|
I went back and forth adjusting the blade guides, tracking, and whatnot over and over again trying to get my Harbor Freight red to cut straight. Eventually I realized I was chasing my tail by putting a long straight edge on the vise bringing the saw up and down. At the top of the straight edge, the blade was at least a couple mm to the right (if facing the on-off switch) of where it ended up when it finally came all the way down! So this means the entire head is attached to the table crooked and the head of the saw is coming down to the table at an angle, rather than perpendicular. Ugh.
Is there any way I can deal with this problem? The saw assembly seems to pivot on this big pin that is between two pillow block-like things that are part of the table casting. I don't see anywhere that I could add a shim or anything to correct this. Is there something I can do to get this cutting straight down and perpendicular with the table? Is the whole thing just junk because of this manufacturing flaw?
|
Hi Morgon The saw is not junk, but it is the most difficult problem to fix on a 4x6. There are 2 things that must be met for a saw to cut vertically square:? 1. The bottom of the workpiece must be parallel to the PIVOT SHAFT (normally met by the vice table being parallel to the length of the pivot shaft in elevation (looking from the front?over the vice table)) and 2. The blade-body (the steel band above the teeth) must be square to the pivot shaft,?(This is always adjustable).? Everything to do with squarenes relates to the pivot shaft?The description you gave shows that the?surface of the vice table is not parallel?to the pivot shaft.? This is quite a common?fault caused by boring?the?ears out of?parallel to the vice table or, the?casting twisting as it stress-relieves after machining (not sure which, maybe both) Although there are multiple ways to address it. There are a couple of quite viable quick fixes, though each has its limitations,
but none of the permanent fixes are easy.?
Quick fixes One quick fix is to create what is in effect a small sine bar to put on the vice table underneath the workpiece to make the base of the workpiece parallel to the pivot shaft.? You need 2 identical ones, each about 1/4" wide x 1/4" high x 6" long.? You can easily make them from key steel with a small v.short grubscrew?in one end, to tilt it the required?amount.? Any square steel will do but key steel is best because it is hardened and ground square and straight but still soft enough to tap the screw?thread. You won't?be able to accurately cut anything less than 1/4" wide, but they have the advantage of being adjustable so you can tune it to be just right.? You have to remember to put them in each time,?use the?2nd one for wider workpieces.?
Another quick fix (that I use) is to stick a strip of shim stock to the proper side of the vice table with double sided adhesive tape
to correct the parallelism?problem (see attached pic).? Stick the strip down outside the area where the movable vice jaw runs.? It is the quickest and you can cut any width but only if the workpiece?is longer than the vice infeed table is wide. As you can see if the shim is thin, even stainless shim dings and it needs replacing from time to time.
Measuring?how much it's?out of parallel To figure out how thick?the shim (or how big sine bar?correction) needs to be, use the squareness measuring method given in my article on buying a 4x6.? It's near the bottom of the 4th page (article in the Files section of the site: /g/4x6bandsaw/files/Buying%20a%20Used%204x6%20Bandsaw%20v4.pdf).? Remember the difference in thickness from one end of the test piece to the other is twice?the thickness of the shim you need (or offset in the sine bar).? You need to subtract
tape thickness from the shim thickness (Sellotape brand double sided tape is 0.004" thick).
Permanent fixes 1. The one that you can do by hand involves drilling out at least one ear of the pivot shaft bearing in the base casting and filing it out so that a thin brass bush (15mm ID available from any bearing supply?place) can be centred with 3 grubscrews so the pivot shaft is parallel to the existing vice table, then epoxying the bush into the ear.? Tedious but needs no machinery. 2. Mill or grind the surface?of the vice table so its parallel with the pivot shaft.? You might also have to mill the underside to the vice-nut ways to get them back parallel if the vice table was humped in the middle.? This will cost more than the saw is worth?if you don't have access to the machinery.? 3.? Overlay the vice table with a laser-cut ground steel plate, screwed and glued in place that is set parallel to the pivot shaft. Lots of work and potentially expensive.
My advice is to try a quick fix and if you can't put up with the inconvenience, sell it and get a saw that you check out before buying - jv?
