a question for tinkerers

[sunnybob]

My jet lunchbox thicknesser annoys me. I have done a lot of "fettling", removed the tables and use a long one piece board, but it still leaves snipe at both ends.
Trying to run small pieces through it is a nightmare of co-ordination constantly feeding sacrificial pieces in front and back of the work. If the work pieces are narrow i even have to put long scrap runners each side to get a smooth finish without the carriage moving sideways.

So I'm thinking..... The two rollers are lower than the cutter (the front is 5 mm lower, the back only about 2 mm), its the angled lift and drop of the rollers that leaves the snipe.
How about if I modify the rollers to be barely a mm lower than the blades and remove the springs. That would make for a solid carriage.
i know I would only be able to remove the 1 mm per pass, but thats all I need most of the time, and I'm not working to any deadlines.

 

[custard]

How about if I modify the rollers to be barely a mm lower than the blades and remove the springs.

That's one way to find out if the anti kick-back teeth are working properly!

Seriously, besides being dangerous you might even make the problem worse. Here's some other stuff to try first.

-Are you able to lock-off the cutter head on your machine? If so always do that for the final couple of passes.
-Try setting the depth of cut with the final adjustment being up rather than down.
-Are the knives sharp?
-Was the underneath reference surface planed adequately flat?
-Is the workpiece properly supported on both the indeed and outfeed side?
-If your machine has fold down infeed and outfeed tables are they flat and true?
-If your machine has rollers at the end of the infeed and outfeed tables are they running true?

 

[sunnybob]

-Are you able to lock-off the cutter head on your machine? If so always do that for the final couple of passes.
I dont understand that, so I'm guessing I cant. I only use this machine to flatten sawn boards and would ideally like to use it for smaller (sub 2ft x 1 ft) pieces, but I'm losing at least 3" off each end.

-Try setting the depth of cut with the final adjustment being up rather than down.
I dont understand that either, sorry.

-Are the knives sharp?
Yes.

-Was the underneath reference surface planed adequately flat?
I'm using a 4 ft long piece of contiboard fully supported underneath.

-Is the workpiece properly supported on both the indeed and outfeed side?
see above

-If your machine has fold down infeed and outfeed tables are they flat and true?
Tables removed

-If your machine has rollers at the end of the infeed and outfeed tables are they running true?
See above.

 

[loftyhermes]

When feeding the board through my thicknesser (Makita) I find I get less snipe if I lift the board when it overhangs the outfeed table. My reasoning behind this is that these thicknessers have short tables and when the board passes by the infeed roller it springs up a little into the blades and causes the snipe. I also take more passes taking a little off rather than fewer passes taking a lot off.

 

[custard]

-Are you able to lock-off the cutter head on your machine? If so always do that for the final couple of passes.
I dont understand that, so I'm guessing I cant. I only use this machine to flatten sawn boards and would ideally like to use it for smaller (sub 2ft x 1 ft) pieces, but I'm losing at least 3" off each end.

Snipe on a lunchbox thicknesser can be caused because the rollers act not only to keep the workpiece down, but also push the cutter head up. Some machines recognise this and have a method to lock off the cutter head at a certain height. Sounds like it's not relevant here.

-Try setting the depth of cut with the final adjustment being up rather than down.
I dont understand that either, sorry.

It builds on the previous point, it's experimenting to remove backlash from the system. The normal method of operation is to progressively wind down the cutter head, so you're generally always turning the handle in one particular direction, try turning it an extra half turn in that direction but then backing it off half a turn. It might help, it might not. But it's worth trying.

-Are the knives sharp?
Yes.

-Was the underneath reference surface planed adequately flat?
I'm using a 4 ft long piece of contiboard fully supported underneath.

I meant the underside of the workpiece, the face that rides on the table. If this is banana shaped it's a cause of snipe, if the snipe is worse/better at the outside edges then it's a clue that the underside reference face is cupped.

-Is the workpiece properly supported on both the indeed and outfeed side?
see above

-If your machine has fold down infeed and outfeed tables are they flat and true?
Tables removed

-If your machine has rollers at the end of the infeed and outfeed tables are they running true?
See above.

 

[dzj]

Do your rollers bottom out properly?
Sometimes dust and gunk accumulates in their pathways and they don't engage the
board with adequate downward pressure, hence the snipe.

 

[marcros]

why have you removed the tables? On my axi the rollers on the end are critical for support. The contact on a flat board is the indeed and outfield roller, and the 6" under the cutters.

 

[sunnybob]

The head contains two rollers, both spring loaded, with the cutter in between.
As the board enters the machine, the first roller lifts up onto the wood, tilting the cutter downwards and making the first snipe cut untill the wood passes the cutter and pushes the second roller up onto it, levelling out the cut.
When the wood passes the first roller on the way out the head tilts back lowering the cutter and causing the end snipe, untill the wood passes the second roller.

The tables were almost impossible to square up exactly so I removed them both and fit the 4 ft board straight through the machine when I use it.

I have had the cutter head apart a few times trying to remove the snipe, it appears to be impossible. I only take shallow cuts. If I start the board off with the roller only and wind the cutter down untill it touches the board then the rear snipe is there. but Then the front of the board is too high, so if I pass it through again then i get snipe at both ends.

Lifting the wood before and after makes no real difference, maybe slightly shallower snipe, but its still there, wasting the wood every time.

 

[custard]

It sounds like you've fully investigated the problem, sorted all the obvious stuff, but that you're now hitting the design limits for this particular machine. Without a way of locking off the cutter head, or a more robust mechanism that will keep the feed rollers and the cutter head aligned, then snipe seems inevitable. You'll either have to finish the final 1/16" of thicknessing by hand with a bench plane, use over length components and trim off the snipe, or pass sacrificial pieces through the machine immediately before and after the actual workpiece.

You say your machine is a Jet, Fine Woodworking ran a large test on bench top thicknessers a few years ago, most machines fell down in terms of either snipe or being out of parallel. The best was the DeWalt DW733, but that's about £600, at which point many prospective buyers think that instead of an excellent lunch box thicknesser they'd rather buy a bottom end planer/thicknesser for similar money. The Jet JWP-12DX sat somewhere in the middle, but that particular Jet model did have the facility to lock-off the cutter head.

 

[sunnybob]

I cant access the fine woodworking test without signing up. I cant find any mention of locking the cutter head, are you thinking of a planer / thicknesseer? I have the bench top 12" jet.

i might strip it yet again this afternoon and see if there is any way of stopping the block pivoting.

 

[sunnybob]

I've just pulled it apart, and I have to retract my earlier statement. The head on this one does NOT tilt. The cutter is solidly mounted into the head which is very firm on the four corner pillars. But both rollers are sprung.
But that leaves me even more befuddled.
If I am running a piece of wood along a straight surface with a fixed head cutter, why am i still getting snipe?

Length of wood makes no difference. 2.5 metre x 20cm plank, or 40 cm x 6 cm stave. I still get snipe on both ends of the wood. And I'm not talking a cm or two, I'm looking at 75 mm each end and a step of 1mm or more, which is just unacceptable.
I'll run it without covers tomorrow and watch from the side as the wood passes through to see whats happening

 

[dzj]

Not to rain on your parade Bob, but there'll always be a bit of snipe on these machines.
Keep your blades sharp, set things up the best you can...
Allow for some extra length, run your stock one after the other or add longer parallel pieces are the usual ways people deal with it.

 

[JWD]

Bob, forgive me please if i'm being dense, but if you got a couple of floor-standing rollers and set one on both the infeed and outfeed about 1-2mm higher than the feeder table would that not help cut the snipe? in this scenario on the infeed the front of the board goes in slightly angled towards the floor due to the free standing infeed roller, is then made parallel by the roller which in my head eliminates the snipe... again i'm convinced i'm being daft but maybe try that.

can you adjust the rollers? 5mm sounds massive to me

 

[ScaredyCat]

I may have missed it but have you tried extending the bed by placing a long flat piece of MDF/plywood through the mouth and extending out the back beyond, fixed so it wont move. Then feed your stock through on top of that. I know that's improved my situation with my much maligned Triton lunchbox. That might not have been explained that well so https://www.youtube.com/watch?v=KOzRB30gxpE might help


.

