No room to use mounted rotary table and chuck. Help.

[zeeprogrammer]

Hi all.

I'm building the Oscillating 2A. Well trying to. So far every part I've made is off. But I'm learning. (You all need a category below 'newbie'...one for people like me.)

Anyway, I need to drill the four holes used to hold the head and bottom cap casting to the cylinder as well as make the 8 holes in the cylinder.

I thought a rotary table would be great so I bought one.

I mounted the RT to the mini-mill and used the provided adapter to mount the 3-jaw chuck from the mini-lathe.

No room to get a drill bit into the chuck!
And, I'm told there are no collets available to take a 9/64 bit!

What do I do?

One suggestion was to get a kit that would extend the z travel of the mini-mill. That requires some mods to the mill and I hesitate to do that until I have more experience.

Is my approach wrong? Was there any point to getting the rotary table if I can't get at it?

Your help is greatly appreciated.

 

[websterz]

R8 collets? Put the drill in an 1/8" collet...they are good for +/- 1/64" easy. I do it all the time!

 

[kf2qd]

Instead of putting your cylinder/crankcase/etc on the rotary table you could make some drill jigs out of thinner stock and drill them on the rotary table and then drill through your drill jigs to drill the other pieces. you cam make the drill jig 2 sided if necesary so one jig can drill both mating parts.

 

[GailInNM]

For drilling, I find that it is easier and faster to us XY coordinates to locate the holes.

For four holes, if they are on axis, then just set the dials at the radius of the holes.

If they are at 45 degrees to the mounting of the part, then divide the radius by the square root of 2 (0.707) and set each axis at that. Be sure to compensate for back lash on the lead screws if yo do not have a digital readout on the milling machine.

For other than 4 equally spaced holes, it may take a little bit of trig to locate the holes, or there are tables for bolt circles in Machinery's handbook, and I am fairly sure that Marv has a program for that on his website.
http://www.myvirtualnetwork.com/mklotz
Gail in NM,USA

 

[zeeprogrammer]

Websterz: I tried the 1/8 collet. No way. Is there some trick? Maybe there's something wrong with it. I measured the bit and it's fine. I would have to spread the fingers somehow. Is that what you do?

kf2qd: Excuse my being so new...can you point me to an example of such a jig or similar?

GailInNM: Yes could. I still have the problem of holding the part. Chuck on RT seemed easy. Plus I would learn something about the RT.

Still wondering if an RT on a mini-mill has any usability. In particular with a chuck. Seems like it would be a good method for a number of things. But even if a chuck is not used...room is still needed to mount a part and there doesn't seem to be much left for a tool. Has anyone actually used an RT on a mini-mill?

Thanks to all for your responses.

 

[tel]

Yeah, I have, plenty of times. And I have a little 3 jaw chuck from an Emco Compact 5 that fits it and leaves plenty of room overhead. You don't say what size RT you got - 4" is about the max for the X2

 

[Jasonb]

As gail says its easier to drill them using co ordinates.

If you want to use the rotary table use a 1/8" shank center or spot drill in your collet chuck to position the holes then take the work off the RT/Chuck and open them up to size in the drill press/mill

You could also do away with the chuck by turning a locating peg, one end to fit the hole in the RT the other to fit the cyl bore, then hold the work down onto the RT with studs & clamps. I often use this method and have built up quite a collection of different sized pegs.

Jason

 

[kvom]

I have been advised at school not use use collets unless they are within +/- .003. Otherwise the steel can be sprung. One option could be to get an "emergency collet" and drill it to the 9/64 diameter. You could also determine if the 9/64 diameter is critical, and if not use a 1/8" or 5/32" drill instead.

Calculating the hole locations is still probably best, as others have suggested.

 

[Mainer]

I wouldn't try to put a 9/64 drill in a 1/8 collet.

