On this page you will find some helpful reference information about leather for use by leatherworkers.
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Leather Thickness Conversion
ozmminch 10.41/64 20.81/32 31.23/64 41.61/16 52.05/64 62.43/32 72.87/64 83.21/8 93.69/64 104.05/32 114.411/64 124.83/16 135.213/64 145.67/32Traditionally leather is measured in &#;ounces&#;, confusingly not a measurement of weight but of thickness. Ounces is really quite a useless measurement as it doesn&#;t directly relate to any other measurements which you will use however it is still used out of tradition.
In the UK you may find leather for sale by mm or by ounce, in the US it will be predominantly by the ounce (in other countries I&#;m not sure what you will find). Either way you must know how to interpret both types of measurement.
Leather is almost always sold in a range e.g. &#;8-9oz&#; or &#;3.2-3.6mm&#;, this is because leather varies across a piece and will never be completely exact or consistent enough to simply give it a measurement such as 3.5mm (as you could with steel or wood).
To the left is a table of conversion from ounce to mm, remember that 1oz = 0.4mm so as long as you know your 4 times table you can easily convert this in your head (6x4 = 24, 6oz = 2.4mm and so on).
I have also included fractional inches in the table although you are unlikely to see leather for sale by those, 1 ounce = 1/64inch.
Parts of the Hide
Depending on the animal in question a hide or skin may be sold in whole or in part. Examples of skins which will almost always be sold in whole are all small animals such as snakes, rabbits, stingrays etc. You may also often buy a whole hide for smaller animals such as a kangaroo, or for young animals e.g. calf skins.
For a larger animal (most commonly a full grown cow) the leather can be bought by the hide or by a cut (subsection) of the hide.
Factories making leather goods or large scale producers may buy whole large hides but the home leatherworker often may not as they are big and expensive (see below for sizing guide).
Different manufacturers may refer to the same cut as different things so where possible I have included alternate names. Click on each cut name in the list to show the leather included in the diagram:
Sizes of Cuts
A whole cowhide may be more than many leather workers need to buy at once or have space to process (the image below shows two sides which when laid out take up my whole lounge floor nearly).
Remember that all the leather you buy also has to be stored somewhere! On the left you can see the sorts of sizes which different cuts of a hide may give you (not to scale).
Of course, no two animals are alike so the yield will vary from animal to animal, these are some averages only for cowhides which will be the most common.
When you buy your leather it may usually be sold by the square foot. This is often referred to as &#;by the foot&#; though you are buying by area not length as you would with fabric.
If a company sells by the square foot then your piece will cost the foot price multiplied by the piece size e.g. 14ft2 @ £8/ft2 = £112
Other companies such as Tandy Leather now price by the piece to make things simpler, so you may be able to buy a double shoulder with an average yield of 15ft2 but whether the piece you get is 14ft2 or 16ft2 it will cost exactly the same. Companies selling in this way should err on the side of the customer and in general you should be getting at or above the stated size rather than below.
Remember that the size is not measured by the extremities of the piece, tanneries have machines which can scan a piece of leather and then mark it with an accurate size.
For example a piece may fit roughly into a 2'x6' rectangle but it could be marked as 10.8ft2 (rather than 12ft2) due to irregular edges. When you receive a piece of leather you may be able to see this measurement marked on the flesh side, this is what the shop will refer to when selling you your piece (see image to the right).
Waste and Scrap Leather
With all leather pieces there will be waste, it&#;s just not possible to use every scrap of leather that you buy. This waste may be:
All cuts of leather will have cutting waste (which can be minimised with careful cutting and planning) however the amount of scrap leather will vary by the cut.
For example a bend/butt is the best part of the hide and doesn&#;t include any scrap leather such as belly/cheek etc., in other words you should be able to use just about all of the leather which you receive.
Pictured to the left are two bridle butts, as you can see almost the entire piece is usable leather except the very tail section to the top of the image (which was kept really to give the tannery somewhere to hang the pieces as you can see by the holes).
Other cuts such as a shoulder may include some cheek and foreleg parts on the edges which will be stretchy, marked, rough to the flesh side and generally unusable.
Whichever cut you buy you will be paying for the whole thing though, in other words with certain cuts you&#;re paying for leather which you will never use. However, the better cuts are inherently more expensive so it balances out in the end.
Remember that some scraps can be kept and used for small projects, testing stamps, testing the sharpness of tools, testing dyes etc. but be realistic and bin anything which is unusable.