I went back and forth adjusting the blade guides, tracking, and whatnot over and over again trying to get my Harbor Freight red to cut straight. Eventually I realized I was chasing my tail by putting a long straight edge on the vise bringing the saw up and down. At the top of the straight edge, the blade was at least a couple mm to the right (if facing the on-off switch) of where it ended up when it finally came all the way down! So this means the entire head is attached to the table crooked and the head of the saw is coming down to the table at an angle, rather than perpendicular. Ugh.
Is there any way I can deal with this problem? The saw assembly seems to pivot on this big pin that is between two pillow block-like things that are part of the table casting. I don't see anywhere that I could add a shim or anything to correct this. Is there something I can do to get this cutting straight down and perpendicular with the table? Is the whole thing just junk because of this manufacturing flaw?
|
I also have this problem. It makes my saw almost useless for cutting in the vise.? I resort to cutting on the little table whenever possible.
toggle quoted message
Show quoted text
I went back and forth adjusting the blade guides, tracking, and whatnot over and over again trying to get my Harbor Freight red to cut straight. Eventually I realized I was chasing my tail by putting a long straight edge on the vise bringing the saw up and down. At the top of the straight edge, the blade was at least a couple mm to the right (if facing the on-off switch) of where it ended up when it finally came all the way down! So this means the entire head is attached to the table crooked and the head of the saw is coming down to the table at an angle, rather than perpendicular. Ugh.
Is there any way I can deal with this problem? The saw assembly seems to pivot on this big pin that is between two pillow block-like things that are part of the table casting. I don't see anywhere that I could add a shim or anything to correct this. Is there something I can do to get this cutting straight down and perpendicular with the table? Is the whole thing just junk because of this manufacturing flaw?
|
toggle quoted message
Show quoted text
On Nov 24, 2020, at 8:14 PM, Jack Dinan <jack@...> wrote:
? I also have this problem. It makes my saw almost useless for cutting in the vise.? I resort to cutting on the little table whenever possible. ?
I went back and forth adjusting the blade guides, tracking, and whatnot over and over again trying to get my Harbor Freight red to cut straight. Eventually I realized I was chasing my tail by putting a long straight edge on the vise bringing the saw up and down. At the top of the straight edge, the blade was at least a couple mm to the right (if facing the on-off switch) of where it ended up when it finally came all the way down! So this means the entire head is attached to the table crooked and the head of the saw is coming down to the table at an angle, rather than perpendicular. Ugh.
Is there any way I can deal with this problem? The saw assembly seems to pivot on this big pin that is between two pillow block-like things that are part of the table casting. I don't see anywhere that I could add a shim or anything to correct this. Is there something I can do to get this cutting straight down and perpendicular with the table? Is the whole thing just junk because of this manufacturing flaw?
|
If you have a lathe or have access to one you might be able to turn one of the ends of the hinge pin down to correct the angle.? That side will drop by the amount you take off the radius so you will want to carefully measure the angle and calculate how much you need to remove.? The original pin is held in place with a roll pin so it wouldn't be too difficult to make one, rather than risking the original.
There are some limits to how much of a correction you can achieve this way.? Turning the pin down a lot will make it weaker; and the other end of the pin must have enough "slop" so it can rotate through a small angle.? Based on John's permanent fix #1, I have to assume there is enough free play to accommodate at least some angular displacement.
That's not an ideal solution by itself because it also introduces more play in the hinge.? To address that, you can use John's grub screw suggestion.? Drilling and tapping 2 or 3 holes can be done with a hand drill and tap.? The grub screws also might assist in correcting minor alignment problems on the horizontal axis.
The advantage to this approach is that you can always go back to the original condition of the saw, since the casting(s) have not been substantially altered to the point where they're not compatible with the OEM replacement parts.? Plus that way you have a hole to apply lube to the hinge :).
Mark?
|
I just had another thought.? As an alternative to drilling/tapping 2-3 holes on the side that is highest, drill/tap ONE hole on the other side, on the very top of the fixed part of the hinge.? ?In addition to being turned down a bit, the pin on that side will have a drilled/tapped hole so a bolt can be run through the hole in the hinge and pull the pin UP.? This also will fix the pin in place, no added "slop" (but would remove the ability to correct for a horizontal alignment problem).? If need be, a bit of shim could be put in there to get the vertical alignment dead on.? I'm not saying it would be easy to shim, but if there's motivation there's going to be a way.
