Drilling large deep holes on lathe with forestner dit

[Bernie Kopfer]

This is a follow up question from a previous link Powermatic 3520b quill problem (https://sawmillcreek.org/showthread.php?293638-Powermatic-3520b-quill-problem). I received the new quill and sure enough it moves in and out smooth as can be.
So I apparently bent the old quill by attempting to drill a deep( 8") hole x3" Dia in a semi green piece of maple for a vase. I had recently sharpened the bit but the wood was hard and I was going slow with suction removing the chips as best possible. It did bind up a couple of times if I pushed too fast Deep in the hole it started to bind up whenever I tried to back out. I have to admit the wood had a very slight wobble to it and I'm blaming that for the bend, but nothing worse than I had done before.
How do you go about drilling deep holes for vases and such? (And I like to sometimes drill an hole to proper depth before hollowing out a bowl.) Should the wood be really green and soft?

[Grant Wilkinson]

I drill them on the lathe. My lathe motor has lots more torque at low speeds than my drill press, I can hold the piece more securely, and I can gradually increase the bit size since the piece is centered. YMMV, of course.

[Tim Elett]

I was reading a post, where a suggestion was made to drill center out in a drill press. I have no experience in hollowing, I wonder if that would be better.

[Bernie Kopfer]

I drill them on the lathe. My lathe motor has lots more torque at low speeds than my drill press, I can hold the piece more securely, and I can gradually increase the bit size since the piece is centered. YMMV, of course.

I was wondering about drilling initially with a smaller diameter bit and then moving up in size. That would certainly take some load off the larger bit. I’ve never done that so wonder if others have and any recommendations for sizes and steps?

[Dwight Rutherford]

When I use 1” and larger Forstner bits I keep lathe at or below 300 rpm and back the bit out every 1/2”. Anything faster causes heat build up. This also clears chips. I don’t feed the bit into the wood aggressively as that also causes heat build up and binding.

[Dan Gaylin]

A good, sharp bit is also key. I learned about higher quality bits from folks on this forum. Generic HSS porter cable bits, despite my best efforts to sharpen them, were not doing the job on the lathe. I have upgraded to Famag carbide Forstner bits (and Freud carbide Forstner bits) and it goes much better. Freud are not as good as the Famag but the Famag get prohibitively expensive in the larger sizes.

[Prashun Patel]

Drill in stages. This may sound counterintuitive but it works:

Drill 1/2” deep with a 3” bit.
Then drill 1/2” deep with 2” bit.
Then 1/2” deep with 1” bit.
Then all the way through with a 1/2” twist bit.

Then widen the hole by going up in diametter from 1, to 2, to 3”. The bits have to work less hard this way and they can find their center by the first three stepped pilot holes. I do this whenever using a forstner beyond the depth of the flutes.

[Stan Calow]

Green (and wet) is worse.

[John K Jordan]

… I was going slow with suction removing the chips as best possible. It did bind up a couple of times if I pushed too fast Deep in the hole it started to bind up whenever I tried to back out. …

Instead of using suction to remove chips, for many years i’ve used a different method. I never read this anywhere but made it up:

Force a strong stream of compressed air into the back of the Fostner bit while drilling the entire depth of the hole. This not only clears the chips and sawdust but cools the bit. With this method I've never jammed a bit on the hole. I drill deep holes by adding an extension when needed.

Another thing, unless the hole needs to be a very precise diameter I never use high quality steel bits. They dull too quickly on deep holes. Instead, I reach for inexpensive carbide Forstner bits. The hole is not as smooth but for many applications this doesn’t matter. They often have more open space for the compressed air too.

JKJ
.

[Richard Coers]

As far as I am concerned, forstner bits are not for hollowing vases. Especially a 3" one that makes it nearly impossible when boring deeply and also to keep it from spinning in the drill chuck. I drill a 1/2" hole and then bring in the hollowing tools. For what you've spent on a 3" bit and a replacement quill, you'd have spent about half what you need to get into hollowing. I make my own hollowing tools, so I got into it for a fraction of the cost of a 3" drill bit.

[Edward Weber]

I'm with Richard on this.
A reasonable sized pilot hole is all that's required. Green wet wood hollows quickly but can be more difficult to drill.

[Eugene Dixon]

Sometimes I step through it. Drill a shallow hole with the bigger diameter for alignment later when drilling deep. Then fall back to a smaller diameter bit, drill in some reasonable distance. Step up the diameter and drill almost to the same depth of the previous bit. Rinse and repeat. Stepping deeper across all diameters until the final depth is reached with the smallest diameter. Then step through the bits until the final diameter is reached.

But hollowing tools can be faster.

[Thomas Canfield]

Drill in stages. This may sound counterintuitive but it works:

Drill 1/2” deep with a 3” bit.
Then drill 1/2” deep with 2” bit.
Then 1/2” deep with 1” bit.
Then all the way through with a 1/2” twist bit.

