New Plane of Reality (IV)

The adventure continues with my newly-received SCM S-630 planer. I’ve been doing a fair bit of research on Tersa heads, past and present, including looking over the original patents, been in touch with people in Italy, in Switzerland, the US and Canada. Both MBM in Italy and the fellow at in Canada agreed that the head has to come out and be sent to the factory to be re-assembled and rebalanced. I had a talk with a tech rep at SCM in Georgia, and he suggested, however, a way where I could try to replace the bolts and carefully fit the knives back in. His explanation didn’t make total sense, as he talked about tightening the gib plate down to where it wouldn’t let the knives insert, then unscrew the bolts gradually, counting the turns, until the knife would just insert.

But, all things considered, it made sense to at least try and re-set the bolts holding the plates and see if the head will lock up the knives properly and plane wood cleanly. If it won’t then I’ll be looking at either sending the head back to the factory, or buying a new head. Prices for new insert knife heads did not excite me. Here’s the breakdown of what I found:

  • SCM factory replacement: $3380.00, lead time of 6~8 weeks
  • Byrd Shelix head: $3495.00, lead time of 10~12 weeks
  • Terminus head: $3800~4000.00, lead time of 8 weeks
  • Tersa factory head: $3400.00, lead time of 3~4 weeks

Uh, ouch! Still researching costs on other options too, but for the time being, I decided to try a re-fit of the plates, as that was by far the least costly solution. These gib plates were not removable after I took all the bolts out, so I wasn’t able to get in there and clean every nook and cranny as I might have liked. So, I gave the head another once over with rust cleaning chemical, then sprayed a product called PB Blaster in to the gibs, which is a penetrating solvent intended for loosening sticky mechanisms. After letting that soak in a while, I used compressed air to blow the grooves as clean as I could. Then I chased all the threads and put the bolts back in.

Contrary to the advice of the SCM tech, it was not possible to even fit the knives at all until the gib plates were well tightened down. I think he must have been thinking about some later or earlier style of head which had some sort of spring loading underneath the gib plate, who knows?  Anyway, I was pleased to find that the gib plate needed to be fully tightened before the knives could even be slid into place. I had a small piece of tersa knife blade about 3/4″ long which I used as a gauge and to slid along and clean the inside space some. It seemed to work well. After a few hours of work i had all the knives back in, and all the bolts in, save one.

One bolt had snapped during dis-assembly, so I was left with the grim prospect of removing a frozen, red loctite-fixed bolt which was buried under the gib plate. I’ve done enough wrenching on rusty vehicles, both cars and bicycles, to have had a few run ins with the dreaded rusty snapped off bolt. I’ve come to a few strategies for getting them out, techniques which generally work well for me, 9 times out of 10. Your mileage may vary of course, but I thought it might be of interest to at least some readers to run through how I tackled this problem.

The bolt in question is 6mmx16mm, and had sheared off just underneath the bolt head, leaving a fairly flat topped stub in the bore. I started with a small drill, about 3/32″, and carefully drilled a hole as close to the middle of the bolt as I could. The result:

It’s a little off center, but not too bad.

Next, in the hope of softening that red Loctite (the ‘permanent’ thread-locking chemical), I used a heat gun for a while:

Not sure how much that would help, but it was worth a shot.

Next, I grabbed a LH-spiral cobalt drill bit, 1/8″ size, put the drill in reverse, and drilled out the hole:

I’ve learned not to bother with the ‘Easy-out’ type of screw extractor, as they can all-too-easily snap off in the hole and give you an even bigger headache than you started out with. They are made of a very hard and brittle steel, so if one breaks off, there’s no ready way to drill through the remnant.

Continuing on, I vacuumed out the hole as best I could:

Next, on to a slightly larger LH cobalt drill:

I repeated the same steps again, until I was drilling out the hole with a 7/32″ LH drill bit. This bit is a little shy of the ideal size bit for drilling the hole if you wanted to later tap it – a 13/64″ bit is the right size for that – however the 7/32″ bit removes most of the waste while accommodating some slight off-centeredness with the drill hole.

