Stitching Groovers weaken seam?

[Johanna]

Bruce, I've seen that trick to hide the stitch line, and it's not only functional, but it can be attractively "invisible".

I've heard both sides of the stitching groover debate, and the protection from abrasion on the stitches makes sense to me, as long as the leather is thick enough. A groover should make more of a "scratch" than a "channel", anyway. Anytime you sew (punch holes in leather), you have a weak spot. The trick is to spread the tension over a big enough area, and to teach the consumer to properly care for the item to avoid dry rot and have it come apart no matter how it's been sewn. (I always felt bad for people who brought us old neglected things for repair/restoration and were disappointed that we couldn't "save" the original leather because it wasn't in good enough condition to hold a stitch.) I was also taught to pound stitches into the leather. If you can run a fingernail down your stitch line and the thread catches, there is a potential problem, and you should probably pull the thread out and start over.

Johanna

[barra]

If The stitching is prone to wear I will use a stitch groover/adjustable racer or American racer to recess the stitching. I sometimes use a tool which I think is actually a boot makers tool for stitching soles. It has a small slightly curved blade (about 1/4" wide X 5/8" long). The blade cuts into the grain side at about a 30 degree angle and leaves the grain side intact. This then lets me open up this groove to stitch in. I can then glue the grain back down. If I rub over this with my smasher then it is almost invisible. This technique is described in Stohlman Vol 2, page 364, where a round knife is used.

Barra

[bruce johnson]

Barra,

I think you are describing what I call a channeler. It is an old shoe tool, some are a straight and others are angled. I have not used one yet, but have one "in the mail" from Bob Douglas to try out. I plan on using it for the hidden stitch on cantle bindings.

The way this guy did it on his skirts and riggings was to cut the groove with a border guide on his swivel knife - a vertical cut down through the grain partway, not in from the edge like a hidden stitch. He then stitched it, put some cement in the groove, and pounded it over enough to close that slit over the stitch line. This was the first time I had seen this done. Made for a clean look, but was, well, odd.

I am not sure how deep he cut the groove. Since there is not a pull against the seam, I would guess a guy could go fairly deep (half maybe??) and be alright. I think this guy was from Montana or Idaho, and was sharing a booth space with a guy who made some pretty cool chinks. At the NFR tradeshows, that is still pretty vague I know. Anybody know more about doing this, or who I might be talking about?

Bruce

[CitizenKate]

The pieces I sew are anywhere from 3-4oz to 5-6oz. The piece I was able to tear was 3-4oz, and it was right along the grooved line where it tore. I can tear a piece of 5-6oz., too, but only with vice-grips.

What ounce weight and type of leather were you using in the instance where you could tear it after using the groover?

Very good points to consider, Darc, and I agree that different pieces have different considerations. I know the effects of the groove on the strength of the leather are as much of a consideration when you're using heavier leather, just as I mentioned previously.

I think that the item being made and the weight of the leather needs to be taken into consideration when making the decision to groove or not groove. As a saddlemaker, I would'nt even consider the idea of not using a stitch groover because most areas of the saddle receive alot of rubbing over the years and it is important to protect the stitching in this manner. Simply creasing the leather will not achieve this as effectively.

In some areas such as flat plate rigging,which receives alot of stress, I groove the same line twice on the upper stitching. This is so after it is sewn, the threads are deep enough that the edge of the groove can be pushed over the stitching, almost completely covering the stitching from the constant motion of fenders and stirrup leathers rubbing back and forth. On a saddle I have never seen a problem that can be solely blamed on a stitch groove. I can't speak so much for lighter leathers, but on heavy leathers there doesn't seem to be any reason not to groove.

Kate

Edited June 12, 2007 by CitizenKate

[K-Man]

The pieces I sew are anywhere from 3-4oz to 5-6oz. The piece I was able to tear was 3-4oz, and it was right along the grooved line where it tore. I can tear a piece of 5-6oz., too, but only with vice-grips.

Very good points to consider, Darc, and I agree that different pieces have different considerations. I know the effects of the groove on the strength of the leather are as much of a consideration when you're using heavier leather, just as I mentioned previously.

