I'm interested in purchasing a used 20" scmi planer and swapping the existing cutter head for a modern tersa head. Anybody out there tried this? Advice?

If I was going to swap the head I would go with a Shelix type cutter. Quieter, 4 rotations of the cutters, I believe they use less HP. We run a lot of wood through our SCM planer and I would not have another type of head in the future.

I had a 24" Sicar planer with a Tersa head and loved the knife changes. It took no more than 5 minutes to change 4 knives, and I never had to reset pressure bars or chip breakers.

The knives are available in 2-3 types of steel and then carbide. They were throw away. Very counter-intuitive to slide them in and then just turn the machine on to set them. Against all the rules for this old school guy.

The head itself is fine - it has a chip limiting design, so we could not take much more than 5/16" at a pass, but the finish was smooth and very clean.

The Shelix heads all seem to leave match lines once they have a little age, while the Tersa finish was immaculate. I think an earlier thread described the 'takes less horsepower' as inaccurate.

Thanks for the responses, but I didn't mean to continue the debate about the virtues of a particular cutter head. Instead I should have been more specific in my question which is what are specifics involved in changing a cutter head. Is it mechanically very complicated, is it difficult to find necessary parts in the proper sizes, what are the compatibility issues between a new head and an old. Are the arbor sizes the same, do the pillow blocks need to be swapped, can a reasonably handy person accomplish the Change or is it necessary to hire a machinery tech, will it save money or end up costing as much as a new machine, etc. ? Thanks,
David.

See if you can talk to a SCMI service tech. Often, planer bearings require a machine shop to remove and reset bearings. Not a big deal, but plan on it. Insure that the people selling your new head will make the head to fit your machine and the machine people agree that the head can be put into the machine. Your due diligence should include both other parties.

Beyond that, it is just basic mechanics and knowing how to set up the planer correctly for optimum performance.

David is correct. Bearings are press fit into the casting. You can remove the head assembly, take to a machine shop with the new Tersa head (Tersa gives the best finish, least amount of time to change knives-and a lesser cost of knives). Machine shop can remove and replace the heads/bearings

The 20" SCM planer is fairly common and thus obtaining a matching Tersa head should not be much of a problem. It's been done before. SCM makes a Tersa head for the 20" - it's standard on newer models as far as I know - so that would be the simplest route for obtaining the Tersa cutter block if your machine is not too ancient, but likely not the cheapest. SCM parts are expensive by and large.

SCM tech support is poor generally I have found, and they aren't likely to want to spend any time with you at all if you haven't ponied up several hundred bucks for the service contract. A lot of info their tech guys gave me turned out to be flat out wrong. They know their newer machines, but if you have something more than 10 years old don't expect them to be familiar with it. Also, a customer with questions about parts for a second hand planer is not likely going to get the same keen attention as a customer with a brand new CNC machining center, put it that way.

As for removing the cutter head on an SCM planer, it is not the simplest of tasks. It would be nice if you could simply remove the cutter block and leave the rest, but the way it is designed the cutter block sits in a cast carrier on both sides that also supports the in feed and out feed rollers. You have to remove the carrier completely - basically removing the entire drive assembly, and strip it apart to get the cutter head out.

If you have bearing pullers, it is no big deal to remove the bearings. The bearings on mine were not a tight fit in the castings. To put the bearings back in, it is ideal to have a press and the correct size sleeve to press with.

Thanks everyone for the responses.
Thanks
Chris, i have had similar experience of late with SCMI tech support, and agree that they are not likely to want to discuss issues with a second hand machine they did not sell to me.
If I go this route I will relay my experience, success or failure.
David.

Are there any updates on this? Did you manage the switch? Looking at doing similar.