Cutting straight lines!

[Nelleyarm]

I am new to leatherwork, though not to sewing and construction with fabrics.   I understand the need for sharp knives.   I also understand that without straight cuts, it is pretty much senseless to try to put something together.   It seems I am, so far, totally incapable of cutting a straight line!  Multiple knives, roller cutter, fresh blades, scalpels, all tried.   The biggest challenges are leathers about 2-3 mm of different types.  Those of looser temper are most challenging.

A couple of questions about approach.  I prefer to stand, and have a sit-stand work area so can adjust the height.   Is it better to be closer to the work?  Does distance of upper body (being closer) help with application of pressure on the knife?  What is the best way to get a smooth continuous...and straight...cut?

One major issue is keeping the leather still and flat, and holding the pattern on the leather...one or the other always seems to move, even on short runs of 8-10 inches.  Longer runs wiggle more.  I have tried weights with limited effectiveness.  Do have self-healing mats and all sorts of rulers and straight edges and squares.

So that is the first area needing some input.  I see the pros and semi pros cutting giant pieces of leather perfectly straight by eye on You Tube.  Obviously some of the control will come with experience.   What are some other tricks?

The other major question is how to hide or fix mistakes...that one (or 10) crooked or out of line stitch, a hole in the wrong spot, those wiggly lines that need straightening.    Oh yeah, and how to keep hole punches from bouncing and making 2 impressions.

If any of you have suggestions, tricks, tips, videos, It would be grand if you could share a few on these areas.    Thanks!

[bikermutt07]

It drove me crazy in the beginning too. The leather would always stretch at the end of the corner giving that jut out of square.

Knives sharp enough for one pass is what I have found to work best. 

If you have a round knife you can roll thru the end of the cut and not cause the leather to stretch. 

Sand paper comes in handy for cleaning up uneven cuts, or even a Dremel sometimes.

These are my go to knives. They are all Knischield knives. I use the round knife the most. The curved detail knife is really handy for those tight spots. The bevel point knife doesn't get used much. But it is really awesome at cutting card pockets on thin flimsy leather. I can basically push the knife straight down chopping the line instead of cutting it with a stroke. 

I am a hobbyist and this is over 500 bucks worth of knives, but cutting has become so comfortable with them. I slowly collected them so the money wasn't missed that much.

If I could only have one it would the round knife. Followed by the curved knife.

Also I go around my templates with a scratch awl the cut them out. That usually works pretty well.

And I do use a rotary cutter on the long stuff.

As far as hole punches bouncing, you need something firm. Granite is what most of us use with a rubber mat or poundo board on top.

[brmax]

For the punch bounce, I found it required a real stationary table and or at the corner would help. CS osborne 603 cutting pad works great. I havent a clue what kinda vinyl rubber it is but it is in no way a mud flap or hard like hdpe. 

 

Good day

Floyd

[Stetson912]

Mutt has the answers. 

A hard dense surface for punching with something to protect your tools on to like mutt mentioned

A roller cutter will help with the stretch. Anything that had downward cutting or chopping pressure instead of more lateral or slicing cutting. 

Use multiple passes when cutting thicker stuff. Nothing wrong with that. Strait edges are your friend as well. 

[plinkercases]

As above, rotary cutters, head knifes, straight edges, clamps.

I have a 3x5x1/4 HDPE sheet on my cutting table so able to get a good continuous run at long straight cuts. and punching on 1" HDPE on about 3/4 granite on 3 inches of built up wood directly over a 4x4 leg to the concrete and for some tools all that with a poundo matt on top. and 2lb polly head mallet or maul.

Misplaced stitch you can remove and re-place right away with a careful placement of a new hole with the awl, wobbly lines (made with a creaser or round stylus type indent line) can often be smoothed with a modelling spoon/tool then done....hole in the wrong place.... bad... or adapt the design! use it in a new way or cover it or add one systemically off the other side of the piece and call it part of the design.

Welcome aboard and lets some of your work as you go.

 

[battlemunky]

One of those Olfa opaque quilting rulers helped me straighten up a good deal. Also, holding down your straightedge through the cut is imperative. Misplaced stitches happen from time to time but practice, practice, practice will tighten that skill up dramatically.

[VabaX]

dunno 'bout you, but I use a ruler....

[RockyAussie]

8 hours ago, Nelleyarm said:

 What is the best way to get a smooth continuous...and straight...cut?

The best way to get straight cuts so far other than perhaps a laser I do as below.  This shows a 100 shoulders to be straighten up to then run through a belt strip cutting machine.

