Troubleshooting Uneven Pitch Marks from a Jointer
From contributor C:
Uneven pitch marks as opposed to uniform ones can be a sign of something beyond the number of the knives being jointed.
It could be one or more of many things:
From the original questioner:
Thank you. I have already reduced some of the cutterblocks from 8 to 4 knife. Some of the mouldings done on this machine have been reduced from 6 to 3 knives per block. I am in the process of having blocks rebalanced. I have pretty much eliminated the blocks themselves as the problem. I was considering changing the cutting angle on my straight knife and profile grinders. I have also had extensive work done on the machine re-aligning beds, fences, jointers, spindles and pressure pads. Spindle and outboard bearings are relatively new. The drive belts are the old fashioned V shape as opposed to the more common newer flat belts and pulleys. The problem with the uneven pitch marks is similar to the effect of overcutting (too many knives for feed speed) but the pitch is around 1.5 to 2mm with spindle speed of 6000rpm. Conversations with current and ex-engineers have highlighted an inherent problem with this particular make and model (Wadkin xjs around 20 years old).
From contributor J:
Do you hear a vibration when this occurs? Is it constant or periodic?
From David Rankin, forum technical advisor:
My experience with this model has presented the following areas of discovery.
1. Adjusting tails not parallel and tensioned to maintain a parallel spindle to the table allows for vibration.
2. Worn pulleys or belts. The V-groove in the pulleys can wear and this can cause a poor finish.
3. Loose clamping areas around the spindle occurs when the casting wears, caused by running the machine in an unlocked condition or years of use.
4. Improper lubrication of the spindle bearings.
From contributor A:
One thing you may want to play with is the hardness of your jointing stones. The harder a stone is, the less forgiving it is when applying the joint. Older machines' jointing mechanisms can be stickier or have more slop in them. Changing to a softer stone can compensate somewhat for these issues. Another interesting test is to use a black sharpie and run it along the cutting edge of a fresh set of blades to be sharpened. Then apply your joint to the knives. After the head stops, take a light and examine the heel produced on each knife. Make sure every knife has been hit and that the heels are all relatively the same size. Too big a heel on one or more knives can mess up a joint. It can indicate bad bearings or profile grinding that is too uneven.
Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?
Have you reviewed the related Knowledge Base areas below?