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Drill press slop and general imprecision

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Forum topic by toddbeaulieu posted 08-31-2015 01:13 PM 953 views 0 times favorited 26 replies Add to Favorites Watch
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toddbeaulieu

780 posts in 2463 days


08-31-2015 01:13 PM

I spent some time yesterday working on a proof of concept that requires precision drilling around the perimeter of a round piece. For my test I routed a six inch “donut” from a scrap of 4/4 cedar.

For this particular task I want to drill two-stepped holes that will allow a screw shank or bolt shank to slide, but not come through because of the head being captured on the outer edge. This video of a box that uses centrifugal force to unlock it shows what I’m trying to build. I’ll experiment with wood screws that have been drilled below the shoulder, stainless socket head bolts cut down and even nails.

Boy does this present a number of challenges and I’d love to hear whatever thoughts you have on conquering imprecision when drilling. I wonder if my old Delta just needs some expert tune-up or if I really need to buy into a different class of machine? Puzzle/machine making really needs precision!

- Chuck wobble (is it called run out?). I’ve tried various things like pressing it down hard on a planed board and even holding a pipe up against it while running.

- Bit wobble. It’s really easy, apparently, to bend a bit.

- Hold work piece steady and even positioning it in the first place! Ever try to position a donut to drill around the perimeter?

- Two-stepped holes. What’s a good way to drill a hole that gets narrower half-way through? Obviously, that’s two drilling steps that have to be precisely centered and parallel.


26 replies so far

View rwe2156's profile

rwe2156

2187 posts in 940 days


#1 posted 08-31-2015 03:49 PM

I don’t think there’s anything you can do about the run out except try a different chuck.

You could build some type of jig?
Use clamp or hold down?

-- Everything is a prototype thats why its one of a kind!!

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isotope

145 posts in 1083 days


#2 posted 08-31-2015 04:48 PM

I don’t have a lot of experience with this, but it might be worth looking into using a stepped drill bit. Something along the lines of what is used for pocket holes. I recently watch a YouTube video where the buy makes his own bit, but grinding a standard twist bit.

View ForestGrl's profile

ForestGrl

445 posts in 545 days


#3 posted 08-31-2015 06:33 PM


I spent some time yesterday working on a proof of concept that requires precision drilling around the perimeter of a round piece. For my test I routed a six inch “donut” from a scrap of 4/4 cedar.

[Snip]

Boy does this present a number of challenges and I d love to hear whatever thoughts you have on conquering imprecision when drilling. I wonder if my old Delta just needs some expert tune-up or if I really need to buy into a different class of machine? Puzzle/machine making really needs precision!

- Chuck wobble (is it called run out?). I ve tried various things like pressing it down hard on a planed board and even holding a pipe up against it while running.


You might try removing the chuck, cleaning everything up, and re-installing. If it still wobbles, sounds like a new chuck or a new drill-press. :-(

- Bit wobble. It s really easy, apparently, to bend a bit.

Forgive me being snarky here, but only if you’re not paying attention. How big are the bits you’ll be using? No benefit to pushing things too hard

- – Hold work piece steady and even positioning it in the first place! Ever try to position a donut to drill around the perimeter?
-
I would build a jig that has a center piece (such as a dowel) to position the stock precisely, and then an indexing pin on the perimeter. Drill the first hole, rotate stock in position for the indexing pin to fall into that hole, drill the next hole. Something like that. Pin would need to be springy and located on the periphery of the stock.
- – Two-stepped holes. What s a good way to drill a hole that gets narrower half-way through? Obviously, that s two drilling steps that have to be precisely centered and parallel.
-
If you can’t find a stepped bit, or make one as mentioned above, you need to drill the big hole first, precisely to depth. If you make a sleeve that fits this hole, with it’s own hole in the middle to guide the narrower bit, that should work.

This is all off the top of my head, with only one cup of coffee. Hope it makes sense.

-- My mother said that anyone learning to cook needed a large dog to eat the mistakes. As a sculptor of wood I have always tried to keep a fireplace. (Norman Ridenour)

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toddbeaulieu

780 posts in 2463 days


#4 posted 08-31-2015 06:45 PM

Some pretty useful feedback. I had the chuck off a while back. I should remove it again, clean it and try to get it on better. I really like the idea of the sleeve. Hadn’t thought of that. While I’ve put quite a bit of effort into reusable jigs, I don’t give specialty jigs enough respect. I think I need to convince myself to put more effort into things like this and to not move forward until I have a solution that’s guaranteed to hold the piece perfectly registered. Cost of doing business.

Thanks for the thoughts.

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TheFridge

5764 posts in 945 days


#5 posted 08-31-2015 06:57 PM

Also try turning the chuck 180 degrees

Edit: I meant the arbor and chuck assembly.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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ForestGrl

445 posts in 545 days


#6 posted 08-31-2015 08:21 PM


[Snip] I think I need to convince myself to put more effort into things like this and to not move forward until I have a solution that s guaranteed to hold the piece perfectly registered. Cost of doing business.

Thanks for the thoughts.

