JPT-310: HSS, Spiral TCT, and feed speed; upgrade thoughts

[ivan]

We've had the HSS version of this PT for some years. Despite fiddling with backbevels it still tends to tear out ripply grain, especially when thicknessing. The cutting geometry and feed speed (7M.min) seem designed for softwood.
Some TC helical blocks hold the inserts so they still cut at 90deg - no "slicing" cut to lower the angle - so the main advantage would appear to be lower noise through a progressive cut, rather than reduced tearout.
Other spiral TC blocks hold the inserts so the cutting edge follows a helical path round the block, thus giving a "slicing" cut. This effectively lowers the higher (than HSS) angle at the cutting edge somewhat. The skewed cut will also generate a small force at right angles to the cutting direction - perhaps this is what helps reduce tearout?
In the case of the JPT-310 230V, the TC spiral block version has the feed speed reduced by half - presumably this block needs more power than the HSS version. Some part of the better results with hard woods, must be due to the lower feed speed, surely?
Some years back a spiral block for this machine was over $600 in the USA. A replacement motor pulley (spare part) - all that 's needed to reduce the feed speed to 3.5M/min - should be a bit less....
More sensible to try just changing the motor pulley/feed speed before shelling out for the spiral block? What do you think?

 

[Trevanion]

I’d say try the pulley first and ideally look around for one with a matching bore and similar size that’s much cheaper rather than a spares specialist. If you half the feed speed it should be a night and day difference in finish.

If you were going to go spiral I would seriously suggest selling your machine and buying a new one with one prefitted, probably be far cheaper than buying the block and fitting it. Have a look at how much your existing machine will fetch on eBay and remove that from the price of a new one and compare it to buying a helical head, there’s probably not a lot in the price. Plus the fact that adding a helical head to your machine probably will only increase the value of the machine by 50% the price of the helical head or so. I’d say it’s not worth retrofitting a cutterhead to a Jet, an old Wadkin or something like that would be worth the time and money since it will hold value far better.

 

[ivan]

The Jet has only one motor, so the drive pulley carries 2 belts, on different diameters - cutterhead, and feed drive. Until I realised the spiral model had 1/2 speed feed, being handy mechanically, was considering fitting a second small motor for the feed drive. A pulley swap is simples! Some forum members have done the full upgrade to spiral on this PT, but ever the cheapskate, was wondering how much inprovement lowering feed rate would bring - night and day must be worth a new dual belt pulley!

 

[sunnybob]

Do you have really good extraction on it? i find that I get rippled tear out on my hardwoods if I dont use extraction, or the pipe is kinked reducing it on my jet thicknesser.
Strong extraction leaves a pretty good finish, as does a final 0.5 mm cut.

 

[Trevanion]

You’d be surprised as the at the sheer amount of pulley sizes in a double size that can be had. Even if you can get the matching size pulley for the cutter block speed with an incorrect size feed pulley they can be turned down to size by pretty much any engineering company or hobbyist for peanuts. Alternatively you could change the pulley on the feed mechanism for a larger pulley which will reduce the speed if you’ve got enough clearance.

Do you know what size the existing pulley is and what belts go on it such as a SPZ or a different sized belt?

 

[ivan]

Thanks for your thoughts!
Hello SunnyBob, its on a Fercel 1.5HP bag system, which has 6" inlet plumbed in with 150mm soil pipe to 4" flex close to machine. Don't see any significent waste on the thicknesser table, and stuff without a ripple looks good.
Trevenion, didn't realise you could get twin pulleys with different diameters. Can't size for shure without a look, but the motor is 2pole, so the head is geared up by around 1.5. "A" size belt is standard on mine.Thus the diameter for the head belt will be about 3 - 4", and the feed drive diameter is Very small on my HSS machine; the spiral version will be smaller still - perhaps Jet specify a cogged V belt. Didn't like the look of very small pulleys and solid (chinese?)belts with 3Hp motor, so replaced them with cogged wedge types from the start.

 

[Trevanion]

Thus the diameter for the head belt will be about 3 - 4", and the feed drive diameter is Very small on my HSS machine; the spiral version will be smaller still

If that's the case you possibly won't be able to go much smaller to get the RPM down on the motor end, what size is the pulley on the other end of the belt that drives the feed?

 

[no idea]

I converted my JPT310 from a standard straight knife cutter head to a helical head. The change in feed speed is achieved by using a motor pulley from a JPT260 but you will also have to change the drive pulley and belt since the 260 uses a flat belt to drive the rollers.

There were a few other bits to change when converting the head but this can be worked out by comparing the parts manuals for the two versions (I don't have the list of parts I used for the conversion any longer).

 

[ivan]

Thanks, no idea.
Having blown up the parts pix to A3, it looks as if Jet now fit 2 separate pulleys on the motor shaft, not a double as on mine. There may well be other differences between my older PT and the current HSS model. Time to dig out my paper manual. Presumably easier mfr-ing for the now 2 versions, in both 50 and 60 cycle versions. A flat belt will enable the smaller diameter for reducing feed speed to half. (Trevanion, the bigger feed drive pulley is from memory about 100 - 125mm dia).

 

[no idea]

From memory the 260 uses two separate motor pullies because it uses two different belt types (which is the case with the helical head 310) but the standard knife 310 has a double pulley because both of the belts that are driven by the motor are the same type. If you are planning to convert a 50Hz model make sure you use the parts manual for the European/UK models because there are some differences to the American helical head versions.

 

[ivan]

Hello!
Thanks for the follow up.
I'm in the UK, not all that far from Axminster, who sold me the PT. I've found .pdf paperwork from Switzerland for both HSS and Spiral 310. Now have my manual to hand, which came with the PT, will compare that to the newer machines part Nos., and then sound out Ax's technical guy.