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...-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...-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.