I Created a Smooth Bore With a Tap

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SteveHGraham
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I Created a Smooth Bore With a Tap

Post by SteveHGraham »

I decided to be a man and redo the wheels on my wood vise. I bought some cast wheels from Enco, and I found a great deal on a 3/4-6 Acme tap on Ebay.

Today I bored a wheel out to about 0.590", which is correct, and I put the wheel in my drill press vise. I did not have a tap wrench big enough for the tap, so I used a socket wrench extension held in the drill press chuck.

I applied a little tapping oil, because I read somewhere that it's a good idea with cast iron. Then I applied pressure with the press while cranking the chuck manually.

I ended up with a smooth bore with the exact same profile as the tap. It cleaned out the wheel without making threads.

Explain. Immediately.
Last edited by SteveHGraham on Sun Apr 03, 2016 11:43 am, edited 1 time in total.
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John Evans
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Re: I Created a Smooth Bore With a Tap

Post by John Evans »

Pictures??
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SteveHGraham
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Re: I Created a Smooth Bore With a Tap

Post by SteveHGraham »

For diagnostic purposes or just so you can laugh?
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SteveHGraham
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Re: I Created a Smooth Bore With a Tap

Post by SteveHGraham »

This is really all I have.

This is after I took the socket thing out. The tap wasn't wobbling, so I put a pointy thing in the drill chuck and inserted in the center hole on the tap, and then I cranked with a wrench while pushing down on the tap with the drill press.
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04 02 16 tapping cast iron wheel on drill press.jpg
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GlennW
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Re: I Created a Smooth Bore With a Tap

Post by GlennW »

Too much pressure with the press while turning.
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SteveHGraham
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Re: I Created a Smooth Bore With a Tap

Post by SteveHGraham »

You're kidding. I was thinking the opposite. Are you sure? It felt like it was never going to bite.
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John Evans
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Re: I Created a Smooth Bore With a Tap

Post by John Evans »

Turning the tap in the correct direction??
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GlennW
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Re: I Created a Smooth Bore With a Tap

Post by GlennW »

SteveHGraham wrote:You're kidding. I was thinking the opposite.
That depends on how much and when.

If it didn't bite, it may very well have bored the hole while turning due to not pulling itself along with the helix.

If forced too hard the leading edges of the tap "teeth" could have cut faster than the natural helix action when being turned.
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SteveHGraham
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Re: I Created a Smooth Bore With a Tap

Post by SteveHGraham »

Slap John for me.

I'm not sure what to do with the next one now. I guess I'll try it with less pressure. Wheels are cheap.
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Magicniner
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Re: I Created a Smooth Bore With a Tap

Post by Magicniner »

If your tap doesn't bite then the hole may be undersize, even if it's to spec it can still be too tight for the tap and the conditions under which you're using it,

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SteveHGraham
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Re: I Created a Smooth Bore With a Tap

Post by SteveHGraham »

The tap seems really tight in the hole, but it measures 0.590" by calipers and telescoping gage, so you would think it was okay.
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scmods
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Re: I Created a Smooth Bore With a Tap

Post by scmods »

Steve,

Well, there goes your hundred attaboys!

Apparently the tap acted like a succession of square ended single tools rather than a helical cutter. The basic bore seems to be adequate, maybe even a little large according to the general table. Perhaps the tap did not have sufficient taper at the start (bottoming), or was dull. I don't have a lot of experience with Acme, but it is an awful lot of cut to make from scratch.

Why not try a boring bar with suitable tool and positive feed to make gradual cuts to rough this out and then finish with the tap. Cast iron should have ehough graphite for lubrication, and will not retain the crumbly chips like a fluid.

Hope this helps.

Bill Walck
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