Drill Fixtures

JimDawson

JimDawson

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The weather here has been beautiful the last few days, so have been getting in a bit of shop time.

A customer asked me to build a drill fixture for drilling some wood parts for her project. Her parts are 1x2x12 inches with a series of hole in them so here's what I came up with.

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So I started with the drill bushing holder, an aluminum 1x2x3 block, nicely squared up and ready to start chewing on.

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And done. Nothing too magic here, just a normal setup. Note the relief channels on either side, Prevents crud building up in the corners and gumming up the works. But the next operation is more fun. I need to make the 5/16 drill bushings, but they need to be easy to replace and buildable with common hand and power tools that you might find in a home woodworking shop. So a 1/2-13 grade 8 bolt will work just fine.

Since I already knew exactly where the hole in the bushing holder is, it made sense to just use the the part as the fixture to drill the bolts. That way I know the hole in the holder and the hole in the bolt are exactly concentric.

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Then I did a round over with a 1/32 R corner rounding end mill
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And done
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So next I need an aligning pin to drop in the hole to locate the part for the next hole. So looking around the shop I found the perfect head for it and I have hundreds of them. So that and a 1.5 inch long shoulder bolt is the perfect combination.

We make several hundred of these in each run. 5/8 OD 303 SS.

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So part it off and drill & tap for 1/4-20 and instant aligning pin with an ez-grip knob.

Now that's working close to the chuck, about 0.010 clearance. :eek: ( yes I carefully checked the clearance before starting the lathe) No problems, it parted off nicely.
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Then I parted off the head of the shoulder bolt and rounded over the end with my trusty Harbor Freight round over router bit.
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And done
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So next is the base and the fixture guide

Square up the MDF base. The end mill is 0.015'' off the table. I set the max depth with a feeler gauge under the end mill. I trust my machine and I know the Z axis repeats to +/- 0.0001 consistently.
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Squared up and the screw pilot holes drilled. You almost can't see the pilot holes just above the blue lines.
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Then drill and screw down the plastic guide for the next operations.
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Remove the clamps to allow unrestricted access to the top, finish drilling the mounting holes and screw down. Also drill the alignment holes.
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And machining is complete, well almost :cautious: Note that there is no chamfer on the drill clearance hole. It is on size. This is to help prevent tear out of the wood as the drill breaks through, I have also let her know to use brad point bits. Should make a clean hole.
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I had to put a little divot in the side of the drill bushing holder to clear the larger knob than I was originally going to use.
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Still need to build the end stop, I'll do that in the morning. But otherwise complete.
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After I build the end stop, I need to make another drill fixture for a mating part. I'll post that in this thread tomorrow. This should have been about a 3 hour project, but I managed to stretch it into about 12 hours. I just don't move as fast as I used to.:faint: I'll be lucky if I even make minimum wage on this one.
 
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Paul135 said:
I like the ingenious use of the router bit. How do you find it holds up?

Paul
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They hold up very well. I use solid carbide and carbide tipped router bits in all materials, even stainless steel. Both on the lathe and milling machine. They are not as robust as metal working cutters so you need to use a bit lighter touch, but they are inexpensive and available everywhere.
 
Thats neat Jim, thanks for sharing! I love the router bit idea, i have used radius end-mills in that way but the roter bit never occurred to me Even have some hanging around here. Nice “trick”.
 
Yes, thanks from me too. I need to turn a 5/16 radius end on the end of a 5/8" rod and was going to grind a HSS form tool. I may just give a routerbit a go as I have loads of them.
 
JimDawson said:
They hold up very well. I use solid carbide and carbide tipped router bits in all materials, even stainless steel. Both on the lathe and milling machine. They are not as robust as metal working cutters so you need to use a bit lighter touch, but they are inexpensive and available everywhere.
Click to expand...
Thank you Jim for such a good idea. It is also interesting as there is such a wide range of router bit profiles and sizes available, From a hobby point of view using a light touch isn't a problem as time isn't normally critical, though do you experience chatter when using them on the lathe? What size shank router bits are you using? From your photos it looks like you are using a 102 type tool holder. Have you screwed down directly on the router bit shank or have you made up split bushes to give a bigger diameter to clamp on? Not having built a tool grinder yet I can see this technique being very useful.

Paul
 
Paul135 said:
Thank you Jim for such a good idea. It is also interesting as there is such a wide range of router bit profiles and sizes available, From a hobby point of view using a light touch isn't a problem as time isn't normally critical, though do you experience chatter when using them on the lathe? What size shank router bits are you using? From your photos it looks like you are using a 102 type tool holder. Have you screwed down directly on the router bit shank or have you made up split bushes to give a bigger diameter to clamp on? Not having built a tool grinder yet I can see this technique being very useful.

Paul
Click to expand...

Yes, they sometimes chatter, you just have to be careful and not take a too wide cut.

That bit in the picture is 1/4'' shank, but I use 1/2'' shank where possible.

Yes, a 102 type holder, V-notch style. Just screwed directly on the shank.
 
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