Forstner bit problems

[Dan Gaylin]

So I was doing the rare bit of spindle work (I mostly do bowls) and I was trying to get a 1 3/4” diameter recess for a candle in a cherry candlestick I had turned. I put my 2 MT drill chuck in the tail stock and put a 1 3/4” forstner bit into the chuck. Set my lathe to its lowest speed. Brought the tailstock up to the piece and was unable to get it to do much drilling. After about 1/16” of depth I decided it would be much easier to just hollow it out with my turning tools. Which indeed it was.

So I’m wondering why this didn’t work. Perhaps it’s because the lathe is a .75 hp Nova Comet 2 (not enough torque?) and the forstner bit is by Porter Cable? Bit seems reasonably sharp though and it cuts cherry fine (albeit slowly) in my drill press.

Thanks for your insights

-dan

[Dave Mount]

Explain more about the failure to cut. Did you stall the lathe or did it just spin without biting? Did you put a lot of force on it with the tailstock advance? What rpm is the lowest lathe speed? Was this end grain or face grain you were drilling into?

Forstner bits can resist biting in, especially if they're not super sharp. The drill press has a lot of mechanical leverage to force the bit into the workpiece. End grain is notoriously hard to drill with a Forstner because it's set up for a fairly shallow angle planing cut for most of the stock removal.

[Thomas Canfield]

To drill larger diameter holes with Forstner bits, I will often mark the face with the largest bit, then use a smaller diameter bit ( or multiple smaller bits) to drill the hole. For example, for 2" hole, face with 2". then 1-1/4", then drill with 3/4" to depth and increase backwards to final size. That works well for endgrain work which you are doing with spindle. Drilling the face diameter centers the larger bit to start, and same for decreasing down. If you just drill smaller and enlarge, the hole center can wander off easier. Not that complicated as it sounds.

[Dan Gaylin]

Thanks for the helpful replies. Lowest speed is 250 rpm. Slower than the lowest speed on my drill press. It was end grain drilling. Lathe did not stall, but I put a lot of force on it and it just didn't bite in. Basically got sawdust instead of shavings. Thomas, I've definitely worked up to larger bits from smaller bits before but not with Forstner bits. What do mean by "facing" with the 2" bit and the 1-1/4" bit -- if they won't bite, won't a just get a very shallow circle with a dimple in the middle?

[Richard Coers]

Thanks for the helpful replies. Lowest speed is 250 rpm. Slower than the lowest speed on my drill press. It was end grain drilling. Lathe did not stall, but I put a lot of force on it and it just didn't bite in. Basically got sawdust instead of shavings. Thomas, I've definitely worked up to larger bits from smaller bits before but not with Forstner bits. What do mean by "facing" with the 2" bit and the 1-1/4" bit -- if they won't bite, won't a just get a very shallow circle with a dimple in the middle?
You ever drill into end grain on the drill press? You don't get much for curls on end grain, but I suggest that bit isn't in as nearly as good as shape as you think. Didn't have the lathe in reverse did you?

[John K Jordan]

So I was doing the rare bit of spindle work (I mostly do bowls) and I was trying to get a 1 3/4” diameter recess for a candle in a cherry candlestick I had turned. I put my 2 MT drill chuck in the tail stock and put a 1 3/4” forstner bit into the chuck. Set my lathe to its lowest speed. Brought the tailstock up to the piece and was unable to get it to do much drilling. After about 1/16” of depth I decided it would be much easier to just hollow it out with my turning tools. Which indeed it was.

So I’m wondering why this didn’t work. Perhaps it’s because the lathe is a .75 hp Nova Comet 2 (not enough torque?) and the forstner bit is by Porter Cable? Bit seems reasonably sharp though and it cuts cherry fine (albeit slowly) in my drill press.

Thanks for your insights

-dan

That's odd. I've drilled a lot of holes in both side and end grain on the lathe using forstner bits. They always cut. I'm wondering if the bit was not sharp - can usually touch one up with a diamond hone. But I agree that just turning a shallow hole like that is the way to go. (A sharp box scraper works well and keeps the sides parallel, and I hollow handbell ornaments with a standard parting tool.) In any case, I usually drill a smaller hole with a twist drill to set the depth.