Here I use a 1+1/2" x 1/4" piece of flat steel which I screw down to the table on one end and put a nail at the other end at the back behind the steel so I do not have to worry about it sliding away as I cut. I lift the steel and slide the leather under and drop it down again to cut. Note that there is a niko line under that shows me where the leather has to go past for cutting. The steel is flexible enough to follow and table irregularities.

With the back side of a sharp tipped knife I deeply scribe where I want to cut and then I position the steel back for the main cut. The steel weight helps to keep the leather still as well.

Here I like to use my round knife due to its edge holding up for generally most of the job. note at this stage I assist the cut by gently pulling the waste up and toward me.

8 hours ago, Nelleyarm said:

I also understand that without straight cuts, it is pretty much senseless to try to put something together.

Yeah I know what you mean. I just generally don't do it. Most of the time I design almost every thing to be first cut oversize and then be second cut when the pieces are attached together. That I normally do with made to shape cutting knives on a clicker press but sometimes by hand as in some of these pictures below.

8 hours ago, Nelleyarm said:

One major issue is keeping the leather still and flat, and holding the pattern on the leather...one or the other always seems to move, even on short runs of 8-10 inches.  Longer runs wiggle more.  I have tried weights with limited effectiveness

For cutting on a pattern which I normally print onto cardboard I start by printing the sheet and then spray gluing the sheet before cutting it out on my cutting table after the glue has tacked of well. These are often re glued and allowed to track off again before attaching to the leather I want to cut. This picture shows some pieces of a pattern spray glued and drying.

Here showing that even on very bumpy croc skin I can have the pattern hold still as I cut it or mark out for first cutting.

This one shows a pattern for the back of a bag being cut out.

Even on small pieces this method I use . I do hold it with my other hand normally but here I taking the picture with it.

This one below does not have the leather fully attached together as it has to have straps in it after the edging gets applied but again the tacky surface helps me cut exactly to size.

This is one of the finished bags of the patterns above. I have been trying to find time to post the full break down steps for it for some time but there are a huge amounts of pictures and words to do before that happens.

I hope that this is of some help to you and look forward to you posting some of yours in the future. Brian

 

[JerseyFirefighter]

I still would like to get an inside track on Springfield's cam and rail type cutter they use. I would buy one of those in a heartbeat. 

[battlemunky]

@RockyAussie, thanks for the above and that croc bag is quite awesome!

[TonySFLDLTHR]

8 hours ago, JerseyFirefighter said:

I still would like to get an inside track on Springfield's cam and rail type cutter they use. I would buy one of those in a heartbeat. 

We are currently in research to make these available. No ETA on this project, but just want to let you know this is in the works. 

[ScoobyNewbie]

Score! I want a cutter as well!!!!

That bag is gorgeous!

I have found that I tend to cut better when I transfer the pattern onto the suede side of the fabric and cut from there. That way I can use my leather scissors for softer leathers and they work a bit like fabric, or thick/stiffer denim. 

On thicker leathers I am still kind of jiggly. I have found that I like to cut a bit away from my real edge, that way I have room to smooth and sand the edge into submission. 

Also I seem to like to use my chisels too close to my edge, I’ve sanded some of the stitches right off before burnishing. Oops! So I try, VERY HARD, to make my chisel lines at least a quarter inch away from my actual cut line.

[RockyAussie]

6 hours ago, TonySFLDLTHR said:

We are currently in research to make these available. No ETA on this project, but just want to let you know this is in the works. 

Looking forward to hearing more about it.

[JerseyFirefighter]

13 hours ago, TonySFLDLTHR said:

We are currently in research to make these available. No ETA on this project, but just want to let you know this is in the works. 

Be still my beating heart. Thank you for chiming in and attempting to bring it to market. One of the few things I do that I thought could use streamlining was squaring up sides. That thing looks majestic. 

[billybopp]

Lots of good advice above!   

I'd love to have a straight edge anchored to a workbench like @RockyAussie shows above, but I don't have a workbench!  I'll do something like that one day when I do have one.  But for now, I have a BIG self-healing mat and kitchen floor for now, and for pieces that will fit, I use a Logan matt cutter that lets me cut up to 60".  Sure, it's meant for cutting mats for picture framing (something that I also do) but also does nicely on leather.

But without those, you can still make good cuts!  There are a number of things that can help you get that cut.

A rubber or cork backed straight edge will help keep it from moving around during the cut.  An extra pair of hands (or even feet) can help hold it down tight to help keep it from wandering.  I have a 48" ruler that I put self-adhesive cork on just for that purpose, and also have a 24" ruler that came with a rubber backing (even better than cork).  The quilting rulers that @battlemunky mentioned also work well since they have a LOT of surface area to help you hold it stable, and you can see through to your leather to help positioning over a pattern. 

Put your straight edge on the pattern side when cutting.  That way if the knife wanders away from the straight edge, the cut will be on scrap rather than into your piece.

