MFT dog tolerances - Qwas raildogs and Lee Valley

[sonicfedora]

Little back story.

There is a resale place down the road that buys amazon returns and resells them.  The longer something has been there the lower the price.  I was digging deep one day and found an MFT/3 replacement top with a smashed corner.  Their original price was $90 but it was there for so long it was 90% off.  So I got an mft top for $10.  I know... I suck.

I was wanting to get an MFT anyways and thought it was meant to be that I build an MFT instead.

So... all of that to say that the "heritage" of my top is a little in question.  Don't know if the smashed corner is why it was sent back or if that happened afterwards.

I bought a set of QWAS raildogs (from Bob Marino... holy crap... they were in Nashville THE NEXT DAY... INCREDIBLE SERVICE!) and two pairs of the small 20mm dogs from Lee Valley.  I got those because they were cheaper and threaded which seems like it'll come in handy.

Well the raildogs when tightened all the way down don't securely lock into the rail.  Am I missing something?  I feel like it shouldn't slide around.  Maybe the screw is bottoming out and I just need to get a smaller screw or maybe I don't understand how something works.

Also both brands of dogs wiggle in the holes a bit.  Is this normal?  I kind of expected them to be tighter than they are.  I just want to make sure that they are supposed to have a little wiggle room and that my top isn't defective.

I know I'm probably explaining all of this poorly so I made a video.  

 

[Ivanhoe]

I know when I ordered my qwas dogs direct from Qwas, he asked specifically if my MFT top was new or old, so there must be some small deviation in hole size.

 

[promark747]

1. The Rail Dogs should definitely not move once you tighten them.  You should adjust the bolt just enough so it can slide onto the rail.
2. Once you insert the two Rail Dogs onto the rail, place them in the desired MFT holes loosely.  Then reach under the table, apply lateral force on each Rail Dog toward each other, and tighten.  There should now be no slop, but yet you'll be able to take the guide rail off the MFT.
3. The Lee Valley dogs are a looser fit than Qwas Dogs (which are the best I've found).

 

[sonicfedora]

1. The Rail Dogs should definitely not move once you tighten them.  You should adjust the bolt just enough so it can slide onto the rail.
2. Once you insert the two Rail Dogs onto the rail, place them in the desired MFT holes loosely.  Then reach under the table, apply lateral force on each Rail Dog toward each other, and tighten.  There should now be no slop, but yet you'll be able to take the guide rail off the MFT.
3. The Lee Valley dogs are a looser fit than Qwas Dogs (which are the best I've found).

Hmmm... maybe I should get in touch with Qwas or Bob Marino then.  Cause these bolts have got to be too long and it'd be nice to get replacement square head bolts.

Do you think the Lee Valley dogs are too sloppy to use for calibration?

 

[BUTTER]

Do you think the Lee Valley dogs are too sloppy to use for calibration?

You might as well test to see if this is the case for yourself using the 5 cut method. 

 

[grbmds]

I have used the Lee Valley dogs (with the flat face) for positioning the fence on the MFT/3 and was satisfied with the result, meaning that, based on my testing of cuts, the fence was then parallel to the MFT holes. I then used a square I have confidence in to square the guide rail to the fence. Based that experience I am satisified that the Lee Valley dogs are accurate enough for this purpose. However, there are a variety of products on the market, like Parf dogs, Quas dogs, etc., which all would appear to work just as well. I also have Parf dogs and, once the fence was lined up with the Lee Valley dogs and the guide rail square to the fence, I was able to use the Parf dogs positioned to cut a perfect 45 degree angles for a picture frame I made. I believe the miters were the most accurate I've ever been able to cut. I've used a table saw and a very good miter saw in the past, but these were the best and fit together extremely well and without any additional work. Based on that, I would say the Lee Valley dogs will work fine, but I would agree you should test it out yourself. That is the only way I am usually satisified something works for me.

 

[promark747]

1. The Rail Dogs should definitely not move once you tighten them.  You should adjust the bolt just enough so it can slide onto the rail.
2. Once you insert the two Rail Dogs onto the rail, place them in the desired MFT holes loosely.  Then reach under the table, apply lateral force on each Rail Dog toward each other, and tighten.  There should now be no slop, but yet you'll be able to take the guide rail off the MFT.
3. The Lee Valley dogs are a looser fit than Qwas Dogs (which are the best I've found).

Hmmm... maybe I should get in touch with Qwas or Bob Marino then.  Cause these bolts have got to be too long and it'd be nice to get replacement square head bolts.

Do you think the Lee Valley dogs are too sloppy to use for calibration?

