I was doing some work on a pulling tractor engine today. I had to open up the lifter bores to allow the use of roller lifters. The lifters mic .842 and I was trying to hold about . clearance between the lifters and these new bores. The lifter bores are down so far in the block that you can't use a normal dial bore gauge. I ground a gauge pin that mics .843. I have never used gauge pins before so I don't really know what to expect. Most all my work has been on bores that I could I.D. mics. I am just wondering that if both the bore and gauge pin are round and straight, how much clearance would it take for a gauge pin to fit? In other words, would a .843 pin fit in a .843 bore. I am thinking that it would take atleast a few tenths of clearance before the gauge pin would slide in.
I got all the lifter bores opened up and my .843 pin just barely slides in and the lifters fit fine but I am just concerned that the bores may still be a little tight.
In other words, would a .843 pin fit in a .843 bore.
Yep, but only with pressure, meaning pressing or driving it in. When I replace typical machine tool bearings, clearances are commonly ." or so, and you still can't just slide them together. You can tap gently, as long as everything is square.
Heck, I rebuilt a live-center tailstock quill once that had about ." clearance between the quill OD and casting bore. I lathered it up with waylube before sliding it back in, and couldn't move it by hand. Had to pull it back out, clean it, and put it back in with lighter oil. That was a surprise to me.
You're talking about something that needs to reciprocate, and quickly, so I would think .-.". But, have you asked an engine builder? I would defer to them.
Thanks for the reply. I know that the clearance needs to be about . but what I need to know is what size my bore actually is if my .843 pin will just slip in. I have no accurate way to measure these bores beings they are so far down in the block. I know that I have atleast .001 clearance but I don't know for sure exactly how much I have.
After many years of custom fitting ball bearings into electric motor endbells, I'd say it takes ." clearance to assemble a close fit. This is because it is a practical impossibility to hold perfect alignment (by hand) between the two parts. After you get the two parts fully engaged in their fitting length, you may find that they move quite freely, and you would think you should have reduced the clearance. But if you redo the fit and make it tighter, you'll have a whole lot of trouble getting them to engage again.
The normal use of gage pins is to have two pins, a GO and NOGO, each of which are sized to the target hole size +/- 1/10 of the target tolerance. To get the right size gage pins, you need to establish not just target hole diameter, but also tolerance.
If you internet search "go nogo gage", or similar, you'll find plenty of references. Here's one explaining sizing and use of gage pins:
http://www.aajansson.com/pdfs/understanding fixed limit gages.pdf
The metrology forum would be a good place to ask detail questions about gaging.
You need 2 pin gages. A go and no-go.
The question, as I understood it, is what size is the hole if you can get the pin guage to enter it? All the go gauge tells you is that "this pin enters the hole", and does not tell you the diameter of the hole. The No go pin may actually represent the diameter of the hole, but you won't slide it in by hand.
There are many variables at work here. If the main concern is your diameter then you need to get a gage to fit where you need it to measure. There is no standard for fit clearance. We make parts that freely slide together with 30 millionths of an inch clearance. Some people can NOT make parts that slide together with .001 clearance. The geometry of the work part is very important.
There are split ball bore gages that have extensions to reach into deep bores. Both Mitituyo, Mahr and Sunnen make these gages.
Athack
The question, as I understood it, is what size is the hole if you can get the pin guage to enter it? All the go gauge tells you is that "this pin enters the hole", and does not tell you the diameter of the hole. The No go pin may actually represent the diameter of the hole, but you won't slide it in by hand.
The go gauge tells you a little bit more than "pin enters hole" -- it also tells you the hole is larger* than than gauge pin. Conversely, the nogo pin tells you that the hole is smaller* than the pin. Hence, the go/nogo pair tells you that the hole is in between those two sizes. Although the OP implied he wanted to know what the bore diameter is, the application could be satisfied by a requirement that the bore be between two diameters, as defined by a target diameter and the tolerance limits, and this is what gauge pins are for.
In other words, he really wants a hole that is . +./-. and for that, you can use gauge pins. The actual diameter isn't terribly important.
*smaller and larger is subject to the bore and pin being, in OP's words, "round and straight", but of course each of those have their own tolerance that affects both gauging and measuring.
