Need to drill a flat bottomed 29/64" hole in wood 1/8" deep.

[SmokeWalker]

Thanks everybody for the suggestions! All of these are possibilities when Tuesday morning comes around and I can go shopping.

I sanded the busted 29/64" bit to flat, put a few degrees of relief on the cutting edges, and used that to enlarge a hole I drilled to correct depth with my 5/16" end mill. The bottom is flat enough, I just need to see if I can make this hole work for my purposes. This might be good enough. I'm a little sketchy on getting the 29/64" end mill, or the forstner bit, because in either case, it's going to wear out. Maybe I should take the time to practice sharpening bits.

11.5mm end mills can be found for less, I just checked. With an ER collet (if you have ER) you probably have a size that will hold it.

Can you find a 15/32" spade bit that has spurs on the outer corners?

Several times I've taken spade bits and filed the edges down on the sides to drill a smaller hole. The metal is not real hard so it can be filed.

You can also take a larger spade bit even without the spurs, file it to size on the sides and cut spurs into the end, done that too.

The cost of the $40 end mill amortized over the number of parts that you need to build might be a reasonable cost per unit. If 0.003 oversize is acceptable then use the 7/16 end mill. Another option would be to have an end mill re-sharpened to your specs.

I used to have trouble sharpening drill bits until I grabbed a large drill bit one day, and with the grinder turned off, I followed the face of the drill bit until I got the motion down correctly. The secret is: Don't rotate the bit while sharpening.

I'm not a wood worker, but I'm pretty sure I have seen bits designed for drilling holes to insert plugs, that might be what you are looking for. Another option might be a 29/64 router bit if you can find one.

 

[bob vaughan]

Grinding your own brad point bit takes a little practice, but not much. The equipment is the thing and the key is the Norton A60 OBNA2 reinforced cut-off wheel in a bench grinder. Second is a magnifying glass. Here's a few rigs I've used over the years.













instructions written during the nine-pin dot matrix days

 

[Dr. Duzlittler]

Thanks everybody for the suggestions! All of these are possibilities when Tuesday morning comes around and I can go shopping.

I sanded the busted 29/64" bit to flat, put a few degrees of relief on the cutting edges, and used that to enlarge a hole I drilled to correct depth with my 5/16" end mill. The bottom is flat enough, I just need to see if I can make this hole work for my purposes. This might be good enough. I'm a little sketchy on getting the 29/64" end mill, or the forstner bit, because in either case, it's going to wear out. Maybe I should take the time to practice sharpening bits.

How about a boring head with a small boring bar, you can make the hole diameter whatever you want it to be. Then you don't have to worry about any spindle run-out that you could possibly have with the "proper" size end mill or drill bit.

 

[Andre]

A endmill won't cut a flat bottomed hole anyway, it will leave a 1-2 degree point in the center. Maybe a boring and facing head? Possibly a member here has one and might be willing to let you borrow it.

 

[Ted208]

There's a 29/64" Forstner bit in US on eBay now ......

 

[SmokeWalker]

Re: Need to drill a flat bottomed 29/64" hole in wood 1/8" deep.

Grinding your own brad point bit takes a little practice, but not much. The equipment is the thing and the key is the Norton A60 OBNA2 reinforced cut-off wheel in a bench grinder. Second is a magnifying glass. Here's a few rigs I've used over the years.













instructions written during the nine-pin dot matrix days

That's a really phenomenal setup. Thanks so much for sharing what you have.
1. I need more space for it.
2. Even after the equipment invested, I know I'll need practice before I can come up with bits that actually work like they're supposed to. Like being good at golf is part having nice clubs, and part having a nice "swing". Lathes! Swing!

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How about a boring head with a small boring bar, you can make the hole diameter whatever you want it to be. Then you don't have to worry about any spindle run-out that you could possibly have with the "proper" size end mill or drill bit.

Have you ever made a small boring head and bar? I like the idea of using a boring bar, but I am having trouble working out how I can make one that will fit in my 5/8" turret that I can adjust. Any advice?

 

[Ripthorn]

Could you drill at 7/16 and use a chucking reamer? If you have to make lots of parts, a Forster that you can resharpen would be best.

 

[GadgetBuilder]

If you can tolerate a shallow guide hole in the center then consider making a counterbore from drill rod:
http://www.gadgetbuilder.com/CounterBore.html

If you can't tolerate the guide hole then leave the pilot out - but you'll need to hold the part securely and pre-drill then use a drill press or mill etc to hold the counterbore while you finish up. Not appropriate if you're using a hand drill, of course.

Counterbores are fairly quick and easy to make and one made from mild steel - unhardened - should last long enough to see if the concept works for your task. You may need to make a simple jig to aid in accurately sharpening it although even a filed edge should work in wood. Much simpler to sharpen than a twist drill.

John

 

[bob vaughan]

Re: Need to drill a flat bottomed 29/64" hole in wood 1/8" deep.

I like the idea of using a boring bar, but I am having trouble working out how I can make one that will fit in my 5/8" turret that I can adjust. Any advice?

Photobucket isn't working for me now.

Use an adjustable boring head. I took an old 1/2" shank single flute HSS router bit and ground most of it away leaving a cutting spur to pare the wood fibers upon entry, then a flat bottom raker to clean things out.

here's a thread about making a wooden collet rack that used that bit. what you'll have to use will have to be modified to fit the smaller hole.

http://www.owwm.org/viewtopic.php?f=79&t=100587&p=685752&hilit=collet+rack#p685752

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here it is

 

[Jimsehr]

And I want to avoid buying a $40 end mill just for this one task.
Any ideas? I have a 7/16" end mill that seems to cut about .003" (dia.) oversized for 29/64.
I need to make many of these.

Oh, and I had an anger breakdown yesterday trying to sharpen my 29/64 machine screw drill bit. I am no good at sharpening bits. For lack of a better word, I felt like a tool.

I'm thinking I could use a 3/8" end mill to get the right depth, and then fashion my own brad point-ish bit at 29/64 (w/o the point) to get the right diameter.

Thoughts?

I went out to shop and ground a flat bottomed drill and drilled a piece of metal with it. It would last a long time if all it was cutting was wood. I took a drill and cut it shorter to make it stiffer. But with wood I don;t think you would need to do that. I cut 3 holes .125 deep . I could have drilled the whole plate but 3 holes was enough to show how drill worked. I checked bottom and it is flat within a few thousands. I have been doing this for about 50 years. See pics of drill and steel plate below.
jimsehr




https://lh6.googleusercontent.com/-...kcATkpY/w1112-h695-no/flat+bottomed+drill.jpg