Centre drilling jig

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Shopgeezer

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I bought one of these jigs some time ago and dug it out recently to centre drill some steel rod. It is quite slick in terms of quickly centring the drill to the work but I find it impossible to hold the work. The tall sides of the jig make it hard to use a clamp. Hand holding is not an option on a mill. I finally dug out all my mill table clamps and hold down bolts and jury rigged a poor clamping setup. Anybody used one of these and figured out how to hold the work?
 

Shopgeezer

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Definitely in my "must buy" list, which grows longer by the day. No easy way to bolt this setup down to the mill table that I can see. Have to use clamps? Also the space between the vertical clamps doesn't allow for centring the drill in the blocks. Hmmm.
 

lennardhme

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The most stable method would be to make some sacrificial jaws for your machine vice & groove them inside horizontally to hold rod, Further you can machine a ledge on each inner edge to hold plate etc.
I make mine from cast iron, aluminium or brass.
cheers,
Lennard
 

IanN

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Hi "Thread"

I agree with Dnalot - every workshop with a mill and/or pillar drill will have vee-blocks (a "proper" shop will have matched pairs but most sets seem to separate and wander off in different directions over time....)

Using vee-blocks is a standard workshop technique for cross-drilling - I teach engineering apprentices and vee-blocks are covered at some point in the first six months. In addition, one of their assessed pieces on the mill/surface grinder is to produce a matched pair of vee-blocks (yes - apprentices still make (some of) their own tools in the UK)

The device shown in the original post is a simple, cheap, alternative to precision blocks - which would be ideal for simple cross-drilling tasks. It looks like it is an aluminium extrusion (such material can be produced to surprisingly high levels of flatness and dimensional accuracy) so I doubt if it would be appropriate to attempt milling using it as part of the clamping system

The same tooling is simple to use for cross-drilling in the lathe - see the thread:


All the best,
Ian
 

Shopgeezer

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I am thinking about milling down the tall sides of this jig. It is designed for centre dilling pipe. I don't need to drill 6" sewer pipe so if I get the sides down so that the work is exposed it should be easier to get a clamp on the work. It wouldn't take much of a "V" to hold metal rod in the sizes I use. I'll give it a try and report back.

DonM
 

ChazzC

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Don,

I suggest that you leave the jig as-is so that in the future you can cross-drill larger pipe/tubing (or even square stock on the diagonal - you never know). Yes, you will need to use toe clamps to fix it to the table, and will probably also need to use toe clamps to hold the rod stock in place (on the ends for rod stock that is smaller than the sides of the jig). Once the jig & rod are securely clamped you can achieve reasonable precision (given that this is an extruded piece of aluminum and not ground hardened steel Vee Blocks) for your current task. I'll try to get you a photo or two of a suggested setup tomorrow.

I got one of these jigs when I still had my bench top drill press, and it worked well for non-precision work; however, I had to sacrifice the drill press when I needed the bench space for my mini mill. I still use it for larger workpieces which usually do not require a high degree of accuracy.


Charlie
 

Henry K

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I just use a wiggler with a ball end. Move the ball up and down. The ball oscillations get smaller (to have the ball curve and the workpiece curve touch each other at the diameter of the ball. Then feed the table in 1/2 the ball diameter and 1/2 the work-piece diameter. Done carefully, you should be within 0.001" or 0.002" of being on the center-line. Really quite easy with a little practice.
 

Henry K

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I forgot to mention. You need a milling machine or an x-y table for this to work.
 

SteveM

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Something cheap and readily available like this could work well for that setup. The clamp could easily be mounted onto a block to increase the height.
Drill Table Clamp

51iq91AgUUL._AC_SY355_.jpg
 

Ripon

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I built the Hemingway cross drilling jig which works very well.
 

ChazzC

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Quinn Dunki also has a fixture on BlondiHacks:



Not as complex as the Hemingway and would require the use of an external parts stop, but perhaps more flexible due to its simplicity:

Blondie Cross-Drilling Fixture.png
 

ShopShoe

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I have one of those jigs, and I have used it for simple jobs on the drill press. For milling, I bought a set of vee blocks on one of my first orders for mill tooling after I ordered my mill.

I agree that these jigs are best for the quick jobs on a drill press, but vee blocks are proper mill tooling. I now have three sets of vee blocks.

As an aside, I was unaware early on about the jigs that can be made for cross drilling that use drill jig bushings to support the drill bit. Clearly a good thing if you need to set up for "production" of many rods with cross holes.

Mr. Pete, aka the US Tubalcain, aka Lyle Peterson, has a video about them:


--ShopShoe
 

Weldsol

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A very long time ago in Model Engineers mag, they described a parallel bar method (see PDF) using a drill bush
As this can be made to cover a wide range of sizes, also as you are using a drill bush there is very little setting up required so can be easily used on a pillar drill.
I have not put dimensions on the PDF as you can make what ever size you want, the only critical thing is all the hole centres on the cross pieces are the same and a good fit with the fixings and the drill bushes

Paul
 

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Weldsol

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Not clear on how that one works. Seems to be two bars in a parallelogram jig.
You are almost correct in what you said
I suppose if I had drawn it in 3D it may have made its workings clearer.
The two bars are the clamping part, your part to be drilled is placed between the two bars ( they are gripped in your drill vice )
Because the two bars are linked they will close parallel and as your drill bush is in the exact centre of one of the links it will always be on centreline of the bar you want to drill.
If you want to go a stage further you can put a vee groove or even multi size vee grooves in the inside vertical faces of the two bars
Hope this makes sense

Paul
 

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