indexing w/o a rotary table?
 

I'm finding myself in need of a reliable way to index some rod stock for counter bored holes. I don't have a rotary table, so I'm scratching my head at a way to accomplish this. Feel free to offer up any ideas."thumbsup"

Re: indexing w/o a rotary table?
 

What exactly are you trying to do?

Re: indexing w/o a rotary table?
 

I'm making a few bench top cannons, I need to be able to locate holes 180* apart for trunnions.

Re: indexing w/o a rotary table?
 

Can you just drill them through?

A pic might be helpful, my guess is that it is just round stock that you are going to drill or bore for the bore of the cannon and then you want to hold it to the base with two screws.

If that is the case here are my suggestions:

1.This one costs nothing assuming that you have a mill and general tooling already. Simply mill flats down two sides of the stock, make sure that they are even and parallel to one another. Now you have something to grab the stock by that will give you a good reliable way to position the stock. You could mill it into a hex or buy hex stock, I think that would be a cool look anyways.

2.Small investment, similar to number 1 but make a fixture that the barrel slides into and lock it in with a set screw. The fixture will have the two (or 4 or 6 or 8 or whatever you want) flats on it and once the barrel is in dont remove it until you are done with your holes.

3.Larger investment, I assume that you already have some 5c collets so you can pick up a collet block set. They usually come with two blocks, one is 4 sided and the other is 6 sided so you can use them for a bunch of stuff. Combine that with a vise stop and they are very flexible. shars.com - 5C Collet Block Set

There are other ways but I think those are the best.

Re: indexing w/o a rotary table?
 

the most relaible and simple i have used is a v notch cut in almost anything. i use channel. the tube will always find center that way. then its a simple mater of measuring up from the table on either side of the tube.

Re: indexing w/o a rotary table?
 

How are you planning on rotating it exactly 180*?

Re: indexing w/o a rotary table?
 

I used this tool to drill holes exactly 90 degrees apart.
http://i302.photobucket.com/albums/n...2/IMG_0058.jpg

With the holder laying down I drilled the first holes and made a backstop in the vise to locate it left to right.
http://i302.photobucket.com/albums/n...2/IMG_0062.jpg

Then I loosened the vise, rotated the tool 90 degrees and drilled the second holes.
http://i302.photobucket.com/albums/n...2/IMG_0063.jpg

I don't know the name of the tool but C*H*U*D would, he bought I I think.

Re: indexing w/o a rotary table?
 

i dont, 180* is super simple and you dont need to rotate anything. heres another way with out measuring, set the tube in the V notch, and with a small square mark the point where the square touches the tube on both sides, 180*.

theres another way that involves lots of math, i dont do math but its simple if you know numbers. calulate the length of your tube if rolled out straight, print off a scale on paper in 1/4-1/2-3/4-1 and when you wrap it round the tube you can do both 180 and 90 with that, you can break that scale down to whatever you want, even 1* increments for a full 360* wrap in literally any degree you want.

Re: indexing w/o a rotary table?
 

not enough information given to produce an accurate answer..

Re: indexing w/o a rotary table?
 

If you want two holes 180* apart and they are blind holes then you need to rotate the tube...

A square wont touch two opposite sides of something that is round at the same time...

Re: indexing w/o a rotary table?
 

you didnt knock down the math style of doing this, i'm sure you have a reason pi and division doesnt work either,,,,,,,, your making it way to hard.

Re: indexing w/o a rotary table?
 

This one gets my vote. The fixture Grizz shows is also a very handy tool to have but will cost more.

Re: indexing w/o a rotary table?
 

I was trying to be nice, your printer probably doesnt have the accuracy to print out your scale perfectly and even if it did you are still lining up the holes by eye.

We are not making this too hard, like I said I dont know the type of precision the OP is trying to achieve but coming from a background of holding very tight tolerances on prototype parts for medical devices I dont suggest anything that does not have a reasonable amount of accuracy. Every method I posted should have good accuracy and are reliable methods of making multiple copies of the same part.


Yea those blocks have saved me quite a few times, the other great thing about them is that they are very low profile compared to the larger stationary collet blocks.

Re: indexing w/o a rotary table?
 

I agree, but right now I don't have the tooling or the option of buying anything else right now. I can't cross drill the hole, as it would pass through the bore of the cannon. I have thought about some type of degree wheel that I could glue to the end of the cannon and rotate it inside of the V blocks. It's about as ghetto as it gets, so it really isn't an option that I want to use.

Re: indexing w/o a rotary table?
 

After clicking the link that SMR provided, that tooling isn't overly expensive. I'd still have to buy collets. Another possible issue is the size of the round stock, I had to use 1.25" diameter brass. It's at the end of what my mini-machines can handle.

This project was just something to do, just to see if I could make a novelty item that makes a loud boom.:mrgreen:

Re: indexing w/o a rotary table?
 

Here's all that I have to work with right now. I had to go with a low dollar vise, the 4" Kurt style would have used up most of the bed and really cut down on Z travel. I know that I won't keep these Micro Mark machines for too long, so I can't justify spending a ton of cash on tooling and if I buy the better quality, larger tooling for a bigger mill and lathe for future use, I wouldn't be able to use them right now. It's a catch 22 situation.

Here's the 3" vise.
http://www.rccrawler.com/forum/membe...2876-37253.jpg


Here's the first cannon to see if I can pull this off. If I can figure out how to do it safely and accurately, I'll make a dozen of these to be used as gifts for friends and relatives.

http://www.rccrawler.com/forum/membe...2876-37254.jpg
http://www.rccrawler.com/forum/membe...2876-37255.jpg

After looking at Grizzy's pics, it looks like he is rotating the entire tool 90* in the vise, which would rotate the parts. Interesting idea..

Re: indexing w/o a rotary table?
 

5c collets are basically the standard collet up to 1" and are useful for many applications. They are the standard collet for most of the standard sized industrial lathes so it isnt a bad investment because they and your tooling can move to a bigger machine with you when/if you ever upgrade.

The largest 5c collet is 1-1/8" so it should fit your application, you could buy that one collet for now or buy an inexpensive set although most of the inexpensive sets end at 1".

If I was you I would just mill both sides of the brass before turning it (you dont need too much of a flat something like .025" of depth should work fine) and then you can drill the holes, then turn it and bore it...that should allow you to cut the flats back off when you turn it so you wont even be able to tell they were ever there. You could skip milling one side if you want it just adds another setup vs. milling both sides because you will have to flip the part with the flat towards the back of the vise on both holes. If you are making a bunch just setup a vise stop and you could bang them out quickly.

Re: indexing w/o a rotary table?
 

its cool guys, however accurate you want to be is fine, for me, a couple thousands,, ok maybe hundreds of an inch is a-ok. thats prolly all the more accurate a hobby grade machine is good for anyway. not that your using a hobby grade machine, just pointing it out.

i just came up with another super duper easy way and its literally fool proof, cut a strip of paper, wrap it round your tube and mark where the paper overlaps and cut off the extra, now just fold the paper in half and fold in half again, bammo, 90* and 180* instersects on the creases. i know i know, its not aerospace accuracy but its pretty dam close for us guys without machine tooling.

SMR, i appreciate you trying to be nice, but maybe instead of shooting something down you can simply point out that you have a more accurate method. i mean, the OP did ask for a cheap and easy way to do it w/o buying tooling.


PS, thats gonna be a cool little canon,,, will it be a working model and shoot .22's?

Re: indexing w/o a rotary table?
 

The bore is at .377 so I can use 3/8" ball bearings.

I appreciate all of the feedback. My background is in aerospace tooling, so I just cringe at the thought of not being within a .001 of where I need to be but being unemployed again, it's frustrating knowing how to build something w/o having the access to the equipment to do it accurately.

These little machines are fully capable of holding a decent tolerance, it just takes time. You need to make small cuts and use low feed rates.

Re: indexing w/o a rotary table?
 

"thumbsup" This was actually one of the ways I thought about, I just wasn't sure if I would still be able to turn down the flats enough to blend into the body. I have a chunk of aluminum rod, I'll give it a try to see if this will work better for me.