I'd probably make, say, a 3/8 dia bushing with a 1/8 hole and Loctite (#609) a 1/8 drill into it so I could hold it in a 3/8 collet.

 

[mklotz]

Setting up an RT to drill a bolt hole pattern is a waste of time.

If you consider the errors inherent in hand layout combined with the errors inherent in centering over a set of scribed lines, I believe you'll realize that the most accurate layout tool you own is the mill itself. If you're mathematically challenged, my BOLTCIRC program will do the calculations for you.

Don't get in the habit of putting oversized material in collets. They're precision devices and don't take kindly to such abuse.

As has been mentioned, mounting work directly to the RT table saves headroom. Oftentimes, doing so can be simplified by making a sacrificial plate fitted with an array of tapped holes and attaching this to the table top, thus providing convenient tie-down points for clamp studs as well as protecting the table.

If you anticipate having headroom problems in the future, consider buying a set of screw machine length drills. They're shorter than standard jobber length.

 

[zeeprogrammer]

Thanks everyone. Very helpful.

Jasonb...if you could direct me to any pics that show what you're talking about...it would be greatly appreciated.

Thanks again.

On the road between Sgt. Shultz ("I know nothing") and Professor Fate ("Genius! A work of genius!"), I'm to the left of sarge.

 

[stevehuckss396]

Don't laugh but a while ago I had to raise the head on a round column mill to fit a drill bit in a chuck. Doing that would cause me to lose my position on the DRO because the head swings around on the round column. Being to lazy to re-position, I cut the drill bit down with an abrasive disk cutter about 3/4 of an inch.

I dont know how close you are to fitting the drill bit in above your work. It might work for you.

I said don't laugh!!

 

[fdew]

I would drill the head and cap first, Then use a transfer punch (looks like a drill bit with no flutes and a point on the end) to mark the holes in the cylinder. that way if you are off a bit on the holes in the cap, they will still fit your cylinder, also the cap and head may fit in your setup better. for the drill, Use a center drill, then a 1/8 drill in your collet, Then you can enlarge it with the 9/64 without using the RT ETC.

Frank

 

[shred]

If you're already all set up on the RT, I 2nd the idea of drilling 1/8" with a drill in a collet (or even a center drill or something equally stubby), then enlarging elsewhere... mill, drill press, careful hand drill, etc

Sometimes you can sneak a tad more Z by putting the drill in the chuck with the workpiece out of the way (crank it out of the way, then back after loading, or put the drill in before loading the work.)

Nowdays I do a lot of small drilling with an R8 ER-16 holder and drills held in ER-16 collets. It's a bit expensive to get one just for drilling, (and somewhat slower changing over than a drill chuck) but I use mine for a ton of work with cutters up to 3/8" as well.

 

[zeeprogrammer]

Steve,

Laugh? Not at any of you.

After all my mistakes, the engine will never run. So I 'brute forced' things enough to at least put it together and see what it looks like. Now that's to laugh at. Still, the learning is great. I have a 2nd kit to apply that learning (and a 3rd on the way). Maybe by the 4th kit I'll feel confident enough to shows before/after pictures.

Frank and Shred,

Good stuff. It's one of the things I'm learning and enjoy about this hobby. Improvisation is good (and often necessary).

Thanks to all.

And now to continue justifying the expense to my wife...

 

[fdew]

Improvisation is good (and often necessary)

There was a very popular thread on one of forums called "Show us your setup." all about improvisation among the pros. As a designer, I have observed others setups long before attempting my own. My favorate was a bridgeport mill head on it's side bolted to a steel plate, the plate welded to a building support post. When I asked, the owner just said "We didn't have a lathe big enough". He also added that a bridgeport doesn't know it is a mill. If you make it be a lathe it will! These guys were pros and good ones.

BTW They were doing a big job for us that required a big stiff rotary table, so they removed the X and Y table from a large horizontal mill and mounted a rotary table. They did our job, and at the same time rebuilt the X Y table.

Frank