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ID micrometer, is it worth buying one?

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  • Spin Doctor
    replied
    IMO ID micrometers are well worth the money. And not just for checking bores. Need to set a lathe stop for a long cut. If you don't have DRO or a Trav-a-dial touch the start surface of the cut with the tool and use the ID micrometer to set your length. No Jo blocks or Cadillac Height Gage. Set the ID micrometer to length and hold in vee block with one end against the surface plate. Instant height gage. And for what is worth I perfer the tubular style rather than the solid rod type. With the tubular you can make extension rods if you have to. The Starrett's have a 5/16th-40 thread

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  • RussZHC
    replied
    I already can easily come to within 0.2mm of the final dimension using my caliper. My problem is, after I am very close, I need to know how much more to advance the cross dial. I want to take that last portion off in one cut so that the seat is exactly the OD of the bearing. Then I can use a sandpaper etc to massage the final 0.01mm or so...
    part of the answer maybe to do a bit of quick calculation...assuming you are not making just one cut and that is the final cut. One earlier cuts, try to find several different DOC (may have to be done in conjunction with sfpm numbers) and then once one DOC reliably gets you the finish you are after be sure to note specifications and leave yourself that much for the final cut.
    This definitely relates to what Black Forest and Pixman are talking about.
    I don't have a lot of experience but early on this business of sneaking up on something did not seem to go well, or rather, not well consistently. Never "knew" what to expect. This was with HSS (experience so far has told me this is even more true for inserts) and mystery metal.
    Once I went to math and figured out, OK if I can take a real heavy DOC taking off the little amount needed to finish will be tough but if I adjust feed and DOC so as to leave enough to really cut rather than just skitter around...much better. For me it also made a difference distinctly separating a "roughing" cut from a "finishing" cut i.e. less cutting done in-between those two.

    Edit: when I wrote the above I had just external turning in mind, don't know that it should be any different for boring but it maybe more difficult to judge due to troublesome viewpoint and you may not have as many attempts to find the "sweet spot".
    Last edited by RussZHC; 01-31-2013, 02:57 PM.

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  • RLWP
    replied
    Originally posted by Jaakko Fagerlund View Post
    What he meant is that the insert has certain DOC it needs to cut properly and thus he can't use them to shave off 0.01's off millimeters at a time.
    Then surely he is using the wrong insert

    Richard

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  • MaxxLagg
    replied
    Originally posted by Jaakko Fagerlund View Post
    But with an outside mic they do precision work, as I previously explained. No guess work, they provide the same accuracy as the telescoping gages. Only disadvantage is that you are only able to measure up to a depth of the jaws length.
    I disagree. If you're trying to hold +/- .0002 on a bore diameter using calipers like you would a telescoping gage they aren't going to achieve that. First, you're never going to get the same, repeatable sweep of the maximum ID of the bore as you can with telescoping gages. Secondly, take a close look at the faces of the jaws on the inside measuring jaws. I have four calipers sitting here in front of me of various makes, sizes and styles. That, albeit small, flat that each jaw has is going to prevent you from fully measuring the ID of the bore. By how much? Well, mathematically you could determine this amount by calculating the height of the chord that results by the width of the flat and multiplying this product by two and adding it to your measurement. But to do this you would need to know the radius of the bore to input into the formula for figuring chord height, which you don't.

    If you're happy with +/- .001 (or if you're really lucky, through chance but not by design) +/- .0005, then calipers will do the job. I'm not trying to say that it won't achieve the results you're hoping for. I'm just trying to impress their limitations for this type of work and to try to convince many on this board that telescoping gages aren't the black magic to use that they think, based on their lack of understanding or poor results in the past through poor technique. They're a VERY inexpensive tool that measures a wide range of sizes.

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  • Black Forest
    replied
    I have a Mahr 35 -60mm inside bore measuring device on its way to me. If I don't like it Taydin you have to pay for it. After all it is your fault I bought it!

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  • Black Forest
    replied
    Originally posted by Jaakko Fagerlund View Post
    What he meant is that the insert has certain DOC it needs to cut properly and thus he can't use them to shave off 0.01's off millimeters at a time.
    That was a hard lesson for me. To figure out what the nose radius of the insert had to take to get a good finish. Once Pixman beat it into my head that I should stop being a wimp and trying to sneak up on the final diameter things got much better. I was amazed at how much my surface finish and how much easier it was to actually obtain my final demension.