The nice outcome with these LH spiral bits is that once you have punched out most of the bolt, the resistance of the bolt falls away and then the drill bit will catch the bolt and unscrew it right out, like this:

I find this sort of work a bit stressful, so I was quite elated when I felt the bolt give up its fight and came back out of the hole. As it does, it tends to clean up the threads too!

Then on to cleaning up the threads with a fresh tap (this was necessary as my other tap snapped unexpectedly when starting to clean out the hole and I had to spend 15 minutes teasing the tap remnant back out):

Then the bolt could be reinstalled, at least temporarily:

Whew! Made it through without excessive trauma. What a relief.

Now, the bolts I removed from the head originally are of uncertain condition, given that one snapped and others were removed with an impact driver and did put up a fight. Those bolts might be stressed and could fail prematurely when re-tightened, so a wise course is to toss them I think. I picked up some 6x16mm bolts from the local hardware store, however I cannot expect these to be decent quality (just like most of the stuff in the hardware store these days, sad to say). Metric bolts come in several strength grades, the toughest of which is 12.9, So, I found an online supplier, based in Massachusetts, called Bolt Depot, that stocked grade 12.9 bolts in a 6x16mm size, and to boot their price was about 1/3 of what the local hardware store was charging for cheap quality bolts. So I ordered up a full set of 36 bolts to replace all the cap screws – these I will put on with blue Loctite and sequentially torque down to a setting something like 10% lower than the bolt is rated for, to be on the safe side.

Meanwhile, I have hooked the air compressor up to the planer and completed the dust collection piping for the machine as well. The planer is now on the floor in final position. I have close to 12 feet of room on the infeed end, which should be plenty.

I peeked in at the side of the planer motor and could make out its data plate. Turns out that I have a 9Kw, or 12 h.p. machine, not a 10 h.p. machine. The more the better – yeah baby! This planer was pretty lavishly optioned, and I appreciate that.

I did some calculations given the motor’s horse power, 208v., 3-phase power supply from 100′ away, motor efficiency which I estimated at the standard 85.5%, and motor power factor of 0.85, means that the machine will consume about 34 amps peak, and require an electrical feed with 8 gauge wire.  I have hooked up a new power cable to the machine, using 8 gauge, 4-strand jacketed wire. Since I am crossing over the 30 amp threshold for the first time, equipment-wise, I can’t use the same plugs and receptacles that my other 3-phase machines happily operate on. Ideally, I would go to a 40 amp plug and socket, but they don’t seem to make those. After 30 amp, the next size up is 50 amp, and a 50-amp rated plug and socket cost me $110.00. I have the receptacle mounted on the post next to the planer and need to put in some EMT conduit. I did some conduit wire fill calculations, and 4 strands of 8 gauge wire need a 1″ conduit size.You can only fill 40% or the conduit’s interior area with wire, by provisions of NEC (electrical code).

I think I should be able to put power to the planer in the next couple of days, and I am excited to see it come alive and have fingers crossed that the Tersa head will work as it should. All for now, over and out – thanks for your visit!  On to post 5

14 Replies to “New Plane of Reality (IV)”

  1. Well done on the screw extraction. My experiences with “easy outs” is similar to yours, best avoid them. That looks like a fantastic planer. I hope it works out for you.

    Harlan Barnhart

  2. Harlan,

    thanks, and my apologies for all the typos in the above piece. I really should have given it another proof read before posting, but I was in that, you know, tired and hungry phase. I'll let you know how the planer works out once I get it running and have run some wood through. it does promise to be a good machine.


  3. LH Drills!!!!
    This Blog never fails to have something out of the ordinary.
    Good luck with the Planer, Chris.

  4. Gordon,

    yes, indeed! I have often wondered what other purpose, besides extracting bolt remnants, that led to the development of LH drills – apparently they were developed originally for use of industrial drilling machines for certain situations where the machine's spindle could not be readily reversed. I'm glad they're around as they really are the best option.

