kgg

If you mean the copper or brass rivets with burrs I use a dremel to grind the shaft off so the shaft of the rivet is below the burr but doing it slowly so as not to over heat the rivet or burr which would damage the leather. If you mean the double or single cap rivets I just wedge a screwdriver under the small cap end and pop it off the rivets shaft. kgg

The 135 x 16 or 17 needles will fit in the needle bar. This a fairly simple tinkering task of raising the needle bar up by about 5mm. That is about the length difference between the domestic needles that come with the machine and the system 135 needles. This is done by slacking the existing clevis attachment at the top of the needle bar and sliding the needle bar up. Just make sure you can just barely feel the tip of the needle at it's lowest point in the downward cycle on the bottom side of the cylinder arm. kgg

Yes the faster the slotted disc rotates the more it acts like a solid disc. kgg

I would suggest you consider something like a cylinder bed machine like Juki LS-341 or LS-1341 or clone with a table top attachment. The flatbed machines are good for wallets / belts but the bags are probably better done on cylinder bed. Having a cylinder bed machine with a table top attachment would cover all the bases. kgg

The constants you have as I understand them: 1. the size of the motor pulley for set 1 pulley is 2" 2. the size of the handwheel for set 2 pulleys and you want to use a 5" large pulley 3. the speed of the motor max to be 350 4. the rpm of the set 2 pulley to be 30 when sewing around corners What I would suggest according to the calculator to get 30 rpm is 1. set 1 small pulley 2" (motor pulley) with a 5" large pulley and set 2 would be a 1.5 small pulley alongside the 5" on the same shaft giving the handwheel a speed of 30 rpm with 150 rpm on the motor When you increase your motor speed up to 350 rpm (max setting) by fully depressing the foot pedal the handwheel rpm would be 70. The pulley alongside the 5" pulley has to be smaller then the handwheel pulley. kgg

Slack the bolt holding the center presser foot to the shaft then move the presser foot so it lines up allowing the needle to be in the center of the presser foot hole and then retighten it on the shaft. kgg

Those machines are for the true tinkers. I have one of those "Tinkers Delights " and it has given many hours of pleasurable tinkering or hours of pure frustration depending on how you look at it. Save your money and get one of the one armed bandits from Cowboy, Weaver or Tippmann if you want a hand operated machine that will do holsters without pre punching the thread holes. kgg

The center pressor foot needs to be centered by slacking the nut which holds it in place on the shaft. Here is a good needle to thread size chart that will help you. ( https://www.tolindsewmach.com/thread-chart.html ) The suggested needle size for a thread size will need to be upped a size when in thicker tougher material, I would personally suggest using a #18 needle for V69. You may will find that you will have to change to V92 or greater with a larger needle to help reduce needle deflection / strikes in thicker / tougher leather. kgg

Just my thoughts. What are you planning on making as a flatbed may not be the proper or best machine for your needs/wants. Also what is your budget. kgg

If it was a Juki 563 that would be roughly the price to be expected for a used one over here in Ontario, Canada. They tend to range from $500 to $1000 depending on condition. For a well used clone I wouldn't pay anywhere near that amount. If it was in the $350 mark, maybe but you have to be prepared for those little unexpected potentially expensive problems. Since this is your first machine I would suggest you go to one of the dealers / repair shops and there a few in the Montreal area to get a machine that has been gone over and in working order. kgg

Proves "Necessity is the mother of invention". That is definitely a KISS approach. That piece of rubber was probably left over from retreading a truck tire, waste not want not. Thanks for sharing. kgg

I think you were brewing them for a while and at least they were the smooth ones not the star shaped ones. The main thing is how slow do you want to go and what you are going to set the rpm of the servo motor too. So you will have to play with the pulley sizes on the calculator as well as the rpm of the servo motor. kgg

That is never good, I know first hand that birthing process. Take it easy for few days. kgg

You may have to expand you search radius. kgg

When you checkout the machines tomorrow check and make sure it reverses into the same holes as the forward stitches made. kgg

I did forgot to mention the Cowboy 2500, it maybe be another option as it can handle the middle ground of thread sizing, V138 to V346, but it is a bottom feed machine. Just another thought. kgg

