Line Boring Accuracy

Troubleshooting a 2 millimeter discrepancy when boring long panels in the 32mm system. February 26, 2007

I have looked through a lot of the forums and discussions on 32mm line boring and everything seems to pertain to bases and uppers. I recently purchased a Ritter 23 spindle machine. When boring a 2432mm length panel we drop from one end any number divisible by 32 and start our first hole on center. Our last hole at the opposite end is consistently off by 2mm. Am I missing something obvious?

Forum Responses
(Cabinetmaking Forum)
From contributor R:
How about indexing off the top front from rip to install?

From contributor L:
As in all woodworking you have to keep the same reference. If you bore one line starting at the top you have to bore the second line starting at the top. I'm not familiar with the Ritter but all good woodworking equipment has to use the constant reference system. If the Ritter uses only one line of drills and you have to reverse ends there is probably some play in the reference pin that is used for multiple moves down the line.

Try shifting the direction you hold the panel against the pin for each line to help cancel the error. If you do a lot of this it would probably be worth the investment to get a double head line bore machine. There are lots of used T machines available that are solid. Weve still got our old Morbidelli T machine (3 heads) and it is still very good after 20 years of running in a commercial shop. Its not used for line bore anymore but kept for special setups offline.

From contributor C:
How about line boring a couple of strips - say 2" or so and rigging them on your line borer and using a drill bit in the holes to provide a stop? That way you could extend the capacity of your machine and drill accurately from one end to the other.

From contributor R:
It's the machine. You will never get it perfect with a Ritter there just not made with tight tolerances. I had one and never could get any long panel within 2mm.

From contributor H:
If you are using a single line machine then check that your panel is square first. This could be throwing you off. If you are using the index pin, then you can rarely get any accuracy. Use stops on the fences only.