Kate

Sure, I could see tearing a piece of 3-4 oz (2.5-4.5 actual) that's been grooved, as well as doing a piece of 5-6 oz (4.5-6.5 actual) with a set of vice grips. I think a couple of things would contribute to the ability to do that. One is the quality/tannage of the leather. The other is the depth of the groove. I've made over 3,000 holsters in the last few years, always grooved the line for stitching and never, ever had a failure of any kind. Any stitching above the grooved line is more apt to suffer failure or potential abrasion, as reported by others here, long before the leather itself fails IMHO.

[Johanna]

I am not sure how deep he cut the groove. Since there is not a pull against the seam, I would guess a guy could go fairly deep (half maybe??)

bruce

The way I've seen it done is on an angle like you describe, and the cut is made halfway into the leather. I suppose 8/9 oz would be the "thinnest" leather I would attempt to stitch like that. The work I saw was done on skirting leather- 10/14 oz. weights. You can either wet the leather after stitching and pound it, or use cement. When pounding, insert a scrap piece in between the work and the hammer (a cobblers hammer is wonderful for job like this, and lacing, too) so you don't accidentally mar the leather near the seam. I have also seen this technique used in SCA armor (to be period authentic maybe?) and now I'm going to have to look it up and find out the historical significance because I'm curious.

Johanna

[CitizenKate]

Your point is well taken. When I first posted on this topic, I was only considering how the strength of the leather is affected by having the grain broken by a groover. If the seam is going to be exposed to a lot of abrasion, as you and Darc have pointed out, then slightly compromizing the strength of the leather is a sensible trade-off to protect the thread from abrasion, which is more likely to cause a failed seam, especially with heavier leather.

With the items I make, the seams are exposed to very little abraision, but since the leather I work with is relatively light, such as with a wallet interior, the seam is more likely to fail because someone tried to stuff too many coins into a zippered pouch, and the strength of the leather at the seam is a much bigger factor.

So I will amend my original position about grooving, based on some very good discussion by you and Darc. My position now is: "It depends."

Thanks for the "clue-by-four" of leatherworking wisdom!

Kate

Sure, I could see tearing a piece of 3-4 oz (2.5-4.5 actual) that's been grooved, as well as doing a piece of 5-6 oz (4.5-6.5 actual) with a set of vice grips. I think a couple of things would contribute to the ability to do that. One is the quality/tannage of the leather. The other is the depth of the groove. I've made over 3,000 holsters in the last few years, always grooved the line for stitching and never, ever had a failure of any kind. Any stitching above the grooved line is more apt to suffer failure or potential abrasion, as reported by others here, long before the leather itself fails IMHO.

[Soybomb]

Anyone ever heard by using this tool that you're creating a weak point on the leather/item? Apparently there's a holster maker who claims that by using the stitch groover, you're creating that.

I believe I've heard one make that claim but I can't put a name to it right off hand. Anyway I've heard very few complaints from anyone about failures of modern concealment holsters. The only ones I can recall though are thread problems and not tears so I think if there is a tradeoff its probably for the best to protect the threads on holsters but I'm not sure its anything to worry about either way. Out of curiosity do the big boys with sewing machines make grooves? My machine stitched holsters don't make it feel like they do.

[Art]

Hi Bomb,

I do crease the grain (just the top for D&S) with a screw crease. I also have a "bump" on the center presser foot on some of my machines that pushes the thread down a little. I will crease with a screwcrease and then go back over it with a regular crease to make really deep grooves on ranger belt billets and even go over them with a wheel after stitching so that the belt buckle won't wear the stitches. You can also go after the back edge of the buckle with a felt bob on a foredom or dremel to smooth them a bit if needed, although it will wear the plating off. Most buckles are ok from the plating process, and don't need relief.

Art

I believe I've heard one make that claim but I can't put a name to it right off hand. Anyway I've heard very few complaints from anyone about failures of modern concealment holsters. The only ones I can recall though are thread problems and not tears so I think if there is a tradeoff its probably for the best to protect the threads on holsters but I'm not sure its anything to worry about either way. Out of curiosity do the big boys with sewing machines make grooves? My machine stitched holsters don't make it feel like they do.