The V277 seems to be the cross over thread size for most machines from the system 135 needles to the system 7 / 794 needles. I have seen the same claims of machines being able to handle V277 thread but with a system 135 #24 needle being the max size of needle their machines can handle. Maybe you can stuff V277 thread through the eye of the needle but I question whether it would sew in 3/8" thick tough leather with V277 in the bobbin. Hopefully someone can clarify that point. A couple of options that maybe worth considering would be one of the one armed bandits (Cowboy Outlaw, Tippmann Boss or Weaver Cub) or something similar to the Cowboy 3500/4500/5500 with the new plate and feed dog setup like RockyAussie came up with. kgg

Saves a lot of time and figuring. I came across this calculator when I had to change the pulley system on my wood furnace a few years back. kgg

I forgot to add the calculator I used for your arrangement so you can decide what arrangement would work with your setup: ( https://www.blocklayer.com/pulley-belteng ) kgg

With the arrangement of the set 1 pulley = 2" (servo motor) with a large pulley = 5" and set 2 pulley = 2" with the machine pulley = 3" (handwheel) then: 1. servo motor at 100 rpm the handwheel will turn at 27 rpm's 2. the center of the pulley on the servo motor to the center of the reducer pulley (2" x 5") should be 10" 3. the center of the reducer pulley (2" x 5") to the center of the 3" handwheel should be 14" 4. the reduction ratio is 1:3.75 at the handwheel kgg

You need to increase the speed slightly so the sanding drum acts like a sleeve drum. The rougher the grid the faster the drum needs to spin or it can feel like you are hooking / tearing the material rather then sanding. Just my experience. kgg

Another rivet option maybe to use copper or steel rivets and cover the backside as fredk suggested or use chicago screws with locktight . That way there is less of a rivet head protruding into the clip area. kgg

I haven't had any problems with the Kobe LS-1341 machine. In this class maybe another one too consider would be the Cowboy CB341. kgg

Yes I do have a clone LS-1341. I went to actually pickup a Juki LS-1341 and I said I'll give the Kobe a try. The dealer sells both the Juki line of machines and his branded clones. Compared to other clones in this class it's a pretty good machine and I find the dealer to be excellent to deal with. Most of the clones in this class are in reality clones of the older Juki LS-341. When I am searching for another new machine I set a 4 hour (one way) travel distance. New machines whether brand name or clone aren't cheap so I think you really should at least have some hands on before buying if at all possible. Before I bought my Juki DNU-1541S I thought I had found a nice clone machine with decent machine reviews. So cash in hand I drove about an hour to that dealer / repair shop and gave it a run. The thing sounded like a bucket of bolts banging around in a 5 gallon metal bucket. Shortly after I drove 3 1/2 hours and bought the Juki. Don't be apprehensive about industrial sewing machines this day and age with the servo motor they are quieter and more energy efficient then the old clutch motor driven machines. They are even easier to operate / control then the small foot pedal operated machines like what the old domestic Singers had or the portable walking foot machines. kgg

I do like the Juki machines and yes they are expensive but they are easier to sell and command a higher resale value while parts and accessories are readily available. They are usually the ones that the clones are copied after and the quality is excellent. I like to get my machines shall we say fresh off the boat and the Juki's right out of the box are ready to work. They have the engineering and quality controls in place right down to proper operating and engineering manuals unlike some clones where instructions are to say the least needing or they refer you to a Juki manual. Since this is going to be your main machine buy the best you can afford and invest in a table top attachment if you decide on a cylinder bed machine for things that are better done normally on a flatbed machine. If most of items you are sewing are better done on flatbed get a new flatbed and pickup a good used cylinder bed for the occasions you need a cylinder bed machine or vise versa. Since this is going to be expensive I would take a sample of the thickest material including seams along with the max thread size that you are going to sew and visit a couple of dealers, clone or brand name. Some clones rate there machine thread capacity by what is the largest needle that can be inserted while Juki actually underrates their max thread capacity so it will take the max size thread in both the top thread and in the bobbin in thick stuff. kgg