Drilling High Speed Steel

Trying to widen a hole on a planer blade that goes over a alignment pin on the cutterhead (DW735). I tried using a cobalt bit (rigid) and it ended up getting chewed up and cut very little metal.
Is there a way to do this in a home shop? Do I need a diamond or carbide bit? Would it be worth taking the knives to a metal shop? What do you guys think?
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I'm not a woodworker, in fact, I think wood is for heating and stone is for building but you are asking a metalworking question so I have a thought on this. That blade is very hard so you will have no luck with a standard drill bit. You could do this with a solid carbide straight flute drill but you have to have a slow speed chuck, fine feed and rigid workholding. They are quite expensive and can be easily broken if you do it wrong. Here is a link to them at MSC, they have what you need. So, my advice would be to bring it to a metal shop and have them do it. I suppose you could hone it out with a diamond file but it may not be accurate enough for locating a blade.
http://tinyurl.com/7a87v5e
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Well, if you need it for alignment, I'm not sure my suggestion is valid. Get a diamond bit for a dremel, and gently enlarge the hole. You can climb cut with it and it will take off a little at a time and keep it relatively round. That being said, if you need it accurate take it to a machine shop.
On 3/12/2012 7:51 PM, snipped-for-privacy@garagewoodworks.com wrote:

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When it comes to fine tuning a hole you are better to do it by hand.
First it is a must to use good cutting oil.
Next a quality round file properly sized (Nicholson Round Bastard File or better)
to do the job. You may already have one in your toolboxes.
If you have some blue marker I would use it on the hole to
give you an idea of how much material you are removing.
Do not waste your time with an inferior quality file.
If you have a great amount of material to remove
you have to build a drill jig. And use carbide for drilling
with cutting oil.
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.
That is a possibility regarding the screw holes. There is some slop in between the screw holes and the screws. Probably enough to work with. The alignment pin - hole has zero slop as one would expect.

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On 3/12/2012 6:51 PM, snipped-for-privacy@garagewoodworks.com wrote:

Would an end mill bit do the trick? And with that in mind, if you make the alignment hole wider will you be able to properly align the blade when putting it back in the planer?
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I don't know about the end mill bit, but the alignment part is the easy part. I made a dial indicator jig that is first zeroed on a surface plate. I would be able to adjust all the knives above the cutter head the same amount using a magnet attached to a bolt which goes through a piece of wood (turn the bolt and it raises or lowers the knives - one per side). Cake.
The hard part is making these dam holes in the knives. For my old planer (Delta) I would sharpen the "disposable" knives all the time (still have the original set). No alignment pins were used but springs and a jig which came with the planer.
I'm not sure if this was a tactic by Dewalt to sell more knives or if they thought they were making things easier.

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On 3/12/2012 8:40 PM, snipped-for-privacy@garagewoodworks.com wrote:

Ok, so you sound pretty sure that the magnets are strong enough to hold the blade while tightening the retaining bolts. Further, I assume you are making the indexing holes larger so that you can adjust the blade in the machine vs. in your sharpening jig. I don't see any problems there assuming the cutting edge is not hardened differently than the rest of the knife. If it is, once past a certain point the blade may not hold an edge as well. Just something to think about.

Absolutely a tactic to sell more knives. I had one of the very first bench top planers, an AP10 Ryobi. It had standard style blades that had probably 1/4" of resharpenable area. The blades and their holders fit in a jig for correct positioning after sharpening. Then that assembly fit onto indexing pins on the cutter head. All adjusting took place outside the planer. Had DeWalt or any one else these days wanted to simply make it easier they would have come up with a set up similar to that first of its kind, Ryobi.

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On 3/12/2012 7:51 PM, snipped-for-privacy@garagewoodworks.com wrote:

Solid carbide ball nose end mill and rigid setup solidly clamped to a drill press table. I don't know how hard the material is but I would start with the slowest speed the drill press allows with a light but firm feed (don't bounce the cutter). If it doesn't cut at first (no chips) don't force it, try a bit more speed until it bites. Once it bites (starts throwing chips) it will go through like butter.
Do your best to center the cutter in the existing hole and use oil as a lubricant, whatever you have on hand, but you won't need a lot.
John
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Don't do it. I would first try another blade, if you have the same problem, then the problem is with the pin not the hole. Better to repaire one pin than a dozen blades. I would also check with the mfg. of the unit and see if anyone else has had the same problem, and if they did what was the fix they used. Steel can be brittle, and any grinding, drilling etc. can weaken it causing it to break, you do not need the experience of flying metal comming out of a planer in all directions. Just my 2 cents worth.

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If the hole size is not critical, you could use a carbide or diamond bit in a die grinder. They are commonly pneumatic powered and reasonably priced if you have an air compressor adequate to power one. Here's an electric version from HF that is a good value for the price: http://www.harborfreight.com/electric-die-grinder-with-long-shaft-44141.html
It's about 3 times as big and heavy as a pneumatic tool but I've found it very useful, even though I do have an air compressor.
--
There is always an easy solution to every human problem -- neat,
plausible, and wrong." (H L Mencken)
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If you're not going to be using the alignment pin as such, is there any possibility of pulling or cutting them off flush ???
"If you voted for Obama in 2008 to prove you're not a racist you'll have to vote for someone else in 2012 to prove you're not stupid!"
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Their parts list shows the pins as dowel pins ... if so, the should be capable of being pulled out & replaced at will (within reason).
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