Tippmann Boss - Help With Timing Please

[niftycurly]

Unfortunately, the amazing Ben at Tippmann has gone home for the weekend so I'm hopeful that the Boss owners out here might have an answer for this. I've scoured the forums and still can't figure is out.

I was merrily sewing along quite successfully (upholstery plus 8oz veg tan, it's a shoe upper plus sole leather, 277 thread with appropriate needle) until the bobbin ran out. Replaced bobbin and then all sorts of unhappiness ensued. Top tensions went haywire, carefully unthreaded and rethreaded the whole machine, reset tensions, double checked bobbin, etc. Work started getting stuck on the needle, rechecked presser foot tension and noticed a burr at my needle tip, replaced with same type/size, Handle action felt rough so I opened the shuttle assembly to check for loose thread, debris. Nothing in there but noticed that timing was way off so reset that. Checked thread take up arm, rock solid.

Now the needle thread refuses to engage the bobbin thread at all. I've reset the needle several times at various angles, rechecked the timing, even set it back to the original out of whack setting, oiled the whole monster and am totally stuck. Everything feels like butter but that danged stitch just isn't happening. Prior to this the machine was working fine for months.

Anyone know what I'm missing?

Edited September 28, 2012 by niftycurly

[dirtclod]

Do you have the needle facing the right way ? Groove on the left.

[niftycurly]

Yes, needle is in correct position.

[mlapaglia]

Is the bobbin in the right way. By that I mean is the thread coming off in the right direction? Counterclockwise off the spool.

[niftycurly]

Yes

[Denster]

There is nothing in the shuttle area that you use to set timing it only goes together correctly one way. You did reinstall the spacer ring correctly I hope.

[niftycurly]

Yes, the shuttle area is put back together as it was when it was working properly.

The timing being off was that the long ear of the shuttle was at 11 instead of 12 o'clock. I made the adjustment in the rack stop bolt. Thank you.

[Denster]

To check the timing with the machine assembled and the handle fully upright the hook of the shuttle (the tip of which picks up the thead) should be right at 7:00. Changing the position of the rack stop doesn't effect timing it only effects the depth the needle goes and consequently how large a loop is formed for the hook to catch on the upstroke. Lowering the stop plate allows for a larger loop to form. If the machine is in time, and it is virtually impossible to get a boss out of time unless you break something, and you can't pick up the thread from the bobbin then check the hook to needle clearance. Unthread the machine and take off the needle plate so you can see and slowely cycle the machine and note how much clearance there is between the hook and the needle as it passes. It should only be a very small amount like .020 or a little more. If it is a lot more and the machine was working before it is not assembled correctly.

[Denster]

A couple of other things. You said the top tension went haywire/ What did you mean by that? You also said that the machine felt rough for a bit. Are you using bonded nylon thread? I have a reason for asking this.

[niftycurly]

Hi Denster -

Shuttle hook at 7 o'clock when handle fully upright, check.

I took off the needle plate per your suggestion and noticed two things.

1) the needle clearance is quite tight, almost touching. The hook tip passes just under the needle eye.

2) this is more curious and perhaps indicative of bigger problems. I'd always assumed the occasional "rough" action was due to thread jamming in the shuttle area but it appears that occasionally the hook jams itself against the right rear of the needle foot instead of clearing just behind as it should on a good clean stroke. Like either the needle foot is late going up or the hook is arriving too early. There appears to be no pattern for when it does this and I keep the shuttle area well oiled. There is some clear wear on the needle foot where contact occurs.

As for tension - the upper thread had sprung off the spool without me noticing wrapped itself around various spots it shouldn't be and popped out of the tensioners. I'm using 277 Linhanyl bonded nylon thread and it's an older cast iron Boss if that makes a difference.

Thanks kindly for the detailed query and suggestions.