Thread: Annular cutter grinding

SAM_0677.jpgSAM_0675.jpgHello from Geebung.
The first pic has the after ground finish. I grind with 2 facets and all obtuse angles. This gives good life and some resistance to re engaging the work on top of chips. The second pic shows how it came in. Only 1 facet and one of the angles very accute. The saw shops don't realise metal cutting geometry is different. From the same shop I have seen countersinks offhand ground on a bench grinder and annular cutters reduced in diameter by grinding the margins on a linisher. At $42.00 ea.
Regards
BC

Nice job. I tried on two occasions to get the rotabroach cutters at work sharpened after finally convincing the boss it was a good idea rather than just replacing them, which due to his knucklehead son we did a lot (pushing cutters through truck chassis with no coolant/lubricant among many other sins). First attempt I took them to a saw shop that had been in business for many years. Of the 15 I took in, 7 would not cut at all, while the remainder were lacklustre at best. Against my wishes, we never took the shop to task over this. The second attempt was with a newer small saw shop just down the road from work. He assured me he could do the job, which was partially true, as we received a dozen well sharpened cutters back nearly a month after we dropped them off - he had sent them from Tasmania to South Australia to have them sharpened.
I gave up after that.

Hi Guys,

Sharpening any multi tooth cutter is not a job for the faint of heart. It very rapidly becomes a single tooth fly cutter.

Hello from the old goat.
Cutter grinding has a lot of mystery about it but with basic equipment it can be done at home. Break it down into the basic elements and it becomes clear. Power head, sliding table, tool holding, indexing, and micrometer infeed or lead screw infeed. Harold Hall's book Tool and Cutter Sharpening is a good start and Youtube has a lot of info. I suggest researching 1 topic at a time. One Youtube site worth looking at is Toollife. He only has 4 videos but the setup is amazing to watch and nothing is hidden. Sat I'll try to put up pics of a simple axial relief grinding attachment that is easy to build.
Regards
BC

Hi BC,
I'm usually pretty decent with finding things on the 'net, but can't find the Toollife videos you're referring too.
Just seem to be getting a bunch of references to tool life discussion and calculation etc.
Can you point me in the right direction?

Steve

Originally Posted by OxxAndBert

Hi BC,
I'm usually pretty decent with finding things on the 'net, but can't find the Toollife videos you're referring too.
Just seem to be getting a bunch of references to tool life discussion and calculation etc.
Can you point me in the right direction?

Steve

Back again.
The videos are on Youtube. Search in the top bar. I think I found him searching for 4 facet drill grinding.
BC

Originally Posted by Karl Robbers

Nice job. I tried on two occasions to get the rotabroach cutters at work sharpened after finally convincing the boss it was a good idea rather than just replacing them, which due to his knucklehead son we did a lot (pushing cutters through truck chassis with no coolant/lubricant among many other sins). First attempt I took them to a saw shop that had been in business for many years. Of the 15 I took in, 7 would not cut at all, while the remainder were lacklustre at best. Against my wishes, we never took the shop to task over this. The second attempt was with a newer small saw shop just down the road from work. He assured me he could do the job, which was partially true, as we received a dozen well sharpened cutters back nearly a month after we dropped them off - he had sent them from Tasmania to South Australia to have them sharpened.
I gave up after that.

Hi Karl. For high strength material like truck chassis can I suggest get a sparky to fit a speed control between the mag drill switch and motor. just as important as cutting oil is the right speed. Small mag drills have a no load speed of 700 rpm. A 25mm cutter in Weld 1080 needs 150 rpm or less. Be careful as the low speed reduces cooling air flow.
Regards
BC

Originally Posted by steamloco1954

Hi Karl. For high strength material like truck chassis can I suggest get a sparky to fit a speed control between the mag drill switch and motor. just as important as cutting oil is the right speed. Small mag drills have a no load speed of 700 rpm. A 25mm cutter in Weld 1080 needs 150 rpm or less. Be careful as the low speed reduces cooling air flow.
Regards
BC

Thankfully most of the chassis that we worked on were Japanese in origin and although better than mild steel, they weren't too tough in the scheme of things. The Son in question was pure unadulterated early twenties testosterone laden knuckle head who was too lazy to mix up another batch of coolant as he "only had a couple of holes to do and he couldn't be....." Also being the bosses Son, he had the unending shield and was never taken to task. Our rotabroach did 350RPM from memory, so not too bad for 14-17mm holes.
I totally understand where you are coming from though.

https://www.youtube.com/channel/UC8j...nxwIZSqWlV8EXg

Thanks for that StrayAlien - I still hadn't managed to find them but have just educated myself on how to filter the youtube search for just channel names.

You're right BC - nice videos - much appreciated.
What is the inspection software/tool he's using at the end of the videos? Looks like an electronic microscope on steroids specially for tool inspection....

Steve