Drilling top dead center AND vertical on a tube?

Drilling top dead center AND vertical on a tube?

Joined: October 21st, 2001, 3:36 am

November 3rd, 2008, 4:17 am #1

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

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Joined: August 22nd, 2001, 3:27 pm

November 3rd, 2008, 12:49 pm #2

snug fit in the TP. hole. I put one end in the TP. hole, and chuck the other end in the drill chuck, now I know the hole is alined, I position the vise jaws To grab the part exactly as it's being held, by the chuck. hth.
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Joined: July 31st, 2003, 11:16 pm

November 3rd, 2008, 2:07 pm #3

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

nm
Last edited by Haywood_Jablomi on November 3rd, 2008, 2:14 pm, edited 1 time in total.
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Joined: October 30th, 2007, 2:27 am

November 3rd, 2008, 4:03 pm #4

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

And you can use an edge finder to pick up the edge and move the exact distance to center. If it has to be exact that's the best way.

A good trick on the drill press is to turn a short round piece of the same diameter and ream a hole through the exact center that's the diameter of the bit. Then mount the work in the drill press vise with the round piece above. Being the same diameter the vise should grip both and put the bushing on center. Of course it doesn't always work that well depending on your vise...

Nick,
From ruralburbian Philomath.
anotherairgunblog.blogspot.com
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Joined: October 21st, 2001, 3:36 am

November 3rd, 2008, 10:37 pm #5

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

I thought of the metal dowel or drill bit into the holle and it seems it's the most practical solution in conjunction with the tube centering jig.

Still open to all ideas.

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Joined: October 12th, 2008, 7:19 pm

November 10th, 2008, 2:35 am #6

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

<p>For Example:  Say I want a 1/4" hole centered in 1/2" bar stock.  I secure a piece of scrap material (plastic, wood, metal, whatever...) in my vise & clamp my vise down.  Then I would drill a 1/2" hole into the scrap.  Remove the 1/2" drill bit, but don't move anything else, place my 1/2" bar in the hole from above if short or from below if longer.  This will center the  1/2" bar directly under my chuck.  Now you can place your drill bits into the chuck to step up to the desired hole </p><p>This is just the only way I figured out how to do it, but I have formal shop training, so if this is a bad way, would someone PLEASE let me Farrow. I can use all the guidance I can get. </p><p>Tight Groups,  Brent</p>

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Have some S410 vids at
http://www.youtube.com/JustMyVids01


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Joined: July 9th, 2003, 7:23 am

November 15th, 2008, 3:24 am #7

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

If the hole is deep enough the new oversized drill bit will follow the hole, same for the tap. You could first use a drill bit that fits into the existing hole then change up to the size you want. If for example your enlarging the port hole size then it really wont make much differance as the wall is pretty thin. If your using just a drill press then you can use "V" blocks, if you have a close fitting drill bit you can align it that way. Gage pins are another way to center an existing hole.
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Joined: February 4th, 2005, 11:51 pm

November 20th, 2008, 3:23 pm #8

I have the tube centering jig and I saw the trick of putting a ruler/straight edge on the top of a tube and bringing the drill press down on the straight edge, if it's horizontal you're TDC but is this it? Are there any "shop" or production methods to determine TDC and that an existing hole in the cylinder TDC also.

I want to tap the existing treads in a Crosman valve retaining screw and enlarge some exitisting barrel ports and I want to make sure I'm TDC and the existing holes are truly vertical, I don't want the new threads or barrel port at an angle.

...you can also use a chucked dial test indicator to find TDC.
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