Boring Head

[Alan Gordon 4Participant @alangordon4]

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.

Alan

[Alan Gordon 4Participant @alangordon4]

[JohnFParticipant @johnf59703]

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

[JasonBModerator @jasonb]

Wandering drill?

[Andy CarruthersParticipant @andycarruthers33275]

Is table locked too?

[fishy-steveParticipant @fishy-steve]

Have you trammed the head?

[chris stephensParticipant @chrisstephens63393]

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

[not done it yetParticipant @notdoneityet]

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 4Participant @alangordon4]

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.

[Author]

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