Since the bandsaw head will have to be removed anyway in order to remove and replace the pin, either side of the hinge can be modified this way.?
Caveat:? This is all speculative.? Based on examination of my own band saw, my gut feeling is that it could work; and it won't make it impossible to go back to the saw's original state if it doesn't pan out.
Mark
|
I did a bit of testing today. The saw itself wasn't level, so I leveled it out (using the roller feet to come down to the ground and stay level). It helped a little bit...the difference from the top of my square to the bottom (about 4") became < 0.04" (as measured by my calipers). Probably about 0.038" mean measurement.
Then, figuring I'd stress-relieve the table, I untorqued all the bolts that attached the table to the base and then retightened them. To my surprise it made the problem worse again (> 0.04" as measured by the calipers), and the table was no longer level.
I'm thinking I should probably just untorque the bolts and leave them snugged but not torqued down.
|
Wow! That’s amazing! I would have thought that the cast iron saw?bed would be a lot?more rigid than that!
Very disappointing?that the loosening of the table-to-base bolting affects blade?alignment to that degree.
Good luck, Man! Sent from AOL Mobile Mail
Get the new AOL app:
I did a bit of testing today. The saw itself wasn't level, so I leveled it out (using the roller feet to come down to the ground and stay level). It helped a little bit...the difference from the top of my square to the bottom (about 4") became < 0.04" (as measured by my calipers). Probably about 0.038" mean measurement.
Then, figuring I'd stress-relieve the table, I untorqued all the bolts that attached the table to the base and then retightened them. To my surprise it made the problem worse again (> 0.04" as measured by the calipers), and the table was no longer level.
I'm thinking I should probably just untorque the bolts and leave them snugged but not torqued down.
|
Wow Mark!? Yes I'm pretty sure this will work.?? From OEM, the pivot shaft is locked in the sawframe casting with a grubscrew?,or maybe a roll pin for some folks, and the shaft rotates in the base casting ears.?? Removing this?grubscrew/roll pin, so the pivot shaft can rotate in the sawframe ears and immobilising the pivot shaft in the base casting ears with a grubscrew from the top of the ear downward after taking a skim?off one side of the pivot shaft at the proper end, will correct the out-of-parallel.? It's a permanent fix that will restore accuracy to any saw with?only?handtools!? You can use a file or a bench?grinder to remove material from one side of the shaft in the area of one of the base casting bearing?ears, because it's?not depending on the 'ground out' area for the accuracy?of the pivot.? Brilliant!??
If you remove little bit too much, rotating the shaft can bring it to perfect alignment albeit at the expense of realigning the horizontal squareness a fraction (this is done at the joint between the pivot arm casting and the sawframe casting at the LHS back and is independent of the pivot and its bearings). The bearings will be wider apart than OEM, so will?make the pivoting action more stable and accurate than OEM. This will also work for people who have worn bearings in their base casting ears.? The shaft never rotated in the sawframe ears so those bearing surfaces will still be perfect. You don't need to remove the sawframe?casting from the base to? modify the pivot shaft.? Just block the sawframe up from the base in the horizontal position at about the balance point and you can remove the shaft easily.? I've done it this way a few times.? It's unstable if there is no pivot shaft, but if you use another smaller shaft (say 1/2" or 9/16" diameter) to tap out the original it is safe. What I thought of as the?worst possible fault that was v. difficult to fix, suddenly becomes something anyone can do relatively easily with tools everyone has got. I'll? try it on?an RF128 I've got that's?pretty bad and let everyone know. - jv??
I just had another thought.? As an alternative to drilling/tapping 2-3 holes on the side that is highest, drill/tap ONE hole on the other side, on the very top of the fixed part of the hinge.? ?In addition to being turned down a bit, the pin on that side will have a drilled/tapped hole so a bolt can be run through the hole in the hinge and pull the pin UP.? This also will fix the pin in place, no added "slop" (but would remove the ability to correct for a horizontal alignment problem).? If need be, a bit of shim could be put in there to get the vertical alignment dead on.? I'm not saying it would be easy to shim, but if there's motivation there's going to be a way.
