Deep Drilling In aluminum block

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mayhugh1

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Hi everyone,

A while back I purchased the Martin Ohrndorf V-12 plans. I've been studying them for a while to get an idea of the construction. I found a supply for 7075 aluminum for the crankcase at a reasonable price. One part has me a bit stumped so I'm trying to wrap my head around the problem before considering starting the project.
The main bore is 42mm through the crankcase which is approximately 8 1/2" long. I've been trying to find a 1.5" drill bit to have a starting point for line boring but usually the bits are way too short on unreasonably priced.

At my disposal I have a Bridgeport and a 13x40 lathe. My first thought was mount the block on the carriage and find the right drill bit and mount that in the spindle. Then leave the setup and install a line boring bar to get to the final dimension.

The crankshaft has aluminum bearing supports, which match the 42mm hole diameter and have press fit bearing. The consistency of the holes seems more critical than the dimensionally accuracy as these parts can be made to suit.

Thank you for any feedback,
Kyle
Maybe leave some excess stock on all sides of your workpiece so you can re-square it around the hole if drilling wonders off. - zterry
 

ajoeiam

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I meant gun drills sorry


also try graingers
Graingers likes to price its stuff in the platinum/palladium category in my looking!
Great for big outfits that want to single source but not very friendly for little folks!
 

Bentwings

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Graingers likes to price its stuff in the platinum/palladium category in my looking!
Great for big outfits that want to single source but not very friendly for little folks!
If you look on he internet under blondiehaks you tube there is a good video and explanation of how she did a lone bore on her lathe. By the way she does some excellent work and explains ans mistakes and how she fixed them she is an excellent model machinist and a young lady besides. I worked with a “ roadie the riveter “ type woman in my early years she was all navy flaming red hair and personality to match. Very good machinist. Too. Blonde has a smaller lathe Ethan yours so you might have to work at the extreme limits and make your own boring bar but it can be done.
Byron
 

Bentwings

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If you look on he internet under blondiehaks you tube there is a good video and explanation of how she did a lone bore on her lathe. By the way she does some excellent work and explains ans mistakes and how she fixed them she is an excellent model machinist and a young lady besides. I worked with a “ roadie the riveter “ type woman in my early years she was all navy flaming red hair and personality to match. Very good machinist. Too. Blonde has a smaller lathe Ethan yours so you might have to work at the extreme limits and make your own boring bar but it can be done.
Byron
im sorry I didn’t mean to toss something out that you might not know about.
Gun drills are usually long single flute drills. Often hollow so cool at can be plumped through them drill pints are ground to be self centering like split point you usually center drill and maybe counter sink a short ways to get started. Obviously they are long skinny things so you have to be gentle drilling small holes. You need to make sure you are cleaning chips out too . The coolant hole using pressure helps flush chips out. It takes a fancy holder/ spindle arrangement to provide coolant though the drill. You cal do manual drilling as long as you can clear chipset often a lot of cranking drill handle up and down . It’s been awhile sinice I’ve used them but I’ve done some small long holes over the years early car crankshafts didn’t always have the best oil holes they are tough materials too . Often these are carbide tipped but with nice cutting edges already ground in they drill pretty well

byron
 

giel

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sandvik-coromat they havr them in the collection deep hole drills.. but you can also do it what they call kotteren in the Netherlands.. using a smaller drill and offsetting it you can drill holes 40% wider than the drillbit,big advantage is the chips can exit very easy and it aids in precision
 

kylenlord

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Thanks again for all the feedback guys.

I think at the very least Terry's approach is spot on. I made sure to get a big enough block that if the drill should wander, there's enough room to account for everything else.

Petertha, very nice job on the rendering. I may do the same in fusion. I'm toying with the idea of cnc routing the top deck features. I'll have to do some practicing first. I do have access to McMaster through my work. Most of my materials and tooling comes from them. We work in small enough sizes most materials don't break the bank.

By any chance did you look at how the intake and exhaust tubes mount to the heads? The plans basically say to glue them in, which I would want to try for something more elegant.

Bentwings, thank you. Yes I follow blondie hacks on Instagram, I'll go back and review her video on line boring. I saw she was making a steam engine which is pretty neat.

Thanks again everyone
Kyle
 

petertha

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By any chance did you look at how the intake and exhaust tubes mount to the heads? The plans basically say to glue them in, which I would want to try for something more elegant.

I didn't get that far in the assembly model yet, but you've raised another good point I was pondering. His radials use a threaded nut screwed into the head for both intake & exhaust. The nut presses on an upturn or pipe flange (and in my case, a Teflon washer between pipe & head flange). I strayed from the design a bit, but same basic concept.

I noticed no thread callouts on the V12 heads which I took note of as potential oversight and maybe 'glue' could mean 'sealant' in translation. He doesn't make (many! LOL) mistakes so I wonder if the V12 lends itself to permanent tubing extension 'stacks' that can be assembled & sealed to the manifold itself, mitigating these nuts altogether. It would simply things because my experience with the shallow counterbore + odd angle port axis into head + shallow bottoming threads + sealing the pipes is a collective PITA. I told myself next engine will be flanged & screwed one way or another. Even the radial was challenged in that respect as the flange screws & valve cage features & other issues didn't want to play nice together. On one hand I can see mini pipe stack being easier, but I can also think of some disadvantages.

(pic) FWIW I did some experiments bonding aluminum unions to the pipe. I didn't have to go this route but it could be a way of fixing pipes into position, kind of like a glue version of silver soldering. This was JB weld but flavors of Loctite would work well.
 

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petertha

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I looked on AliExpress & some of my other offshore haunts for less expensive spade drills. They look to be +/- the same price as N-Am offerings. If I did a lot of this kind of work it might pay to buy an arbor. The replaceable cuttters are reasonable but arbors come in bracketed diameter & reach ranges, so one would have to be choosey because they are spendy. Shop making the arbor is another option if one were so inclined

In my KBC catalog I found several good, conventional drill candidates in the $35 range that could pilot drill the crankcase half way from both ends. I don't think it has to be a pretty hole, just enough to pass a line boring bar through. And even if 2 line boring bars were required (slim & larger/finisher) probably still a cheaper way to go. It looks like the process will require lots of incremental cutter adjustments in any event, so will take some time to get it right.

I cant think of a good way to make a split case in order to hog out the core with end mill & permanently bond the halves together before line boring. There just isn't a lot of sidewall meat for pins & screws & such.
 

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