Drilling a deep hole

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lampy

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I'm working on a non engine related project and I need to drill a 3/4" hole 6" deep through a piece of aluminum square stock. I need to fit a 3/4" DOM tube in the block, the finish on the hole isn't critical I will hone / size the hole for the fit I need. I will be using my 12X36 Craftsman lathe with a 4 jaw to do this.
I have 3/4" drill rod I'm going to make a D-bit from, my question is should I put a point on the D-bit or leave it square on the end with a slight chamfer on the edge?
My plan is to predrill with a smaller size, I have a 3/8" D-bit made that is long enough. I could make up a 1/2" D-bit to follow up with then finish with the 3/4" D-bit.
My other thought is to use a 3/4" ball end mill I have to start the hole then finish boring it through with the D-bit.
Thoughts and opinions please.....
 
Have you checked the size and roundness of the conduit? I would expect that it's neither 3/4" diameter nor round. Are you looking for a slip fit or are you locking it in place? If you're locking it the size and roundness might not matter as much, I'd be tempted to just drill through with a 3/4" drill and be done - it'll likely come out a little oversize anyway. You can also singlepoint bore 6" with no problem,. easier than making a d-bit for a non-precision hole.
 
i to would just drill it 3/4. do it in a piece of scrape to see how it will fit. the d bit is like a reamer and is made to only remove a small amount of stock, not 3/8 if you use the 3/8 drill first, which if it is d bit will not drill to good. good luck jonesie
 
The pipe will be locked into place with a fastener of some sort, I'll work out that detail later. I did buy a coffee can full of bits at an auction last year I'll have to look through it and see if there is a 3/4" bit in it. I could make a collet to add the extra inch or so I will need to finish the hole. I thought about using a boring bar but don't have one long enough. I'm trying to avoid having to disturb the setup once I get it lined up in the four jaw but may end up going that route. Drill or boring bar to the middle, flip the work around and hope the two holes meet somewhat lined up....
 
I'm not familiar with a Swiss bit, looks a lot like what I know as a D-bit....
 
lampy said:
I'm working on a non engine related project and I need to drill a 3/4" hole 6" deep through a piece of aluminum square stock. I need to fit a 3/4" DOM tube in the block, the finish on the hole isn't critical I will hone / size the hole for the fit I need. I will be using my 12X36 Craftsman lathe with a 4 jaw to do this.
I have 3/4" drill rod I'm going to make a D-bit from, my question is should I put a point on the D-bit or leave it square on the end with a slight chamfer on the edge?
My plan is to predrill with a smaller size, I have a 3/8" D-bit made that is long enough. I could make up a 1/2" D-bit to follow up with then finish with the 3/4" D-bit.
My other thought is to use a 3/4" ball end mill I have to start the hole then finish boring it through with the D-bit.
Thoughts and opinions please.....

I would have thought that the best solution is to drill the hole to the min diameter of the longest boring bar you have and then finish the hole with the boring bar, bore it to size.

Regards,

A.G
 
lensman57 said:
I would have thought that the best solution is to drill the hole to the min diameter of the longest boring bar you have and then finish the hole with the boring bar, bore it to size.

Regards,

A.G
I'm not clear on what you are saying..... The longest boring bar I have is to short to bore a 6" hole, I would have to remove the work from the 4 jaw chuck to flip it .... disturbing my setup and more than likely the two holes will not align perfectly. I may end up going this route if I can't come up with a workable solution.
 
Clamp and dialup the block onto your cross slide.
Make a long bar with a cutting tool in the middle.
Then line bore.
You can also put the tool to one end if needed so you can end for end it to do even longer holes ( so long as you dial up the boring bar first ).
Hope this helps. :)

line bore.jpg
 
I thought about this method, a lot more set up time but it's an option I'm keeping in mind. Thanks
 
I really think that you're over thinking the problem - it doesn't seem to be a precision hole in any way - just poke it through. If you don't have a 3/4 drill bit get one from the hardware store, if they're too expensive get one from eBay (150288859242 is $10 before shipping and seems to be MT2). If it's too short or can't be grippeddrill into the shank (it's softish) and silver solder some 1/2 round steel to extend the drill and give you something to hold onto.

The number of hours I worried about the best way to do something and avoided doing anything probably could have been put to making a dozen engines. Just poke the hole through and get it over with.
 
rkepler said:
The number of hours I worried about the best way to do something and avoided doing anything probably could have been put to making a dozen engines. Just poke the hole through and get it over with.

Yep if the hole ain't a holier than thou hole, drill it and forget it. ;D

Best Regards
Bob
 
There is not too much thinking to do, you've got to get your deep hole made.

Either drill it from both ends then bore it to exact size, or buy or make a long series drill, drill from one end and then bore or ream it. You can't drill from both ends and expect to ream it, it will just follow the most probably two offset holes and you will end up with a banana shaped oversized hole.

If you haven't got a boring bar, then you will have to make or buy one, otherwise that hole is never going to get finished.

BTW, on some jobs it can take hours to set up and only seconds or minutes to machine it. That is the name of the game and the secret to what we do..

Have a look at my signature line below.

John
 
lampy said:
I'm not clear on what you are saying..... The longest boring bar I have is to short to bore a 6" hole, I would have to remove the work from the 4 jaw chuck to flip it .... disturbing my setup and more than likely the two holes will not align perfectly. I may end up going this route if I can't come up with a workable solution.

Hi,

As suggested by others, you will have to either drill undersize and bore it to size while the work is on the 4 Jaws, or the work has be mounted on the cross slide and bored using a long, home made boring bar. Reaming does not unfortunately guarantee the hole is true as it follows the path the drill has made, it just brings the hole to size. No matter what method you choose, this is going to be a time consuming job if you want to do it right.

Regards,

A.G
 
Thanks for all the input, I'm off to the Enco web sight.....
 

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