Full jig x simple angle iron jig

[fpavao]

Hey again, velonistas. This forum has been very useful to me, so I've got another question for you guys.

I currently use a jig I've built myself based on this:



It's been pretty useful, but it's not the most accurate when setting ht and st angles and bb height. I use it to tack the tubes, then take the frame off and braze it on a stand.

I'm thinking about a building a simple jig using angle iron (not sure if thats the term) to set ht and st angles before mounting the tubes on the full jig. Something like this, only a lot sturdier:


(only image I could find that resemble what I have in mind)

But with the possibility to set any angle I want more easily, maybe with a pivot on the middle, fixed by a screw or something. I haven't thought about details yet. Also somewhere to fix it while welding would be good.

Advantages I think I'll have: setting angles will be much easier using a digital angle finder I already have or markings; more access to joint; decreased setup time; maybe less distortion when brazing if I want to do the entire braze on the jig, not just tack it.

Anyone can think of a reason not to do this? The only difficulty I thought I could have would be when brazing tubes of different outer diameters, but that could be corrected with a metal sheet under the smaller tube or maybe just by matching the miters.

[Will Neide]

Hey again, velonistas. This forum has been very useful to me, so I've got another question for you guys.

I currently use a jig I've built myself based on this:



It's been pretty useful, but it's not the most accurate when setting ht and st angles and bb height. I use it to tack the tubes, then take the frame off and braze it on a stand.

I'm thinking about a building a simple jig using angle iron (not sure if thats the term) to set ht and st angles before mounting the tubes on the full jig. Something like this, only a lot sturdier:


(only image I could find that resemble what I have in mind)

But with the possibility to set any angle I want more easily, maybe with a pivot on the middle, fixed by a screw or something. I haven't thought about details yet. Also somewhere to fix it while welding would be good.

Advantages I think I'll have: setting angles will be much easier using a digital angle finder I already have or markings; more access to joint; decreased setup time; maybe less distortion when brazing if I want to do the entire braze on the jig, not just tack it.

Anyone can think of a reason not to do this? The only difficulty I thought I could have would be when brazing tubes of different outer diameters, but that could be corrected with a metal sheet under the smaller tube or maybe just by matching the miters.

How about something like those Alex Meade blocks that hold tubes over a drawing on a flat surface? You can do any angle, it's simple, any tube size, and it's accurate.

Maybe I'm confused. Why do you want to tack tubes together before placing in a jig if you already have a jig?

[fpavao]

How about something like those Alex Meade blocks that hold tubes over a drawing on a flat surface? You can do any angle, it's simple, any tube size, and it's accurate.

Maybe I'm confused. Why do you want to tack tubes together before placing in a jig if you already have a jig?

My flat surface is granite for now, I don't think it could work. Could it?

I want to tack first because my jig sucks and I can't set the angles on it. I have errors of 5 degrees sometimes.

[Clockwork]

5 degrees? Just relying on your miters with no jig should be a lot closer than that.

-Joel

[fpavao]

5 degrees? Just relying on your miters with no jig should be a lot closer than that.

-Joel

Maybe I'm exaggerating a bit. Last bike I've made, my fifth, I wanted a 73º ht angle and ended up with 75º. Because I tacked it in two points, I got lazy and just brazed the whole bike like that anyway...

I'm just saying that there is no way I can get the angles dead-on on my current jig, it's just to messy to work with it. I'd like at least a .5º precision.

[Andrew R Stewart]

How are you setting the angles on your jig? How do you measure them after joining to find out how close to your plan they are? Have you tried to build in sub assemblies on your jig yet? (hockey stick like). Have you tried to use a full size drawing yet? Andy.

[fpavao]

How are you setting the angles on your jig? How do you measure them after joining to find out how close to your plan they are? Have you tried to build in sub assemblies on your jig yet? (hockey stick like). Have you tried to use a full size drawing yet? Andy.

I measure it with an angle finder. It's got no markings nor anything. It's got some looseness on the moving parts, wich are also hard to set on the place I want because I made it with what I had access at the time. After tacked, I check in a small flat surface (not big enough to fit a full size drawing). I've tried sub assemblies, but had about the same results because of the same problems

Look, I know what's wrong with my jig: it's just not well built. I can either use some of its parts to make a better one, or go with the simple version, the one I asked about earlier on. I'm really leaning towards the simpler version because I know simple stuff will rarely malfunction. Even if it takes a little bit extra time to braze the whole bike. And the more simple, the cheaper.