BTW, I drill most end grain holes with carbide forstner bits. I have an inexpensive set and the holes are not as clean as when drilled with the expensive steel bits but that doesn't usually matter for what I'm doing and the bits haven't dulled in 15 years of drilling. Also, to clear chips/dust and cool the bit I always direct a strong stream of compressed air into the hole behind the bit while drilling. I realize this won't help if the bit isn't drilling at all!

[Dan Gaylin]

The lathe was not in reverse, but I did check it :-) given how little progress I made. I have done end grain drilling on the drill press with cherry using a smaller 1.5" (and better, USA made older Vermont American) Forstner bit. Mostly got shavings. With the lathe, when I say sawdust, I'm talking about a very little bit. It took like several minutes and a lot of pressure to get 1/16" of depth. So not a lot of sawdust.

John -- I had been eyeing carbide Forstner bits for the reasons you state. Is there a brand you'd recommend? Anyone have a good set of carbide tipped Forstner bits.

thanks

-dan

[Prashun Patel]

If your lathe wasn't in reverse (which would certainly have been my issue) I suspect your bit is dull. Did you try a different bit?

Also, with forstners, the bits can overheat once they bury to the shank; the chips have nowhere to go, so the drilling stops and bit starts to heat.

Instead, I find it best do drill a 1/4" deep starter hole with your desired diameter, then switch to brad point or twist bit narrower than that to hog out much of the waste, and finally switch back to the original bit. It will feed with much more ease as it has less work to do. Preserves the life of the bit too...

[Reed Gray]

I would suspect a dull bit. Depending on the quality of the bit you used, some go quicker than others. If you can find a saw shop/sharpening service, a good one can have the bit sharper than it was in the package. You can touch them up by hand, but I found it far easier to take mine to a shop. I did find one that did a really good job.

robo hippy

[Jamie Buxton]

As a turner, you're familiar with the need to sharpen steel cutting tools. You're usually aware a lathe chisel needs sharpening when it doesn't cut the way it should. A Forstner bit is a steel cutting tool. It does need sharpening when it doesn't cut the way it should.

[John K Jordan]

...John -- I had been eyeing carbide Forstner bits for the reasons you state. Is there a brand you'd recommend? Anyone have a good set of carbide tipped Forstner bits.


I have several sets, the set I mostly use I got from Woodcraft a long time ago. No brand name on the box. I also bought a matching set of HSS bits at the same time but rarely use them. Although they can cut smoother holes, for my woodturning use this isn't nearly as important as the bits staying sharp practically forever. (I just bought a carbide chainsaw chain for the same reason.)

I buy individual carbide forstner bits in special sizes from amazon, for example 2-1/16" and 2-1/8" to drill temporary recesses in turning blanks. For example, this one has worked well:
https://www.amazon.com/gp/product/B00CCBSESU

JKJ

[Barry McFadden]

If your lathe wasn't in reverse (which would certainly have been my issue) I suspect your bit is dull. Did you try a different bit?

Also, with forstners, the bits can overheat once they bury to the shank; the chips have nowhere to go, so the drilling stops and bit starts to heat.

Instead, I find it best do drill a 1/4" deep starter hole with your desired diameter, then switch to brad point or twist bit narrower than that to hog out much of the waste, and finally switch back to the original bit. It will feed with much more ease as it has less work to do. Preserves the life of the bit too...

Prashun...... I'm not sure what bits you use but all my Forstner bits have large slots for chip removal... https://www.leevalley.com/en-ca/shop/tools/power-tool-accessories/drill-bits/102818-imperial-hss-forstner-bits

[Brice Rogers]

Dan Gaylin, It is pretty easy to sharpen a Forstner bit. There are some videos on youtube. I remember one from Captain Eddie Castilien. If you have a diamond sharpener card/file and a steady hand you can pretty easily do it. I suspect that in a pinch, that a person could use sandpaper (silicon carbide?) glued to a piece of wood.

If you are familiar with being able to "see" if a skew is dull by seeing the "glint" on the edge when moving it under a strong light, you can to the same thing with a Forstner. The actual cutting/material removal is done by the two straight edge going from the center to the perimeter. If you were not putting out long curls of wood, but instead were putting out fine particles, you probably had a dull Forstner.

