Replacement spring for Pilot Press

I need the demensions for the Rocker Lock Spring for a 6”x10” New Style Pilot. Does anyone know the length compressed and uncompressed? I am guessing by the broken one that came on the press it is either 3.5” or 4”. Plenty of choices on MacMaster- Carr but I would like to get it right the first time. Any help appreciated.

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One or two possibilities, is it not as simple as removing the unbroken spring, for test/check and comparison with your hardware supplier(s) stock and then replace both anyway, would seem expedient so to do, rather than one weak and one strong,???
Here in U.K. in the same situation, we would go to our specialist supplier with broken parts and original whole item, they would put caliper vernier on one coil, ascertain exact size, count the number of turns originally involved, and supply springs with a compressive strength accurate to within 2 or 3% of original spec. Ocassionally for accuracy and to account for deteroration over time, supply a compound of 2 per side (with) steel spacers to replicate original spec. Good Luck or apologies for rubbish.!!!
No Commercial included.???

We have used a variety of springs in the restoration of many many Pilots both N.S. and O.S. These spring are often broken given the fact that perhaps they are were under designed. So it is questionable what the original was. We are doing a Pilot Restoration at the moment which I believe could be very late in the production of the N.S. Pilot. The presence of a foundry mark on many but not all of the parts, makes me think they are the latest production parts. It is a triangle with the letters F C F B. Anyway the spring on this press is also broken yet the dimensions are 4.0” long, wire diameter is .135”, The I.D. is ~ .50” and the O.D. is ~ .800. You will find a usable cut to length spring but you may have to buy a package of 4 or 5 11-12” long from McMaster Carr. I can send you one cut to length for $5 plus small box USPS flat rate if you wish to go that route.


Thanks Tom & Mick. I think I have located one. It does seem to me that the amount of compression is excessive. Roughly 60% of full size according to McMaster Carr. I will keep you in mind if the spring I am getting does not work.

L D P, info of no practical help from afar, but may provoke relevant questions & answers!! Our specialist hardware shop has a device built around a Fishermans style spring balance, which apparently works in pull and compression mode, when we source a spring or springs, with some unknown factors, they test springs of the shelf, (we always try for a matching pair) they cut to length PLUS 2 extra coils, in each and every case, they or we, temper the last complete coil and grind flat (or vice versa) to abut the rear retaining washer, And the rear abutment of the roller arm, D.I.Y. efforts tend to end up with a raw edge, that end up scoring or diigging in and make the spring hunch backed, on compression, and I reiterate Nylon or Brass washers at each end of the spring(s) since the early 60,s on all Our Adana models, including the Floor Standing T.P. 48 models, Possibly watch in slow motion or slow as possible, the natural action of the spring when compressing is to try to rotate, if the ends are *raw* & *Jagged* they try to dig in, with washers they are free to rotate, try it. Or check with your local friendly Auto Mechanic, McPhearson struts on Autos/Cars are ALWAYS mounted in this manner, i.e. normally the top mounting has a built in thrust bearing for this very reason, this may be where the principle was *borrowed * from, OR from our Thompson British Auto Platen, the springs on those machine,s had & still have several pounds of thrust, on compression. Admittedly small platens are in the minor league but any and every friction reducing ploy must help.
Good luck Mick.

Mick, I do understand what you are saying. It did seem to me that the ends should be flat. Perhaps the reason the spring was shot on the press we are repairing is that it had no washers whatsoever.

L D P up to a point washers not essential, but, since a long time back proved to be beneficial.!! There has to be a washer at the back end to retain the spring(s) against the pin, (normally). This op. was prompted originally when a spring Or springs snapped on the Thompson (Platen) spares could not be supplied within hours more like 3/4 days, consequently to *keep running* often the broken spring was removed, irrespective of which proportions, as long as it was only one break, we tempered both broken ends for one coil, each, ground them flat, and then re-assembled, but with 3 washers, i.e one each at working ends, and one between newly contoured ends, CRUDE maybe, but had the effect of bringing the working extent of the 2 parts, back to rough semblance of original, until replacements arrived.
At a pinch the principle could, possibly, be transposed down, to smaller application just to *get by*

I swear the following is true, as Health & Safety was still in the future as were, D.I.Y. Gas blow torches, hence we tempered the spring ends, with a Paraffin (TVO) Blowlamp on the fist available imposing stone.

A replacement spring is on its way. Delighted we could help.


T and T Press Restoration