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Boring Head

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Alan Gordon 417/05/2018 10:02:46
81 forum posts
3 photos

Hi Guys, I have scrapped a small crank case due to the bored hole being off centre !!

I have started a new crankcase and ensured that all was centred and locked down, I installed a new Vertex boring head and a new cutter and turned the head by hand very slowly, I was amazed to see that when the cutter was set to just graze the inside surface of the pre drilled hole but when turned 180 Degrees it wanted to over cut ? This why the first hole was off centre. I am sure I am doing something daft but I cannot figure this out. Any help would be appreciated.


JohnF17/05/2018 10:28:53
966 forum posts
142 photos

Alan, where did you zero your spindle centre ? did you clock the inside of the crank case or did you clock the drilled hole ? On first thoughts it seems to me you zeroed the spindle to the inside of the crank case and the drill hole is already off centre ??

A photo or drawing of the job may well help.

I have PM you as well John

JasonB17/05/2018 12:26:03
17864 forum posts
1954 photos
1 articles

Wandering drill?

Andy Carruthers17/05/2018 12:36:11
274 forum posts
23 photos

Is table locked too?

fishy-steve17/05/2018 12:39:01
122 forum posts
30 photos

Have you trammed the head?

chris stephens17/05/2018 12:48:38
1045 forum posts
1 photos

Second for tramming your head, the boring head is probably longer than the drill so will be more to one side.

not done it yet17/05/2018 12:48:40
4507 forum posts
16 photos

Assuming here the boring head has been changed on the same machine/workpiece setting?

Changed head height on a round column machine? Relying on a drilled hole to be straight?

If not, you could try removing the boring head and installing it at 180 degrees in the machine and look for a different result. Possibly there is something (foreign body or a burr) inside your spindle that needs cleaning out?

Possible tramming error and one side is off centre when drilled?

If I want to drill something true, I use an end mill, not a drill.

Several possibilities so, yes, a pic and detailed method of working is likely required to see what is wrong.

Alan Gordon 417/05/2018 12:52:09
81 forum posts
3 photos

Thanks guys for your advice, I have taken all advice and I believe the problem was backlash. I ensured that I took out as much backlash as possible on X and Y axis and kept checking my DRO to ensure that 0.000 was always showing with no drift. Mission acomplished.

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