Then widen the hole by going up in diametter from 1, to 2, to 3”. The bits have to work less hard this way and they can find their center by the first three stepped pilot holes. I do this whenever using a forstner beyond the depth of the flutes.
I follow Prashum plan but only do about 1/4" depth, enough to register the smaller bit using the center of the larger bit. Sure makes a big difference using smaller bits to depth first just enlarging from there, especially as bits get a little dull and cutting endgrain. You can pick some unused sizes that still give a range of diameters and not be held to the standards. I often will use a 7/8 amd 1-5/8" as example instead of 1" and 1-1/2" since the actual size is not important until the end.

[roger wiegand]

I'd use a bowl gouge to remove 90% of the waste then the forstner to clean it up. To be honest I'd probably forego the forstner at that point and just finish it with a gouge and NRS, but if you need the square corner and flat bottom of the drill for your design then the drill may be the right way to go. Even so, a tearout-free surface from the drill is a lot to ask.

Edit: Didn't notice how deep you were going, edit to say I'd use a hollowing tool to remove most of the waste and then the Forstner. 8" is a big reach with a bowl gouge!

[Dick Strauss]

I don't have any issue with drilling a 2.5" hole 12+" deep. You need to back the bit out every 3/4" or so to clear the shavings once you get the drill chuck inside the piece, otherwise it will get stuck. I loosen the tailstock lock and slide the whole assembly out to clear the shavings.

You also need to make sure you've got a full-sized tenon (max tenon length with flat shoulder to fit the chuck at the minimum diameter that the chuck will close around snugly).

A steady rest will help as well.

This process takes less than 10 minutes to set up and get to a full 12" depth.

[Dick Strauss]

I do not like to use forstner bits to follow another smaller diameter bit. Until the forstner bit point is engaged in wood, I find the bit will tend to want to walk off axis slightly when starting the cut which is a recipe for bad things to happen.

[Dick Strauss]

I should have mentioned that I hold the drilling assembly against the quill as I move the tailstock out to clear the shavings. I also hold the assembly while drilling just to make sure it doesn't want to spin in the mt2.

[Bernie Kopfer]

Thanks for all the advice and options. Since I don’t presently intend to do a lot of vases I’ll hold off on acquiring and learning to use a hollowing system. Step drilling has its naysayers and advocates but for me appears to be the option I will try. Anybody recommend a particular brand of carbide forestner bit?

[Reed Gray]

Using forstner bits to hollow out a vessel or box does work, but I find it to be very slow. I would guess the only exception would be for salt and pepper mills where you need specific sizes of holes. This is especially true with the bigger forstner bits. Once the center hole is drilled, it is much faster to use hollowing tools.

robo hippy

[John K Jordan]

As far as I am concerned, forstner bits are not for hollowing vases. Especially a 3" one that makes it nearly impossible when boring deeply and also to keep it from spinning in the drill chuck. I drill a 1/2" hole and then bring in the hollowing tools. For what you've spent on a 3" bit and a replacement quill, you'd have spent about half what you need to get into hollowing. I make my own hollowing tools, so I got into it for a fraction of the cost of a 3" drill bit.

Agreed, not for hogging out wood. But Forstner bits are fantastic for drilling holes of specific sizes, such as those needed for peppermills and the like.

For hollowing forms, boxes, etc, I generally drill a 3/8" hole for the primary purpose of setting the depth and the secondary purpose of making the cut at the center a tiny bit easier by eliminating the nub.

JKJ

[Lawrence Duckworth]

I should have mentioned that I hold the drilling assembly against the quill as I move the tailstock out to clear the shavings. I also hold the assembly while drilling just to make sure it doesn't want to spin in the mt2.


I'm glad to see you bring this up .... awhile back I drilled a hole with a forstner and when I backed the bit out the bit and chuck fell out of the tail stock.... cheap thrill :)... Now I always hold onto the assembly when drilling.


Today I drilled down to 3-3/4"x1"with a spade bit, then cleaned it up square to 3"dia with a carbide....no problem.

...12"deep???donno-maybe problem:)

[John K Jordan]

I should have mentioned that I hold the drilling assembly against the quill as I move the tailstock out to clear the shavings. I also hold the assembly while drilling just to make sure it doesn't want to spin in the mt2.

Spinning the chuck or other holder in the quill MT can, of course, badly gall and scar the MT socket so preventing that is helpful. I often use vice grips to hold a bit, letting the handle slide along the tool rest:

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If using a conventional keyed Jacob's chuck, I hold the chuck with a bar in one of the holes. Doesn't work with keyless chucks. Better than holding the chuck with the hand with a large bit.

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BTW, for twist drill bits, I've become a big fan of taper shank bits. They fit directly into the tailstock quill (with an adapter for smaller bits) and eliminate much of the length and perhaps some runout. I bought a big stock of these new for about $1 each on closeout. The larger ones are fantastic for drilling deep holes for hollowing. For drilling into the end of goblets Rudy Lopez modifies a 1" drill like this by cutting it short and regrinding. Good idea.

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For Forstner bits with 3/8" shanks, I bought an inexpensive 3/8" end mill holder that fits directly into the 2MT quill. I keep one 2-1/8" Forstner bit mounted in this all the time for drilling recesses in bowl and platter blanks.
I use this one: https://www.amazon.com/gp/product/B01MXSP25W If used in the headstock, it can be held tight with a drawbar.

