Might be diagnostic in some capacity to try each block independently and make an offset tenon (one cheek/shoulder) with them to see what the measurements are. Use each of them over and under the stock.
Might be diagnostic in some capacity to try each block independently and make an offset tenon (one cheek/shoulder) with them to see what the measurements are. Use each of them over and under the stock.
Contributor
Try running a rail into the shaper to the point where the tenon cutters are top dead center, then back out. See if it's tapered. Then put [pencil lines on the work piece, and run tit through . Look to see if and where the pencil lines are being cut off.
On a tenoner, I run one head at a time when truing up the copes and tenon heads. The other side is not cut. If there's taper, I can tell by measuring the thickness from the un cut face to the cut face. On a shaper, I would pull the top cutter off, and see if the bottom cutter is running weird. Then try just the top cutter.
I get the bottom cope head parallel to the table by tilting the table to match the cope head.
Contributor
I cant visualize how that is possible other than if there were two cutter heads cutting 90 degrees to make the tennon like in a tennon machine. Have you called the tooling company and id also call the shaper company if its an SCM sliding gizmo then id be asking. Both of them should have many years experience at least if older people working there. The fact that you are getting different results means something is moving or loose or has play in it. there is some issue with movement there.
Id prefer a digital caliper that reads to .0005. take test pieces and go through one time cut and label the measures in the four critical places with a fine sharpie. Once labelled id pull them back and see what changes you get.
Member
I've watched the video multiple times and to me it appears that the sliding jig raises and lowers as the piece is passing through the cutter. Hard to confirm suspicions without actually seeing it in operation though. All I can suggest is some possibles, so take it with a grain of salt. Confirm the spindle is perpendicular to the table and there is no vertical play in the spindle. Check each of the cutters (with power disconnected) with a dial indicator to insure they are true. Check the sliding table to insure whether it's raising and lowering while cutting as it appears to be happening in the video.
That's where I'd start and go from there.
Contributor
This is a really hard problem. I took a screen shot of the material just before Albert pulled it back through the cutters. It looks like the tenon is already tapered at this point. The only thing I can come up with is incorrectly installed cutter knives.
post_cutter_pic.JPG
It's a very long piece of material. It might be possible that the sliding jig is tilting the material down and then up at some point during the movement.
Contributor
After some thought, I think the cutters are just fine and square. I think the piece is tilting down or up as it's being moved through the cutter. One of two things could be happening here:
1. It is a very long board that needs to be supported at a perfect 90 degree to the cutter. If your clamp/jig in the only thing that is supporting the board, the weight of the board could be pulling it down when it passes off the table (or something similar is happening as weight of the board or weight of the clamp/jig moves towards the back of the machine).
2. The sliding table could have a twist in the slider alignment which could cause the sliding table to tilt up/down as the material is being run through the cut. I don't know if you can do alignment on the slider or if it's non-adjustable. I would put a straight edge on the sliding table and then move the slider back and forth to see if the end of the slider is tilting up or down during movement.
One thing you could do to verify the cutter is by doing a tenon cut operation using a smaller piece of material and running from right-to-left on the front table. That should prove the cutter is not the problem.
One other quick check that could offer diagnostic information is the comparison of the tenon thickness to actual tenon disk spacing. If the greatest tenon thickness (at the shoulder) is less than the spacing of the discs then that would be another nugget of information.
Contributor
Very strange for sure Albert. Did you ever figure anything out? Your material looks like fast growth pine? Is it dry? I have seen tenon thickness vary when using Red Grandis scantlings for our window building workshops. It’s a sketchy material with a mind of its own but the variation is nowhere near what you are getting!Originally Posted by Albert Lee
Member
Watching again it looks like its burning mid cut, then cleans up as the knife passes again.
Screenshot_20230515_070426_YouTube.jpg
Contributor
Yep , and go a little faster . I can tell you are your own boss ‘cuz you ain’t been fired ! The wood moves as it’s being cut.
I saw that too, but it looks like an artifact of the camera to me....shutter trying to resolve looking through the gap in the spinning discs. When he pauses at the end before pulling back, it's not there.
Member
If you watch at reduced speed It's cleaning up the burn as it passes the knife tje second time on the back of the cutting circle.
Knife set to low, discs flexing or table flexing all seem like possibilities.
Screenshot_20230515_101835_Gallery.jpg
Something in here is rubbing and burning. If it's rubbing it's deflecting the discs apart and likely the reason for the taper.
Screenshot_20230515_102243_Chrome.jpg
Last edited by Jared Sankovich; 05-15-2023 at 10:25 AM.
I misunderstood you, I thought by "passes again" you meant the back stroke. That could be a tenon too long for the discs (the boss there could be rubbing) or the discs aren't inverted, can't get a shot of the orientation. Typically adjustable groovers (which is what this set is, not true tenon discs) when used for tenoning need to be inverted from groovers orientation. I believe these were installed inverted, can't really see, my subscription expired so I cant see the posted pictures above.
Last edited by brent stanley; 05-15-2023 at 11:10 AM.
Contributor
Brent they are set correctly for tenoning. You can tell by the position of the knickers. Yes, true tenon disks are better as the adj groovers sometimes are depth limited for this operation. But if he was hitting the raised part of the disk the wood would be burned. Also if the knives are set higher than the knickers you would see burning on the top knife edge. I don’t see that but hard to tell from the pictures.
the video is shaky so had to really see what is happening.
Tough to armchair quarterback without hearing back from Albert.
I expect there would be a lot of back pressure too and doubtful the burning from that would get cleaned up . I need to get my subscription renewed so I can see pics again!
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