How would you attack this problem?

ValiantOne · Feb 11, 2009

I need to bore some recesses in the tapered side of the cannon I am building for the lower part of the trunion to sit in. I have my SB lathe and I have a drill press. No mill though.

I was wondering if I could turn the shank of a end mill down to fit in the chuck of my drill press and then use it to "drill out" that area. ???

Any other thoughts? Thanks for any opinions!

Chris

Racer Al · Feb 11, 2009

Chris, I'm not sure what you're asking -- do you need to put a taper to match your cannon barrel in the trunnion, or is it something else?

The answer to the trunnion question is that you need to build a fixture to hold the trunnions in your lathe in the same relationship that they will be located on the barrel, then bore both of them at the same time with the correct taper.

ValiantOne · Feb 11, 2009

Al, I I could figure a way to do what you are saying that would be great. For the life of me I cannot thing of a way to hold that piece of trunion in the chuck such that I could use the compound rest to cut a taper.

My idea was to drill a hole into the side of the barrel, in the tapered section where the hole in the photo is. That hole would be drilled at 90 degrees to the bore of the cannon. Like a counter sink hole for a bolt head, only 1-1/8th inches in diameter.

the areas on either side of the taper are still the same diameter, so it will be easy to hold the barrel level when drilling the recess (or counter sink)

does that clarify what I am trying to do?

Can anyone answer these two questions:
-Is the shank of a end milling bit soft enough to turn down in a lathe?
-Can an end mill bit be used like a drill bit, to drill a flat bottomed hole?

Thanks!

Chris E.

Webb Wyman · Feb 11, 2009

Hi There,

Have you a matched pair of Vee blocks? If you have,
you can hold the cannon barrel in the Vee blocks (with
the blocks on their side) and the barrel will be held parallel
to the table surface of the drill press.

When drilling the trunnion hole, use the correct drill size
to establish the hole size and finish with a flat bottoming
drill.

Good Luck!
-Blue Chips-
Webb

Finegrain · Feb 11, 2009

ValiantOne said:
Can anyone answer these two questions:
-Is the shank of a end milling bit soft enough to turn down in a lathe?
-Can an end mill bit be used like a drill bit, to drill a flat bottomed hole?

1. Yes, if you use the right kind of cutter and go slow. I recently turned a 2" EM shank down to 1-1/4". It made for some interesting sounds and took awhile, but came out OK. This was with negative-rake WNMG-432 inserts. I wouldn't try this with positive-rake.

2. Yes, if you do this with a very rigid machine with a robust toolholder. My sense is that you'll have a bad day if you try this in a drill press, with a 1-1/8" reduced-shank EM held in a drill chuck. If you try this, PLZ wear eye protection :crazy:

.

Regards.

Finegrain

Rudd · Feb 11, 2009

V1, I don't know if this is what Al was thinking, but possibly you need to turn the problem around.. How about mounting the trunnions on the cross slide or compound in a fixture, C/L to match spindle C/L, and at an angle to match the taper? You could then go at it with a boring head held, if need be, in a chuck, preferably a 4 jaw, really light cuts, lather, rinse, repeat. A collet would be better.

I hate to say it, but one of those ding dong milling attachments for a lathe would be the cat's pajamas here, absent a real mill.

Side note - I've always kind of wondered how the trunnions on the vintage 1:1 scale cast guns were turned, the closest way I can think of is a machine like the portable crankpin lathe I'm using in my avatar, with some careful setting up to insure alignment between the two.

flathead4 · Feb 11, 2009

I have been considering making a few model cannons, myself. From what I have read on the subject, everyone says drill for the trunions before turning the barrel taper. Too, late for that in your case.

Have you built a tool post drill for your lathe yet? If you have one you could try drilling them with your end mill while you have it between centers on your lathe. Start with light pressure until you get it started.

Tom

Chrono0325 · Feb 11, 2009

Sure you can turn the shank just watch for interuptted cuts,and take light doc and dont rush it. Carbide and coolant or mist for sure to cut the shank down,and start with smaller drills picked up a little bit to leave you a flat bottom.Id say if the hole is a quarter inch now start with 3/8ths then 3/4 then get a drill about .02 or
.05 max smaller or your hole size will not be accurate.For finish just not to much rpm like a 100rpm or so and feed with a nice feel on the press handle.
Done this many times. One thing the less you leave for finish the more accurate the hole will be. Oh and if possible put a small .005 to .010 chamfer on the bottom of the cutting teeth of the end mill.

flathead4 · Feb 11, 2009

Chris,

I just reread your post above and you say the trunions on the cannon will be 1 1/8" diameter. How big is the cannon??

Tom

vettepicking · Feb 11, 2009

do they just sit in the bored hole or do you weld them or what? i would mill it if you send them to me . matt

ValiantOne · Feb 11, 2009

flathead4 said:
I have been considering making a few model cannons, myself. From what I have read on the subject, everyone says drill for the trunions before turning the barrel taper. Too, late for that in your case.

Have you built a tool post drill for your lathe yet? If you have one you could try drilling them with your end mill while you have it between centers on your lathe. Start with light pressure until you get it started.