Vegetable vs Chrome Tanned Leather
Vegetable Tanned Chrome Tanned time to tan6-12 months1 day costmore expensiveSomething which can confuse new leatherworkers is the difference between vegetable and chrome tanned leather. What does it mean, what are they used for and which should you buy? The table to the left highlights some key differences.
I will not go into a detailed description of leather tanning here since it will not be of interest to many people, however vegetable and chrome (or mineral) tanning refers to how a hide is treated beyond a certain point in the process. So most animals after slaughter and skinning will have the hides reduced to rawhide via a series of processes such as hair removal, defleshing and so on. Once the rawhide is made it can be left as rawhide (a stiff leather which is used for things like dog chews but not too often by leatherworkers) or tanned.
During vegetable tanning the leather, over a period of months, is steeped in a solution of barks, plant extracts or similar materials to create beautiful, high quality, nice smelling leather which we often use in leatherwork. The solution will vary from tannery to tannery and will give different properties to the final leathers (colour etc.). This is a lengthy process and as such increases the cost of the leather.
This leather may be further refined (curried) with dyes and finishes to create something like a bridle leather which is ready to use or it may be left as it is and sold as natural tooling leather for the leatherworker to dye and finish as they wish. It may also just be dyed in which case it can still be stamped but will also need finishing.
During chrome tanning the leather is put into large drums with various chemicals (some of them can be quite nasty) and tanned very quickly, often in as little as 1 day. Usually the leather will also be dyed and finished as chrome tanned leather is generally sold as ready to use and requires no further processing by the leatherworker (or factory more commonly).
There is nothing inherently wrong with chrome tanned leather (aside from environmental concerns), indeed almost all leather produced in the world is chrome tanned, but if you are interested in making your own leather goods it&#;s unlikely you&#;ll buy much of it unless you&#;re making clothes.
Veg tanned is more closely associated with leather craft and chrome tanned is more associated with industrial manufacturing. As leatherworkers the properties of traditional veg tanned leather such as the ability to tool it, the high quality, natural markings and so on are what we like.
Of course there are plenty of high quality chrome tanned leathers also which may be used by high end bag makers and the like (companies such as Hermès), it&#;s just more often associated with mass manufacturing. As you learn more leatherwork you will understand the uses and differences more; when starting out the chances are you&#;re after veg tan though.
Sometimes people say they have found or have been given a bit of leather and are unsure of the type. Using the information above including smell, source, colour etc. should help you to identify the type. There are a few other giveaways which will tell you if leather is chrome tanned:
Thread Sizes
mm TigerThis section helps you to compare hand sewing threads, please note that I do not have any information on machine threads as I don&#;t own one!
Different companies use different measurements to indicate the thickness of their thread. To compare two threads where both are measured in something sensible is easy; we know that 0.5mm thread is a bit lighter than 0.6mm thread and so on.
But what if you want to compare some 18/4 linen thread to some 632 Fil Au Chinois thread &#; not so easy! To the left I have made a table showing some common sizes and makes of thread to make comparison as easy as possible.
Linen thread sizes are the most confusing of all, they are traditionally measured as gauge/ply e.g. 18/3 means 18 gauge thread with 3 strands twisted together. If you had 18/4 each strand would be the same thickness but there would be 4 strands not 3, so the overall thickness would be greater. When needing a lighter or heavier thread you could increase or decrease both the gauge and ply count so comparing them quickly becomes difficult.
The gauge of linen thread is a measurement of the length that can be spun from a standard unit, so as the gauge increases the size of the thread decreases. In other words a bigger gauge is smaller thread i.e. 20/3 is smaller than 18/3. Most companies producing linen thread do not seem to publish a mm equivalent and sizes seem to vary from company to company so the linen info in the table (except the Lin Cable thread) may not be totally accurate.
ShunDe supply professional and honest service.
Where possible I stick to using Tiger Thread as it is the best thread you can buy in my opinion. I do also use the Fil Au Chinois for some items as it comes in a broader range of colours though it's not as resilient.
Stitch Sizes
spi example items thread size needles 10-12When hand stitching leather you can choose to shorten or lengthen your stitch to suit the item which you are making. The measurement that we use for this is stitches per inch, often shortened to &#;spi&#;.
There are two considerations to make here; firstly the size of the stitch should match the item and secondly the size of your thread should match the size of your stitch.
