Bolt sizing - vise mounting and general principles...

[BikerDad]

So, I'm about to mount my Athol vise temporarily, and no surprise, I have no instructions. Marking it out and such is no problem, my question concerns the actual size (diameter) of the bolts.

Should I used bolts that exactly match the vise base hole size, and drill the mounting surface 1/16" oversize, or drill the mounting surface to exactly match the base hole size and use bolts that are 1/16" undersize?

In similar vein, what are the general principles for the sizing of through bolts? (Note, I'm not talking about high precision machinery.)

 

[Farmall450]

Find bolts that will fit, drill holes that allow the bolts to pass through. I'd advise washers.

 

[Schurkey]

I would want bolts that were as large as would go through the holes in the vice. I would drill holes in the mounting surface to exactly match the bolts plus the absolute minimum oversize to allow a slip-fit rather than a press-fit. So, no, I would not allow a sixteenth of an inch slop in any part of the mounting if I could avoid it. Two, three, maybe ten thousandths, I could understand. Sixty-two thousandths is excessive.

Larger bolts will hold more securely, and the larger diameter/tighter fit prevents the vice from spinning/slipping if there's any side-force.

 

[larry_g]

What is you mounting surface? If wood then the bolt should be a tight fit in the hole. If metal then drill on size. For a 1/2" bolt then drill a 1/2" hole. Most bolts are a few thou undersize.

https://www.kljack.com/customer/kljaco/pdf/KL_Jack_Fasteners-Technical_Data_and_Charts.pdf

lg
no neat sig line

 

[leg17]

The holes in the vise will have some clearance built in. You won't find screws that 'slip fit' through the vise. There will be some unavoidable clearance that was part of the original design. Use the largest diameter bolt that will fit through the vise. Transfer the hole pattern as carefully as you can and drill the bench about 1/32 or so oversize. If there is too much interference due to misalignment, open the holes a little more. Use washers as advised above. It will be fine.
I am not sure what the intent was of a previous post about ten-thousanths of an inch clearance. The bolts are out-of-round more than that.

 

[rharman]

You are overthinking this.

Use what fits and use fender washers under neath and also on top if there is enough room. My vise is mounted with three 1/2-13's through a metal plate on top of 1-1/2" butcher block. Rock solid.

 

[BikerDad]

Gentlemen, thank you for the responses.

The substrate/mounting surface is a piece of Douglas Fir 1.5" thick. The mounting holes in the base of the vise are a smidge over 1/2" diameter. I went with 1/2" bolts, was originally going to use 7/16", and 1/2" holes through the substrate. When I picked up the bolts I also picked up a 9/16" drill bit in the event I was off on drilling my holes. (Remember, unlike metal, wood likes to steer drill bits wherever it pleases....)

Surprisingly, I was accurate enough, so 1/2"+ (vise base) :: 1/2"- (bolt) :: 1/2" (substrate hole) is the result. I'll be returning the unopened 9/16" bit tomorrow.