Need help with Forstner bit

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Tea Clipper

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Randy: OMG! I went to HF yesterday and while browsing the isles, I found the exact same thing except the handles are black. Mine cost $3.99. Interesting that this item was in the store, but I can't find it in the online catalog...

Daniel: While doing the end grain, there was no chips just dust. As was earlier mentioned, the action was more of a scraping rather than cutting. In cross grain, I was getting litte curls proportional to the feed rate.

Frank: This was definately smoke! Unfortunately, I don't have a VS lathe, so the slowest is 500 (I thought it was 620, but no, its 500).

Ray: Now that I have a diamond needle file set, I'll see if I can't sharpen the edge. And no, I don't think you're rambling. My posts, otoh... they ramble.

Everyone: Thank you all for your thoughts and your patience.
 
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KenV

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I have a bit just like that --

It is a saw tooth bit which is a bit different than the Irwin Forstners I have After grinding down the center point to something less than 1/2 it's original height and grinding some relief on the cutting blades it works marginally. I am drilling face grain in maple using a Taig micro lathe with the bit chucked in the tail stock and using slower range of speeds. The saw tooth bits do not have the rim to run on that the Irwins have.

Some more grinding, diamond file and india stone work and it will be better. Generally poor finish and rough grinding on the original.
 

loglugger

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I don't know if this is something you should do or not but have been doing it for years and seems to help. PUT ON SAFETY GLASSES !!! Take your air blower nozzle and put it down next to the bit and blow the chips and dust out of the hole while you are drilling the hole. Gets rid of the chips and cools the drill bit.
Robert Lee
Lebanon OR.
 

KenV

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I spent some time with diamond file and fine india stone and also sharpened the edges on the sawtooth part of the forstner style bit. It is now sharp. On soft wood it looks like the chips would "hit the ceiling. In the hard maple and yew, the shaving do come out steady and fine. I need to duct tape the sharp edges and drind the center point down so it just enters the wood about 0.05 inch before the spurs cut.

The grind from the factory in China was very coarse and the honed edge leaves a nice smooth bottom.

Maybe I got one from the first shift after a long weekend....
 

Tea Clipper

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Weekend report: What timing! I was just asking how to go about sharpening the forstner bit when Rich Kleinhenz posted a nice tutorial on barrel trimmer sharpening on the Yahoo penturners group. Seeing that the forstner bit is similar enough, I followed his instructions and in no time had a nice sharp bit (I also took the liberty to grind off most of the center point).

Starting with a piece of end grain, I noticed that the sharp bit was certainly cutting a lot better, however there was still plenty of smoke about, and I feel that this is probably as best as it's going to get. As someone mentioned previously, I had found that when the bit does start to cut, then keep feeding it! Otherwise if you go too slow, you'll just grind the surface and build up a lot of heat which glazes over and makes it even more harder to cut. Now of course I'm not cutting the whole thing in one swoop, but I am taking more off per pass. I only have to go 1/4", but its still slow going. [BTW, after each pass, I brush the chips/dust off and wait a few secs before re-entering. I left the chips/dust on in the photos on purpose to show the cutting results.]

After a break to let the bit cool down, I switched over to a cross grain piece. Just like previous reports, cross grain was much simpler to work with. Very little smoke, and not much chip/dust buildup on the bit because it came off so easy. I was able to finish in a fraction of the time it took for end grain. The bit was somewhat warm afterwards, like one would expect.

Although I had been working with two brand new bits, perhaps Randy's concern coupled with Ken's report of coarse grinds from the factory could be a factor. Sharpening certainly helped, but there was still plenty of smoke with the end grain to have me concerned. I guess I can't really do it 'wrong' per se; but being new to this I thought it better to raise the caution flag and ask.

Thanks,
 
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