So for example a watch strap might be stitched at 10spi with a 0.5mm thread, a gun holster might be stitched at 6spi with 1mm thread. The strap would look ridiculous done at 6spi with bulky thread and the holster would not be strong enough done at 10spi with the thin thread, hence you can see how these things must be matched appropriately.
Generally speaking the more stitches per inch you have the finer the work is referred to as being. Smaller stitching is a hallmark of higher end items and overly large stitching can tend to make items look a little more amateurish. Above all though the neatness and consistency of the stitch and integrity of the item is of utmost importance.
Having said that there are no hard and fast rules. People often say &#;what should I stitch this project with?&#; to which my answer will always be &#;something appropriate&#;. As long as your spacing and thread size are appropriate then it&#;s not a problem, there is always some choice and leeway. In the table are some guidelines only as to suggestions for thread and spacing for some common items which you can use as a starting point.
pricking iron and wheel sizes
SPI Seiwa Craft Sha VergezIf you buy an overstitch wheel and wish to to mark your stitches that way it will be sold in spi, i.e. a number 6 will be 6spi.
If you buy a pricking iron, either the marking type or the hammer through type (which some people called a diamond stitching chisel or some such), then it may be sold either in spi or mm.
If it&#;s sold in mm then the mm measurement may refer to either the distance between the points which equates to the stitch length or the distance in between each prong which is commonly half the stitch length.
All types of pricking irons are also sold with different numbers of teeth/prongs, all you really need is a 2 prong for curves and then a 6-10 prong for doing straight bits (these irons must have the same spi or the stitch will look different in the corners).
To find the spi of an iron which uses mm divide 25.4 (the number of mm in one inch) by the stitch length e.g. a 3mm iron gives ~8.5spi (25.4/3 ~= 8.5).
The table to the left shows you the common sizes of irons and wheels available and how they compare. The image below shows you how different real world stitching looks as the size of the thread and stitch increase.
First let me say that the upholstery kits offered are a great value and probably the best thing you can do for your Model T.
In the early &#;70s my best option for upholstering my Yellowstone bus was to buy materials and teach myself. I had done the seats for a couple cars and put a kit in my &#;15 Runabout but had to scrounge for any detail on how the diamond tufting was done. I made a mock-up seat to practice on. Vinyl and foam rubber were my choices. The results are at left and my are at right.
The following are pictures from my upholstery with vinyl and horse hair. I laid out the pattern on a canvas backing after tracing the springs onto it. Next I laid out the pattern on vinyl allowing 1&#; for each button horizontally and &#;&#; vertically. Also I&#; extra was allowed around the perimeter as the material needs to turn down at the edge of the seat springs.
Now the material is stitched from button to button and on the lines to the edges. Leather is often just folded and not stitched unless 2 pieces are being joined. Most examples I have seen are stitched. A distance of &#;&#; is left unsewn at the button. The seam uses almost half of the 1&#; allowance so the material has &#;&#; inch extra vertically and is a little short horizontally compared to the backing. This difference hopefully pulls the material into the diamond shape when the backing is pulled tight over the springs and the material in stretched onto them. Different thicknesses of leather or vinyl would require different spacing. This is where some test pieces will help.
The skirt around the springs needs to fit tightly at the bottom of the springs and loose enough at the top to allow some padding to cover the top spring edge. I then mark off distances for each 1&#; fold at the seams that are to be sewn to it. A cord is sewn into the skirt at the top and bottom. The bottom cord need not be as big. Then the skirt can be sewn to the vinyl gathering 1&#; at the appropriate folds.
If I were using foam rubber I would mark the button locations as I did the backing.
I have not fully mastered the use of horse hair. I made a wooden pocket to stuff the horse hair into and give it the proper shape for the diamond and the end tufts. Where foam rubber has some consistency the hair clumps up and is hard to make an even shape. Then the tuft is tucked into diamond held on three corners by the buttons.
The pronged buttons work well. They are pierced through the vinyl and then the backing and the retainer is forced as close to the button as possible and bent. The buttons that tie can be used and are easier to find.
Now the trick is to put the springs in place and compress them. I takes quite a bit of force to compress the springs. I have had particle board shatter with the pressure. I am not fond of Henry&#;s choice for fastening the material to the spring bottom. I often make a wooden base to tack to but the spring makers have done a nice job of reproducing the channel so I use it here. Someone may have a better technique than using vice vice grips but it works for me and I try to keep from using too much pressure that would cut the material.