BTW, when using a Forstner, even though there is a lot of open area behind the cutting surfaces, they can easily plug up when drilling deeper holes. For that reason, most people either back out the Forstner when the ribbons of wood stop coming out. Alternatively, blowing compressed air in usually works too. Once I was drilling a deep hole (perhaps 7 or 8 inches deep) and had to use a drill extension. I didn't clear the ribbons well enough and (1) the Forstner jammed and (2) the drill extension got loose and (3) when I pulled on the drill extension, it left the Forstner in the hole. I had to remove some wood and then use a vice grip on the 1/4 inch of Forstner that was newly exposed.

[Richard Coers]

Prashun...... I'm not sure what bits you use but all my Forstner bits have large slots for chip removal... https://www.leevalley.com/en-ca/shop/tools/power-tool-accessories/drill-bits/102818-imperial-hss-forstner-bits
Drill in about 2" and you'll understand what he is talking about. More than once I've locked a bit down inside a turning by not clearing the chips every 1/2" or so.

[Prashun Patel]

I have those same bits. I mean once you get past the flutes, and the head is buried, they don't auger up the shank.

This is even a problem with twist or brad point bits (in my experience) if you are drilling green wood. The chips pack tight.

[Barry McFadden]

Drill in about 2" and you'll understand what he is talking about. More than once I've locked a bit down inside a turning by not clearing the chips every 1/2" or so.

I regularly use a forstner bit to drill in 4 -6 inches to set the depth of bowls I do and have never had an issue.....

[Paul Haus]

I've been experimenting with boring holes in vessels (including end grain) in the lathe using both HSS and carbide forstner bits. What I've done is turn the outside round using a chuck and live center then set up the steady rest to stabilize the turning. Swap the live center for a drill chuck and set up for drilling. I first bore a starter hole in the the end with the largest bit I plan to use (maybe 1/4" deep). I have a smaller carbide forstner bit set and will start drilling in with something like a 3/4" bit to depth, then switch to a larger one and keep going till I get to the maximum size I plan to drill. Each time I drill maybe 1/4"-1/2" then clear out the chips which also helps keep the bits from overheating. I've drilled holes up to about 6" deep and done it successfully this way.
All my drill bits are sharp so they cut well. About the only thing i can think of is assuming your bit is sharp is you're trying to take too much out at a time. Maybe try coring out the middle first with a smaller bit and see if that helps. Good luck.

[Thomas Canfield]

Thanks for the helpful replies. Lowest speed is 250 rpm. Slower than the lowest speed on my drill press. It was end grain drilling. Lathe did not stall, but I put a lot of force on it and it just didn't bite in. Basically got sawdust instead of shavings. Thomas, I've definitely worked up to larger bits from smaller bits before but not with Forstner bits. What do mean by "facing" with the 2" bit and the 1-1/4" bit -- if they won't bite, won't a just get a very shallow circle with a dimple in the middle?

Yes, you will get a shallow grove with the outside cutter (facing) and center. The center will align the smaller bits to maintain center and they will also make a grove as you progress down to allow centering as you work back up. If you try to use a larger bit without the center, the bit can start slightly off center moving your center for the desired spot as the bit engages and finds its grove. This also works for spade bits that need a center or pilot hole diameter of larger bit to prevent wandering.

[Dan Gaylin]

Okay folks, thanks for all the helpful thoughts. I will try some different bits. I will look into sharpening options.

[Russell Neyman]

What usually causes a Forstener-style bit to “lock up” is the wood expanding due to heat. This is Exacerbated by moisture in the wood.

One solution is to drill the hole just slightly off-center, which causes a gap on one side. This can be done by moving the headstock (if you have one that pivots) or by placing a business card under one side of the tailstock.

Forster bits give a cleaner hole, but spade bits are more efficient. I use a combination of both and make the hole larger in steps.