 

[monkeybiter]

Have you tried Custard's backlash experiment; wind it down past the required point then back up to where you want it.
Keenly watching this thread...

 

[custard]

Not to rain on your parade Bob, but there'll always be a bit of snipe on these machines.

It depends what you call "a bit of snipe". The Fine Woodworking test I mentioned earlier measured the snipe from the DeWalt DW733 at less than 0.001". I've plenty of experience with that machine and that was what I found too. In addition the DW733 had less than 0.001" difference in thickness from one side to another. By comparison the worst machines in the test were recording snipe and parallelism problems at about 0.007".

Incidentally, I'm not a fan boy for the DeWalt, the Delta 22-850 achieved similar results and was also quieter than the DeWalt.

The best bench top thicknessers can deliver high quality and accurate results with almost zero snipe. But to achieve that they're both expensive and heavy. A lot of users want them for site work so weight is an issue, and lots of hobbyists look at the price for the better models and decide they'd rather buy a really cheap planer/thicknesser instead. In my opinion that's a mistake, but it's their money not mine so they can spend it how they like!

 

[dzj]

How did Bob's Jet fare?

 

[custard]

They had a Jet, but it was a different model, one that had the facility to lock-off the cutter head as an anti snipe measure.

 

[sunnybob]

DZJ....
on a 40 cms piece its madness if I have to add 15 cm of scrap to each piece. i've tried sacrificial before and after pieces, but its a pain in the sit upon and I am looking for a solution to an engineering problem rather than a workaround.

JWD... rollers wont help on a 40 cm piece.

Scaredy cat.... yes you missed it twice that I have a four foot board right through the machine.

Monkeybiter... not yet. That will be tried tomorrow when I get serious.

Custard... agreed. I bought it. I have to live with it or modify it. But in extenuating circumstances, I cant buy any good machinery here and to pay a grand or more in the Uk means I have to add another thousand shipping and handling.
2K is the entire value of ALL of my machines together, and I'm a retired hobbyist who is only just finding out how bad woodworking machinery is while making trinket boxes of very little value.

I have all day tomorrow to just sit and watch it make fire wood. I'll report back if i find anything significant.

 

[custard]

I'm a retired hobbyist who is only just finding out how bad woodworking machinery is

I sympathise Bob, genuinely I do.

The real choices facing a hobbyist woodworker wanting to make furniture (I say furniture because that's what I know about) are these,

1. Hand tools only. You need a lot of skill, a lot of energy, and a lot of time. In reality you're limited to small projects like side tables, anything bigger just isn't realistic for anyone balancing the demands of a job and a family.

2. Hand tools supported by very basic machines. The most arduous jobs in woodworking are hand planing to final thickness and ripping. A bench top thicknesser and a bandsaw will handle the majority of the grunt work, plus they've both got small footprints so they'll take up relatively little space. If you're buying new and looking for acceptable quality you'd have to budget at least £1,500 once you include dust extraction. This removes a lot of the hard physical graft (not all, but a lot); however it still won't remove the skill. So, it's best thought of as labour saving rather than skill saving.

3. Machinery and power tool based woodworking. This is a seductive idea for many new woodworkers; no need to acquire difficult skills, quick, low effort. But it's a mirage. With very good metal working skills (plus a lot of patience) it might just be viable. Otherwise you're looking at a budget of well over £10,000.

Sadly the newcomer faces lots of conspirators all trying to maintain a fantasy. The magazines selling the woodworking dream, internet fanboys pretending rubbish kit is top quality, and the tool catalogues full of stuff that looks fine in a photo but will never deliver in a workshop.

Looking at your projects though you should congratulate yourself, you've overcome a lot and achieved far more than many new woodworkers ever will.