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Thread: Drilling large deep holes on lathe with forestner dit

  1. #16
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    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.

  2. #17
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    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.

  3. #18
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    Thanks for all the advice and options. Since I donít presently intend to do a lot of vases Iíll 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?

  4. #19
    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

  5. #20
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    Quote Originally Posted by Richard Coers View Post
    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

  6. #21
    Quote Originally Posted by Dick Strauss View Post
    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

  7. #22
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    Some things about drilling on the lathe

    Quote Originally Posted by Dick Strauss View Post
    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:

    drill_visegrips.jpg

    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.

    tommy_bar_on_chuck.jpg

    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.

    taper_1_IMG_20160919_094408.jpg taper_2_IMG_20160919_094945.jpg

    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.

    end_mill_holder.jpg

    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.

    center drills.jpg


    Quote Originally Posted by Bernie Kopfer View Post
    ... 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

  8. #23
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    John thank you for taking the time to put this information together.

  9. #24
    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.

  10. #25
    79A516A6-551E-4F3A-8BB8-5CB28EA1FD5D_1_201_a.jpeg

    ....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.

  11. #26
    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

    ED28DD6E-0830-4AA0-A651-5C4F3E5AD476_1_201_a.jpg ED28DD6E-0830-4AA0-A651-5C4F3E5AD476_1_201_a.jpg

  12. #27
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    Drawbars and tailstocks

    Quote Originally Posted by Lawrence Duckworth View Post
    .. 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.

    drawbar_two.jpg

    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.)

    drawbar_long_spindle.jpg

    JKJ

  13. #28
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    John, try cutting down the center of the 1/4-20 with a very thin cutoff wheel for threading.

  14. #29
    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!

  15. #30
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    Quote Originally Posted by Dick Strauss View Post
    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

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