Thread: Reamers
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Old 01-14-2021, 11:58 AM   #9
JayJay
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Join Date: Jan 2020
Location: SF Bay Area
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Default Re: Reamers

Quote:
Originally Posted by Tim Ayers View Post
I have a Snap-On adjustable reamer and an old .814 king pin reamer.

My question is, I seem to have trouble setting the adjustable reamer correctly. Meaning, when I measure the sizing, it fluctuates enough with the slightest movement of the caliper that it's out of spec.

When measuring an adjustable reamer, I'm assuming you want to measure the outer most edge of the cutting blades for the correct sizing.

Any tips for setting up an adjustable reamer would be greatly appreciated.

Thanks,
Tim - I'm not a huge fan of adjustable reamers either, but they do have their place. I never mic an adjustable reamer and then use that as the actual dimension. Instead, what I do is set the reamer well below what I expect is finished dimension, run it through, burnish the hole lightly to get rid of high points, and then measure the diameter using either gage pins or mic. If it's still too small I increase the diameter of the reamer slightly (say 1/4 turn of the adjusting nuts) and repeat until I'm satisfied. Keep track of how much the diameter of the resulting hole increases as you turn the adjusting nuts and that will give you an idea of how the reamer reacts. It's slow, yes, but if that's what you have to work with, you need to take your time.

And it's important that all parts of the adjustable reamer be clean. It relies upon the cutters moving on tapered internals, and you have to be sure all surfaces are clean or else the individual cutters don't have a chance of moving similarly when you adjust them. I take mine apart and clean thoroughly before each use and afterwards (when I remember...). Light machine oil to coat between uses.

As Brent points out, finish quality depends on a lot of things. In general, an adjustable reamer, because the cutters are individually machined and mounted on the reamer instead of gang machined out of a solid piece like a fixed-diameter reamer, will never achieve the quality finish of a good fixed-diameter reamer. And I've not seen a spiral adjustable reamer, only straight (spiral reamers have a shearing action that lends itself to a smoother cut). But for some applications where the fit is not super critical they may be sufficient. For others (e.g., kingpin, distributor) where tolerances are much tighter, I would not recommend using adjustable reamers.

My $0.02 worth.

JayJay
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