Author Topic: How to sharpen Rotabroach  (Read 680 times)

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2268
  • Country: fi
How to sharpen Rotabroach
« on: November 22, 2018, 09:09:14 AM »
My most used Rotabroach is dull.....

Is there easy way to sharpen them?

I have TCG and magnetic table, but not really right spindle ar anything to mount 3/4" weldon shank rotabroach.

Pekka

Offline smiffy

  • Full Member
  • ***
  • Posts: 135
  • Country: gb
Re: How to sharpen Rotabroach
« Reply #1 on: November 22, 2018, 09:49:25 AM »
I used to get mine professional resharpened but they were never as good as a new one .
For some time I think it has been cheaper to buy new cutters  . Resharpening costs about 5 per cutter and a new 14mm cutter costs us about 8
The problem with resharpened cutters is that unless they are done correctly and that requires 5 separate operations per tooth they lose there self centering ability and  can skate on the work before they bite ,the other problem is swarf remova lwhich is also caused by bad sharpening .
If the swarf goes in between the cutter  and bit left in the middle it will cause the cutter to jam and more than likely break , this is often cause by incorrect resharpening.This can in turn cause a problem in getting broken pieces of cutter out of the hole
If correctly cared for the cutters will do lots of work, over the years I have drilled thousands of holes and only now use new cutters
Mike

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2268
  • Country: fi
Re: How to sharpen Rotabroach
« Reply #2 on: November 22, 2018, 10:27:31 AM »
Thank you. At 10/pcs I would not bother to think sharpening.


However, I tried to buy five rotabroach cutters short (25 mm) and long (50 mm) between 12 to 20 mm OD. They were about 18-27/Pcs and shipping the small parcell to Finland from UK was bit over 35.

Ended ordering from Germany, because I got another tool from the same shop. Postage was way less than 1/2 and choice of two couriers.

You mentioned five steps per tooth. How come?

Pekka

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6967
  • Country: gb
  • East Sussex, UK
Re: How to sharpen Rotabroach
« Reply #3 on: November 22, 2018, 11:45:59 AM »
Our UK postage rates, both internally and abroad do seem to be very high compared with most of the rest of the world  :(
Andrew Mawson
East Sussex

Offline smiffy

  • Full Member
  • ***
  • Posts: 135
  • Country: gb
Re: How to sharpen Rotabroach
« Reply #4 on: November 22, 2018, 01:30:07 PM »
The no of grinding operations depends on how badly damaged the cutter is .It might be possible to grind across the front of the tooth ,but if you look at your cutter you will see that the cutting edge is staggered, this is important for the swarf clearance and centering of the cutter so you would also have to grind the lands of the cutter
Then the cutter would possible need  backing of which is 2 more operations. So 4 operation not 5 my mistake
That is how it was described to me by a specialist tool and cutter grinding company  .
I have not tried it myself but if anyone wants to have a go I have a large quantity of used cutters. Mike

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2268
  • Country: fi
Re: How to sharpen Rotabroach
« Reply #5 on: November 22, 2018, 01:42:15 PM »
Thank you.

I noticed that tooths were slightly staggered, but opposite teeth looked symmetrical. Surfaces to touch up looked straight lands (facets?), not that complicated geometrically, but needs pretty controlled and repeatble depth stop (two settings and two angles).

I will not loose much money if I try to sharpen it one day. I ordered exactly same size, and then others fifferent brands, I better check them before and make some notes.

Pekka