Straight line engine question - chatter?

Whaler

New Member
Joined
Sep 7, 2024
Messages
2
My first post, already worried that I’m putting a machine engraving question in the hand engraving forum, but didn’t see a better alternative! Apologies in advance!!!
I‘ve got an old straight line engine I’m trying to get productive, but have run into an issue which I can’t seem to resolve. I’m getting what I would call “chatter” if it was happening on my lathe. As you can see in the photo, there is no smooth line in that one inch brass. The lines closest to my thumb are done with no pattern bar - essentially the SLE is just acting as a mover of the material - and there is a periodic noise in the lines.
I’ve tightened almost everything to remove causes; I’ve sharpened a new graver to a very sharp and smooth face (not mirror finish, but as good as an uncooked amateur could be expected to do); I’ve cut deep and I’ve cut shallow - nothing seems to work - I’ve cut with and without the guide, etc. You can see the engine actually working when using the pattern bar above the first few lines - and how the frequency of the noise doesn’t change. The pattern is hard to see above the noise….
i haven’t locked everything super tight as it’s impossible to operate in that fashion. But that COULD be the issue.
The fact that the problem is so easy to repeat, I’m wondering if I’m missing something. Anyone have a suggestion or a question I could answer to maybe arrive at a guess as to what’s causing the issue? Could it be the shape of the cutter face?

IMG_0001.jpeg
Thanks for any thoughts!
Paul
 

Leonardo

Elite Cafe Member
Joined
Jan 9, 2008
Messages
641
Location
Cordoba - Argentina
Hi Paul,
Something is varying the distance between the plate you want to engrave and the tool.
I would look for some play in the tool head and also in the plate support. Just a very little play will cause this effect.
Another things that I would inspect are the gears. I would look for burs or any kind of defects that might be in the gear teeth and the gear shafts.

Hope this help a bit...
Leonardo
 

AJB

Member
Joined
Oct 27, 2020
Messages
53
i
I’d research milling machine chatter. On a mill, chatter can be caused by looseness in the machine, speed of the cutter, feed rate, dull tooling, and probably some other aspects that I’m not thinking about. Maybe start by tightening down everything, increasing the tool rpm, and slowing the feed rate and see what happens.
 

horologist

Member
Joined
Oct 23, 2015
Messages
46
Location
Melrose, FL
Paul,

I have limited experience with a well tuned rose engine and won't waste your time with my guesses. Wish I still had access.
My recommendation would be to check out Ornamental Turners International.

I think the membership fee isn't bad and this will give you access to information and people with similar machines who can help.

Note, I have never been a member of OTI but was briefly a member of The Society of Ornamental Turners and sadly can't recommend them.

Troy
 

Whaler

New Member
Joined
Sep 7, 2024
Messages
2
Thanks to everyone who’s replied. I’ve spent another few hours tightening and re-tightening as many elements as I can.
1) Chatter wave height has dropped significantly. It’s still there, and at a much higher frequency, but definitely not as bad as it was…
2) After some research, it appears certain forms of brass can be hard for chatter on rose and straight line engines. I’ve shifted over to bronze and aluminum for testing.
3) I’ve been guilloche-ing without a guide - which may be allowing my graver to go to deep - planning to add guide in next phase.
4) Have started building a replacement toothed advance for the chuck - my research on the chatter will be on the back burner for a while.
 

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