Tom

Tom, I have never seen a tool post drill. That sounds like an interesting option. I'll have to do some research on that. It is something that I can build?

Thanks,

ValiantOne · Feb 11, 2009

flathead4 said:
Chris,

I just reread your post above and you say the trunions on the cannon will be 1 1/8" diameter. How big is the cannon??

Tom

Tom the inner portion of the trunion is 1-1/8. The outter part of the trunion that attaches the cannon to the carriage is 9/16. I'll have to post a photo of my drawings. The whole thing is about a foot long.

ValiantOne · Feb 11, 2009

vettepicking said:
do they just sit in the bored hole or do you weld them or what? i would mill it if you send them to me . matt

Matt I was going to drill and tap the center of them where the outter pice of the trunion goes through the wider inner (counter sunk) piece. and thread that into the barrel too. So, it will kind of be screwed on by the outter trunion piece

If that doesn't make me happy I was going to silver solder the whole thing too.

C

ValiantOne · Feb 11, 2009

webb, that would be an interesting way of doing what I was thinking of doing with the end mill. I didn't know there was flat bottoming drills. I'll have to go look at some catalogs. Thank you,

Finegrain, that is what I was worried about. if the whole set up would be too flimsy and wander too much. My drill press isn't all that great to begin with.

Ugh!!!

Maybe I just need to buy a milling fixture for my lathe.

vettepicking · Feb 11, 2009

ValiantOne said:
Matt I was going to drill and tap the center of them where the outter pice of the trunion goes through the wider inner (counter sunk) piece. and thread that into the barrel too. So, it will kind of be screwed on by the outter trunion piece

If that doesn't make me happy I was going to silver solder the whole thing too.

C

ah i see , how about this just came to me ..... i would use a counter bore for a socket head cap screw , they have a centering pilot on them that you can turn down to fit that hole before you tap it. this would keep the hole centered and you could chuck it up in a drill press . they make a flat hole to ... matt

vettepicking · Feb 11, 2009

d

problem solved ....

Mcandrew1894 · Feb 11, 2009

I'm with Rudd on this

Strap it to the cross slide and make up a D bit out of oil hardening to the size of the bore you want. Bore the hole to just under size and finish it with the D bit. If the size consistency is not that crucial, just bore to size.

As far as fixturing the taper, I would make a nest of wood on a substantial plate straped to the cross slide vee way. and then just strap the barrel down tight.....it won't win awards for metal removal rates, but I don't think you care. The nest would look like a tapered vee block with a vee that is complimentary to the barrel taper resulting in the barrel being held horizontally. You should be able to check this with a level on the straight section of the barrel and adjust the taper of wood vee pieces to suite

Here's a sketch......just my .02. worth just what you paid for it..8-)

Rudd, if you turn the idea around, you could turn the OD of a cast trunnion with a boring head mounted in the chuck and the barrel on the saddle.........

flathead4 · Feb 12, 2009

Tom, I have never seen a tool post drill. That sounds like an interesting option. I'll have to do some research on that. It is something that I can build?

Chris,

Here is a picture of the one I'm currently building. It is by no means my idea. I first saw it described here by Bob Wright (aametalmaster). He has detailed pictures over at the Southbend10k Yahoo group. You have to sign up, but it's free and easy. Basically the drill chuck is driven by a portable drill. The drill shaft is perpendicular to the bed and on the center line of your spindle. As you can see, it mounts on your compound.

Tom

http://groups.yahoo.com/group/southbend10k/

Racer Al · Feb 12, 2009

OK, here's a better articulation of my suggestion.

Say the trunnions are 3/4" in diameter, and the ends of the trunnions need to be 2" apart.

Get a 2" square block of sacrificial material and drill a 3/4" hole through the block, centered.

Put set screws or bolts in each end of the block to hold a 2" long piece of 3/4 rod.

Now, with the rod in place in the block, center it in a 4-jaw chuck.

Bore your matching taper for the barrel by drilling a hole first, then use a boring bar in the compound set to the taper angle.

If you keep the speeds down, it will be good. If you're worried about throwing the work out the ends of the block, add a bolt and washer that will capture the 3/4" rod.

You could even use this fixture to drill holes perpendicular to the barrel, or, with a little modification, split it and use it to braze the trunnions on.

ValiantOne · Feb 12, 2009

Vettepicking, I just found a 1-1/8 counter bore at enco. That may be my solution. Thank you!

McAndrew, Rudd and Racer Al,

Thank you for your replies. Even with the diagram I am having trouble seeing how to do this set up, but I want desperately to understand it. I am going to try and draw it out on paper.

Al, if I made a block like you suggested, put the work piece in it, chucked it up to the lathe head (I am with you so far there) How could I cut a taper across the face of the 3/4 bar. With the bar spinning in the chuck I can envision how I could cut a concave, domed, flat or bored hole. But I cannot for the life of me see how I could cut a taper across the face using the compound rest. (Yes I am a bit slow!

)

And I am wondering what a D bit is too.

Flathead4, that is a NEAT rig. I am going to have to join the yahoo group and learn more. I think that would be a fun project to try anyhow.

Again, thank you all very much!

Chris

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