Hi, this has probably been covered before , has anyone any good links to or threads covering saddle cutting for work with tube. Mainly small bore for motorcycle trials frame work.
google "tube mitre" EDIT - its a small programme or "App" where you stick in the diameters and it prints out a template on your home printer great little programme
Other search terms would be 'fishmouth' and tube 'coping', both will find a bunch of threads on the forum. Small dia thin wall (say < 1" OD/2mm wall) and not a lot beats a hacksaw and selection of round/half round files. As dia and/or wall thickness goes up other methods become more appealing... holesaws with a suitable fixture (bought* or improvised) or making the initial angled cuts with power tools instead of a hacksaw etc
Not so much use for the sort of work you're talking about but there are various programmes about which will draw a template that can be printed and wrapped around the tube to give a cut line. There's several in the Links section of the forum as well as scattered about in various threads
Heres what i use for tube chassis/roll cage work,
Called the 'old joint jigger' got it from the US many years back before they available over here,
This one does up to 2" tube and does up to 60 degree notches.
I have done saddle cuts on round tubing a few times with my drill press buy using a milling cutter the same OD as the tubing, the table has a hole in it so I can bring it up to allow the cutter end to pass in to it and I then use the center T slot to guide the tube in to the side of the cutter, just make sure your table is 90° to the cutter.
its not an ideal solution because of the lateral load which most drill presses are not designed for and the morse taper is prone to come loose, I'm also lucky enough to have a jacobs 36B that can hold a 20mm bit, you may well have to make up an adaptor to hold larger sizes of cutter equalling the OD of the tube
What ever jig you use needs to be rigid. I used a simple one and found that the holesaws tended to lose teeth because of snatch when cutting angled joints. OK on 90deg, as long as there was tube both sides. Trying to cut just the bit out of the end was not practical. Thinking back, a tubular guide for the cutter (as I used on other projects) would keep it in line and ensure the teeth had a fair bite.
I use one like chevy2 ....usually fixed in a pillar drill...it works well especially with constant pitch holesaws.
I was using it yesterday to cut 80 notches in cds tubing with no problems.
I have fitted needle roller bearings and shimed out the bearing housing to get it dead on centre.