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Knee mill riser - most useful height?

I know that this is a subjective question depending on work being done/personal preference but overall:
- who here has added a riser to the column of their knee mill?
- what height (inches) did you select?
- did you find the height you selected as being overall useful...or wishing you had gone higher/lower?

Riser heights typically seen are 4, 6, 7 and 8"....and seen feedback about "pain to install..sometimes wishing it wasn't on" and then occasionally the riser is once again posted on eBay from whence it came...
My mill is a 6x30 and I decided on 8 inches having emailed John (Twastard Engineering on Youtube). His is 5 1/2” as I recall. I put my boring bar into the quill, and measured as though I was boring a 6 inch block in my vice...... and I’m hoping I don’t run out of capacity again.

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Active Member
Premium Member
I have a 9X35 with 5 1/2 inches of quill travel. I don't see much advantage to a riser block taller than the quill travell? The more height added the more rigidity lost!


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Premium Member
Its a function of the work you do but its surprising how certain setups can gobble headroom in a hurry. 15" from quill bottom to end of spindle sounds like a lot but.... a typical mill vise can use 4" from the table top, more if it sits on a swivel casting. Or a typical rotary table (5-6") plus maybe a mounted fixture/chuck (4"). Then subtract top side tooling like drill chuck + drill or an end mill arbor + EM (3-6" depending on size). Sometimes there isn't a lot of room remaining for the part. If you use a dividing head or flip the RT perpendicular to table, that can use up 6" or more. Tapping heads are also longish ~6"

My smaller RF45 mill actually had a teeny bit more vertical than baby Bridgeport. I can see where riser blocks are desirable for some. Bigger mills typically have more usable gap. The downside is the draw bar nut is up in the clouds. So unless you are 6'5" or have a power changer the step stool must always be close. Another consideration is shop ceiling height particularly if you are in proximity of things like garage door tracks. Riser block opens the useable range but does nothing for table height, so you may still find you want the mill elevated.
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I don’t know that by going the 8 inches vs 6 sacrifices much rigidity as I used a block 8 inches round and a wall thickness of 3 inches. My thinking was that 5.5 inches would do.... but I have never heard any person complain about having too much capacity or too much mill.......

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my biggest concerns:
1) adding a riser that is so tall that it negates shallow work; you dont want to 'fix' one problem and generate another...and adding/removing a riser would be a lot of effort
2) paying up for a riser (say, 4") and then wishing it was a 8"...considering the amount of risers I see for sale and comments I see on other boards, there appears to be much in the way of 'riser-buyer remorse'....