OK. Reconditioning clapper boxes.
This was on a Gray openside planer of 16 ft stroke with a 2 ft wide table. It had seen several generations of press brake die work. It started as almost a beater but it was level, the bed and table way were in pretty good shape. Someone had rebuilt the rail and saddles. The slide and the clapper boxes were the final step.
The thing that made this tricky was it was supposed to be a lick and a promise fix and there was plenty of wear. I HATE lick and a promise jobs. Do it right. However, funds were tight and time was short. All through the job I was endlessly heckled by the suprintendent: "Are you done yet?"
We've done dovetail slides here before so I won't go into detail. The lick and a promise fix I did on the slide didn't do them justice but there was significant improvement. I reduced the 0.020" hourglass in the slide to about 0.002" and took all the rocking chair out of the female dovetail. Everything blued more or less. Needless to say the fit and the bearing left somethng to be desired.
I wanted to replace the leadscrews and nuts too but I was over-ruled by the customer. I barely got to make an eccentric bushing to restore the slide lead screws to center in their nuts. I performed most of the slide work on a borrowed planer down the street. This greatly shortened the work compared to doing itall with a scraper.
There's only one way to fix a worn clapper and that is to make a new clapper to fit a re-conditioned box. You can't shim it. I ordered DuraBar for new clappers so it could ship while the work on the slides was in progress. While I was on the planer I skimmed all the surfaces of the clapper boxes to prep for scraping and doctored up the radiused slot (I call it the "bail") that clamps the tilt of the clapper box. OK that was the slides. When they went back on they worked pretty well. At least you could traverse them and they wouldn't bind on the ends or flop loose in the middle.
When the material for the clapper came in I had my helper jump on the mill and rough them to my sketch. Meanwhile I scraped and doctored the boxes so the backs were flat and the bottom, sides and ledge were square. The clappers weren't that big a deal but you have to remember the clearance with the cheeks of the box had to be held to a bit less than 0.001". Any more and the tool will side shift, any less and they won't close reliably from their own weight.
It took a couple of times back and forth on the mill to get both clappers rough fitted and drilled for their studs and wear plates. Then I had to scrape the clapper width to suit the width of the box cheeks, then fit the clapper to the bottom of the box and the ledge. This has to be carefully done because the tool lift and thrust force is transmitted to the box by means of the ledge, the bottom flat and the cheeks. The pin remains unloaded except for the moment that wants to roll the clapper out of the box. So all fitting has to be done first before the pin is fitted.
The final step was almost a jig boring task: bore the clapper and box for the clapper pin as an assembly. This is a tapered hole about 1/4" per ft. If the hole was not dead square the clapper when raised would skew and bind. I had my helper make a couple of new HT pins about 5" too long. I had a couple of whopping big taper pin reamers in the range of the overized pin I would be making. It happens my helper was a good lathe hand and he knew how to make the pins to duplicate the reamer dimensions.
So with the clapper and box securely clamped in registry we bored a stepped hole to take the reamer. The corners of the step would guide the reamer so it wouldn't wander. But by bit we drove the reamer into the stepped hole stopping short to try the pin - which naturally needed some adjustment. As it happened the customer had a good cylndrical grinder and my helper made it his job to doctor the pin's taper. At last we had a fit on the first one. It blued full length almost but the pin seemed a little barrel shaped. A little polishing fixed that. Lastly we had to ream just a couple tenths from the clapper so the pin when snugged up wouldn't bind it.
After that, mark the pins, cut them to length, and thread for the retainer nuts.
I should say something about my helper, Jim Short. He was machinist of long experience. Instead of resenting working for an outside guy he jumped right to it and helped me intelligently using his whole skill. He also carefully watched what I was doing, asked sensible quetions, and asked to be taught which I did. I have a hunch next time that outfit needed fancy scraping, Jim would get the first try.
I omitted many details like tuning up the tool lifters, re-fitting the clapper swivels, adding clamping plates for the bail, new strongbacks and wear-plates etc, but that's mostly make and mechanic work. Detailing it would triple the length of this post, bore most people to tears, tax my typing (my legs are going to sleep), and detract from the lesson which is how to overhaul a planer (or shaper) clapper box.