I think the LV (Parf) dogs are probably fine...especially as you can screw them down, which you can't do (but don't need to) with the Qwas dogs.

I'm not exactly sure why the Qwas dogs fit so well; there may be a very slight taper right below the shoulder that creates the perfectly snug fit -- but I haven't checked with calipers.

 

[bkharman]

My favorites are the Precision Dogs. They fit like a glove in my stock MFT as well as other things I have drilled 20mm holes in. The have a small relief area at the top where the 20mm post meets the top of the dog.

 

[Mangler]

Had the same problem with Qwas rail dogs which arrived last week. (very nicely made by the way) I initially thought the bolt was bottoming out in the hole. Not the case - the bolt's shoulder stopped the bolt from threading all the way down the length of it. My solution was to reduce the outer diameter of a 1/4" washer to less than .490" so it would fit into the rail. Using the washer under the head of the bolt created a nice tight Qwas rail dog. Hope this helped.

 

[bkharman]

Your rail dogs should have a collar on to to fit on the rail below. Like this:

That goes in the bottom groove of the rail and the square head bolt holds it tight.  Like this:

Am I missing something?

 

[sonicfedora]

I just got this response from Bob Marino.  Haven't had a chance to try it yet.

Hi Ben
Sometimes that can happen. But if you hold the rail dog in your hand and tighten with a wrench, it almost always works to rethread and tighten them down all the way.
Let me know.

Bob

 

[bkharman]

I just got this response from Bob Marino.  Haven't had a chance to try it yet.

Hi Ben
Sometimes that can happen. But if you hold the rail dog in your hand and tighten with a wrench, it almost always works to rethread and tighten them down all the way.
Let me know.

Bob

I got it now...  I didn't realize that you were stating that the bolt wasn't going all the way into the dog. Yes, just tighten until it hits the collar. Once you get that low, no need to tighten against the collar as you won't go that far down once the dog is in the rail.

 

[Mangler]

I emailed Bob about my bolts not threading in far enough, I received the same instructions. Unfortunately I couldn't get the bolt to thread any farther, this led me to make the washers. Hope your results are different. 

 

[rst]

The easiest way to cure this is grind or cut the end to the threaded bolt off so it doesn't bottom out.

 

[kdzito]

I emailed Bob about my bolts not threading in far enough, I received the same instructions. Unfortunately I couldn't get the bolt to thread any farther, this led me to make the washers. Hope your results are different.  

I tried Bob's method first, but to no avail. Rather than to wait for an exchange, I used a 1/4-20 tap to re-thread into the dog deeper. The bolt now threads in all the way and tight to the dog's collar. 

 

[sonicfedora]

I'm a little dissapointed. I'll probably just break out a tap and thread more out.

Shouldn't have to. When they showed up I excitedly showed them to my wife. I said "I bet you're wondering why they were so much money".

She said "no. They do a specific job well and are made to very high tolerances". I was proud that she realizes stuff like that.

For the money I shouldn't have to modify anything. 

 

[bpitch]

I'm a little dissapointed. I'll probably just break out a tap and thread more out.

Shouldn't have to. When they showed up I excitedly showed them to my wife. I said "I bet you're wondering why they were so much money".

She said "no. They do a specific job well and are made to very high tolerances". I was proud that she realizes stuff like that.

For the money I shouldn't have to modify anything. 

If the problem is with screws being too long, I would suggest just getting a pair of shorter screws. Will be way easier than tapping. Home Depot should carry 1/4 screws in various length.
Hope this helps

 

[sonicfedora]

If the problem is with screws being too long, I would suggest just getting a pair of shorter screws. Will be way easier than tapping. Home Depot should carry 1/4 screws in various length.
Hope this helps

Far too simple!

The more I think about it there is no real benefit to the square head bolt.

 

[grbmds]

I'm a little dissapointed. I'll probably just break out a tap and thread more out.

Shouldn't have to. When they showed up I excitedly showed them to my wife. I said "I bet you're wondering why they were so much money".

She said "no. They do a specific job well and are made to very high tolerances". I was proud that she realizes stuff like that.

For the money I shouldn't have to modify anything. 

You are right! You shouldn't have to modify them for any price. Send them back. I would guess the company would stand behind them. If not, then I would question buying something from them in the future. Any product can be defective. It's what the company does to correct that defect or replace the product which is the test of the product and the company.

 

[bkharman]

I agree with folks that you shouldn't have to trim bolts or tap anything out.

Contact Qwas, I am sure they would want to hear about quality issues. They are a great company with great products.

I also don't know that a regular 6 sided bolt head will fit in the channel on the bottom of the rail. You might have to check.

Cheers. Bryan.