LumberJocks

Circle Jig help

  • Advertise with us

« back to Jigs & Fixtures forum

Forum topic by Karda posted 05-06-2018 08:02 PM 883 views 0 times favorited 33 replies Add to Favorites Watch
View Karda's profile

Karda

1170 posts in 634 days


05-06-2018 08:02 PM

Hi, I made a circle jig but it cuts over. I made the pivot hole at 5” for a 10” circle but it cuts 10 1/8. I need exactly 10” or even a little under but not over. What did I do wrong in making the jig. thanks


33 replies so far

View Rayne's profile

Rayne

963 posts in 1620 days


#1 posted 05-06-2018 08:27 PM

Need pictures of your jig to see where the issue might be.

View MrUnix's profile (online now)

MrUnix

6845 posts in 2279 days


#2 posted 05-06-2018 08:36 PM

What did I do wrong in making the jig.

Obviously didn’t measure right :)

Pictures would help. Circle jig for what? Router? Band Saw? Jig saw? Did you take into account the diameter of the pivot pin being used?

Quick fix would be to just make another pivot hole… or multiple pivot holes to get you different diameters.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Karda's profile

Karda

1170 posts in 634 days


#3 posted 05-06-2018 11:37 PM

sorry the jig is for my band saw, the peg is centered at 5” heres a pic its on black might be hard to see.

View BFamous's profile

BFamous

143 posts in 201 days


#4 posted 05-07-2018 12:46 AM

I’ll believe tour peg is 5” on center to the blade, but it looks like there is about a 1×8” gap to the outside of the blade allowing for deflection as you turn your piece. Your blade is going to want to go straight, so I’ll push outwards as you spin.

Just my guess.

Though the “easiest” way to correct it, outside of making a new job, is go to a larger peg, bringing the center into 4 7/8”

-- Brian Famous :: Charlotte, NC :: http://www.FamousArtisan.com

View msinc's profile

msinc

477 posts in 584 days


#5 posted 05-07-2018 12:49 AM

The best way to have a circle jig for your bandsaw is to have the centering pin {for lack of a better term} on a slide. If you google bandsaw circle cutting jig there are several good youtube videos on the design. Having the pin on a slide is ideal because you can now set it for any size circle you want and you can double check that it is right with scrap and make any adjustments needed BEFORE you cut the piece you intend to use.

View GR8HUNTER's profile

GR8HUNTER

4316 posts in 792 days


#6 posted 05-07-2018 12:58 AM

simply make a jig for your belt/ disc sander then you will get perfect 10 inch circles or 9and15/16 :<))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN

View Karda's profile

Karda

1170 posts in 634 days


#7 posted 05-07-2018 01:32 AM

I have thought of a moving pin but can’t find the track nor do i have the tools to make one. How is a larger peg going to work if the center is the same. I was going to plug hole but how do i measure so i don’t do it wrong again. Can’t do sander because this jig is for cutting bowl blanks

View Loren's profile

Loren

10477 posts in 3728 days


#8 posted 05-07-2018 01:59 AM

For a quick fix double-stick tape on the
back of a 10” square piece of ply would
do the trick. Put the pin in and test it.
Peel it off and re-tape until it’s where you
want and then screw or nail it if needed.

View Rayne's profile

Rayne

963 posts in 1620 days


#9 posted 05-07-2018 02:24 AM

For a permanent fix, glue the pin or dowel in the hole, cut/sand flush, redrill with a brad point for a new pin. Just make sure to measure from the center of the Pin itself to the blade. If you’re using a tape measure to measure this, make sure to either account for the movable end-hook or start measure from 1. That end-hook moves 1/8”.

View woodbutcherbynight's profile

woodbutcherbynight

5486 posts in 2489 days


#10 posted 05-07-2018 03:07 AM



I have thought of a moving pin but can t find the track nor do i have the tools to make one. How is a larger peg going to work if the center is the same. I was going to plug hole but how do i measure so i don t do it wrong again. Can t do sander because this jig is for cutting bowl blanks

- Karda

Use a french cleat slide something like this.

attach a recessed ruler and you are in business. Even if it is off you can adjust after a test cut.

I built this from nothing but scrap I had on hand. Used a 1/4 drill bit end for my center dowel.

-- Live to tell the stories, they sound better that way.

View JBrow's profile

JBrow

1366 posts in 1000 days


#11 posted 05-07-2018 03:48 AM

Karda,

It is difficult to say what went wrong. Several factors occur to me that could affect accuracy, aside from an inaccurate measurement. The first two deal with geometry and the remaining with setup and technique.

The first could be from taking the radius measurement after the pin was installed and thus taken from the outside wall of the pivot pin. The radius measurement should be from the center of the pivot pin. If this is the problem then the radius of the disk would be larger by the radius of the pivot pin.

Second is that the point at which the blade begins cutting does not form a line that is perpendicular to the blade and intersecting the point at the center of the pivot pin. This could result in a radius longer than expected.

Third potential cause could be related to the blade. A ¾” wide blade cannot cut a 5” radius. Assuming a 5/8” or narrower blade, the blade could be flexing due to a dull blade, excessive feed rate, inadequate blade tension, and/or roller guides set too high above the workpiece.

Lastly, if the jig moved slightly during the cut, the radius could be off a little, but then the resulting disk would not be perfect round and would have been noticed.

One idea for correcting the jig without extensive reworking of the jig is to recut the kerf so that the pivot pin is 1/16” closer to the blade. This should result in the 10” diameter you are after. Moving the pivot pin closer to the blade by 1/16” would begin with clamping the jig to the band saw table in the position that resulted in a disk that was 10-1/8” diameter. If the jig has been repositioned since last used, the jig could be re-installed and a test cut made in some scrap and the resulting radius measured. In this case the thickness of the shim (below) would have to be adjusted to match the error.

Next a shim such as a long piece of scrap cut to a thickness of 1/16” can be held against the edge (opposite from the band saw column) of the band saw table while a fence (a straight piece of wood) is clamped to the underside of the jig so that the fence is snug against the shim and the shim is sandwiched tight between the edge of the table and the fence. With the fence clamped in place, it can be screwed to the jig. Once screwed in place the fence will be the thickness-of-the-shim away from the edge of the band saw table.

The jig can be un-clamped and removed from the band saw, and the shim set aside. The kerf in the jig can be re-cut by keeping the fence screwed to the underside of the jig firmly against the edge of the band saw table until the cutting edge of blade reaches the line from the center of the pivot pin. The fence can then be used to clamp the jig to the band saw table.

If the fence extends a few inches beyond the edge of the jig, engaging the fence and keeping it firmly against the edge of the band saw table may cutting the new kerf little easier.

View Karda's profile

Karda

1170 posts in 634 days


#12 posted 05-07-2018 05:33 AM

thanks everybody for you information, I plugged the hole and I’ll try again, maybe get it right this time. The thing that is so irritating is that I have made jig and got perfect circles. but now can’t

View msinc's profile

msinc

477 posts in 584 days


#13 posted 05-07-2018 05:49 AM


I have thought of a moving pin but can t find the track nor do i have the tools to make one. How is a larger peg going to work if the center is the same. I was going to plug hole but how do i measure so i don t do it wrong again. Can t do sander because this jig is for cutting bowl blanks

- Karda

Use a french cleat slide something like this.

attach a recessed ruler and you are in business. Even if it is off you can adjust after a test cut.

I built this from nothing but scrap I had on hand. Used a 1/4 drill bit end for my center dowel.

- woodbutcherbynight

That’s it!!!!! Not the only way to fly…...but definitely a way to fly!!!!! You might think you only have to cut one size circle and you can get it right the way you are doing it, but you will have to cut other sizes eventually. Might as well get it set up so you can perfectly adjust to whatever size you need when you need to do so.

View Woodknack's profile

Woodknack

12215 posts in 2460 days


#14 posted 05-07-2018 07:35 AM

For a 10” diameter circle, your radius must be 5”. It’s an unfair law of nature, like evolution and thermodynamics.

-- Rick M, http://thewoodknack.blogspot.com/

View Karda's profile

Karda

1170 posts in 634 days


#15 posted 05-07-2018 03:27 PM

I agree that is what I have 5” to the center of the hole yet it cuts over.

showing 1 through 15 of 33 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com