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23rd December 2013, 09:58 PM #1Philomath in training
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Something to check for on small bandsaws
When my 4x6" bandsaw was new it cut beautifully square but as time has passed it was less so. I attributed this to the blades and the idiot who welded them but today noticed something which is worth checking for. This is the lower blade guide -
P1010983 (Medium).JPG
like a lot of small bandsaws, the blade guides are small deep groove ball bearings - in this case 5mm ID and 16mm OD and attached with a bolt (M5). The blade is 0.8mm thick and the gap between the bearings should be too. However, I noticed some daylight in there. It looks like over time the bearings have moved a little (0.1 to 0.2mm by feeler gauge) and have therefore not been keeping the blade upright. I loosened off the SHCS holding the guides and then pushing them together tightened them up. Guides both ends of the cutting area had daylight showing. The first photo (on some 30mm tube) shows that there is almost a 2 degree angle on the cut.
P1010988 (Medium).JPG
After re-tightening, there is no airgap between the guide and the blade and the cut is square.
P1010992 (Medium).JPG
Large industrial bandsaws have the guide axles fitted to a method of adjusting them (like an eccentric) but at this end of the price range that is a little too sophisticated. It may be a retrofit project one day perhaps.
Regardless, I would suggest checking the gap between the guides on your saw as if it is not cutting square the cause could be as simple as the guides moving.
Michael
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23rd December 2013 09:58 PM # ADSGoogle Adsense Advertisement
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23rd December 2013, 10:16 PM #2
Mine are on eccentric shafts, I thought they all where?
When I fit my blades I put them in the guides first, thinking about your problem this way you would pick up on it right away.
DaveUsing Tapatalk
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24th December 2013, 12:17 AM #3
I have an eccentric shaft/bolt on each guide. Some people have reported having all 4 bolts as eccentric. The first thing to do when changing the blade is to loosen them off to provide clearance.
I want to cut some 3mm acrylic to shape for a new window pane on our ute canopy. I threw the original table away as it was useless. I am now making another one that will hopefully work. 3mm steel plate. I am thinking about mounting a heavier plate underneath to make it more rigid. It has a slot cut for the blade more than half way through the length.
Dean
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24th December 2013, 07:14 AM #4Philomath in training
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It's one of those things where I've never really looked because I knew they were fixed. I only noticed the other day because the light was at just the right angle. I seem to be in the minority having fixed guides, but still worth checking even if you do have eccentrics (probably more so as they are designed to move).
4 would run the risk of throwing out the squareness of the blade in the other direction if you did not have them right. 2 should be ample. My blades just slide in, so no need from that point of view.
If you drill a few holes in the 3mm plate you could spot/ puddle weld some angle or even some strip on to stiffen it rather than use heavier plate (dress the weld back to flush of course)
Michael
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24th December 2013, 07:31 AM #5
I never touch my guides when changing blades. My blades are all the same thickness but if you had different thickness ones you would have to adjust them each time.
DaveUsing Tapatalk
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24th December 2013, 11:00 AM #64 would run the risk of throwing out the squareness of the blade in the other direction if you did not have them right. 2 should be ample. My blades just slide in, so no need from that point of view.
If you drill a few holes in the 3mm plate you could spot/ puddle weld some angle or even some strip on to stiffen it rather than use heavier plate (dress the weld back to flush of course)
I never touch my guides when changing blades. My blades are all the same thickness but if you had different thickness ones you would have to adjust them each time.
Dave
Dean
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24th December 2013, 11:56 AM #7GOLD MEMBER
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Hi Michael,
The heska has eccentric adjustable blade guides. When I first adjusted them, I made them a nice snug fit but I ran into problems with the blade tracking. Where the blade has been welded and joined, it's a little thicker and when it passes through the guides it tend to skip or ride downwards on the guide.
I quickly learnt that I had to leave the small amount of clearance for the blade. I hope they last a while, 12 bearings for the 2 guides tends to get expensive!
The eccentric is adjusted with an allen key and then tightened with a grub screw to stop the shaft rotating. It's a little bit fiddly but once it's set it's not too bad a system. When I swap blades, I can get a feel for the blade clearance in the guide while feeding the blade through.
Cheers,
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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24th December 2013, 12:00 PM #8
I am constantly changing from blade to blade to cut different steel. The course blade does not like thin wall stuff.
I picked up a bigger bandsaw earlier this year so once its up and running I wont have to change blades anywhere near as often.
DaveUsing Tapatalk
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24th December 2013, 05:30 PM #9Philomath in training
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24th December 2013, 06:18 PM #10
I finished the table. Its around 230mm x 230mm. I spot welded some angle to the bottom. The mount point on the bandsaw was not machined. Still bare cast surface and not flat. I milled it flat and milled a flat section inside the angle pieces to suit. Welded the 2 angle pieces together behind the slot. It is now very rigid and much better than the original.
Dean
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24th December 2013, 08:41 PM #11
On the subject of guides check these out.you are looking at the slide component s which allow for the longitudinal and vertical adjustment.
Call me old fashioned or traditional but shouldn't these keys be parallel close fitting with the female parts of the guides. They are not centralised or nor are they as deep as the femele
The taper is 3mm difference from one end to the other. The female part (not shown) is 3mm wider and parallel to the casting edges.
Are these dimensions (?) standard on the 6 x 4 horizontal bandsaws that you own or am I missing something?
Merry Xmas to you and yours guys
Grahame
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24th December 2013, 09:08 PM #12
Mine are the same Grahame, machined by a blind man with an angle grinder......or maybe an angry mouse......
Cheers,
Ew1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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24th December 2013, 09:38 PM #13
As I have just had both parts from the motor end, off the saw and carefully examined I can happily say that mine do not look like that. There is clearance between male and female parts but machining looks quite good. Definitely looks square and matching. I did think for a short time about making a mod to enable precision adjustment of the vertical blade angle but decided that I had already done enough jobs to do jobs to........ The machined surface of the bearing holding part (female) which I milled for the table mount did rock on the mill table but a quick rub on emery fixed that. All I want to do is cut out a couple of bits of perspex. I am now ready to cut the perspex.
Dean
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25th December 2013, 01:28 AM #14GOLD MEMBER
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Hi all and a Merry Christmas to each and everyone.
I asked where I get my blades from about this, and was told that the loose fit was designed that way to allow for the correction of twist on the blade to cut square.(As each component is made in someones backyard, there is no quality control)!!!!!
On one saw I had, a file had to be taken to it and a taper filed as there wasn't enough twist for it to cut straight, 5mm out over 100 deep cut.
Be very careful when adjusting the bearings, that they are not tight on the top of the blade as this will after a while thin the top of the blade and cause a problem with the blade to go a funny shape bit like a banana. DAMHIKT.
Kryn
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25th December 2013, 01:47 AM #15
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