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Thu Aug 27, 2015 7:31 am

Just thought this would help. I bought a set of HF telescoping snap gauges to measure inside of the bores and bearing journals of my engine. I'm not a big fan of HF tools as I truly believe you get what you pay for but I brought these to work and measured them against a set of Starrett snap gauges and they were fairly close. Measurements were within a couple thousandths.

Not too bad for a cheapo set of gauges you may only use once. Of course, if you wanted a set to use on a regular basis I would definitely buy a much better gauge.

Thu Aug 27, 2015 7:43 am

jpjohns wrote: Measurements were within a couple thousandths.

and that is all it takes to make or break good oil pressure.

Thu Aug 27, 2015 8:29 am

jpjohns wrote: Just thought this would help. I bought a set of HF telescoping snap gauges to measure inside of the bores and bearing journals of my engine. I'm not a big fan of HF tools as I truly believe you get what you pay for but I brought these to work and measured them against a set of Starrett snap gauges and they were fairly close. Measurements were within a couple thousandths.

Not too bad for a cheapo set of gauges you may only use once. Of course, if you wanted a set to use on a regular basis I would definitely buy a much better gauge.

Those would be fine since you don't actually measure with them. Once you have them set by sliding them across the bore, you still have to use a micrometer to measure over the tips. A good mic is where the accuracy comes from.

Thu Aug 27, 2015 8:38 am

Someone knowing how to properly use a +/- .0001 mic, or even which tips you want on it is a completely different story.

Thu Aug 27, 2015 8:51 am

some of those gauges expand or contract when tightened . so.....not a lot of good. I tried to rework a set, there just machined too rough on the inner workings.(well the set I got was, so ill keep using my good ones)

Thu Aug 27, 2015 10:52 am

If you polish the the ends on those they work fine. I got repeatable results with them but by the nature of the beast ,you have to have a lot of patients and have the technique down. I have a higher quality one for cylinder bores only and it makes the HF feel look like a POS. :D

Thu Aug 27, 2015 11:16 am

For the $15 those cost, they are not horrible. They have to be very carefully used. They are poorly hardened and wear quickly compared to good ones.

Also if you dont have good micrometers to measure with...WITH a micrometer clamp to hold them....they are very poor for measuring bores.

For not much more....if you only do a few engines.... http://www.ebay.com/itm/HFS-2-6-DIAL-INDICATOR-BOR...41894052d9

This set works just fine. I replaced the dial gauge it came with, with a Starrett i had that is accurate to .0001" that slips right in (standard dial gauge size)

I tested it next to a Mitutoyo and a Sunnen and it is just as accurate.

the issue you will find with it is that the insulator on the handle does not prevent heat transfer (make something like I did)....and the contact points are not hardened well so they will wear if you work with these gauges constantly...like every day.

While they are plenty accurate and repeatable with a good dial gauge mounted in them...they are noot long term repeatable as a professional tool.

But as cheap as they are...if you build 1-2 engines a year or even only a couple every 3-4 years...at the cost for engine parts there is no excuse for NOT having at least a gauge like this of minimum quality. Ray

Thu Aug 27, 2015 1:08 pm

" fairly close. Measurements were within a couple thousandths"

That does not cut it for bearing work.

Thu Aug 27, 2015 4:35 pm

Basically junk. I made the same mistake Mark did, trying to improve them, wasted time. Not hardened steel !:roll:

Thu Aug 27, 2015 5:08 pm

A measuring device can't have hardly any force on it anyways or it will temporarily change the dimensions of the tool.

Adjust the bore tool so it is a little bigger than the bore but have the clamping mechanism loose enough so when you sweep it through (tilt one end) the gauge sizes it's self to the size of the bore but tight enough so that it holds the measurement. Put the tool back in and notice that you still have wiggling room. Use a calipar to make the guage longer little by little in steps until you can only VERY carefully get the tool to sweep through a arc at one end without having it bind with no wiggle room. As you sweep the tool you will notice that the arc from side (Pivot the tool) to side gets smaller and smaller. When the sidesways arc is as small as you can get it and still pass the arc in the tilting direction ,the measurement is accurate from what I can tell.

