29K70/71 - Making my own parts

[Constabulary]

You can adust the the foot lift on a small cam on the backside of the head. It´s marked H M L for High, Medium, and Low foot lift depending on the material thickness you want to sew.

The "official" stitch length for the 29K models range somewhere between 4.5mm and 5.1mm (I have seen both mentioned in official Singer documents). On the 29K model you have a pendulum effect - meaning the thicker the material the shorter the stitches - thats normal. So when you are close to 5 SPI on thin material that is a perfect result for a used patcher of this type!

EDIT:

BTW - seems you have used the front hole for mounting the lamp. This is a "tool hole" for adjusting the small timing eccentric. If it was my machine I´d put the lamp on the back side.

Edited February 13, 2020 by Constabulary

[Snakeoil]

Had not considered the pendulum effect and of course, this is a key variable in the stitch length equation. I'd like to think this would have finally dawned on me if I stared at the machine long enough. Thanks for short circuiting my slow thought process.

I discovered another factor that might come in to play from time to time. I took a thicker piece of cardboard and ran it thru the machine. It would feed fine and not feed fine. If I pushed it or pulled it, all was well. But it would stop every so often. What I found was that the needle upset the backside of the cardboard enough that it was apparently getting pushed into the needle hole on the needle plate and in essence, getting a "grip" on the plate. Have not seen that happen with leather or cloth. But some leathers might do this. I made a case the other day for a spotting scope lens from a cardboard tube. The bottom side of the cardboard had felt plus being curved, the area at the needle hole was raised off the plate a bit. But if I were covering a flat cardboard based case with something, I could see this happening.

Yeah, I figured that hole was there for a purpose. I also considered mounting the lamp on the back. Every other machine I've seen has the lamp mounted on the back in some fashion. I did not want to drill the base. I hate modifying original equipment. The hole was there, convenient and expedient. I may search the machine for another mounting point. What I like about it on the front is it lets me light the bobbin winding process. I have the machine squirreled away in a spot in the basement. I probably should just put an LED shop lamp over the machine and brighten up the entire area.

[plasmaguy]

Beautiful work !!!

[Wizcrafts]

39 minutes ago, Snakeoil said:

Had not considered the pendulum effect and of course, this is a key variable in the stitch length equation.

All sewing machines whose needle bars pivot on top experience the pendulum effect of loss of stitch length at increased thicknesses. In the case of a top feed only machine you can reduce the foot pressure to the minimum needed to hold down the leather to get the best feed.

Patchers use a feed motion bell crank that has a puck shape on the end that rides inside a ring to move the foot. This puck always wears out before the rest of the moving parts. As the puck wears, the stitch length decreases. It is easy to determine how much/badly your bell crank is worn by lifting the foot with the lift lever then push and pull the foot to test for slack. I usually do this with the stitch regulator all the way down against the top of the raised foot. If your crank has a 16th of an inch slack, the maximum stitch length would be around 8 to the inch. On a new machine it would get 5 to the inch at about 6 ounces thickness. A really tight fitting bell crank and ring might even continue getting 5 to the inch at 10 ounces.

[Snakeoil]

Thanks Wiz. Purely by coincidence, I happened to be reading the specs at the front of the 29K71,72,73 machine from the Shoe Systems Plus website. It appears that this is a manual published by Singer.

The specs for those machines, which I would expect to be the same as the K70 since they use the same bell crank, shows the stitch length as 7 to 15 SPI. I wonder if Singer decided to move to a more realistic number.

regards,

Rob

[Wizcrafts]

I have a 29k71 that gets almost 5 to the inch. The feed motion bell crank has a little play in it,

[Snakeoil]

I have another issue with this machine. Two actually, but they may be related.

I checked the timing on the machine today and it is a little late. By that I mean the edge of the shuttle carrier is not covering the first third of the needle hole as described in the manual. In adjusting it, I found that there is quite a bit of rotational play in the needle carrier. I'm thinking that either the drive pinion is worn or the screw that holds the carrier to the pinion is loose. I'll be looking into that issue.

What may be a related issue is when I use a different shuttle than the previous owner used, the machine sews well until the thread for some reason gets wrapped under the shuttle carrier. I have to remove the needle plate to be able to move it out of the way and cut the thread. With that done, I use tweezers to pull the thread chunk out from under the carrier.

It only seems to happen with that shuttle. I like that shuttle better because the tension spring is perfect. The other shuttle has a spring with a razor edge where you work the thread under the spring and it is easy to cut the thread in the process. I compared the shuttles and the appear to be identical and with no difference in wear.

I moved my light to the rear, Constabulary. I needed to get at that hole to adjust the timing and figured I might as well move the light while I had it off.

Thanks,

Rob

[Snakeoil]

Probably should have made the previous post a separate thread. Oh well...

Took the cover plate off gear box. Nothing stood out other than the drive pinion for the shuttle carrier was kind of loose in the gear box bore. I see that on the K71 they modified the design to use a replaceable bushing for the drive pinion bearing. But on the K70, the gearbox is simply bored and the pinion runs in that bore.

I did find that carrier slop I reported in the previous post is due to a combination of lash between the gear and racks and excessive play for the drive pinion.

I was pressed for time so did not take measurements. I'm  hoping the drive gear is the wearing component and replacing that will reduce if not eliminate the play. Another option is to simply machine a thin bushing to take up the clearance. Will revisit this.

With the shuttle drive out, I found it was packed with oily paste from years of use. The carrier spring had signs of wear as well. I have two spares that came with the machine. When I go back into the box to take measurements and see what can be done to tighten things up, I'll probably replace that spring.

I have two needle plates that do not fit this machine. Once has the counterbores for bobbin clearance and the other does not. Both are identical with respect to hole placement and that placement is different than on my K70. The bobbin clearance looks like it is for a large bobbin machine. But the parts diagram I have for K72 machines shows a needle plate that looks like the ones on my K70. Maybe these are from an earlier or later design large bobbin machine. I'd be willing to trade these for K70 parts. They are not unused, but damn close to it.

[JPFrance]

Hi Snakeoil, Hi Members,

I just register to have an account, I am JPFrance, (from France of course!)

I am rebuilting a 29K71, and I have discovered the wonderful parts you made as take-up lever adjuster.

My question: I have all original adjuster parts, in good conditions, but I ignorate the reassembly procedure,  how do you ecalibrate,  adjust it ?

I am looking for that procedure since long time, without success. All the rest is working well.

Many thanks for your help!

JPFrance

[shoepatcher]

Turn the dial it all the way and test it for the amount of take up lift in the lever.  Then turn it all the other way and check.  This should tell you which end of the scale it for less and greater.  Choose somethin in the middle.   Singer engineers in their  stupid thought over engineered this part so that it it way to complicated to dial it in.  The older way was much simpler on the early versions of the 29K58,60,62.  None of the clone machines made today use the complicated dial on the later machines.   Keep it simple stupid as they say.

Anybody needing parts to the more  modern take up lever adjustment, I found a source for them.

glenn