Since the bandsaw head will have to be removed anyway in order to remove and replace the pin, either side of the hinge can be modified this way.?
Caveat:? This is all speculative.? Based on examination of my own band saw, my gut feeling is that it could work; and it won't make it impossible to go back to the saw's original state if it doesn't pan out.
Mark
|
Hi Morgon and?John Nothing is truly rigid, least of all these saws.? My saw will twist so that it doesn't cut square with a 2 foot long? piece 5/8" x 4" mild steel hanging over the edge of the vice, so I use a support frame for long stuff. At extreme accuracy I can tell if its not level on the floor. I set my saw with it level and the base unstressed?and the stand bolts (with extra bracing running between the bottom of the front and back legs) tight and then fix any vertical out-of-square. Don't bother with any quick fixes I suggested Morgon, other than to prove you've got the right amount of offset under one side of the workpiece, Use Mark Kimballs method (or my variation on it) as a permanent fix - jv?
?
I did a bit of testing today. The saw itself wasn't level, so I leveled it out (using the roller feet to come down to the ground and stay level). It helped a little bit...the difference from the top of my square to the bottom (about 4") became < 0.04" (as measured by my calipers). Probably about 0.038" mean measurement.
Then, figuring I'd stress-relieve the table, I untorqued all the bolts that attached the table to the base and then retightened them. To my surprise it made the problem worse again (> 0.04" as measured by the calipers), and the table was no longer level.
I'm thinking I should probably just untorque the bolts and leave them snugged but not torqued down.
|
I noticed the same thing on mine, the previous owner had made a
poorly designed stand, my floor slopes to a centre drain so the
casting would twist and make a difference to the cut depending
where the saw was in the workshop. I could torque the frame to get
a straight cut but with the casting sitting correctly the pivot
was out of alignment with the table surface. I solved this by
doing two things, milling the table parallel to the pivot (luckily
I live close enough to John Vreede for him to help me with this)
and secondly I built a 3 leg stand so I can use the bandsaw
anywhere in the workshop without the floor affecting the cut. Have
attached photo of stand when I first completed it, works very
well, chrome handle slides in when not in use.
From my above experience, if you are going to be moving your saw
round the shop you are better off solving the pivot error in the
cut using one of the methods mentioned in previous posts. If the
saw will always be in one place you could get away with torquing
the frame to induce the correct twist, this is what I was going to
do until I realised it wasn't going to work for my situation.
On 26/11/20 11:08 am, Morgon Kanter
wrote:
toggle quoted message
Show quoted text
I did a bit of testing today. The saw itself wasn't level, so I
leveled it out (using the roller feet to come down to the ground
and stay level). It helped a little bit...the difference from the
top of my square to the bottom (about 4") became < 0.04" (as
measured by my calipers). Probably about 0.038" mean measurement.
Then, figuring I'd stress-relieve the table, I untorqued all the
bolts that attached the table to the base and then retightened
them. To my surprise it made the problem worse again (> 0.04"
as measured by the calipers), and the table was no longer level.
I'm thinking I should probably just untorque the bolts and leave
them snugged but not torqued down.
|
Are you saying it might have been able to cut square until the table bolts were retorqued?
If so, wouldn't that suggest your pivot is bored in fine and you have a table problem?? I'd think that would be much easier to address.
Or, going another direction...
Since it flexes so much, a red-neck idea comes to mind...? you could replace the stand? with something home made.? Have the top of the stand be a small slab of concrete maybe 4" thick.? Include mounting bolts when pouring it.? That concrete slab will not flex, so you can double nut the mounting bolts to flex the base of the saw however you need to.
|
Are you saying it might have been able to cut square until the table bolts were retorqued?
