Having to move from one state to another forced me to disassemble my cnc router. I had been planning to mod one axis by replacing my unsupported rails with supported rails as well as making the axis longer and replacing the lead screw with a ball screw.
So I purchased all the parts as well as the blank metal stock.
This was the easy part. Now I am wondering how I should proceed to mod the axis. How do I measure and drill exactly so that all parts match perfectly.
Can someone lead me to must have measuring equipment and simple tools with which to accomplish the task?
When I looked at Mcmaster catalog for transfer punches, I got overwhelmed by the different types as well as the potential cost.
Or should I simply go to a machine shop and let them do it?
Essentially, these are the tasks:
1. transfer holes from the existing( short ) gantry plate to a longer plate, using the old plate as a template.
2. mount the new gantry plate to the old side gantry plates. Check for perfect alignment.
3. line up the supported rails on the new gantry plate and drill so that both are parallel to each other and the gantry plate.
4.Make a new, wider z axis adapter plate to compensate for new hole positions.
5.. add a ball screw mounts and make sure that all parts are parallel and at the same level.
6. build a new z axis plate for the ballscrew nut and the 4 bearing mounts on the supported rails
7. build a new motor mount.
I realize that the process is linear, meaning that one precise step will lead to another precise step.
Since I don't have a milling machine and the cnc router assembled, I am trying to figure out if all of this can be done by hand, with good measuring practices , a drill press and a few other tools, or I will soon find myself over my head.
tony
Re: How do I extend an axis and drill precise holes
I have a super low tech easy way of drilling holes in the right place.
I spread some play doh on a metal plate and then use it to make an impression of the holes I want to transfer. E.g. If you need to drill holes to fit your bearings blocks on your rails, you line up your bearing blocks and press the play doh covered metal plate onto the screw holes. When you remove the plate, you will have 4 or 8 nipple-like impressions in the play doh where your holes need to be.
I then pour epoxy resin over the play doh and let it set. The next day, I wash off the play doh which leaves a perfect drill jig. I clamp the jig to the surface I want the new holes to be on and use a drill press to drill through the jig into the new plate and they come out perfect.
Other people have their preferred methods but I like this one as I hate measuring holes.
Re: How do I extend an axis and drill precise holes
First a set of transfer punches are ideal for certain operations. If you expect to do machine tool building, repair or modification they can be money well spent.
For some tasks it really pays to have an accurate reference surface to work off. Most of use cant afford the cost nor the space for a suitable granite plate so improvisation is required. To lay out holes for your supported rails you will need a known straight reference surface. You will need to be able to clamp that reference surface to the beam in such a way that you can run spacer blocks against it for scribing a long linear line on the beam. You actually need two blocks. One to scribe the first line and a second longer block that defines your linear rail spacing. You should end up with two precisely parallel lines on your beam. At that point you just need to use a long scale to mark off the hole positions for prick punching. Then you have to go through and prick and center punch each hole location. Done right your punches should be on location by a couple of thousands of an inch. At that point a drill press or hand drill does the rest. The big challenge is getting the initial long lines straight and parallel. Buying a long, quality scale makes positioning the marks for the holes much easier. In the end you should have precisely spaced array of holes for supported rail mounting.
As for the rest of your layout issues you have much the same challenges. Accurate layouts start with accurate reference surfaces. You can do surprisingly accurate work with a machinist combo square and a good caliper to set the head. As long as your reference surface is true you should be able to duplicate hole locations to a few thousands using nothing but hand tools. If any of your plates have at least one good edge layout should be a breeze.
Im not sure about your original machines capability but it might make sense to assemble it to do some of this work for you. Even if it cant handle heavy milling you should be able to get it to spot holes for drilling or boring someplace else. You just need to have the machine squared up good enough. With a carbide spotting drill or even a pointed burr you could have the machine layout many holes for you even in steel plate. The spots simply have to be big enough to find easily so even the most flimsy of machines should be helpful. A more robust machine could of course do much more for you.
If you don't have a drill press accurate drilling with a hand drill is possible but ideally you will have drill guides to keep the holes drilled square to the plate surfaces. You can either make or buy suitable guides. If you are drilling steel you can rent magnetic based drill stands to help keep your holes square. As an aside another great feature of steel is that magnets stick to it.
Using old parts for drill guides can sometimes work but it sounds like in this case you are dealing with large dimensional changes. Still it is worth considering for anything where the changes don't matter. If you need to run tap drills through clearance bores making a drill bushing can help. Drill the tapped holes, with the drill bushings before using the old plates to drill clearance holes.
Make use of a free cad program to layout hole patterns that can then be printed out. Use these to verify your layouts are in the right ball park. I wouldn't trust a run of the mill inkjet for accuracy but such print outs can highlight gross errors. If you have access to high quality print making machines all the better. In either case the prints provide a place to write upon as you are doing your layout work.
If your printer is know to accurately reproduce drawings at full scale you can even glue the drawing onto the work piece. There are however a lot of qualifications here. For one accurately registering the paper is a challenge. The paper wont survive coolants and the like for another issue. In fact it will not survive the heat that is sometimes generated in machining operations. When printed on transparent or semi transparent materials the real advantage is spotting gross layout errors before you start to remove metal.
A height gage can be handy even without a surface plate. It can be a useful alternative to using a square for every thing. It is a traditional machinist layout tool and you do need a way to set it vertically. In a nut shell it gives you an alternative way to scribe lines.
A lit of techniques are rather hard to describe but can be understood quickly via visuals. As such youtube is your friend. Look for machinist videos where manual work is being done. Like wise fabrication videos are applicable. In the end straight and square gets you on your way. It is just difficult in the home shop to sometimes find a truly straight surface. At least in the sense of machine tool building it is.
How do I extend an axis and drill precise holes
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