[AndyA]

I think Mr Stewart is on to something with building sub-assemblies. The angle iron jig is probably easier than the big jig for doing the HT-DT hockey stick, but your big jig is best for ST-BB "polo mallet". And as a user of an angle iron "jig", I don't think anything made out of angle iron comes close to your jig for ability to hold the two sub-assemblies when tacking them together!

Surely if you zero the digital angle finder on your horizontal extrusion, then put it on the ST extrusion it will give you the ST angle? Same for the HT angle? The jig will hold them in that place really well I should think, brazing or welding them together so that they are still pointing in the same direction is probably where your problems lie. I know it's where my problems lie!

[Andrew R Stewart]

I was trying to not give any preference for any one type of jig with my 1st post. More trying to flesh out the OP's methods. But now I can go and cross that line of "how I do it".

AI'veve said over the years i started with only a full size drawing on the floor. I found this to be very good at figuring out the details of clearances and matching the frame tube angles with the drawing's. Then i took a class and used a proper jig. Came home and waconvinceded that this was what i needed to do. Went out and bought some Mic6 plate (I don't even know if 8020 type beams were around back then) and tried to figure out a jig with no mill or other precision tooling. So i used a scale drawing for angle checks and the plate for holding sub assemblies. Tried the various ways of dividing the main frame into halves with no preference developed. Then i got a vernier protractor. I thought this was a cool addition and made angle setting much better. Until i learned that tubes were not straight... Around this point i got a flat surface and got another level of alignment better. I started to use both tube lengths and the vernieprotractoror to establish my main frames. Around then i made a tube holder out of a couple of Alu channels mounted to a couple of sheets that were hinged together. Much better a tube holding method then the plates with a strip of wood clamping the tubes down.

With a good surface plate, good miters, careful tube length control and the vernier protractor i could have continued this method for a long time. I started to do tacking of sub assemblieslies then joining them with more tacks, then aligning before complete triangle brazing. Then i sold a bike shop and with the flush cash decided to treat myself and get a proper jig.

Yet i still find myself hunting down a few mms of length, checking c-c distances and angles as i go along and otherwise not fully relying on the jig only for the set up. I only tack in the jig (main triangle). I still rely on old sfinale finle set ups of the rear triangles.

So while I am very happy with the jig, it does make the mitering go faster (which I do by hand to fit), and would not want to build without one, i find that it is not the end all that so many people seem to think it should be. Were I to start over I would get a surface plate long before a jig again. I also would consider the Fattic sizing jig over an "open" type jig.

With only 5 frames built it's too early to have really found out what type of tooling and process the OP will find works for him. So i suggest he tries another way and see if it is better for him. But do consider a real surface plate and a vernier protractor. Andy.

[Will Neide]

My flat surface is granite for now, I don't think it could work. Could it?

I want to tack first because my jig sucks and I can't set the angles on it. I have errors of 5 degrees sometimes.

I'm on granite now, or I should say will be, and I'm hoping it works. I will be using Alex Meade blocks, but I'm sure if you're crafty enough you could create something of our own. I draw everything out on paper to scale and then line up everything over the paper..........although next time I'm just going to draw directly on the granite (silver sharpie is great!). I use bikecad for the miters.

[fpavao]

Thanks for the ideas and recommendations. I'll try my idea and see if it works.

Unfortunately, my flat surface is very small, 1m x 0.6m, and getting a new one is not on my plans yet.

My ideia is: tack ct and st to bb on my "old" jig, tack (or braze already, haven't decided yet) ht to tt separetely on the other jig and then tack the whole stuff together on the old jig again.

or

st to bb, ht to tt, join these, tack ct to incomplete main triangle.

I'm using rattlecad too and miter with files, for now.

[Todd Mosley]

For my first frame I used v-blocks and an old marble countertop that was 1" thick. The frame came out straight enough.

[afwalker]

Andrew's suggestion of a vernier caliper is very helpful. I found a Mitutoyo vernier protractor with the magnifier on ebay for a good price and it has been very useful. I highly recommend one as it gives a great deal of accuracy and is easier to use than an electronic one.
cheers
andy walker

[adashner]

i've built the last two on a proper surface plate with paragon tube blocks and common machinist's clamps, weights, etceteras- straighter and faster than what i've been getting out of the jig. that said, i spied one of these in a local welding shop the other day and might have to buy one (or ask for one for the upcoming bday):781876_ADJF_1_medium.jpg

made by sumner, they look and feel stout, center channels for tubes up to 2", switchably magnetic, and the locking mechanisms seem super secure. i could see in combination with my current jig-less process that this thing could be worth its weight in gold.

oh, it's made by sumner, the model # is 781876. i think the retail on them is somewhere just south of 200 bones. (i'm not a shill for these guys, promise)