Use body-mechanics to your favor.  It's really hard to cut a straight line when you have to swing your arm around your body to keep it in the cut.  Place your work and straight edge at an angle that will let you keep your wrist / elbow more or less locked.   That'll help to keep the blade from wobbling and wandering.

As you already know, your knife should be SHARP, and stropped!  It's great if you can cut all the way through your leather in a single cut, since that will give you the cleanest edge.  But if the knife and leather don't cooperate there's nothing wrong with multiple passes, you just might have a little more cleanup later on.  

Keep as much of your knife in the cut as you can manage.  IE, keep the handle down close to the leather.  That both makes it easier to cut in a single pass and makes it easier to keep your cut straight.   A longer blade (within reason) lets you engage more leather than does a shorter blade.  Also, don't let the knife lean or wobble side to side for a better cut.  A bigger blade can make that easier, and that is just one of the advantages of a round knife - It stands tall so the slightest variation or wobble is clearly seen!

If you're going to use a utility knife, strop it to improve on the factory edge.  Also, you'll find that the fold-out type has far less blade wobble than the retractable ones do.  For small cuts, an x-acto knife works great if you use the # 2 blades.  The standard #11 blades are pretty flimsy.  All things considered, tho, a good fixed blade knife is best.

Just a few suggestions that you might find useful

-Bill

 

p.s.  @RockyAussie I want that bag.  LOL

 

 

[RockyAussie]

On 16/09/2018 at 12:17 AM, billybopp said:

p.s.  @RockyAussie I want that bag.  LOL

Yea @billybopp I would kida like one for myself as well. It was at least a lot more interesting to make than the bags I have been making the last couple of weeks.Trouble is they sell to well, soon as they go out more orders pour in again. At least the next 50 have have a more interesting style shape. Keep your eye open for a video I hope to load this week showing the missus making the care bags for these using my new zipper guide tool. Turns out they saved her a lot of time and helped keep them neater as well. She now loves them and I have to print like a hundred more so she doesn't need to attach them on the run

[billybopp]

14 hours ago, RockyAussie said:

Yea @billybopp I would kida like one for myself as well. It was at least a lot more interesting to make than the bags I have been making the last couple of weeks.Trouble is they sell to well, soon as they go out more orders pour in again. At least the next 50 have have a more interesting style shape. Keep your eye open for a video I hope to load this week showing the missus making the care bags for these using my new zipper guide tool. Turns out they saved her a lot of time and helped keep them neater as well. She now loves them and I have to print like a hundred more so she doesn't need to attach them on the run

If you've got to have troubles, selling too well is a good one to have!  Can't wait to see the video and it's awesome to hear that the zipper guide is working out well!

- Bill

[Ard Righ Art]

On 9/15/2018 at 10:17 AM, billybopp said:

Lots of good advice above!   

I'd love to have a straight edge anchored to a workbench like @RockyAussie shows above, but I don't have a workbench!  I'll do something like that one day when I do have one.  But for now, I have a BIG self-healing mat and kitchen floor for now, and for pieces that will fit, I use a Logan matt cutter that lets me cut up to 60".  Sure, it's meant for cutting mats for picture framing (something that I also do) but also does nicely on leather.

But without those, you can still make good cuts!  There are a number of things that can help you get that cut.

...-Bill

No workbench?  I have one, but find it easier to grab a piece of OSB, a couple of stanley fat max type clamps, and throw it down on any old table that I can lay out a big piece of leather. Clamp both ends of a long metal straight edge (I have a 4 foot ruler from harbor freight that works well), press down on the middle, and cut away.

The floor sounds awful. The mat cutter, nice. Might have to consider that.

 

 

 

[JazzBass]

On 9/12/2018 at 4:50 PM, Nelleyarm said:

 Oh yeah, and how to keep hole punches from bouncing and making 2 impressions.

 

In addition to a solid surface, I've found that a "Dead-Blow Hammer" is a nearly miraculous tool. They are available in all different weights, and are DIRT CHEAP at Harbor Freight.

It has lead shot inside the head. If you "commit" to a good, solid strike, it transfers all of its energy, and comes right off the tool with NO BOUNCE.
Whoever invented this "better mousetrap" is a genius!

Whether it's 3D stamps, drive punches, etc, nothing does a better job when you need a lot of force IMHO.

[Nelleyarm]

Thank you so much for your help.  Sorry for the delayed response.  I have a couple of dead blow hammers and will try them out!

[Nelleyarm]

OMG, you guys and gals are the best!   The answers I received here are awesome and so helpful.  I have not figured out how to do individual replies to everyone, so pardon my ineptness in the threaded conversations here!  Argh, so much to learn.