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Large forstner bit issues

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Forum topic by Ktockstein posted 07-05-2020 10:54 PM 468 views 0 times favorited 8 replies Add to Favorites Watch
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Ktockstein

1 post in 34 days


07-05-2020 10:54 PM

I have been working with 4×4’s to make candle vessels for my wife’s business. The first round I did with a 3” steel forstner bit and used treated lumber on a 1/3 HP drill press. It worked ok, but the treated had too many cracks down the grain so it wouldn’t work.

I took my brother in law’s (former furniture builder) advice and got cedar 4×4’s. I cut them 3 1/2” long to match their true dimensions and then took a 1/2” off on side with the hole going into the 3 ” side.

I’m now using a carbide tipped 3” forstner bit in a 3/4 HP drill press at 250 rpm and no matter what I do it chips away about an 1/8” and the just stops. The motor is still going and the belts aren’t slipping.

I thought it was my bit which is why I got a new carbide one but it’s doing the same thing as the one I used on treated lumber for the first group I did.

Any advice on what is causing this and how to work around it?


8 replies so far

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JohnDon

125 posts in 1974 days


#1 posted 07-06-2020 12:26 AM

If the motor is running, and the bit stops, there must be slippage somewhere. If not the belts, then the pulley shafts, or more likely, the chuck taper is slipping. I’m no drill press expert, but maybe you could hog out some of the wood by using a slightly smaller hole saw before using the forstner bit. That might reduce some of the resistance your forstner bit is working against.

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ibewjon

1758 posts in 3598 days


#2 posted 07-06-2020 12:45 AM

After starting with the proper size forstner to get a guide hole, go to a smaller forstner to remove some waste. If doing many of these, get a hole hawg bit from Milwaukee. It will cut wood and nails, it has a screw center with fine or coarse threads to pull the bit into the wood. Clamp the wood tightly.

View Karda's profile

Karda

2364 posts in 1359 days


#3 posted 07-06-2020 03:29 AM

could the bit be dull, some time they oops a the factory

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John Smith

2511 posts in 968 days


#4 posted 07-06-2020 12:55 PM

maybe it’s just me, but, I have better success with a Forstner Bit
at a high RPM and lots of down pressure to quickly remove material.
not just wimpily watching each curl of wood come out like it was a sideshow.
all small projects should be clamped firmly to the table.

.

-- there is no educational alternative to having a front row seat in the School of Hard Knocks. --

View GrantA's profile

GrantA

2674 posts in 2213 days


#5 posted 07-06-2020 12:59 PM

You could double your speed and be ok still. Keep it under about 600
I have done repetitive drilling of holes for beer flight trays and can promise you this – next time.I’m making a template to use with a plunge router!

View BurlyBob's profile

BurlyBob

7703 posts in 3070 days


#6 posted 07-06-2020 03:41 PM

I’ve used a 3” forstner bit to drill holes in birch sections for pencil holders. After fighting with things I started using a 1/2” bit to hog out a lot of the material and finish with the 3”.

View Madmark2's profile

Madmark2

1461 posts in 1393 days


#7 posted 07-07-2020 12:36 AM

3” is big for a small drill press. Try pecking at it. Take a shallow cut, raise the bit, another shallow cut, etc. Its tedious but it works.

If time is important (ie production) get a bigger, more powerful drill press.

-- The hump with the stump and the pump!

View therealSteveN's profile

therealSteveN

5934 posts in 1379 days


#8 posted 07-07-2020 06:57 AM

For a long time I thought Forstner bits were something of a scam. Then I got my first Fisch Forstner bit, and damn…. Super clean, super straight holes, every time.

I’ll go on record to say 2 things.

1) All Forstner bits are NOT created equal

2) With a good brand of bit, I don’t see such a need to play with drill speed, pressure, or anything else, just drill it and smile.

They only sound expensive, until you use them. Back when I swapped there were only a few places to get them in the US, now they are becoming a mainstream bit, and I see specials for them that make my wallet moan, because it remembers what they used to cost. Plus they only had one line of Forstners, now they offer low, med, high, and super so you can step in at several price points, and all of them will beat the usual suspects.

-- Think safe, be safe

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