Tenon cutter not cutting square

[Albert Lee]

***UPDATE***

I have resolved this issue today!

for a while I thought I had an issue with my OMAS cutter block, even took it to a machinist to check, the machinist commented maybe it is the sliding table?

I was getting the same issue with another cutter block recently, so I wondered if it was something else, maybe my setup? maybe the sliding table?

I had to do 100 x tenon cut recently. so I finally investigated this today and played around with the spindle moulder.

I know it will create burn mark past mid point, I thought to myself. MAYBE, just MAYBE, the tilt of the spindle is not dead on 90 deg. although it is reading "0" on the screen?

I started with + and - 0.1 degrees on the spindle. no improvement, then + 0.2 deg. slight improvement!!
I cranked it up to + 1 deg. it was creating burnt marks on the other side, so I adjusted back to + 0.9 deg... and EUREKA!!!!

Below is the video I took today. no more burn marks and the cut was square!

https://www.youtube.com/shorts/uespGfV0l7M

a few months ago I did move the machine and the move could have affected the calibration? the tilt was showing a funny number after the move and I thought I zero'ed it but it seems I didnt zero it properly.

[Kevin Jenness]

Good that you cured the issue. I am surprised that you did not tram the spindle to start with, and that it fixed the problem. I thought that the tenon thickness was different at the root and end, but perhaps I misunderstood and the "taper" was a constant thickness tenon out of plane with the workpiece face. I suspect any burning is due to the slow feed rate.

Can you adjust the spindle exactly square to the table manually using a straightedge and taper gauge or feeler gauges and then zero out the display? 0.1 degrees seems rather a coarse interval for calibration (or can you make electronic adjustments in smaller increments?).

[Aaron Inami]

Theory: the floor flatness on the old location may not be the same for the new location. They may have created a twist or un-twist on the main table of the machine and caused the spindle angle to deviate that .9 degree. In any case, it's great that you've solved the problem. You might want to think about adding leveling feet and making sure the table top and perfectly level so that there is no twist. This can affect the accuracy of the sliding table as well.

[Wes Grass]

Not familiar with the shaper you have, but looking at the table insert and the way it's extended on one side, looks to me the spindle tilts in that direction. If so, your sliding table is 90° out from where it should be installed. So you get this, which *should* taper it the opposite way, but maybe something is rubbing.

**** Duh, I had the measurements backwards, it IS thinner at the end ****

Sheesh ...

assy_tenon_tilt.JPG
Vs:

assy_tenon_angle.JPG

If not, well ... like I said ... not familiar ...

[Kevin Jenness]

I suspect Wes has grasped the essential point, that the spindle's rotational axis is at 90 degrees to the travel of the sliding table. It makes sense that it would tilt toward the front of the table for standard edge milling rather than toward the side on which the table is mounted. In that case the slider is meant only for tenons parallel with the table and any forward tilt of the spindle would in fact produce a tapered tenon and even burning if the tilt is sufficient to negate the clearance designed into the cutters.

[Jim Becker]

Cast iron and steel bend/flex. It might be a very small amount, but a different floor can absolutely "move the mark" and cause that little bit of "out" that you describe. Hopefully, you can correct the setup to dead-nuts on in the new location now that you know it's off a proverbial hair.

If I move my Stubby 750 lathe, I have to carefully check things to insure that the center's line up and make adjustments/shim to fix if it's out. That's 800+ lbs of cast iron on a steel base and yes, the floor matters.

[Warren Lake]

Hard to believe a serious shaper with a plate steel base then thick top would flex. Be good to know ive wondered about my saw which is 1,300 lbs and cant tell if it can flex The top of rhe shapers is likely heavier than the saw. Question for SCM

[Wes Grass]

Hard to believe a serious shaper with a plate steel base then thick top would flex. Be good to know ive wondered about my saw which is 1,300 lbs and cant tell if it can flex The top of rhe shapers is likely heavier than the saw. Question for SCM

An 8500 lb cast iron machining center will twist itself out of square if the slab settles under it. Been there. My lathe, roughly the same weight, has 6 pads to dial in twist, and sag, of the bed.

As *someone* once said: 'Everything is made of rubber'.

My little lathe needs one of the pads just barely past touching to be straight. It either warped as it aged, or sat for awhile out of level. Cast iron also 'creeps'.

[Warren Lake]

ill still ask SCM sometime all bases of machines are not the same, tops as well. I had no flexing when lifting and trying to level my table saw, it was annoying to shim it, would have been easier if it did flex. Then add in cast iron sag over time and other like wear from a power feed and more dynamics. Id want to hear it from SCM on that particular machine if and how much it could move.

[Albert Lee]

did a quick check last night, the back of the machine is lower than the front by 2mm over 1000mm. this may have caused the issue. I am going to level the machine today and see if this improves things.

[Albert Lee]

ok this is what I did today.

I levelled the machine first - this was never done after I moved the machine - I assumed the concrete floor was level but it was out by 2-3mm, back being lower.

after levelling I did a test cut - still need that +0.9 deg to cut properly.

I then went through machine's technical setting, there are probably hundreds VERY technical parameters such as rotational speed, acceleration, angular rotation, deceleration time...etc, I dont think touching any of these is a good idea.

on one of the sub window there is a calibration tap. thought I give it a try - machine started calibrating itself. once the calibration is completed, I gave it a test cut. and its PERFECT. even better than my manual "+ 0.9 deg" setting.


spindle moulder test.jpg

[Jim Becker]

No harm in leveling it even if it alone didn't clear the issue! And it's good that the calibration thing did the job. I have a suspicion that leveling the machine didn't hurt that either.

[Warren Lake]

throw it out of level on purpose and see what it does. Its not level anyway it could be sitting supported on four corners equally and have a tilt. I dont have time to try pulling a support out of one corner now so it floats and see what that does. Get the feeling it would be nothing.