Not exactly. Just that it was a little bit better before. It still had like .038" of play over 3-4 inches of vertical travel.
|
Hi all Mark's?idea does work!? It corrects mis-manufactured saws where the head comes down at an angle to the vice table! This is a game changer for all those saws that never cut properly and for ones with worn?pivot shaft?bearings. I have a Paykel RF128 saw that would only cut vertically square with a 1mm spacer stuck down the LHS of the vice table. Test cuts without the strip showed it was out-of-square to 0.011" per inch of cut (0.003"/" is a good standard) and you could see it wasn't square by eye.? At the first try now it?cuts 0.0013"/".? Pretty good by any standard and the process is so controllable,?it would be easy to take a bit more off and get it close to zero! Besides filing a ~1mm (0.040") relief on the pivot saft at the LH pivot shaft bearing in the base casting and drilling & tapping M6 grubscrew?(see photos), I had to flatten the vice table with a file (was just a bit hollow) and ease the diameter of the pivot shaft with a strip of 240g then 600g wet&dry at the LH end because it was tight on the pivot arm?casting.? I needed an aluminium drift to knock out the pivot shaft so as not to swell the end of it. I didn't have to block up the sawframe?casting (didn't even take off the blade or guard) it balanced quite nicely on the saw stop bolt with 1/2" rod through the ears to stabilise it while I?filed the shaft (NB theres a ~1/4" long tube spacer over the pivot shaft between the RHS of the sawframe casting and the base casting that you have to slide the shaft into each time!).?? It needed a 3/4" wide relief halfway around the shaft that was 1mm deep in the middle tapering to nothing at halfway),??though when I reassembled and tested this was not quite deep enough by about 0,17 mm (0.007").? It was easy to file with a?5/8" drill stop collar on the shaft (the pivot shaft is 5/8" not 15mm like? I said earlier), but looked a mess before I used the collar. The pivot bearings are now in the sawframe and the pivot arm castings. They're?almost twice as wide as the originals and unworn. There was enough wiggle room, of the pivot shaft in the old bearings on the base casting, to just?file one side of the pivot shaft??
The process is:? 1. Set the blade body square to the vice table (6" rule clipped?to the blade body) before you measure any squareness.? 2. Get some planed-4-sides 1x4" softwood joinery timber?as test?stock to do the vertical cuts. 2x4 construction lumber is normally not straight/parallel enough and twice as thick as you need so is slower.? Don't use?metal. 3. Find out how much you need to raise one end or the other of the test stock to get it to cut square, use strips of different shim (use a soft mallet to seat the test stock on the strips in a nipped-up vice).? This is the amount you need to file off the underside of pivot shaft at the same end as the shim is stacked? 4.
File the relief
5?
Drill&tap?for a grubscrew?in the upper side of the base casting ear, file a flat for the grubscrew?on the pivot?shaft 180deg away?from the deepest point of the relief 6. Reassemble and test squareness ?- jv
?
On Thu, Nov 26, 2020 at 11:58 AM John Vreede via <vreededesign= [email protected]> wrote: Wow Mark!? Yes I'm pretty sure this will work.?? From OEM, the pivot shaft is locked in the sawframe casting with a grubscrew?,or maybe a roll pin for some folks, and the shaft rotates in the base casting ears.?? Removing this?grubscrew/roll pin, so the pivot shaft can rotate in the sawframe ears and immobilising the pivot shaft in the base casting ears with a grubscrew from the top of the ear downward after taking a skim?off one side of the pivot shaft at the proper end, will correct the out-of-parallel.? It's a permanent fix that will restore accuracy to any saw with?only?handtools!? You can use a file or a bench?grinder to remove material from one side of the shaft in the area of one of the base casting bearing?ears, because it's?not depending on the 'ground out' area for the accuracy?of the pivot.? Brilliant!??
If you remove little bit too much, rotating the shaft can bring it to perfect alignment albeit at the expense of realigning the horizontal squareness a fraction (this is done at the joint between the pivot arm casting and the sawframe casting at the LHS back and is independent of the pivot and its bearings). The bearings will be wider apart than OEM, so will?make the pivoting action more stable and accurate than OEM. This will also work for people who have worn bearings in their base casting ears.? The shaft never rotated in the sawframe ears so those bearing surfaces will still be perfect. You don't need to remove the sawframe?casting from the base to? modify the pivot shaft.? Just block the sawframe up from the base in the horizontal position at about the balance point and you can remove the shaft easily.? I've done it this way a few times.? It's unstable if there is no pivot shaft, but if you use another smaller shaft (say 1/2" or 9/16" diameter) to tap out the original it is safe. What I thought of as the?worst possible fault that was v. difficult to fix, suddenly becomes something anyone can do relatively easily with tools everyone has got. I'll? try it on?an RF128 I've got that's?pretty bad and let everyone know. - jv??
I just had another thought.? As an alternative to drilling/tapping 2-3 holes on the side that is highest, drill/tap ONE hole on the other side, on the very top of the fixed part of the hinge.? ?In addition to being turned down a bit, the pin on that side will have a drilled/tapped hole so a bolt can be run through the hole in the hinge and pull the pin UP.? This also will fix the pin in place, no added "slop" (but would remove the ability to correct for a horizontal alignment problem).? If need be, a bit of shim could be put in there to get the vertical alignment dead on.? I'm not saying it would be easy to shim, but if there's motivation there's going to be a way.
Since the bandsaw head will have to be removed anyway in order to remove and replace the pin, either side of the hinge can be modified this way.?
Caveat:? This is all speculative.? Based on examination of my own band saw, my gut feeling is that it could work; and it won't make it impossible to go back to the saw's original state if it doesn't pan out.
Mark
|
Very cool, John!? I'd been wondering in particular how to determine the amount to take off the pivot shaft to correct? the angle.? Your detailed procedure makes it very clear.? You also deserve full credit for turning my vague suggestion into a concrete result, and a procedure that anyone can follow.? Nicely done!
-Mark
|
I've been messing around with a compass and drawing paper and think I've come up with a relatively simple way to machine the pivot shaft -- IF you have a lathe.? The approach removes the minimum amount of material possible, while ensuring that the machined pivot shaft settles down properly in the bearing.? My motivation:? My band saw could use this mod, too; and I happen to have a lathe :)
1.? Perform step #3 in John's procedure to get the necessary shim stack to correct the angle.? Measure the shim stack with calipers or a micrometer.? NOTE:? the distance between the position of the shim stack and cut must be the the same as the distance between the left-hand and right-hand fixed bearings.
2.? Install the pivot shaft in your lathe, placing the shim stack between one of the chuck jaws and shaft to offset the shaft to one side.
3.? Mark the area you need to machine, or note the positions of the start and stop points.
4.? Rotate the chuck so the shaft is closest to your lathe bit, and advance the cross slide until the cutter just touches the shaft.? You also could turn the lathe on and advance the carriage until you see the cutter begin to mark the work.? Zero your DRO or cross slide dial.
5.? Turn the lathe on and machine the shaft between the start and stop points, advancing the cutter until you have reached the same depth as the shim stack's thickness.? A good indication that you have hit the right depth is that the machined portion of the shaft should only cover one half of the shaft circumference (this is where my compass doodling came in handy).? Removing less than this won't permit the shaft to drop down far enough, and more than that weakens the shaft more than necessary.
From here, follow John's procedure to file a flat on the opposite side for the grub screw, install the grub screw and re-install the pivot shaft.
If your band saw isn't particularly out of vertical alignment, a very simple approach would be to simply reduce the radius of the pivot shaft by the shim stack amount.?The advantage here:? there is no rotational dependency so you don't need to worry about getting the pivot shaft installed correctly.? I'd only do this if I just needed to remove a little bit to correct the angle.? You don't want to turn down the very end of the pivot shaft because (1) it would tilt the saw frame over too far and (2) it would be too loose in the saw frame's bearing, allowing excess play.
Mark
|
Hi John and Mark,
I have read your post a number of times and can't really understand what you are saying.? ?Could you please take some pictures?? ?John, I don't understand your "left" and "right" terminologies and how that relates with your saw cutting incorrectly.
I've been playing with my saw.? I've been testing the following:
1.? Place 1.5" diameter bar in the vise.? Cut off about 0.100"? ?
2.? Make to "TOP" of the bar.
3.? Rotate the bar 180 degrees
4.? Cut off about 0.100"?
5.? Measure the TOP and BOTTOM thickness
The TOP thickness is roughly 0.022" thicker than the BOTTOM thickness.? ?
I adjusted my blade guides so that the blade is perpendicular to the table by clipping a straight edge to the blade and comparing it with a machinist square set on the table.
I have adjusted our the side-to-side variation with my vice.
I am not sure about your step 3 on where to place the shim stock?.? ?Could you please show some pictures?
I assume that I will have to place shims under the test bar near the blade to make it cut square.? I will have to have shims on the side of the test bar nearest to blade and away from the blade.? ?The need for shims on both sides is to insure that I have the distance between the blade side and non blade side equal to the pivot bearings on the saw casting.? ?I assume I'll use the difference between these shims to off set the shaft off of center in my lathe 4 jaw chuck.? I will then cut the shaft till 1/2 of the shaft is has material removed.
I have some 5/8" cold rolled steel bar stock.? ?Maybe I'll make a test sample and see how it works (and leave my stock shaft alone).
I would appreciate you guys taking some more pics of how to measure the required shim thickness so I can figure out how to make my saw cut true.
Thanks,
Dave
|
Hi Dave?
Sorry for any confusion.? Just because I know what I'm writing doesn't mean anyone else can follow, so hopefully this will help.
In all my explanations of left-right, up-down, back-front etc, I mean you're looking at the vice handwheel with the sawframe casting vertical from the perspective of the two photos.?
From what I understand from what you've written, all of what you've said in the above email are the correct things to do.?
Can I offer some suggestions.
You are limiting your testing by using 1.5" round bar. I can understand that you get a measure of both horizontal and vertical accuracy by doing so.? BUT its only 1.5 " tall and wide, you cant turn it exactly 180deg each time and it takes ~3min for each cut.
It helps to understand that the adjustments for horizontal squareness and vertical squareness only share "...the blade is perpendicular to the table..." as you put it .? Everything other adjustment is separate.? So forget about the horizontal adjustments and just do the vertical.?
Using 1"x4" wood makes the squareness test ~2.5x as sensitive because its length-of-cut dependent, your test pieces will be 0.055" different instead of 0.022", it flips180deg every time, its easier to shim and you can do a test in less than 30seconds for zero cost.
I think you said you need to put the shim under the side next to the blade (RHS of the infeed table).? You can do so by setting the movable vice jaw to the left and lay the strips right next to the slot for the blade. Don't worry about the distance between the shim and the edges of the vice table compared to the distance between the base casting ears? - there are errors which compensate for each other which means it doesn't matter.
I've written a document for the Files section detailing how to do this fix with lots more info, but its not quite ready yet.? Mark and I are just finalising it now.? I'll send you a copy by PM and you can use it as it is, since your need is urgent. I will post it to the Files section when its ready.
Rgds - jv
|
For what it's worth, I did a little experiment today to double-check my idea on cutting the relief using a lathe.? The pivot shaft would be placed in the chuck, and offset by the shim pack that was determined to correct the vertical angle.? It works fine, so would appear to be a nice way to modify the shaft if you have a lathe.
Since there likely is some difference in the placement of the shim pack compared to the width of the sawframe bearings (plus the chuck jaws will probably compress the shim pack some), it would be a good idea to stop the lathe operation before removing the full shim pack thickness.? It's easy to remove more material, a bit harder to put it back!
In my experiment I used a scrap piece of 1/2" steel rod and a 1mm thick piece of styrene I got from a local hobby store.
Mark
|
In message #15498 below I said "?there is no rotational dependency so you don't need to worry about getting the pivot shaft installed correctly. "? This was regard to a simplified lathe-based mod of the pivot shaft.? However, as John indicates in his forthcoming document, this is not true if your band saw happens to be one where the pivot shaft is fixed in place with a grub screw.? I missed this point because my bandsaw uses a spring pin, not a screw.? I'm jumping the gun a bit here because I feel responsible for potentially causing a problem with someone's machine.
If any folks with that setup are considering doing the mod I strongly suggest waiting until John comes out with the finalized version of his document.? ?There are a lot of good pointers in it regardless of what particular flavor of 4x6 bandsaw you've got.
Mark
|
John Vreede