Cross Drilling Round Stock
I often have the need to cross drill directly through the center of round stock or tube. This seems like it should be fairly rudimentary but more often than not I miss the center.
What I need is a good idea for a jig that will accommodate 1/2 - 2" stock and can be used in a drill press. I have a cross feed vise on the drill press.
I've seen some sort of V type jig somewhere, but don't have any details.
Thanks for the help.
Last edited by flatfendershop; 12-27-2009 at 10:21 PM.
Reason: i messed up.
How centered do you need this? Getting lined up with a drill press is going to be far from perfect, even with a V block. Main thing that will help is to start your hole with a short stiff center drill instead of a twist drill that is going to walk off one side.
A quick way to get on center in a drill press with a vise is to ease the table up with a center drill in the chuck , swinging the table slightly, or sliding the unclamped vise until the center drill just barely brushes across the top of the work. It will make a little line on the work when it drags. The middle of that line is the center. Nail it down, use the center drill to start a hole in the middle of the scribed line, replace with your twist drill and go to it.
there is a couple of things i can think of one is make a mini vee block to go in to your drill chuck just a bit of small angle welded on to a piece of 1/2 inch round bar, this will have to be welded fairly accuratly and you may even want to machine it after welding depending on how accurate you want it. Then you just put the round bar in the drill chuck and the vee of the angle over the round bar lock the table and you will be dead centre of the work piece.
I have one of these and it works very well: http://www.heinrichco.com/drill_jig_hand-op.htm
You can get them with pneumatic clamps for even more money
Problem is you'd need at least two sizes to accommodate up to 2" stock, and they're pricey. They do show up on fleabay sometimes, not often.
But looking at the design should give you some ideas about making your own jigs.
I think the key to the design is the drill bushing, which keeps the bit from wandering off top dead center.
A dowel pin jig like this should work, as long as it's big enough. I think mine was about $25 a couple or 20 years ago.
PLUS, you can make a couple of 2 x 4's into a 2 x 8
A long time ago, before my mill, I had a lengthy run of cross-drilling to do in 2" shafting on the drillpress.
I used a piece of pipe, 4" long that fit over the shaft. Then welded a small piece of pipe that just fit over the drill bit, about 1" long vertically on top. I clamped the pipe in a vise mounted on the table.
I could slide the shaft inside the pipe, then use the vertical pipe as a guide for the bit. Later on another job, I split the main pipe lengthwise on both sides. so that I could put the shaft in and clamp the whole thing in a vise.
If you have a table saw, you can make a nice V block out of a piece of wood with the blade turned to 45º. I have one and have been using it for years. It is not "machinist" accurate, but it works pretty good. I align the jig under a drill bit to the center of the V, then clamp down the jig. As said before, always start your hole with a short stiff bit.
This is not answering your question but here is a method I was taught in vocational school using a drill press vise to hold/drill round stock on a drill press. Be your own judge here....Obviously more critical applications will require better holding/ locating.
First make a center punch mark where you want the hole as close to vertical on the round stock as you can eyeball.
Using a scale working from the vise jaw set the punch mark on center. (3/4 stock, set the mark 3/8 from the jaw...and so on...yada yada) I use a small dia drill bit (around .093) to drill the first 3/32 to 1/8 deep. The theory here is that the smaller dia drill will flex to follow the punch mark. Then using a larger dia. bit drill through step drilling as/if needed. I not clamp the vise in place but rather let the work piece float and contact the column if long enough or clamp a C clamp to the table for the vise to stop against.
We do repeated cross drilling for placement of roll pins in round stock. The method that we use is to weld a piece of square tubing,of the apropriate size to a 4" x6" 1/4 inch plate, locating the square tubing centered across on the 4" axis. Locate center of square tubing and drill your hole through the square tubing. We just weld a nut on top of the whole but a drill bushing would work better. Clamp this in your vise on the 6" axis leaving the open end of the square tubing open to slide the round stock in. Slide in your stock drill a hole repeat. I don't know if this meets your accuracy requirements but it works for me. Rodl
Cut a 1" length off some spare stock of the same size as the work.
Drill a hole through the center of this piece while chucked in the lathe using the drill size wanted.
Now you have a drill bushing.
lay the work in the bottom of the vise, and place the newly made bushing over the desired hole location. Clamp up, using paper shims if needed to hold the bushing and the work snug.
drill through the whole in the bushing, centered on your round stock.
Good for a lot of work types. Large stock takes deep vise jaws, but add-on jaws are easy.
Great Ideas, thanks a lot for the help. I'll try some of these in the shop tonight and see what works best for the set-up I have.
If one's work requires much cross drilling of round parts it is worthwhile to obtain a motorized cross drilling spindle, adjusted such that its spindle centre line coincides with the lathe centre line.
A smallish one that fits directly onto the quick change tool post will save a tremendous amount of time and trouble. The right angle to the lathe centre line is easily adjusted with parallels or 123 blocks placed between the tooling spindle and the front of the lathe chuck or face plate.
Even if the hole size required is larger than this spindle's capacity it is worthwhile because once an accurately places cross hole exists it is easily set-up in the drill press to enlarge it.
Originally Posted by flatfendershop
I've been using one of these tools for years.....cheep and effective.
one idea is to file or mill a small flat so the drill is not on top of a curved surface. Maybe a small grinding wheel in the dp then without moving the work switch to a drill.
I feel like these are all shots in the dark without tolerance info. For example, the little indicator Rex links to works great, but if you want it within .005" you're just not gonna get it. My own shot in the dark is to get a shaft vise*. It is essentially a vee block with two arms that close down in unison to hold round stock centered.
*At least, that is what MSC calls them. They list one with minimum 1/2", max 2.5". I always considered these style vises common... but the ones at MSC are the only ones I can dig up at the moment.
I have a skid of misc drill press type vices in the storage building, but I think I have a gaylord of crushed pop cans setting on top of it right now, so I can't quick/easy git to them to look at what is on it right now.
Next time I am moving stuff around I will give it a look see and try to remember this thread.
Think Snow Eh!
One more tip, just like setting tool height on the lathe. Chuck a concentric point and bring it down on a steel ruler on the bar. when it's level you're pretty close.
Setup on the drill press or mill is the majority of the time cost. If you are just doing one-offs, the lathe with a drill in the head, and a crotch center in the tailstock, may be more efficient.
I made myself a cross drilling jig, and it has come in very handy. It was a fun little project, and it handles anything from 1/4" to 2-1/2" diameter:
I made up the drill bushings in 1/32" increments.
Here's a full illustrated write-up: