Cut off blades, Inside diameter measurments, and backhoe woes

[TIB]

And can someone tell me how to get accurate inside diameter measurements? Am turning bushings for an OLD (1965) Case backhoe, and am having a hard time getting accurate inside measurements on the holes I've bored.

I've gotten to the point of turning a round stock a few thousands under the desired size, then inserting it into the bored hole. Using feeler gages I can a size and turn a bushing to fit. But this is a painfully slow process.

FYI. Have been honing the inside of the bore to get the surface smooth, andusing 220 grit emery cloth on the OD of the bushing to get its surface smooth.

Also

I've noticed there are different "P" series ofcut off blades. For example P3 and P4 Both have the same width, height andlength. What are the differences?

 

[Ray C]

As far as bore measurement, ball gauges or ID telescoping gauges work pretty well for 90% of my tasks. If you take your time with these, you can easily measure into the half-thou range. Once you fit the gauge inside the bore, you remove it and measure with a regular mic. These are from Shars.com...

If you really need to get the inside of a bore smooth and even, you'll have a hard time with emery cloth. If you can, set it up in a lathe or mill and power-ream it. That's the 1st line of defense. Next takes some specialized stuff such as an internal post grinder. There are various designs ranging from expensive versions of a dremel tool to adapter shafts on traditional tool post grinders.

Ray

And can someone tell me how to get accurate inside diameter measurements? Am turning bushings for an OLD (1965) Case backhoe, and am having a hard time getting accurate inside measurements on the holes I've bored.

I've gotten to the point of turning a round stock a few thousands under the desired size, then inserting it into the bored hole. Using feeler gages I can a size and turn a bushing to fit. But this is a painfully slow process.

FYI. Have been honing the inside of the bore to get the surface smooth, andusing 220 grit emery cloth on the OD of the bushing to get its surface smooth.

Also

I've noticed there are different "P" series ofcut off blades. For example P3 and P4 Both have the same width, height andlength. What are the differences?

 

[valleyboy101]

I agree with Ray. For work the size of the pins in a backhoe I would use telescoping gauges and then measure with a micrometer or at a minimum a caliper. The ultimate would be an inside micrometer but you probably don't need that degree of accuracy.
Michael

 

[TIB]

Thanks for the reply and help. Probably should explain that I was talking about the OD of the bushings for the pins and the ID of holes I bored. In this present situation I’m working on the outriggers. The machine did not have bushings in the outrigger brackets originally, and the wear made boring necessary.

I’m using O1 drill rod hardened then tempered for the bushings, and old hydraulic cylinder rams for the pins. Don’t know how well either will last, but the machine only gets 100 to 200 hours a year on it. The only reason I cleaned up the OD of the bushing and the ID of the bored hole is so the mating surfaces have more consistent contact areas.

This afternoon I did set down and practiced with the telescopic gage, but still could not get closer than .003 consistently. I am checking the telescopic gage with a 1 to 2” micrometer.

I think it will take more experience on my part to get very accurate with the telescopic gage.

The bushings are hard enough that they don’t seem tocompress when pressed into place.

Just FYI I’m working with 1-1/2 to 2 inch pin size.

Thanks again for the advise,
Tom

 

[Ray C]

I gotcha now... You're drilling the frame of the machine and will stuff a bushing in there then, a pin goes inside the bushing... If that's the case, the hole you drilled is probably pretty rough. Is there any chance you can ream that hole to clean it up? If so, you won't need to measure the hole when you're done because it will just be the size of the reamer you used. Reamers are only good for taking off 2-3 thou so get the hole undersized but close and use the reamer to straighten and get the ridges out.

What is the bushing material made of? If it's brass or bronze, it should go inside the hole without too much fuss.

The ball and telescopic gauges take a little practice. You must hold the shaft straight. One end is wider than the the other. Compress the gauge, insert in the hole, release the telescope, hold it straight and steady while tightening then, tip it out so the skinny end of the telescope comes toward you. That way, it won't compress it. If you tip it toward the fat end, it will compress a little.

Ray

Thanks for the reply and help. Probably should explain that I was talking about the OD of the bushings for the pins and the ID of holes I bored. In this present situation I’m working on the outriggers. The machine did not have bushings in the outrigger brackets originally, and the wear made boring necessary.

I’m using O1 drill rod hardened then tempered for the bushings, and old hydraulic cylinder rams for the pins. Don’t know how well either will last, but the machine only gets 100 to 200 hours a year on it. The only reason I cleaned up the OD of the bushing and the ID of the bored hole is so the mating surfaces have more consistent contact areas.