    Thanks for your comment!


  5. Hello Chris

    A few remarks:

    1. Power is not so important. Only if You take deep cuts in wide boards with high speed. Otherwise I do not see the point to have many many horses. I have three V-belts in my 640 mm planer main shaft as standard. But I have taken off two of them, because I almost never take so heavy cuts and it will save bearings a lot and let the motor turn more easily-less noise, vibration etc. It is rather simple to put them back if it is needed.
    2. Electric motor (asynchronous) take nominal current (written in name plate) only if You load it with nominal load. But this is not the case normally. So if You take easy cuts, motor is almost idle running (of course including losses in belts, bearings etc)But still it is a fraction of nominal motor current. The only trouble is start of the motor, beacuse starting currents can exceed nominal 10 times (Also circuit breakers have capability to carry those high currents during start without switch off depending on their time/current curves). Therefore we are using in Europa so called star/delta start. Initially motor is switched to the net so that windings are in star connection and impedance is during this time higher (also motor start current is lower at this time). When motor has reached nominal rpm, windings will be switched over to delta connection. What i want to say is that more problematic is starting, as at this time currents are high and breaker can trip.
    Probably You know that, I just wanted to mention.


  6. Priit,

    thanks for your input and points, which are well made, concerning motor power issues. I don't see having more powerful motors as a negative in any way. Interesting idea about running the motor on a single belt instead of three. I'm thinking about using link belt, though the pulley's current belt is fairly slim so I'm not sure if linkbelt will fit.

    This planer does not, I think, have star/delta, from what I can tell, though it was a factory option. I'm curious to get the machine running so I can confirm whether it has star-delta or not, and whether the motor has a brake. Hopefully by early next week all these issue will no longer be a mystery.


  7. Hello
    1. Have no experience with link belts, but searching the internet:Link belts were invented for industrial machinery repairs that need to be made quickly, without having to rely on having the exact right-sized belt available, and for replacing belts in situations in which you might have to partially disassemble the machine to get a regular v-belt off and on. A correctly-sized v-belt is preferable, however. Link belts, believe it or not, will actually cause more wear on the machinery, because they do slip in the sheaves more easily.
    2. Brake-If You can see thin two wire cable going outside motor body from motor terminal box to ventilator housing, then it has certainly brake. Also ventilator cover is a bit longer compared to “normal” if it is equipped with brake. Star-Delta: It is automatic in newer machines (I mean switching from star to delta is not manual) so it is impossible to see it otherwise You open the switchboard.
    Answers of both questions should be also in manual.

  8. Priit,

    hello again! Interesting that you've found link belts cause more machinery wear. I've never heard that though I understand the belts themselves last 15 times longer than a standard v-belt and reduce belt noise significantly, which is the main reason for any interest I might have. I think the narrowest they come in is 1/2″, which is too fat for the sheaves on this machine, so I expect I'll stick with stock belts.

    The manual I have doesn't seem to mention star delta, and the wiring diagram shows a circle around a different configuration, however the SCM tech seemed to think it did have star delta. The factory machine brochure shows an options star-delta switch which could be placed on the control panel. I'm really not sure what's in there.

    All will be revealed when I put power to it.


  9. Chris.
    Sorry to hear about the glitch with getting your planner going. But it looks like you have really moved things foward with all the progress with the present shop space you occupy. Seems a few months back you were posting pics of a small home shop…Glad to see you have gottten it togeather to this level. It's always a source of inspiration to to see someone succeed and accomplish big things and share in the details of thier path.

