Pros and cons of larger chucking machine reamers V. Boring bar

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Glenn Brooks
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Pros and cons of larger chucking machine reamers V. Boring bar

Postby Glenn Brooks » Sun Aug 13, 2017 12:33 am

I have 25 to 30 6" diameter cast iron RR wheels that I need to turn for 1" ID axles. Maybe 1.25" ID, haven't decided final axle size yet.

Are there any deal breaker issues with drilling and reaming the holes in the wheels with a 1.0" machine chucking reamer, versus boring to size with a boring bar?

I haven't bought the reamer yet, but found some good prices on NOS 1" and larger reamers, which I could order - if this is a feasible procedure on a manual 14" lathe.

Thanks
Glenn
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Harold_V
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Re: Pros and cons of larger chucking machine reamers V. Boring bar

Postby Harold_V » Sun Aug 13, 2017 1:53 am

Frankly, I wouldn't ream even if I owned the required reamer. I'd bore, and for more than one reason.
One of the issues you'll face with a reamer is alignment. As large as this one would be, it won't be forgiving of misalignment, which is very common in lathes. It can yield various problems, none of them to your benefit. Taper is one of them, as is out of round. It also may or may not cut size, with the likelihood being better that it will if you ream only a few thou. That, of course, would depend on alignment, once again, or if you use a floating reamer holder.

One more thing to consider. Drilling and reaming often yields eccentric holes. Boring, even if followed by reaming, is highly recommended. By making that decision, you can leave just a few thou (no more than five) for the reamer. The less material you remove, the better the chance the reamer will cut on location, and size. A damaged flute on a reamer, accompanied by an excessive amount of material to be removed can often result in the reamer being deflected, creating an oversize (bell mouthed) hole, which gradually returns to proper size as the reamer deepens in the hole.

From the above comment, you likely understand that a reamer has the capability of yielding various sizes, often in the same hole. Not suggesting that it would in your case, but it's one of the things you need to keep in mind. Also, assuming it yields a tapered hole, if you're relying on a press fit, you may or may not end up with one, or it may have enough taper to permit the wheel to walk on the axle. All in all, boring, done properly, is heads and shoulders better. It's just slower, and demands a little skill on the part of the operator.

H
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Glenn Brooks
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Re: Pros and cons of larger chucking machine reamers V. Boring bar

Postby Glenn Brooks » Sun Aug 13, 2017 3:34 pm

Thanks Harold,

Good comments, as usual! I'll stick with my boring bar and save the sixty bucks.

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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SteveR
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Re: Pros and cons of larger chucking machine reamers V. Boring bar

Postby SteveR » Sun Aug 13, 2017 7:48 pm

Harold_V wrote:One more thing to consider. Drilling and reaming often yields eccentric holes. Boring, even if followed by reaming, is highly recommended. By making that decision, you can leave just a few thou (no more than five) for the reamer. The less material you remove, the better the chance the reamer will cut on location, and size


So in the interest of productivity, drilling is faster than boring - if I drill to 15/16, then bore this to 63/64, then ream to 1.0000 what is your thought on this?

1) In the context of train wheels for the live steam hobby?
2) In the context of best possible?

Always trying to learn.
SteveR
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Harold_V
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Re: Pros and cons of larger chucking machine reamers V. Boring bar

Postby Harold_V » Mon Aug 14, 2017 1:20 am

My thoughts are no different. If you wish to ream, make sure boring is part of the equation, which guarantees concentricity. It also allows one to choose the amount of material remaining to be reamed. My comments in the previous post should help make that clear, but I'd most likely leave less than .015" for the reamer. Probably more like .005".

So readers understand, I'm not a huge fan of reamers. They work reasonably well in many circumstances, and they're certainly faster than boring, but the negative attributes (bell mouthed holes, out of round (multi-sided) holes and tapered holes, plus the odd poor finish, for me, make them less than desirable. That, of course, depends on the application. I really like them for working with dowel pins, and I keep sets on hand that are known to yield the desired fits. I also used a 3/8" chucking reamer when I ran the face plates for the light switches in my new house. Over 100 holes, which accepted the Delrin push buttons, were reamed with excellent results, but I had to use an extraordinary feed rate (ran the face plates on my Hass CNC toolroom mill) in order to avoid chatter at the entrance, and to achieve a desirable finish. The holes (and the face plates) turned out exceedingly well. Clearly one of the times a reamer was a good choice.

H
Wise people talk because they have something to say. Fools talk because they have to say something.


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