[Pat Scott]

Dan you asked about carbide forstner bits. The good ones are pricey ($50 or more depending on size. A 1-3/4" is $76) but are well worth it if you drill a lot of holes. I've tried cheap $7 carbide forstners that didn't cut very clean or very well. The Bormax3 by Famag is a good carbide forstner, it's effortless drilling into end grain. I wish they made more sizes. My only complaint is their packaging is kind of cheap, after you open/close the package several times the plastic can tear. Several places sell Bormax3, I get them from CarbideProcessors.com. I tried a Freud carbide bit recently and it was OK, but the Bormax3 did a better job drilling end grain for peppermills.

[Dan Gaylin]

Pat thanks for the Bormax3 recommendation. Much appreciated.

-dan

[Perry Hilbert Jr]

I drill a fair amount of holes with forstner bits. Drilling side grain usually chips up and clears fine. End grain will clog up fast once I get about an inch deep.

[John K Jordan]

I drill a fair amount of holes with forstner bits. Drilling side grain usually chips up and clears fine. End grain will clog up fast once I get about an inch deep.

Have you tried the compressed air method while drilling? Use a nozzle to direct a strong stream of air into the hole behind the bit. I've been using it for years and it keeps the chips clear and prevents binding at least for the bits I use, and as a bonus cools bit. I won't drill deep end-grain holes with Forstners without it.

JKJ

[Dan Gaylin]

Thanks John. No I haven’t tried the compressed air method. That is a good tip. But I am very careful with Fortner bits to constantly back off the cut and clear the chips and shavings.

[Bert McMahan]

This chart recommends about 400 RPM for that size bit:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjN0I-ygcjpAhUP7awKHVQuCXoQFjASegQIBBAB&url=https%3A%2F%2Fwww.infinitytools.com%2Ffileuplo ader%2Fdownload%2Fdownload%2F%3Fd%3D0%26file%3Dcus tom%252Fupload%252FFile-1521559846.pdf&usg=AOvVaw13MxzQkdFz0ggEDjDEXQxP

It also has some info on sharpening.

[Kyle Iwamoto]

I use a cheapo spade bit a couple sizes smaller than the Forstner. Spades are cheap, drill fast, easy to sharpen. Yeah they don't go straight and they cut poorly, but they cut fast and I don't have clean out problems. I drill to depth, remember the long pointy part, then follow with the Forstner. Having most of the wood wasted out by the spade, the Forstner now can cut pretty fast, and since there's much less wood being drilled by the Forstner, chip lockup usually is not a problem....

[Pete Staehling]

It never occurred to me to use a spade bit to pre drill the hole in a smaller size. I'll have to try that.

I have done a lot of end grain drilling on the lathe and never had too much trouble other than the fact that it does tend to clog and or heat up if you don't back off and clear it out on deeper boring. Also I second the suggestion that the bits need to be sharp. Oh and it takes quite a lot of pressure to drill end grain. You get a lot more on the drill press than you probably realize.

[Dan Gaylin]

Yeah the spade bit is a good idea. I actually now remember i asked a question like two years ago :D about using spade bits to save the wear and tear on my Forstners like. The beauty of age -- Kyle's suggestion was "new to me".

[Richard Coers]

I regularly use a forstner bit to drill in 4 -6 inches to set the depth of bowls I do and have never had an issue.....
What I was trying to say is if you drill in 2" without clearing the chips, you can easily bind up the bit. I've drilled deeper than 4-6 with an extension, but you must clear the chips very often.

[John K Jordan]

What I was trying to say is if you drill in 2" without clearing the chips, you can easily bind up the bit. I've drilled deeper than 4-6 with an extension, but you must clear the chips very often.

Richard, your experience of easily binding the bit and the absolute need to "clear the chips very often" doesn't seem to be universal.

I didn't read all the thread - have you tried the compressed air method? With a strong stream of compressed air directed behind the bit I don't have to stop and back out to clear chips. The air blows them out. No binding or excess heat.

But maybe it's apples vs oranges since something is obviously different. Speed of rotation, pressure, advance too fast or too slow? Bit sharpness? Perhaps it is the design of the specific bits I use that have more open space and let chips blow loose and not jam. Different bit design - knife edge, sawtooth? (I use carbide spur bits.)

Or maybe the wood makes a difference - the last time I did deep holes like this with an extension was for salt and pepper grinders in very dry cocobolo, dogwood, and cherry.