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How to enlarge the inside diameter of a tube?


freddy333

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Ziggy or anyone - I am looking for a recommendation on the best/safest way to enlarge the inside diameter of a tube that contains splines (which can be removed after installation)

image1-21.jpg

The tube is fairly rare & I have only the 1, so I have to get it right the 1st time. The problem is that the crown shaft is too large to fit through the narrower, inner (splined) diameter of the tube, so I need to remove some of the interior material to fit the crown's shaft through. The 2 methods I am considering are broaching & drilling.

The simplest & safest method is broaching. My thought is to install the tube into the case, after which I can broach out the splines. But I am not sure if a broach is strong enough to be able to remove the steel from the tube?

My alternate idea is to, again, install the tube into the case & then use a drill to enlarge the hole. The trouble with this method is that I can picture the drill biting right into the inside walls of the tube, grabbing ahold of it & then spinning the hell out of it, thus destroying both the tube & the threading in the case. :(

Anyone have experience with this type of procedure?

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I would say the safest way would be to install it in a collet on the lathe, then with a drill in the tailstock you can drill it and control the feed rate.

High speed and cutting fluid should prevent any damage from the drill catching.

I fabricated a new casetube for a genuine PAM crown, and drilled a solid piece of steel this way without any problems or grabbing.

RG

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What is the best/safest non-lathe option (I do not have access to a lathe)?

I would install the crown in the case and then drill it. You would at least have some stability that way. I assume you have a drill press. I have started using reaming bits to enlarge holes (like lug holes). They work much better than regular drill bits. You have such a small amount of material to remove. I think either bit would be fine in this case.

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old school tube eh?

Those old tubes, needed to be installed, then enlarged with a reamer. I've done a couple and it is not that big of a deal, but I wasn't too worried about it, as I was using aftermarket tubes. but do it by hand. safest and easiest way. just take a little material off at a time until your crown fits.

PM automatico... he'll give you the 411.

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My guy at the counter of my local supply house, just sold me a regular reamer. He told me there is a reamer made for this job, but they would have to order it in. If you have an inexpensive aftermarket tube, practice with that first, but I'm sure you will be able to get it the first time around.

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