Drilling larger size holes in the side of 4" bar

vonleyser · Oct 23, 2019

My upcoming task is to machine holes of various size down the length of a 4" diameter bar, 48" long.

My question is what tool/tools would be best to rough
these things out with, and then finish with a boring head, or just
get a 1-1/2" hole in all locations and use boring head to finish.
(I get paid by the hour)

1 piece order with a possible 2 more to follow.

machine 3 horse vertical mill, next size up from a series 1 Bridgeport,
will have to do this in 2 steps.

Thoughts/recommendations lets hear them.

Don't know how to rotate picture ? computer dummy

Rob F. · Oct 23, 2019

Cant help you with boring the holes but whenever I see a print like that, it pisses me off to no end. What are the tolerances on those measurements with 2 decimal places? +- .03, or +- .02?

So if you are within tolerance on each dimension but .01 off of perfection, at say 4.01" and 3.01 on the first one you will be .11 off location of the last hole but still well within the prints tolerance. :eek:

The better way to dimension a part like this is to zero one corner, or edge, and add the location of each holes center progressively down the line. So end is 0, first hole is 3.00, second hole is 7.00, third is 11.00 until the end at 46.72.
This way the tolerances can not stack up, so to follow the same .01 off location each hole will be only off by .01, not the first off by .01 and the last off by .11. This also cleans up the drawing by eliminating all the dimension lines since each measurement should be written right on the center line of each hole.
Rant over :cheers:

Illinoyance · Oct 23, 2019

Ignoring the tolerance issues.
I would drill through 3/4" then follow with the APT multi-tool. Use the blade size appropriate to leave stock for boring.

HuFlungDung · Oct 23, 2019

Rob F. said:
Cant help you with boring the holes but whenever I see a print like that, it pisses me off to no end. What are the tolerances on those measurements with 2 decimal places? +- .03, or +- .02?

So if you are within tolerance on each dimension but .01 off of perfection, at say 4.01" and 3.01 on the first one you will be .11 off location of the last hole but still well within the prints tolerance.
The better way to dimension a part like this is to zero one corner, or edge, and add the location of each holes center progressively down the line. So end is 0, first hole is 3.00, second hole is 7.00, third is 11.00 until the end at 46.72.
This way the tolerances can not stack up, so to follow the same .01 off location each hole will be only off by .01, not the first off by .01 and the last off by .11. This also cleans up the drawing by eliminating all the dimension lines since each measurement should be written right on the center line of each hole.
Rant over

Holes on 4" centers. Is that so damn hard to comprehend?

Rob F. · Oct 23, 2019

HuFlungDung said:
Holes on 4" centers. Is that so damn hard to comprehend?

Yeah, each one measured from the last, Per his other thread of same title, a 2 decimal place tolerance is +- .01 so my analogy would be max tolerance to still have a good part per print but probably useless in reality.
What is the best way to make the part on OP's oversize bridgeport? If he has a dro then start at one end and crank the handle till it reads 3.00 and drill.then do you re zero the dro and go to 4.00 each time or just crank until it reads 7.00, 11.00, 15.00 etc... Has to be more accurate to not keep re-zeroing at every hole.

Not sure it would matter much without dro.

thermite · Oct 23, 2019

Rob F. said:
Cant help you with boring the holes but whenever I see a print like that, it pisses me off to no end. What are the tolerances on those measurements with 2 decimal places? +- .03, or +- .02?

So if you are within tolerance on each dimension but .01 off of perfection, at say 4.01" and 3.01 on the first one you will be .11 off location of the last hole but still well within the prints tolerance.
The better way to dimension a part like this is to zero one corner, or edge, and add the location of each holes center progressively down the line. So end is 0, first hole is 3.00, second hole is 7.00, third is 11.00 until the end at 46.72.
This way the tolerances can not stack up, so to follow the same .01 off location each hole will be only off by .01, not the first off by .01 and the last off by .11. This also cleans up the drawing by eliminating all the dimension lines since each measurement should be written right on the center line of each hole.
Rant over

WTF samattahwichyoo?

No patience? No sense of anticipation?

Machinist should MISS an opportunity to bust a draughtsman or "Design Engineer" CHOPS by making it right in spite of the print, and lecturing his truant ass AFTERWARDS?

Where is Carlye when yah NEED her?

YouTube

Gittin' right instant-gratification lazy, we are...

Rob F. · Oct 23, 2019

HuFlungDung said:
Holes on 4" centers. Is that so damn hard to comprehend?

If you were the customer I was making the part for and gave me an answer like that I would be VERY tempted to make sure each hole was .008 off location. This would be well inside the .010 tolerance stated on the print, yet putting your last hole .088 off of its perfect location. Point is to make a drawing that is useful for everyone, this one is a bullshit drawing.

Cole2534 · Oct 23, 2019

Rob F. said:
If you were the customer I was making the part for and gave me an answer like that I would be VERY tempted to make sure each hole was .008 off location. This would be well inside the .010 tolerance stated on the print, yet putting your last hole .088 off of its perfect location. Point is to make a drawing that is useful for everyone, this one is a bullshit drawing.

Being a deliberate pain in the ass doesn't sound like very good customer service.

That project looks pretty damn labor intensive, and I don't see any way to speed it up on a manual mill. Grab a chair, it's going to be a while.

HuFlungDung · Oct 23, 2019

Rob F. said:
If you were the customer I was making the part for and gave me an answer like that I would be VERY tempted to make sure each hole was .008 off location. This would be well inside the .010 tolerance stated on the print, yet putting your last hole .088 off of its perfect location. Point is to make a drawing that is useful for everyone, this one is a bullshit drawing.

You sound like you are arguing that 4 + 4 + 4 = 12.024

Scalar quantities do not have errors in the numbers themselves. The tolerance uncertainty comes from the machine's characteristics, not the drawing's. Whether you have to crank the table screw 16 turns to go 4" or 48 turns to go 12, the error in position is basically one quantity, even if you stop for a rest after every turn. The screw and nut might have .010" backlash, but it's .010" possible error whether you move 1 revolution or 48 revolutions. It is NOT going to be .480 out of position after 48 revs.

thermite · Oct 23, 2019

Cole2534 said:
Being a deliberate pain in the ass doesn't sound like very good customer service.

Dunno. It's California.

Bullshit-drawing seems to pay better than Powerball drawings.

Pain in the ass seems to have been working a right treat for various Congress-critters as get re-elected year after year, his State.

What could possibly go wrong? Get various holes out of line?

More the merrier. Just run the hole-production batch of 'em for Pretzelbent at the same time, see which ones are Russian ass-ettes!

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Drilling larger size holes in the side of 4" bar

vonleyser

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Rob F.

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HuFlungDung

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Rob F.

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thermite

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Rob F.

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Cole2534

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thermite

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