Facing backlash issue

START FACE FROM THE CENTER OUTWARDS.
Use a colbalt tool bits.
Robbie

Robbie's Machine Service
 
I've never had much luck starting in the center. That is, unless there is a center hole, or it is tubing or some such. For flat plate, the zero surface speed at the center, and the inserted tools I use just doesn't seem to work out. I believe you though, with HSS, and a sharp point, you can plunge in and do OK. Seems it will still leave a nib though. Or chip the point as you cross center.
 
In Or Out?

How about some of each? I usually take the bulk of stock off cutting towards the center. Then to get a better finish I cut the last .002" from center towards edge. the longer lead of the cutting edge seems to wipe on a smoother finish.
Plunging a tool in at center raises clearance issues as the uncut stock passes under the tool. Think boring bar clearance.
I guess there's alot of variables to consider.

Ed
 
Tony Wells said:
I've never had much luck starting in the center. That is, unless there is a center hole, or it is tubing or some such. For flat plate, the zero surface speed at the center, and the inserted tools I use just doesn't seem to work out. I believe you though, with HSS, and a sharp point, you can plunge in and do OK. Seems it will still leave a nib though. Or chip the point as you cross center.
Click to expand...

+1
I do the same thing and have had the same problems.

Dave
 
Davo J said:
Just try not to run them to fast or get them to hot or they will go blunt quick. A HSS tool bit sharpened right should last around an hour before needing touching up, it just depends on the job and the cuts.
You will also find you get a better finish and the tool will last longer if you hone the tool with a oil stone after grinding.
Another thing to consider is the HSS quality. If you are using Chinese ones they don't last as long as good quality and if you can get them with cobalt, even better.

Dave
Click to expand...

I have tried honing with both a diamond hone and sharpening stone and cant say it makes much difference either right after grinding or to resharpen. Maybe its my technique, I just hone the cutting edge, where it is shiny and worn, not the entire face.
So, to resharpen, what I normally do, is just regrind one side, ie: the right side of a LH bit (never the top). I have used both chinese and some "made in England" toolbits but don't notice a significant difference. It's difficult to source non asian bits here in Canada.

Here are some Chinese 5% cobalt bits I have been considering:
http://www.ebay.com/itm/5pc-Cobalt-...ultDomain_0&hash=item3362af8bec#ht_500wt_1180
 
Last edited:
Hi,
You should have the whole side of the tool on the oil stone where it has been ground. You can put more finger pressure toward the top/front of the tool as the bottom doesn't have to be honed, but not lift it up to do only the edge.
There is a bit of technique to it t keep the tool flat, and I have even seen guys make up holders with wheels on them to keep it at the right angle on the stone.

Also the top should be honed after it's first ground.

Dave.
 
Thats one of the sites I saw a honing tool made, there is another one around somewhere as well.

Dave
 
martik, it takes a lot of practice to grind a tool bit. Clearance on the front and sides, under the cutting edge is important. Too Much clearance will let the tool wear quickly, and too little will rub underneath. There's information on the internet to show how to grind a tool to a proper shape. Sorry I don't have any links to offer. Another thing to consider, the pointier you make the tool, The more heat builds up at the tip, leads to short tool life. Keep experimenting and you'll get it. I also hone the entire face of the clearance angles on a flat stone, and then a quick touch up on top. I usuall yput a small (.010") radius on the end with my bench stone, by hand. At the bench grinder, try to keep the grinding direction the same way as the metal chips will flow across the tool. Good Luck

Ed Hoc
 
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