommodate wear as the gib wears during the use.

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    Default Making Lathe Taper Gibs

    I have used magnetic sign chucks and then demag the gibs. easy peasy . Here is a great thread by a former member Texas Tunado. Look at post 51. It shows how he made gibs. One of the best thread I have seen on here.
    SAG 12 Restoration Progress

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    Richard, really great info, thx.

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    Going back to look at all the great information in this thread i do hope I or someone else mentioned the wheel to grind a long and perhaps a thin part. stress relieving does little good if if one would burn the part surface and so put in new stresses in the part.
    Every one owning a surface grinder should invest in a few very open, larger grit wheels for roughing in and even finishing a part that might burn.
    Thin parts are more likely to burn because there is less material to absorb the generated heat. longer over travel at the part ends is some help but may not be enough. Coolant is best but even that may not be enough.
    The 46 wheel is perhaps the smallest grit to use and that being an open wheel so having greater spaces between the abrasive grit stones. A 36 or 24 grit is even better. I like a white wheel for avoiding burn but have found some pink and ruby wheels that were very good. brown and black wheels are good for long life but poor for avoiding burs IMHO.


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