These are the final seat bottoms for my &#;14. The front seat has wrinkles in the center of each diamond cause by allowing too much fullness in the vertical direction. (1&#;) The rear seat came out better but has a problem of gathering material at the first row of buttons. It would have been better to just gather it in two places on each side.
The seat backs on a &#;14 simply had channels. I believe Henry should have continued the half diamonds another year or two. I opted for them but they developed some puckers I&#;m not proud of. There is some discussion on them here.
http://www.mtfca.com/discus/messages//.html
I like to try new things. Practicing on a mock up rather than the real thing has worked well for me other times. This car doesn&#;t require perfection and I can redo it when it bothers me enough. There are other ways to accomplish this and I am sure there are those who can offer some of their knowledge. This is simply how I have done this project FWIW.
Rich
By Denny Seth - Jefferson, Ohio on Wednesday, April 04, - 02:42 pm:
Thank you for sharing this information and how to pictures. How many hours do you have in one seat?
By Richard Eagle Idaho Falls on Wednesday, April 04, - 02:50 pm:
I can do the layout and stitching in one day and the stuffing and installation in another (per seat). I often spend a couple of days trying to remember what I did last time (10 years ago) and finding where I put the materials. The vinyl and buttons are left over from the Bus and other projects.
Rich
(Message edited by rich eagle on April 04, )
By Mark Strange - Hillsboro, MO on Wednesday, April 04, - 02:59 pm:
Great work as usual, Richard!
By Iowa John L Williams on Wednesday, April 04, - 03:15 pm:
Hi From Iowa! Very Nice - Thanks for sharing! I wish I could learn this great SKILL! Thanks John
By Erik Johnson on Wednesday, April 04, - 03:22 pm:
Leather can be diamond tufted or square tufted without being stitched.
However, leatherette (imitation leather, Naugahyde, vinyl, etc.) must be stitched because the folds will not stay regardless of how deep they are.
Also, sometimes a layer of cotton batting is put between the horsehair and the leather. This gives a smoother appearance by reducing the "telegraphing" of the horsehair on the surface of the leather. It may also have been done for comfort. I don't know it was done on Model Ts, but it was done on other cars and furniture, etc.
By Adrian Whiteman, New Zealand on Wednesday, April 04, - 04:36 pm:
Thank you for your post.
Experience like this is hard won and I appreciate your sharing with us about to face the challenge :-)
Kind regards
Adrian
By Gary Schreiber- Santa Isabel Ecuador on Wednesday, April 04, - 06:05 pm:
Looks wonderful and an excellent pictorial
By Richard Eagle Idaho Falls on Wednesday, April 04, - 07:16 pm:
Erik, batting would surely smooth it out. I'm sure they used it with the cloth in closed cars. This '26 seat seems to be all batting with burlap.
I like the texture the horse hair gives. It seems to make the vinyl look more like leather.
At any rate I hope this helps if any of you venture into diamond tufting. And will possibly be amusing to those who don't. {;o)
(Message edited by rich eagle on April 04, )
By Allan Bennett - Australia on Wednesday, April 04, - 07:29 pm:
Richard, thank you for your sharing of your work. I have fitted a Carter's Cut and Cover kit in my tourer and well remember the tussle my wife and I had with that. I am forever thankful that I ordered the side curtains without the fittings installed. My trimmer had the job of fitting the top kit and then making the curtains fit. It was a neat job in the end, but not one with which I was comfortable.
Eric's comment that leather can be diamond tufted without stitching is in accord with what I had been told. I was not aware that vinyl had to be stitched.
All power to you and your abilities to be able to make a success of such a demanding job. Well done.
Allan from down under.
By Jim Derocher on Thursday, April 05, - 08:52 pm:
That's some fine workmanship there Rich. Thank You for posting! JD
By Jem Bowkett, Spalding United Kingdom on Monday, April 09, - 06:08 am:
I bookmarked this so I could read again at leisure. Looking over my shoulder, my wife says there is free board and lodging if you would care to come and sort out our car!
By John Codman on Monday, April 09, - 09:53 am:
Slightly off-topic but I'm hoping that somebody interested in upholstery will comment on this: My '27 touring had redone upholstery in the back and there were buttons about halfway down the vertical stitching on the seat back, and on the seat itself. The front appeared to be original and looked it. The front seat had no buttons and it was reupholstered without the buttons. I'm thinking that Henry would not have gone to the expense of installing buttons. Which is correct, buttons or no buttons?
By Richard Eagle Idaho Falls on Monday, April 09, - 10:51 am:
This is an original '26 or '27 with bottoms.
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