- toddbeaulieu

Yep, if you’re producing many of them, especially if hoping to turn a profit, the jigs are what make it work. The time you spend in developing the jig/fixture pays off by avoiding failed product (especially when you get half-way through, and then drill a hole in the wrong place!) Years ago, I was making stands (bases, sorta) for the cubes that hold autographed baseballs. I made a jig/fixture to use with my router for recessing. But there were 1-cube, 2-cube and 3-cube versions. Had trouble getting them perfect. Then, a forum-friend of mine in Southern California had me send him the specs, and he used a CNC-guided laser to make the jigs, with one holder and spacers depending on 1-, 2-, or 3-. SWEET!!! A laser can make a really tiny hole! :-)

-- My mother said that anyone learning to cook needed a large dog to eat the mistakes. As a sculptor of wood I have always tried to keep a fireplace. (Norman Ridenour)

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Gentile

256 posts in 1278 days


#7 posted 09-01-2015 02:42 PM

How old is your drill press?
I put new bearing in an 1940s Atlas/Craftsman and it runs like a champ…

-- "I cut it twice and it's still too short"

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toddbeaulieu

780 posts in 2463 days


#8 posted 09-01-2015 02:53 PM

Not sure how old it is, but not THAT old. Guessing 80’s or 90’s without doing any research.

I removed the chuck last night and tried aligning it better. It’s possible to knock it around a bit with a hammer while it’s spinning but I’m not sure how to get it accurate. I do have a dial indicator, but would need to rig up some sort of jig to try to determine the wobble. My assumption is that I’d then tap it around a bit while hand turning it until it’s centered to better tolerance. I guess I should do some searching for that procedure. It must be a known procedure.

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hairy

2384 posts in 2991 days


#9 posted 09-01-2015 03:06 PM

I have a Jet 17” DP, maybe 15 years old, I bought it used. There is one thing I’ve noticed that I don’t understand. When I pull down on the handle to lower the bit, when it goes down as far as it can go, the bit deflects to the side, maybe 1/16” inch to a little more. It’s obvious when I hold a square next to the bit and move it up and down. Changing the depth stop has no effect on this. I don’t think it’s caused a problem yet, everything I’ve drilled lines up where it should. I wonder if I need new column bearings, but I also think if the bearings are worn out the deflection would not be regular, it would be random deflection. I don’t feel any slop in the chuck when I wiggle it.

In answer to your ?, check the bearings.

-- stay thirsty my friends...

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Julian

1033 posts in 2150 days


#10 posted 09-02-2015 02:59 PM

You can check the run out with an inexpensive dial indicator and magnetic holder from Harbor Freight. Most basic drill presses will have some amount of run out (about .003-.005”). I had a similar problem with a new Delta drill press I purchased about 6 years ago. I found a tiny bit of metal shaving that prevented the arbor from seating properly. You can find several videos on Youtube on how to fine tune a drill press.

-- Julian

View ForestGrl's profile

ForestGrl

445 posts in 545 days


#11 posted 09-02-2015 09:27 PM

The idea that a bit has bent is seeming odd to me. Drill bits are quite brittle—I’ve broken a couple really small ones when chucking too close to the milled part where it’s weak—but it seems strange that they would bend. They can, however, chuck up off-center and not run true.

-- My mother said that anyone learning to cook needed a large dog to eat the mistakes. As a sculptor of wood I have always tried to keep a fireplace. (Norman Ridenour)

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toddbeaulieu

780 posts in 2463 days


#12 posted 09-02-2015 09:33 PM

Don’t get too hung up on that remark. It’s not my primary concern, although it’s actually quite easy to bend the larger bits, especially when cutting g through heavy metal with a powerful hand drill.

If I were smart I’d buy new metal bits and use them just for that, while getting wood cutting bits in larger sizes so I’m not forced to use gp bits in my Woodworking.

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ForestGrl

445 posts in 545 days


#13 posted 09-03-2015 01:54 AM


it s actually quite easy to bend the larger bits, especially when cutting g through heavy metal with a powerful hand drill.

- toddbeaulieu

Only time I tried that, almost broke my wrist Definitely not strong enough, LOL.

-- My mother said that anyone learning to cook needed a large dog to eat the mistakes. As a sculptor of wood I have always tried to keep a fireplace. (Norman Ridenour)

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MrUnix

4202 posts in 1658 days


#14 posted 09-03-2015 02:26 AM

- Two-stepped holes. What s a good way to drill a hole that gets narrower half-way through? Obviously, that s two drilling steps that have to be precisely centered and parallel.

Drill smaller diameter first, then use it as a pilot hole for the larger diameter drilled to depth. As long as you are doing it on a press, the ‘parallel’ part is already taken care of, and using the small hole as a pilot takes care of the centering part. Am I missing something here (with all the above recommendations to drill the larger hole first)?

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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toddbeaulieu

780 posts in 2463 days


#15 posted 09-03-2015 02:31 AM

Tonight I did a test with my Kreg bit and it was pretty darned nice. It does dictate what I can use for the sliding pin because of the diameter of the “pilot” part of the bit, though. The hole was too large for my brass screws that I cut down, so I went to the stainless bolts and had to do exactly what you suggested, using that pilot as a guide to widen it a bit. This brought me to another pet peeve or challenge that I’ve always had with drilling, which is the ragged entry/exit point, regardless of attempts at using a backer. After drilling I ripped the piece to remove both surfaces and it came out pretty sweet. Just takes quite a bit pf planning to come up with the perfect set up.

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