Drill press inaccurate - Page 2 - Woodworking Talk - Woodworkers Forum
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post #21 of 31 Old 10-09-2019, 07:44 AM
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Quote:
Originally Posted by enchant View Post
So how about this... What if, rather than drilling a preliminary pilot/centering hole, I mount the center punch in the drill press, and with it turned off and using my alignment jig, put the the center punch dents into my wood that way?
Aye, thatd work, probably. You wont have any rotating forces trying to push the punch somewhere else, but theres still the risk that the quill doesnt always come to the exact same spot.

If youre already using a jig, might not be a bad idea to rethink how the jig works. By the sound of it, your jig is secured to the table and just used to register the work piece in the same spot, yes? What i would do would be to grab a piece of sheet good, something like MDF, and drill the holes in that as accurately as possible. The, take that piece and secure it to your workpiece with the holes where you want to go and use the holes in the template to guide the drill. This way, even if the quill wanders the drill itself cant go anywhere, since the jig is keeping it in place.

Picture something like a dowel jig for ideas:


A bushing guides the drill, so even if the tool is inaccurate the drill can only go where you want it

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post #22 of 31 Old 10-09-2019, 01:49 PM
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If you have movement in the quill you will not mark or drill a hole accurately, most lower end drill presses suffer from this, as they age the problem often gets worse. Adjustment may eliminate much of the movement but on some drills the quill can no longer be tightened evenly along the entire stroke. It is always wise to check quill movement on any drill press you are purchasing in person, it is amazing how many you will reject immediately. Run out is another factor but often compounded by a loose quill.

If there is movement in the quill the bit has to be guided so it can't deflect as has been suggested in previous threads.

Twist drill bits are not ideal nor designed for woodworking, brad point or Forstner bits will tend to wander less and cut much cleaner, and any guide bushing will last longer using them.

Saddly most drill presses available from your local hardware store are not precision machines, hence most metal workers prefer to invest in a milling machine to drill accurate holes with the added advantage of the other uses for the machine.
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post #23 of 31 Old 10-09-2019, 05:32 PM
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I do not think that anywhere in this long thread did I ever see just what accuracy was required and why. ???? It would help to know that when making suggestions as to how to solve the problem.



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post #24 of 31 Old 10-09-2019, 06:01 PM Thread Starter
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Originally Posted by CharleyL View Post
A "center drill" like the tool makers and machinists use, will make a significant improvement in your drilling accuracy.
My center drills arrived today and I've got to say, they work great! I took four pieces of 2x3 stock, drilled down into them with the center drill until the 1/4" hole was at least 1/8" deep. Then I swapped in the 1/4" twist bit and the hole and drilled through. The acid test for me is to turn the drilled piece over and see that the drill comes down perfectly inside the hole. Previously, it was clear that the whole was drilled inaccurately.
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post #25 of 31 Old 10-09-2019, 06:12 PM Thread Starter
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Quote:
Originally Posted by GeorgeC View Post
I do not think that anywhere in this long thread did I ever see just what accuracy was required and why. ???? It would help to know that when making suggestions as to how to solve the problem.
I really don't understand why. I'd like to learn how to accurately drill a hole on an imperfect surface with my drill press, regardless of what today's specific project is. It's my experience that if I say exactly what it is I'm trying to do, people will suggest alternative methods based on their particular skill sets and tools. What I'm doing is working great. I just needed this specific issue solved and I'm very appreciative for the several suggestions that gave me alternate methods to try.
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post #26 of 31 Old 10-10-2019, 07:55 PM
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I had that same problem then bought a set of brad point bits.

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post #27 of 31 Old 10-10-2019, 08:45 PM
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Marlin and others have a point about using a well ground brad point bit. There's a lot of trashy brad point bits out there. Brad point bits are for wood. All other bits are mainly designed for metal and are often used for wood as a make-do. Metal working bits really shred the wood fibers, particularly in soft wood.

The press in question (11-120 Homecraft) uses an 11/16 x 5/8" bore bushing. Not real easy to find. I just did one of those quills last week. Once the new bushings are in place, the bore needs to be reamed to 5/8" again because when the bushings are pressed in, they shrink ever so slightly and the spindle won't fit. That model drill was an 'economy' model and the least expensive drill press Delta made. Speeds from 700 rpm to 4700 rpm were pretty rough on those sleeve bearings. All of that model (and the radial drill model) that I've ever come across needed new bushings. Likely that's why they were for sale in the first place. With new bushings, that makes for a very quiet drill press.

https://www.woodworkingtalk.com/atta...379631&thumb=1
A good brad point bit. Not the outside cutting spurs and the well formed brad point.

https://www.woodworkingtalk.com/atta...379633&thumb=1
Delta 11-120
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post #28 of 31 Old 10-13-2019, 10:21 PM
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brad point drill bit
available all over for less than $3

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post #29 of 31 Old 10-14-2019, 12:28 PM
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Hi


If you decide to replace the bushings, here is a place that still sells them. Here is the Delta part # 920750112796 for the bushings.



https://www.renovoparts.com/920-75-011-2796-bushing/
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post #30 of 31 Old 10-14-2019, 02:59 PM Thread Starter
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Thanks, but my new drill press arrives today, so the bushings will have to be the next owner's problem.
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post #31 of 31 Old 10-14-2019, 06:34 PM
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From my post no. 13 ........

A spur bit or brad point drill, is the first thing that came to my mind like this:
https://www.woodcraft.com/products/f...xoCxFAQAvD_BwE

https://www.amazon.com/Bosch-B14603-.../dp/B0065EPHSK


Quote:
Originally Posted by _Ogre View Post
brad point drill bit
available all over for less than $3



The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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