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  • Jaakko Fagerlund
    replied
    Originally posted by RLWP View Post
    Can I suggest that you solve that problem first then? You are always going to have trouble doing precision work if your tools don't cut predictably

    Richard
    What he meant is that the insert has certain DOC it needs to cut properly and thus he can't use them to shave off 0.01's off millimeters at a time.

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  • Boucher
    replied
    I was faced with a similar problem recently. In my case I left the spigot that the bearing was going it longer than needed. I set the compound to a small angle like 3° and bored the pocket at this angle until the bearing would go a short distance into the hole. I then blued up the hole and inserted the bearing to mark the contact point. I then used that to set my tool to bore a little undersize because I wanted a light shrink fit. Then the spigot was faced to the required dimension. A very sharp HSS cutter with oil and proper speed will make very fine cuts.

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  • RLWP
    replied
    Originally posted by taydin View Post
    {snip} my insert doesn't really cut and just smears the material on the surface, giving a bad surface finish.
    Can I suggest that you solve that problem first then? You are always going to have trouble doing precision work if your tools don't cut predictably

    Richard

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  • Black Forest
    replied
    Originally posted by taydin View Post
    Hi Black Forest, I am following your post about the boring bar. Hopefully you sort out and fix the problem with that boring head. BTW, a boring head with auto feed, how cool is that!!!
    Yes this head is cool. There is a knurled ring at the top and to advance the cutter I just grab the knurled ring and hold for a second or two and let go. Then start the feed into the bore. It saves a lot of time not having to stop the spindle every time I need to advance the cutter. When I get close I do stop the spindle and watch the dial to get it exactly. To face with the boring head a rod is threaded into the knurled ring and either hand held or let it rest against something to stop it from going round and round. There are three speeds at which it advances. Also there are stops that can be set to stop the advance.

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  • taydin
    replied
    Originally posted by dian View Post
    these are not precision bearings, right? why not glue them in? if you manage to put them on the shaft for gluing, they will be perfectly aligned.
    Hi dian, I am noting the gluing solution as a backup in case a bearing falls into one of the seats I make. But I really want to make the seating properly, just to advance my machining skills.
    Last edited by taydin; 01-31-2013, 09:07 AM.

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  • taydin
    replied
    Originally posted by Black Forest View Post
    When I broke my boring head I was boring a pocket for a 47mm outside diameter bearing just like the one in your picture. Now that you talked about how to measure and the various methods I am on the hunt for a good quality bore gauge size 35mm to 50mm. They are quite proud of these type of instruments!
    Hi Black Forest, I am following your post about the boring bar. Hopefully you sort out and fix the problem with that boring head. BTW, a boring head with auto feed, how cool is that!!!

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  • taydin
    replied
    Originally posted by Black_Moons View Post
    Make your own go-nogo or multi step/tapered gauge outta some scrap steel if you don't do precision inside jobs often and need to do the same job over and over.

    ie: if you need 4" exactly, make a gauge with 3.990" 3.995 3.998 3.999 3.995 3.998 3.999 4.000 4.0005
    Or similar steps. (or more then one guage, one for sneaking up on the size, another for the last few thou, if you need that kinda accuracy)
    There were several suggestions to make go/no go gauges like this, but, being a noob, I just don't understand how this is going to make things easier ...

    I already can easily come to within 0.2mm of the final dimension using my caliper. My problem is, after I am very close, I need to know how much more to advance the cross dial. I want to take that last portion off in one cut so that the seat is exactly the OD of the bearing. Then I can use a sandpaper etc to massage the final 0.01mm or so...

    In the past, I tried going in half cross dial division increments. But this just doesn't work, because with such small increments, my insert doesn't really cut and just smears the material on the surface, giving a bad surface finish.
    Last edited by taydin; 01-31-2013, 08:49 AM.

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  • taydin
    replied
    Originally posted by oldtiffie View Post
    I'd suggest that you use a standard outside micrometer and a telescopic bore gauge - with practice you should be able to accurately and consistently keep to ot hold 0.01mm (0.0004") and with further practice 0.005mm (0.0002").
    Unfortunately, wasn't able to find any seller that has telescoping gauges... If a nice set is around 50$, I might be able to order one from ebay without risking them getting stuck at Turkish customs. But I need a solution for the short term...

    Originally posted by oldtiffie View Post
    I normally opt for spring calipers as I can hold 0.01mm easily and 0.005mm with a bit of prior practice and care.
    The spring calipers are widely available here, but I'm sensing a lot of frustration until I get those wildly flexing legs under control.

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  • dian
    replied
    these are not precision bearings, right? why not glue them in? if you manage to put them on the shaft for gluing, they will be perfectly aligned.

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