  10. Ward,

    a pleasure to hear from you. My shop is gradually getting there, and I've come a fairly good way along from working in my kitchen on a sawhorse just three years ago. When you visited me on Gabriola I had a shop with some equipment, but then moving to the US meant selling almost all of it off, save the Hitachi re-saw, and it has taken a long time in a crappy economy to crawl my way back. And a certain distance to go yet: still need a sliding tablesaw, a lathe, maybe a milling machine…


  11. Chris,

    3/8″ link belts are available. I believe the size is called 3L. About 1 year ago, I purchased some off ebay from a company called sulfer grove tool. I think the belt is made by fenner.

  12. There are several manufacturers of these carbide bit cuttter systems with diferent names and designs. Spiral cutter head, byrd, helical etc. What are the differences if any???? My opinion is no matter which one you have on a jointer or planner the noise is reduced so much as to make working withoput ear protection painless. And you can can say goodbye to timely blade changing. and expensive sharpening…Possibly smoother cuts!!!!

  13. Ward,

    thanks for your comment.

    There are differences in the spiral heads on the market when it comes to design and execution. Some manufacturers use small insert knives which are square, and they arrange these knives in a helical fashion around the cutter, however the knife's edges are still square to the boards being fed across or through. An example of this type would be the Oliver 'Itch' head from yesteryear. Some, like the Byrd Shelix, arrange the knives in a helix and have the knife normal to the helix so that the cut is not square to the boards being fed, but is at a shearing angle. The small knives in this system are not square but are four-sided, each side of the knife being slightly convex. Then there are helical knife heads which have a single or multi-piece knife which is twisted in a helix. An example of this knife style would be found in the Festool portable planer.

    Tersa, Terminus, and Centrolock are not helical. These heads employ thin insert knives which run across the head just like a traditional style knife and gib system. Unlike a gib system, with Tersa, there is no knife setting ordeal to worry about. You remove the dull knife, flip it lengthwise 180˚ to expose the fresh side, and reinsert. Then on to the next one. Once all the knives are in you turn the machine on and the centrifugal force of the head spinning locks the knives in place. Takes a couple of minutes to change all the knives, and a perfect cutting circle is the result.

    Insert knife systems employ thin knives, which is an advantage since the knife can be kept much closer to its supports. Less knife projection means less air being beaten by the knife, less deflection while cutting, and this results in a far quieter cutterhead when in operation.

    I remain a bit skeptical about the helical systems, though I do have a Shelix cutter for the Shaper. Helical cutters, as there is continual knife contact with the board, tend to draw a bit more amperage than other cutter heads.

    The premise of these systems is that if a knife (or knives) gets nicked, one can simply turn the affected knives around in their seats to a fresh cutting face. There are two problems with this idea. One, if the knife seat is not completely clean then the reset knife can project slightly or not seat properly, affecting the cut and possibly marking the board. Two, the issue of cutting circle. As you run wood through the planer, the knives wear, progressively getting decreasing the diameter of the cutting circle. Taking some of those knives and rotating them to a fresh cutter means that those rotated knives will be proud of the cutting circle given by the rest of the work cutters, which should make for marks on the board and heavier wear on those fresh knife faces.

    Finally, the insert knife systems tend to have somewhat pricey knives. The old-fashioned knives were cheaper to buy, however when you factor in the cost of professional sharpening, shipping the blades to and from the sharpener, down time, and the time and fussing it takes to refit the knives to the head, well, the cost difference evaporates as far as I'm concerned. With the Tersa and Terminus type of head, knife change is extremely fast. With the helical insert knife systems, rotating a damaged knife or three doesn't take very long, however turning all the knives in a head probably takes about as long as a traditional knife system.

    I think the helical head planer makes the most sense in a production setting where wood is going from the planer directly into the wide belt sander, and any issues with knife tracking marks are rendered irrelevant.

    Personally, I'm sticking with Tersa as it gives excellent cut quality second to none, quiet running, a choice of 5 knife materials, options to mix and match knife materials or quantities (eg. running a 4-knife head with only 2-knives and 2 dummy knives to economize), and super fast knife changes. Works for me, and I'm glad to at last be free of the traditional knife systems in my planer and jointer.


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