If you want to get some experience on the cheap of using one they will work if you feel like putting a polished surface on the balls.I used a rotodisc on them after I took them apart so I could easily spin the ball part with my fingers.

Thu Aug 27, 2015 5:42 pm

If your using Chinese parts for the rest of your engine the Chinese gauges will work perfectly [-o<

Fri Aug 28, 2015 4:21 am

I found a really old machining book once that had a method of measuring hole ID's using a rod slightly smaller than the hole. You needed an accurate measurement on this fixed rod and then you measured how much the rod moved on the one end side to side and calculated the hole size.

The movement had to be less than a certain amount of degrees, but I remember using it once for fun and it's an accurate way of determining hole size.

This is a very old school machinist method and won't be in modern books as you just need to "buy the tool". It might be in my one book with the correct definition of the engine lathe...one that isn't powered by your feet but some kind of motor (steam, gas, electric,etc).

Anyways, you might be able to use those Harbor Freight pieces as fixed rods to accurately measure any ID....if I can find that book.

Fri Aug 28, 2015 4:39 am

Found the book, it's the Machinist's Bedside Reader and he believed it to be an old Railroad method of method of measuring large holes for press fits.

Hole Size = Rod Length + C
C = (A*A)/(2B) - this will be in thousandths of an inch so divide by 1000 to get into inches for adding to rod length
A = sixteenth's of an inch of side to side movement
B = Rod Length

His example was a 4" hole....so the rod measurement being off by .005" leads to the formulas being off 7 millionths of an inch and 64th off on side to side movement results in less than a half thou off in the formula.

Obviously measuring the rod wrong will make your hole size wrong that you measure, but it shows the formulas aren't that sensitive to errors.

Fri Aug 28, 2015 8:42 am

I have a few harbor freight measuring tools, a dial indicator with mag base, a set of digital calipers and a measuring tape. i only use the calipers and indicator when the drawing calls for +- .030". anything better and a use my cheapo SPI tools. they're not near as good as starret or mititoyo, but the HF tools are an absolute joke. a freakin pair af calipers without a thumb wheel? really? :roll:

Fri Aug 28, 2015 4:22 pm

Casting Timmy wrote:
Hole Size = Rod Length + C
C = (A*A)/(2B) - this will be in thousandths of an inch so divide by 1000 to get into inches for adding to rod length
A = sixteenth's of an inch of side to side movement
B = Rod Length

Obviously measuring the rod wrong will make your hole size wrong that you measure, but it shows the formulas aren't that sensitive to errors.

Very cool!
it is sensitive to the radius on the end of your measuring rod.
one of the advantages of telescopic gauges is the raduis on the ends is not much sharper than it needs to be, so does not marr bearings, BUT, for the wiggle method you need a sharp raduis or point.

Fri Aug 28, 2015 5:17 pm

Modok, I would think that if the diameter of the tool is less than the bore that is being measuered ,it should work. Is this incorrect? :?

Fri Aug 28, 2015 5:37 pm

Sorry, no, the radius on the end of the rod does change the amount of wiggle. Try it in real life and I think you will understand quickly.
Small radius has more wiggle than large radius.

Fri Aug 28, 2015 5:43 pm

I get it now. It's true when using the Machinist's Bedside Reader method. If you don't use the wiggle method ,it does not apply.

Fri Aug 28, 2015 5:47 pm

RIGHT!
Except if your gauge is worn down, so the raduis is actually bigger than the hole, and then you can still get a good reading but you have to rock the gauge in the mic. I can handle that!
What I can't handle is when they don't slide smooth and tend to stick, giving a wrong reading. That's why they need to be made of hard steel, so there don't develop any sticky spots!!!

Fri Aug 28, 2015 5:51 pm

:wink: