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What's your method for filing miter slots?

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Forum topic by James Clapperton posted 09-23-2011 05:21 AM 1707 views 0 times favorited 10 replies Add to Favorites Watch
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James Clapperton

35 posts in 1923 days


09-23-2011 05:21 AM

Topic tags/keywords: question tight miter slot filing cast iron filing table saw

I have a tight miter slot on the right side of my Shop Fox. Not usually a big deal, but today it stuck more than usual do to some crud build up. It ruined my panel and it’s just plain dangerous when you’re all stretched out like I was at the end of my 30” cut. Do you guys use a store bought file? A stone? Sand paper and a runner? I want to see some options before I commit to grinding this thing out. Thanks guys.
-James


10 replies so far

View TopamaxSurvivor's profile

TopamaxSurvivor

17677 posts in 3143 days


#1 posted 09-23-2011 06:01 AM

Sounds like laping is in order to make it consistent rather than filing.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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James Clapperton

35 posts in 1923 days


#2 posted 09-23-2011 05:28 PM

Topamax- Can you elaborate or point me in the right direction via the web?

Rick- I’ll break out the calipers this morning and let you know what the difference is and how far out of spec the slot is.

cr1- The slot was worse than usual because of some mdf and construction lumber build up, but that’s not the issue. That was just the icing on the cake. What’s wrong with slowly and carefully filing?

To clarify a but, the slot is tight in the rear on the right. It causes a “hiccup” while I’m pushing the last few inches through. This time, because of the build up in the slot, the hiccup caused my large panel to twist a bit and scared the crap out of me.

Thanks guys.

View Sawkerf's profile

Sawkerf

1730 posts in 2536 days


#3 posted 09-23-2011 05:52 PM

IME, miter slots are seldom a problem. More often, it’s the bar (or whatever) that travels in the slot. I think that I would look at what’s riding in the miter slot – and tweaking that – before I started messing with the saw table.

-- Adversity doesn't build character...................it reveals it.

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James Clapperton

35 posts in 1923 days


#4 posted 09-23-2011 05:59 PM

It happens with all of my bars and runners, home made or not. I have the adjustable bar on my Incra 1000se. I’m sure it’s not the bar and is indeed, the miter slot.

View Dallas's profile

Dallas

3599 posts in 1955 days


#5 posted 09-23-2011 06:14 PM

Mike the slot, Mike the bar. Do both in different places along the length of run. I did have one saw tat had a bad slot, many years ago, but it was because of bad casting, not the finishing. This made the miter gauge ride proud after about 6” into the cut.
Have you used some Johnson’s on the bar and the slot? I know that with my BT3100 TS if I don’t wax it every so often on the rails, the fence will stick and then move while I’m pulling the handle down.

-- Improvise.... Adapt...... Overcome!

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James Clapperton

35 posts in 1923 days


#6 posted 09-23-2011 06:32 PM

Okay, Front of slot= .7515, rear of slot=.7505, front of bar .7375, rear of bar .7402. All is in order. I got a exacto blade and started poking around in the track and found a bad spot of casting. A 3/8” section inside the “t” at the very bottom of the track sits proud by about 1/32”. Problem identified. Can someone please tell me the best way to remove it.

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rance

4245 posts in 2628 days


#7 posted 09-23-2011 06:52 PM

I don’t know how you would Mike it, but you could probably mic. it. :) Seriously, to answer your question, a file would take off too much material, too quickly.

If/when you lap or sand it into submission, I’d suggest you only do one side at a time. As a sloppy example, if you wrapped sandpaper around an appropriatly sized block and began widening the slot, you are taking metal off both sides. With that, you loose your point of reference. If I used a sanding block, I’d only sand on one side or the other.

As to which side to sand, try mounting a dial indicator on a block and running that block up against your fence with the DI checking each side of the slot. That should tell you what is going on. All this assumes that your fence is straight of course. I hope you don’t find out your miter slot is doing the Wiggle Worm Boogie.

A DI sufficient to do what you need could be bought at HF.

Edit: Sorry, I didn’t read that you identified the problem. If you had a small stone, you could use it to grind it down without affecting the sides of the slot.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View TopamaxSurvivor's profile

TopamaxSurvivor

17677 posts in 3143 days


#8 posted 09-23-2011 08:34 PM

Probably best to take it to a machine shop. If cost is an issue with that. I would use a file being very careful of the sides or a file with edge cutting only. Maybe a large tri-file would work to take the 32nd off the bottom..

Lapping is the process of using an object of the shape and size you are trying to smooth to file it with polishing compound. Very fine sand paper or emery cloth might work too on something like that. I am only familiar with lapping scope mounts or rifle barrels. Be Careful, you can take a lot more than you think very quickly ;-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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James Clapperton

35 posts in 1923 days


#9 posted 09-23-2011 09:43 PM

Excellent. Thanks for the ideas guys.

View a1Jim's profile

a1Jim

115207 posts in 3045 days


#10 posted 09-24-2011 02:52 AM

Hi James Welcome to LJs
I have filed miters slots before, I used a miter gauge in the slot and kept checking it for fit making sure the miter gauge bar was equal through out it’s whole length. I just took it slowly carefully and checked it frequently. In the end it worked beautifully. Just use a fine file and take your time

-- http://artisticwoodstudio.com Custom furniture

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