This afternoon I did set down and practiced with the telescopic gage, but still could not get closer than .003 consistently. I am checking the telescopic gage with a 1 to 2” micrometer.

I think it will take more experience on my part to get very accurate with the telescopic gage.

The bushings are hard enough that they don’t seem tocompress when pressed into place.

Just FYI I’m working with 1-1/2 to 2 inch pin size.

Thanks again for the advise,
Tom

 

[Tony Wells]

Ray, I have to disagree with your method of using the telescoping gages.The idea is to deliberately set them at a slight angle in the bore, then lightly snug the lock up on them, then pull the handle towards you to compress the telescoping sections until they are exactly the same length as the bore diameter. This happens only if you "sweep" it through the bore. This causes them to self-center in the bore radially, and match the bore perfectly. Of course, a large part of the accuracy you get is just how tight you run the locking rod by turning the end section of the handle. Too tight and you either won't be able to move the gage through that short arc section, or too loose and it won't self-center or won't hold the measurement. You'll never get accurate results guessing at the proper position and then locking the gage for a measurement. It's easy to get within a couple of tenths if you use them right. I'm sure there is a youtube vid of it. If not, someone should make one. Mit makes the best telescoping gage, hands down. Smoothest action. The probably have some instructions in their catalog, too.

 

[TIB]

Ray I'm finally able to get back on to let you know that I've finally gotten the ID readings to be consistant. Found that when tightning my telescopic gauges they were changing. When tightened enough so the micrometer's ratched would not compress the gauge, the gauge moved from the origional position.......guess you get what you pay for.

Ordered a new set of brand name telescopic gauges and can get consistant readings.

By the way I missed the part of your question about what the bushings were made of. I'm using drill rod. Am hardening it and then tempering. Maybe this will keep them from cracking.

You are right about the grinding etc. I'm hoping that working them through to 2000 sand paper then polishing with a buffing wheel on a rotary sheet rock cutoff tool will get them smooth enough to last a few more years.

Thanks again for the help and support.

Tom

 

[Tom Griffin]

Telescoping gauges definitely require some practice to learn how to measure with them with any consistency. As Tony pointed out, the proper way to use them is to hold the handle at a slight angle to the centerline of the bore, snug up the lock a bit and sweep the gauge through the center of the bore. I like to wiggle the handle a bit to help the tips of the gauge to find the largest point on the bore. Once you do the sweep thing, you must resist the urge to tighten the gauge since any telescoping gauge can move after taking a measurement if it's tightened. The tightness of the lock is not as critical as you might think. Practice on a bore and try tightening the lock different amounts so you can see how it affects repeatability.

Tom

 

[Ray C]

Tom: I'm glad you're making some progress. Just a quick note of due caution... If these are for bucket pins or something similar, be cautious about home made parts. A sudden snap can injure people. If this is for your personal equipment and you don't intend to lift the Rock of Gibraltar, you can gradually test the equipment and gain confidence. Stuff like bucket pins are where careful metal selection and heat treating etc play very important roles.


Tony: I'll try that method. Sounds good. Over time, I've managed to get pretty consistent and successful readings with my home brew technique but, I'm not too old to try/learn new tricks.

Ray

Ray I'm finally able to get back on to let you know that I've finally gotten the ID readings to be consistant. Found that when tightning my telescopic gauges they were changing. When tightened enough so the micrometer's ratched would not compress the gauge, the gauge moved from the origional position.......guess you get what you pay for.

Ordered a new set of brand name telescopic gauges and can get consistant readings.

By the way I missed the part of your question about what the bushings were made of. I'm using drill rod. Am hardening it and then tempering. Maybe this will keep them from cracking.

You are right about the grinding etc. I'm hoping that working them through to 2000 sand paper then polishing with a buffing wheel on a rotary sheet rock cutoff tool will get them smooth enough to last a few more years.

Thanks again for the help and support.

Tom

 

[TIB]

Ray you are right on the nose about "Homemade Parts", they are not to be trusted. This is a machine I use on the farm only, and would never do something like this for anyone but me, and if pins and bushings were still available from Case it would have been less expensive to purchase them, even considering that my labor is fairly inexpensive.

For the pins I've used 4340 and 4140. Have not made any attempt to harden them. I hope they wear and produce enought slop that before they break the machine is not usable.

I've had machine for over 20 years, and don't use it enough to warrent anything newer, nor do want to sell as a working machine. Even selling "as is where is" over the years I've done so many repairs I'd hate to be responsible for something going wrong at a critical moment. It's sad, but I don't think you can get away from liability on anything that has the ability to "overhead" lift even years after the fact.

Tom