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BTW2, if you do spin a tapered shaft in the tailstock quill or headstock spindle, a 2MT reamer set is an easy way to clean up any damage. I have this one. I've also used a round file and sandpaper on a stick.

https://www.amazon.com/gp/product/B07933VYD7


Finally, to twist drill any deep hole with precision, I ALWAYS start the hole with a center drill. I keep a couple in spare Jacobs chucks. They tend to start the drill straight and give a much better chance of drilling straight. I also run the lathe at fairly high speed and drill slowly. The taper shank bits help as well by minimizing any play in a drill/Jacob's chuck combination.

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... Anybody recommend a particular brand of carbide forestner bit?

Where I'm not concerned about the precision of the hole I buy the cheapest carbide Forstner bits from Amazon. I have several sets of both Metric and inch sets and several larger bits. These have worked well:

https://www.amazon.com/gp/product/B00CCBSESU
https://www.amazon.com/gp/product/B01MEBWIYM
https://www.amazon.com/gp/product/B01LSAD7BO
https://www.amazon.com/gp/product/B01K4HL9OE

I also keep high quality Forstner bit sets in tool steel for where precision is important. I don't use these for deep, rough work since they get dull quicker.

JKJ

[Bernie Kopfer]

John thank you for taking the time to put this information together.

[Lawrence Duckworth]

Good lesson John.

I went to snooping around and it looks like the powermatic c tailstock might hold a collet and draw bar set up.

[Lawrence Duckworth]

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:)....okay so it turns out my keyless chuck is threaded with a 1/4-20. I used some all-thread as a draw bar and it worked great,...very secure and tight. However the crank is of no use, I'd need to push the entire tail stock assembly by hand in order to drill a hole. not sure if this has any value. :)

[Lawrence Duckworth]

I used a 1-1/2" fostner to start hollowing the cypress box and the walnut vase. finished squaring with carbide scrapers. ..... I keep adding to the gift table :)

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[John K Jordan]

.. However the crank is of no use, I'd need to push the entire tail stock assembly by hand in order to drill a hole. not sure if this has any value. :)

That's the opinion I had when considering the Jacob's chuck in the tailstock. Unfortunately, loosening the tailstock enough to push it to drill detracts from the precision. I have imagined a way to use a drawbar in a tailstock and still use the crank but it would require some major engineering/machining. However, it's usually easy to use the Jacob's chuck in the headstock with a drawbar and hold the work in the tailstock.

Most of my collets and Jacob's chucks and mandrels all have either a 3/8" threads but a few things have 1/4" so I made two drawbars.

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I also use the 1/4" drawbar to hold long, thin spindles in the headstock on occasion. For example this walnut spindle tapered from 1/2" to about 1/16" over about 24". Holding it with a short 2MT turned on the end worked well until the other end got so thin the tailstock pressure was no longer useful. Drilling a hole into the wood and forcing a 1/4"-20 drawbar directly into the wood held it well for finish turning. (I file grooves at the end of the drawbar to turn it into a tap for wood.)

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JKJ

[Dick Strauss]

John, try cutting down the center of the 1/4-20 with a very thin cutoff wheel for threading.

[Lawrence Duckworth]

I bought a new Enco mill back in the late 70's (Bridgeport knock off) it's still a pretty good machine, on it the quill carries the spindle and that I think (a quill) would be the trick on the lathe tailstock to holding a collet or drill chuck properly.

holding the work piece in the headstock with a collet looks like a steady way....2 thumbs up!

[John K Jordan]

John, try cutting down the center of the 1/4-20 with a very thin cutoff wheel for threading.

Do you mean to make a split tap? The grooves do such a good job I've not yet found a need for that. (But I'll probably try it just because. :))

I do usually use a Dremel cutoff wheel to make the grooves. When not handy, a small 3-sided file does a pretty good job, held so the angle is more vertical on the side to be cut. I usually cut three or sometimes four grooves. For some reason I can't explain I generally cut these grooves at an angle. Oh, I remember, if using a file, the angle can make the filing easier, or at least that's what I imagined.

I've been doing this for decades! At first, I made taps to clean up bungled threads in metals. A hardened bolt makes a great tap for that, even cleaning up mild steel nicely. Especially good for larger holes/nuts with odd thread pitch. On occasion I've ground a slight taper around the end to help it get started. Even an non-hardened bolt will work in a pinch. Once or twice I've filed the inside of a largish nut to clean up a bolt. (BTW, for anyone still following a far better way to restore threads of common sizes in metals is with a thread restorer, better than taps and dies. This is the one I bought years ago, comes with a variety of thread files for less common thread sizes: https://www.amazon.com/gp/product/B000P6UNHE)

BTW, for a drawbar holding a turned 2MT end tightly into the headstock spindle the tapped hole doesn't even need to be perfectly centered to work. For the walnut piece I accidentally let the hole get off-center - the drawbar wobbled in the headstock but due to the turned MT none of that wobble affected the wood.

JKJ

[Lawrence Duckworth]

:) ...here ya go John... this one has kind of a steampunk look to it though

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