Gage pins can be a problem in using because of insertion. There is a little modification which makes it easier. In effect it's an "O"-ring groove. The groove needs to be carefully spaced near the pin end and then the "circle" of steel on the pin end is easily inserted. So it's in already and all that needs to be done is to line the pin up and slip the pin in.
The closer the fit the closer the groove is to the pin end. There is a formula, but I don't have it handy.
Maybe this will help.
Regards,
Stan-
The question, as I understood it, is what size is the hole if you can get the pin guage to enter it? All the go gauge tells you is that "this pin enters the hole", and does not tell you the diameter of the hole. The No go pin may actually represent the diameter of the hole, but you won't slide it in by hand.
Assuming everything is clean, are temperature and humidity a big enough factor to effect go/no-go?
Thanks.
Darren Harris
Staten Island, New York.
Reminds me of, after 10 years general machine shop experience, I landed a job in the tool room of a servo and small gear motor manufacturer. I was boring a hole in a piece of 440 stainless, and the plug gage JUST fit in---and stuck. One of the other toolmakers saw my prediciment and came over. He asked if I had put oil on the plug, and I told him no, as several years before I had discovered that oil took up room, and made a loose fit seem tighter. Not olive oil he said. We warmed the piece up with a heat gun, and got the plug out. After everything was back to room temperature, he brought over a bottle of olive oil and put some on the plug--and told me to try it again. It almost slid in and out by itself! I had noticed several bottles of olive oil on various benches, but thought that they were for lunchtime purposes. Lesson learned- I always have a bottle in the shop ever since.
Herb Kephart
Hello all. Starting my travels down the machining path. I wanted to know what others thought about cheapo pin gages versus premium? Has anyone tried the cheap stuff and checked if they are actually within tolerances?
I've been looking at some Vermont Gage and Meyers Gage sets on Ebay.
I like good tools and but don't see myself using pin gages everyday so thought I might get by with a cheap set.
I guess also apply that to gage blocks although I can see where they might be used more.
Thanks in advance for any replies.
You may not use them every day, but when you need them Vermont or Meyers are what you need. Keep in mind they're like gauge blocks in the fact they're used for verification of equipment as well as inspecting hole size and such.
I've come across cheap sets. When you check one of the pins diameter there may be no consistently in roundness up and down its length. I've even found bent pins in a used set. No idea how that happened.
But in the end you have to decide the quality you need.
I don’t use my Vermont pin gages that often, but when I do, I know I can trust them. I don’t have the same faith in cheap tools.
Another thing to think about, people using the cheap sets have reported they rust easily, so if your workshop is located where rust can be a problem, the premium gages might be the better choice.
I have a relatively cheap couple of sets that cover from some fraction of a mm (0.5mm?) up to 10mm. I got them from AliExpress.
I haven't used them yet but I can take a sample and use my mic to give you an idea of how consistent and accurate they are.
I'll pop down to my garage in an hour or so and let you know what I find.
About 4 years ago I needed some gauge pins for a project. I purchased 2 sets on eBay from CME Tools. I haven't used everyone in the sets, but those I have used are true. I purchased the imperial sets that are ." undersize.
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I have a plus set of .061" to .250" and a minus set of .251" to .500" that I bought from Enco not long before they disappeared. I check pins with a micrometer and every pin that I have checked was exactly ." oversize or undersize. I haven't seen any rusting of my sets nor have I seen any imperfections.
It is interesting to note that even the name brand sets don't specify straightness tolerance.
I have a plus set of .061" to .250" and a minus set of .251" to .500" that I bought from Enco not long before they disappeared. I check pins with a micrometer and every pin that I have checked was exactly ." oversize or undersize. I haven't seen any rusting of my sets nor have I seen any imperfections.
It is interesting to note that even the name brand sets don't specify straightness tolerance.
I would expect that the straightness falls into the over/under, otherwise the pin would not register correctly. Imagine a -. being bent by a slight amount, it would now be a + size, and be out of spec.
They are (should be) a buy once thing. Get the highest quality that you can reasonably afford. One thing to be aware of (you may already know this) - you can buy sets with accuracy certificates traceable to NIST etc. golden standards - and you really don't need that unless you are making and selling high percussion parts as a supplier to an industry that demands it.
Also, on the cheap but still good quality used sets show up at tool flea markets with a few pins missing. I got a quality 1/4 - 1/2 by 16th's set for about $30 with only two missing pins. Filled my need for larger pins, I may eventually get a bigger new set.